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MC68HC908AP64A MC68HC908AP32A MC68HC908AP16A MC68HC908AP8A
Data Sheet
M68HC08 Microcontrollers
MC68HC908AP64A Rev. 2 01/2007
freescale.com
MC68HC908AP64A MC68HC908AP32A MC68HC908AP16A MC68HC908AP8A
Data Sheet
To provide the most up-to-date information, the revision of our documents on the World Wide Web will be the most current. Your printed copy may be an earlier revision. To verify you have the latest information available, refer to: http://www.freescale.com The following revision history table summarizes changes contained in this document. For your convenience, the page number designators have been linked to the appropriate location.
FreescaleTM and the Freescale logo are trademarks of Freescale Semiconductor, Inc. This product incorporates SuperFlash(R) technology licensed from SST. (c) Freescale Semiconductor, Inc., 2005, 2007. All rights reserved. MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 3
Revision History
Date Revision Level 2 1 Description 15.7.2 ADC Clock Control Register -- Changed "The ADC clock should be set to between 500kHz and 2MHz" to "The ADC clock should be set to between 500kHz and 1MHz" First general release. Page Number(s) 250 --
January 2007 Mar 2005
MC68HC908AP A-Family Data Sheet, Rev. 2 4 Freescale Semiconductor
List of Chapters
Chapter 1 General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Chapter 2 Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 Chapter 3 Configuration & Mask Option Registers (CONFIG & MOR) . . . . . . . . . . . . . . . .49 Chapter 4 Central Processor Unit (CPU). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55 Chapter 5 Oscillator (OSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71 Chapter 6 Clock Generator Module (CGM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79 Chapter 7 System Integration Module (SIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97 Chapter 8 Monitor ROM (MON) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115 Chapter 9 Timer Interface Module (TIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131 Chapter 10 Timebase Module (TBM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147 Chapter 11 Serial Communications Interface Module (SCI) . . . . . . . . . . . . . . . . . . . . . . .151 Chapter 12 Infrared Serial Communications Interface Module (IRSCI) . . . . . . . . . . . . . .177 Chapter 13 Serial Peripheral Interface Module (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205 Chapter 14 Multi-Master IIC Interface (MMIIC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225 Chapter 15 Analog-to-Digital Converter (ADC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243 Chapter 16 Input/Output (I/O) Ports. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .255 Chapter 17 External Interrupt (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .267 Chapter 18 Keyboard Interrupt Module (KBI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .273 Chapter 19 Computer Operating Properly (COP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279 Chapter 20 Low-Voltage Inhibit (LVI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .283 Chapter 21 Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .287 Chapter 22 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293 Chapter 23 Mechanical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .307 Chapter 24 Ordering Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .311
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 5
List of Chapters
MC68HC908AP A-Family Data Sheet, Rev. 2 6 Freescale Semiconductor
Table of Contents
Chapter 1 General Description
1.1 1.2 1.3 1.4 1.5 1.6 1.7 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pin Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power Supply Bypassing (VDD, VDDA, VSS, VSSA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Regulator Power Supply Configuration (VREG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 19 20 22 25 26 27
Chapter 2 Memory
2.1 2.2 2.3 2.4 2.5 2.5.1 2.5.2 2.5.3 2.5.4 2.5.5 2.5.6 2.5.7 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Input/Output (I/O) Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Monitor ROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Random-Access Memory (RAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Page Erase Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Mass Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Program Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Block Protect Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 29 29 41 42 42 43 43 44 44 45 47
Chapter 3 Configuration & Mask Option Registers (CONFIG & MOR)
3.1 3.2 3.3 3.4 3.5 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Configuration Register 1 (CONFIG1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Configuration Register 2 (CONFIG2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mask Option Register (MOR). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 50 50 52 53
Chapter 4 Central Processor Unit (CPU)
4.1 4.2 4.3 4.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Table of Contents
4.3.2 4.3.3 4.3.4 4.3.5 4.4 4.5 4.5.1 4.5.2 4.6 4.7 4.8
Index Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arithmetic/Logic Unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
56 57 57 58 59 59 59 59 60 60 60
Chapter 5 Oscillator (OSC)
5.1 5.2 5.2.1 5.2.2 5.3 5.4 5.5 5.6 5.6.1 5.6.2 5.6.3 5.6.4 5.6.5 5.6.6 5.7 5.7.1 5.7.2 5.8 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clock Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM Reference Clock Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TBM Reference Clock Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RC Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X-tal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Crystal Amplifier Input Pin (OSC1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Crystal Amplifier Output Pin (OSC2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oscillator Enable Signal (SIMOSCEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM Oscillator Clock (CGMXCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM Reference Clock (CGMRCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oscillator Clock to Time Base Module (OSCCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oscillator During Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 71 72 73 74 75 75 76 76 76 76 77 77 77 77 77 77 77
Chapter 6 Clock Generator Module (CGM)
6.1 6.2 6.3 6.3.1 6.3.2 6.3.3 6.3.4 6.3.5 6.3.6 6.3.7 6.3.8 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oscillator Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Phase-Locked Loop Circuit (PLL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acquisition and Tracking Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Manual and Automatic PLL Bandwidth Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Programming the PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special Programming Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Base Clock Selector Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 79 79 81 81 81 82 83 83 86 86
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6.3.9 6.4 6.4.1 6.4.2 6.4.3 6.4.4 6.4.5 6.4.6 6.4.7 6.4.8 6.5 6.5.1 6.5.2 6.5.3 6.5.4 6.5.5 6.6 6.7 6.7.1 6.7.2 6.7.3 6.8 6.8.1 6.8.2 6.8.3
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Analog Ground Pin (VSSA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oscillator Output Frequency Signal (CGMXCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM Reference Clock (CGMRCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM VCO Clock Output (CGMVCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM Base Clock Output (CGMOUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM CPU Interrupt (CGMINT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Bandwidth Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Multiplier Select Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL VCO Range Select Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Reference Divider Select Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acquisition/Lock Time Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acquisition/Lock Time Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parametric Influences on Reaction Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Choosing a Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
86 87 87 87 87 88 88 88 88 88 88 89 91 92 92 93 93 94 94 94 94 95 95 95 96
Chapter 7 System Integration Module (SIM)
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 7.2 SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 7.2.1 Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 7.2.2 Clock Start-up from POR or LVI Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7.2.3 Clocks in Stop Mode and Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7.3 Reset and System Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7.3.1 External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7.3.2 Active Resets from Internal Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 7.3.2.1 Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 7.3.2.2 Computer Operating Properly (COP) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 7.3.2.3 Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 7.3.2.4 Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.3.2.5 Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.3.2.6 Monitor Mode Entry Module Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.4 SIM Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.4.1 SIM Counter During Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.4.2 SIM Counter During Stop Mode Recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.4.3 SIM Counter and Reset States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 7.5 Exception Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
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7.5.1 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.1.1 Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.1.2 SWI Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.2 Interrupt Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.2.1 Interrupt Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.2.2 Interrupt Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.2.3 Interrupt Status Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.3 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.4 Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.5 Status Flag Protection in Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.7 SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.7.1 SIM Break Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.7.2 SIM Reset Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.7.3 SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
104 105 106 106 107 107 107 109 109 109 109 109 110 111 112 113 114
Chapter 8 Monitor ROM (MON)
8.1 8.2 8.3 8.3.1 8.3.2 8.3.3 8.3.4 8.3.5 8.4 8.5 8.5.1 8.5.2 8.5.3 8.5.4 8.5.5 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Entering Monitor Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Break Signal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baud Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ROM-Resident Routines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PRGRNGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ERARNGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LDRNGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MON_PRGRNGE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MON_ERARNGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 115 115 117 119 120 120 120 124 126 127 128 129 130 130
Chapter 9 Timer Interface Module (TIM)
9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.1 TIM Counter Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.3 Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.3.1 Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.3.2 Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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131 131 131 132 134 134 134 134 135
9.4.4 Pulse Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.4.1 Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.4.2 Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.4.3 PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7 TIM During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9.1 TIM Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9.2 TIM Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9.3 TIM Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9.4 TIM Channel Status and Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.9.5 TIM Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
135 136 137 137 138 138 138 138 138 139 139 139 141 141 142 144
Chapter 10 Timebase Module (TBM)
10.1 10.2 10.3 10.4 10.5 10.6 10.6.1 10.6.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Timebase Register Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 147 147 148 150 150 150 150
Chapter 11 Serial Communications Interface Module (SCI)
11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.1 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.2.1 Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.2.2 Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.2.3 Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.2.4 Idle Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.2.5 Inversion of Transmitted Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.2.6 Transmitter Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.3.1 Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.3.2 Character Reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.3.3 Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 151 152 153 154 154 155 155 155 156 156 156 156 156 156 158
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11.4.3.4 Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.3.5 Baud Rate Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.3.6 Receiver Wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.3.7 Receiver Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.3.8 Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6 SCI During Break Module Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7.1 TxD (Transmit Data). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.7.2 RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.8 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.8.1 SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.8.2 SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.8.3 SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.8.4 SCI Status Register 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.8.5 SCI Status Register 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.8.6 SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.8.7 SCI Baud Rate Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
160 160 161 162 162 163 163 163 163 163 163 164 164 165 167 169 170 173 173 174
Chapter 12 Infrared Serial Communications Interface Module (IRSCI)
12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3 IRSCI Module Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4 Infrared Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.1 Infrared Transmit Encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.2 Infrared Receive Decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5 SCI Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.1 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.2.1 Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.2.2 Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.2.3 Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.2.4 Idle Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.2.5 Transmitter Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.3.1 Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.3.2 Character Reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.3.3 Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.3.4 Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.3.5 Baud Rate Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.3.6 Receiver Wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.3.7 Receiver Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.5.3.8 Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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177 178 179 179 180 180 181 182 182 182 183 184 184 184 185 186 186 186 188 188 190 190 190 191
12.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7 SCI During Break Module Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.8 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.8.1 PTC6/SCTxD (Transmit Data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.8.2 PTC7/SCRxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.9 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.9.1 IRSCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.9.2 IRSCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.9.3 IRSCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.9.4 IRSCI Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.9.5 IRSCI Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.9.6 IRSCI Data Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.9.7 IRSCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.9.8 IRSCI Infrared Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
191 191 191 192 192 192 193 193 195 196 198 200 201 201 204
Chapter 13 Serial Peripheral Interface Module (SPI)
13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3 Pin Name Conventions and I/O Register Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.1 Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.2 Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5 Transmission Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5.1 Clock Phase and Polarity Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5.2 Transmission Format When CPHA = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5.3 Transmission Format When CPHA = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5.4 Transmission Initiation Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.6 Queuing Transmission Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.7 Error Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.7.1 Overflow Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.7.2 Mode Fault Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.9 Resetting the SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.10 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.10.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.10.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.11 SPI During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.12 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.12.1 MISO (Master In/Slave Out). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.12.2 MOSI (Master Out/Slave In). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.12.3 SPSCK (Serial Clock) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.12.4 SS (Slave Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.12.5 CGND (Clock Ground) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.13 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Table of Contents
13.13.1 13.13.2 13.13.3
SPI Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 SPI Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 SPI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
Chapter 14 Multi-Master IIC Interface (MMIIC)
14.1 14.2 14.3 14.4 14.5 14.5.1 14.5.2 14.5.3 14.5.4 14.5.5 14.5.6 14.5.7 14.5.8 14.5.9 14.6 14.6.1 14.6.2 14.6.3 14.6.4 14.6.5 14.6.6 14.6.7 14.6.8 14.7 14.7.1 14.8 14.8.1 14.8.2 14.8.3 14.8.4 14.8.5 14.8.6 14.8.7 14.9 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multi-Master IIC System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multi-Master IIC Bus Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . START Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Slave Address Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Repeated START Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . STOP Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arbitration Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clock Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Handshaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Packet Error Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MMIIC I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MMIIC Address Register (MMADR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MMIIC Control Register 1 (MMCR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MMIIC Control Register 2 (MMCR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MMIIC Status Register (MMSR). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MMIIC Data Transmit Register (MMDTR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MMIIC Data Receive Register (MMDRR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MMIIC CRC Data Register (MMCRCDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MMIIC Frequency Divider Register (MMFDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Program Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SMBus Protocols with PEC and without PEC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Quick Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Send Byte. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Receive Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Write Byte/Word . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Read Byte/Word. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Process Call . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Block Read/Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SMBus Protocol Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 225 226 226 227 227 227 228 228 228 228 228 229 229 229 230 231 232 233 234 235 236 236 237 238 239 239 239 239 240 240 241 241 242
Chapter 15 Analog-to-Digital Converter (ADC)
15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.2 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3.1 ADC Port I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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243 243 244 244
15.3.2 15.3.3 15.3.4 15.3.5 15.3.6 15.3.7 15.3.8 15.4 15.5 15.5.1 15.5.2 15.6 15.6.1 15.6.2 15.6.3 15.6.4 15.6.5 15.7 15.7.1 15.7.2 15.7.3 15.7.4 15.7.5
Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Continuous Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Auto-Scan Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Result Justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Register Interlocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Monotonicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Voltage In (VADIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Analog Ground Pin (VSSA). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Voltage Reference High Pin (VREFH). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Voltage Reference Low Pin (VREFL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Clock Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Data Register 0 (ADRH0 and ADRL0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Auto-Scan Mode Data Registers (ADRL1-ADRL3) . . . . . . . . . . . . . . . . . . . . . . . . . ADC Auto-Scan Control Register (ADASCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
244 245 246 246 247 247 247 247 247 248 248 248 248 248 248 248 248 249 249 250 251 253 253
Chapter 16 Input/Output (I/O) Ports
16.1 16.2 16.2.1 16.2.2 16.2.3 16.3 16.3.1 16.3.2 16.4 16.4.1 16.4.2 16.5 16.5.1 16.5.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port A Data Register (PTA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Direction Register (DDRA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port-A LED Control Register (LEDA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port B Data Register (PTB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Direction Register B (DDRB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port C Data Register (PTC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Direction Register C (DDRC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port D Data Register (PTD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Direction Register D (DDRD). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 257 257 257 259 259 259 260 261 261 262 263 263 264
Chapter 17 External Interrupt (IRQ)
17.1 17.2 17.3 17.4 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IRQ1 and IRQ2 Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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17.5 IRQ Module During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6 IRQ Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6.1 IRQ1 Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6.2 IRQ2 Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
270 270 270 271
Chapter 18 Keyboard Interrupt Module (KBI)
18.1 18.2 18.3 18.4 18.4.1 18.5 18.5.1 18.5.2 18.6 18.6.1 18.6.2 18.7 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keyboard Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keyboard Interrupt Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keyboard Status and Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keyboard Interrupt Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keyboard Module During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 273 273 274 275 275 275 276 277 277 277 277
Chapter 19 Computer Operating Properly (COP)
19.1 19.2 19.3 19.3.1 19.3.2 19.3.3 19.3.4 19.3.5 19.3.6 19.3.7 19.3.8 19.4 19.5 19.6 19.7 19.7.1 19.7.2 19.8 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ICLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . STOP Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internal Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reset Vector Fetch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COPD (COP Disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COPRS (COP Rate Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COP Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COP Module During Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 279 280 280 280 280 280 280 280 280 281 281 281 281 281 282 282 282
Chapter 20 Low-Voltage Inhibit (LVI)
20.1 20.2 20.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
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20.3.1 Low VDD Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.3.2 Low VREG Detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.3.3 Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.3.4 Forced Reset Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.3.5 Voltage Hysteresis Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.4 LVI Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5 LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
284 284 284 285 285 285 285 286 286 286
Chapter 21 Break Module (BRK)
21.1 21.2 21.3 21.3.1 21.3.2 21.3.3 21.3.4 21.4 21.4.1 21.4.2 21.5 21.5.1 21.5.2 21.5.3 21.5.4 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flag Protection During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TIMI and TIM2 During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Break Module Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Break Status and Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SIM Break Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 287 287 288 288 288 288 288 289 289 289 289 290 290 291
Chapter 22 Electrical Specifications
22.1 22.2 22.3 22.4 22.5 22.6 22.7 22.8 22.9 22.10 22.11 22.12 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5V DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5V Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5V Oscillator Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5V ADC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MMIIC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM Electrical Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5V SPI Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 293 294 294 295 296 297 298 299 301 302 305
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Chapter 23 Mechanical Specifications
23.1 23.2 23.3 23.4 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48-Pin Low-Profile Quad Flat Pack (LQFP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44-Pin Quad Flat Pack (QFP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42-Pin Shrink Dual In-Line Package (SDIP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 308 309 310
Chapter 24 Ordering Information
24.1 24.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
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Chapter 1 General Description
1.1 Introduction
The MC68HC908AP64A is a member of the low-cost, high-performance M68HC08 Family of 8-bit microcontroller units (MCUs). All MCUs in the family use the enhanced M68HC08 central processor unit (CPU08) and are available with a variety of modules, memory sizes and types, and package types. Table 1-1. Summary of Device Variations
Device MC68HC908AP64A MC68HC908AP32A MC68HC908AP16A MC68HC908AP8A RAM Size (bytes) 2,048 2,048 1,024 1,024 FLASH Memory Size (bytes) 62,368 32,768 16,384 8,192
1.2 Features
Features of the MC68HC908AP64A include the following: * High-performance M68HC08 architecture * Fully upward-compatible object code with M6805, M146805, and M68HC05 Families * Maximum internal bus frequency: - 8-MHz at 5V operating voltage * Clock input options: - RC-oscillator - 1- to 8-MHz crystal-oscillator with 32MHz internal PLL * User program FLASH memory with security(1) feature - 62,368 bytes for MC68HC908AP64A - 32,768 bytes for MC68HC908AP32A - 16,384 bytes for MC68HC908AP16A - 8,192 bytes for MC68HC908AP8A * On-chip RAM - 2,048 bytes for MC68HC908AP64A and MC68HC908AP32A - 1,024 bytes for MC68HC908AP16A and MC68HC908AP8A * Two 16-bit, 2-channel timer interface modules (TIM1 and TIM2) with selectable input capture, output compare, and PWM capability on each channel
1. No security feature is absolutely secure. However, Freescale's strategy is to make reading or copying the FLASH difficult for unauthorized users. MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 19
General Description
* * * * * * * * * *
* * *
* *
Timebase module Serial communications interface module 1 (SCI) Serial communications interface module 2 (SCI) with infrared (IR) encoder/decoder Serial peripheral interface module (SPI) System management bus (SMBus), version 1.0/1.1 (multi-master IIC bus) 8-channel, 10-bit analog-to-digital converter (ADC) IRQ1 external interrupt pin with integrated pullup IRQ2 external interrupt pin with programmable pullup 8-bit keyboard wakeup port with integrated pullup 32 general-purpose input/output (I/O) pins: - 31 shared-function I/O pins - 8 LED drivers (sink) - 6 x 25mA open-drain I/O with pullup Low-power design (fully static with stop and wait modes) Master reset pin (with integrated pullup) and power-on reset System protection features - Optional computer operating properly (COP) reset, driven by internal RC oscillator - Low-voltage detection with optional reset or interrupt - Illegal opcode detection with reset - Illegal address detection with reset 48-pin low quad flat pack (LQFP), 44-pin quad flat pack (QFP), and 42-pin shrink dual-in-line package (SDIP) Specific features of the MC68HC908AP64A in 42-pin SDIP are: - 30 general-purpose l/Os only - External interrupt on IRQ1 only
Features of the CPU08 include the following: * Enhanced HC05 programming model * Extensive loop control functions * 16 addressing modes (eight more than the HC05) * 16-bit Index register and stack pointer * Memory-to-memory data transfers * Fast 8 x 8 multiply instruction * Fast 16/8 divide instruction * Binary-coded decimal (BCD) instructions * Optimization for controller applications * Efficient C language support
1.3 MCU Block Diagram
Figure 1-1 shows the structure of the MC68HC908AP64A.
MC68HC908AP A-Family Data Sheet, Rev. 2 20 Freescale Semiconductor
MCU Block Diagram
INTERNAL BUS M68HC08 CPU CPU REGISTERS ARITHMETIC/LOGIC UNIT (ALU) 10-BIT ANALOG-TO-DIGITAL CONVERTER MODULE PTA7/ADC7 PTA6/ADC6 PTA5/ADC5 PTA4/ADC4 PTA3/ADC3 PTA2/ADC2 PTA1/ADC1 PTA0/ADC0 PTB7/T2CH1 PTB6/T2CH0 PTB5/T1CH1 PTB4/T1CH0 PTB3/RxD PTB2/TxD PTB1/SCL PTB0/SDA PTC7/SCRxD PTC6/SCTxD PTC5/SPSCK PTC4/SS PTC3/MOSI PTC2/MISO PTC1 # PTC0/IRQ2 **# PTD7/KBI7 *** PTD6/KBI6 *** PTD5/KBI5 *** PTD4/KBI4 *** PTD3/KBI3 *** PTD2/KBI2 *** PTD1/KBI1 *** PTD0/KBI0 ***
CONTROL AND STATUS REGISTERS -- 96 BYTES USER FLASH -- (SEE TABLE) USER RAM -- (SEE TABLE) MONITOR ROM -- 959 BYTES USER FLASH VECTOR SPACE -- 48 BYTES OSCILLATORS AND CLOCK GENERATOR MODULE INTERNAL OSCILLATOR OSC1 OSC2 CGMXFC RC OSCILLATOR X-TAL OSCILLATOR PHASE-LOCKED LOOP
TIMEBASE MODULE
2-CHANNEL TIMER INTERFACE MODULE 1 PORTB PORTD PORTC
2-CHANNEL TIMER INTERFACE MODULE 2
SERIAL COMMUNICATIONS INTERFACE MODULE 1
MULTI-MASTER IIC (SMBUS) INTERFACE MODULE DDRC DDRD . USER RAM (bytes) 2,048 2,048 1,024 1,024
* RST
SYSTEM INTEGRATION MODULE EXTERNAL INTERRUPT MODULE COMPUTER OPERATING PROPERLY MODULE POWER-ON RESET MODULE
SERIAL COMMUNICATIONS INTERFACE MODULE 2 (WITH INFRARED MODULATOR/DEMODULATOR)
* IRQ1 ** IRQ2
SERIAL PERIPHERAL INTERFACE MODULE
KEYBOARD INTERRUPT MODULE
LOW-VOLTAGE INHIBIT MODULE
VDD VDDA VSS VSSA VREG VREFH VREFL
POWER
ADC REFERENCE
* Pin contains integrated pullup device. ** Pin contains configurable pullup device. *** Pin contains integrated pullup device when configured as KBI. Pin is open-drain when configured as output. LED direct sink pin. # Pin not bonded on 42-pin SDIP. USER FLASH (bytes) 62,368 32,768 16,384 8,192
DEVICE MC68HC908AP64A MC68HC908AP32A MC68HC908AP16A MC68HC908AP8A
Figure 1-1. MC68HC908AP64A Block Diagram
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 21
DDRB
PORTA
DDRA
General Description
1.4 Pin Assignment
PTB7/T2CH1
PTD0/KBI0
PTD1/KBI1
PTD2/KBI2
PTD3/KBI3
PTD4/KBI4
PTD5/KBI5
PTD6/KBI6 38
48 CGMXFC
47
46
45
44
43
42
41
40
39
37 PTD7/KBI7 36 VREFH
VDDA
PTB6/T2CH0 1 VREG PTB5/T1CH1 VDD OSC1 OSC2 VSS PTB4/T1CH0 IRQ1 PTB3/RxD RST PTB2/TxD 12 PTB1/SCL 13 2 3 4 5 6 7 8 9 10 11
VSSA
35 34 33 32 31 30 29 28 27 26 14 15 16 17 18 19 20 21 22 23
VREFL NC NC PTA0/ADC0 NC PTA1/ADC1 PTA2/ADC2 PTA3/ADC3 PTA4/ADC4 PTA5/ADC5
25 PTA6/ADC6
PTC3/MOSI
PTC2/MISO
PTC5/SPSCK
PTC6/SCTxD
PTC0/IRQ2
PTB0/SDA
PTC4/SS
PTC1
NC: No connection
Figure 1-2. 48-Pin LQFP Pin Assignments
MC68HC908AP A-Family Data Sheet, Rev. 2 22 Freescale Semiconductor
PTC7/SCRxD
PTA7/ADC7
NC 24
Pin Assignment
PTB7/T2CH1
PTD0/KBI0
PTD1/KBI1
PTD2/KBI2
PTD3/KBI3
PTD4/KBI4
PTD5/KBI5 35
39
38
37
43
42
41
PTB6/T2CH0 1 VREG PTB5/T1CH1 VDD OSC1 OSC2 VSS PTB4/T1CH0 IRQ1 PTB3/RxD RST 11 PTB2/TxD 12 2 3 4 5 6 7 8 9 10
40
36
34 PTD6/KBI6 33 PTD7/KBI7
44 CGMXFC
VDDA
VSSA
32 31 30 29 28 27 26 25 24 20 13 14 15 16 17 18 19 21
VREFH VREFL PTA0/ADC0 PTA1/ADC1 PTA2/ADC2 PTA3/ADC3 PTA4/ADC4 PTA5/ADC5 PTA6/ADC6
23 PTA7/ADC7
PTC5/SPSCK
PTC7/SCRxD
PTC6/SCTxD
PTC3/MOSI
PTC2/MISO
Figure 1-3. 44-Pin QFP Pin Assignments
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 23
PTC0/IRQ2 22
PTB1/SCL
PTB0/SDA
PTC4/SS
PTC1
General Description
PTD2/KBI2 PTD1/KBI1 PTD0/KBI0 PTB7/T2CH1 CGMXFC PTB6/T2CH0 VREG PTB5/T1CH1 VDD OSC1 OSC2 VSS PTB4/T1CH0 IRQ1 PTB3/RxD RST PTB2/TxD PTB1/SCL PTB0/SDA PTC7/SCRxD PTC6/SCTxD
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22
VDDA VSSA PTD3/KBI3 PTD4/KBI4 PTD5/KBI5 PTD6/KBI6 PTD7/KBI7 VREFH VREFL PTA0/ADC0 PTA1/ADC1 PTA2/ADC2 PTA3/ADC3 PTA4/ADC4 PTA5/ADC5 PTA6/ADC6 PTA7/ADC7 PTC2/MISO PTC3/MOSI PTC4/SS PTC5/SPSCK
Pins not available on 42-pin package PTC0/IRQ2 PTC1
Internal connection Unconnected Unconnected
Figure 1-4. 42-Pin SDIP Pin Assignment
MC68HC908AP A-Family Data Sheet, Rev. 2 24 Freescale Semiconductor
Pin Functions
1.5 Pin Functions
Description of the pin functions are provided in Table 1-2. Table 1-2. Pin Functions
PIN NAME VDD VSS VDDA VSSA VREFH VREFL VREG PIN DESCRIPTION IN/OUT In Out In Out In Out Out VOLTAGE LEVEL 4.5 to 5.5 0V VDD VSS VDDA VSSA 2.5V(1) VDD VDD VDD to VTST VREG VREG VREG VREG Analog VDD VREFH VDD
Power supply. Power supply ground. Power supply for analog circuits. Power supply ground for analog circuits. ADC input reference high. ADC input reference low. Internal (2.5V) regulator output. Require external capacitors for decoupling. Reset input, active low; with internal pullup and schmitt trigger input. External IRQ1 pin; with internal pullup and schmitt trigger input. Used for mode entry selection.
RST
In
In In In Out Out Out In/Out In/Out In Out
IRQ1
OSC1
Crystal or RC oscillator input. Crystal OSC option: crystal oscillator output; inverted OSC1.
OSC2
RC OSC option: bus clock output. Internal OSC option: bus clock output.
CGMXFC PTA0/ADC0 : PTA7/ADC7
CGM external filter capacitor connection. 8-bit general purpose I/O port. Pins as ADC inputs, ADC0-ADC7. Each pin has high current sink for LED.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 25
General Description
Table 1-2. Pin Functions
PIN NAME PIN DESCRIPTION 8-bit general purpose I/O port; PTB0-PTB3 are open drain when configured as output. PTB4-PTB7 have schmitt trigger inputs. PTB0 as SDA of MMIIC. PTB0/SDA PTB1/SCL PTB2/TxD PTB3/RxD PTB4/T1CH0 PTB5/T1CH1 PTB6/T2CH0 PTB7/T2CH1 PTB1 as SCL of MMIIC. PTB2 as TxD of SCI; open drain output. PTB3 as RxD of SCI. PTB4 as T1CH0 of TIM1. PTB5 as T1CH1 of TIM1. PTB6 as T2CH0 of TIM2. PTB7 as T2CH1 of TIM2. 8-bit general purpose I/O port; PTC6 and PTC7 are open drain when configured as output. PTC0 is shared with IRQ2 and has schmitt trigger input. PTC0/IRQ2 PTC1 PTC2/MISO PTC3/MOSI PTC4/SS PTC5/SPSCK PTC6/SCTxD PTC7/SCRxD PTC2 as MISO of SPI. PTC3 as MOSI of SPI. PTC4 as SS of SPI. PTC5 as SPSCK of SPI. PTC6 as SCTxD of IRSCI; open drain output. PTC7 as SCRxD of IRSCI. PTD0/KBI0 : PTD7/KBI7 8-bit general purpose I/O port with schmitt trigger inputs. Pins as keyboard interrupts (with pullup), KBI0-KBI7. IN/OUT In/Out In/Out In/Out Out In In/Out In/Out In/Out In/Out In/Out In In Out In In/Out Out In In/Out In VOLTAGE LEVEL VDD VDD VDD VDD VDD VDD VDD VDD VDD VDD VDD VDD VDD VDD VDD VDD VDD VDD VDD
1. See Chapter 22 Electrical Specifications for VREG tolerance.
1.6 Power Supply Bypassing (VDD, VDDA, VSS, VSSA)
VDD and VSS are the power supply and ground pins, the MCU operates from a single power supply together with an on chip voltage regulator. Fast signal transitions on MCU pins place high. short-duration current demands on the power supply. To prevent noise problems, take special care to provide power supply bypassing at the MCU as Figure 1-5 shows. Place the bypass capacitors as close to the MCU power pins as possible. Use high-frequency-response ceramic capacitor for CBYPASS, CBULK are optional bulk current bypass capacitors for use in applications that require the port pins to source high current level.
MC68HC908AP A-Family Data Sheet, Rev. 2 26 Freescale Semiconductor
Regulator Power Supply Configuration (VREG)
VDDA and VSSA are the power supply and ground pins for the analog circuits of the MCU. These pins should be decoupled as per the digital power supply pins.
MCU
VDD VSS VDDA VSSA
C1(a) 0.1 F + C2(a)
C1(b) 0.1 F + C2(b)
VDD
VDD
NOTE: Component values shown represent typical applications.
Figure 1-5. Power Supply Bypassing
1.7 Regulator Power Supply Configuration (VREG)
VREG is the output from the on-chip regulator. All internal logics, except for the I/O pads, are powered by VREG output. VREG requires an external ceramic bypass capacitor of 100 nF as Figure 1-6 shows. Place the bypass capacitor as close to the VREG pin as possible.
MCU
VREG VSS
CVREGBYPASS 100 nF
Figure 1-6. Regulator Power Supply Bypassing
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 27
General Description
MC68HC908AP A-Family Data Sheet, Rev. 2 28 Freescale Semiconductor
Chapter 2 Memory
2.1 Introduction
The CPU08 can address 64k-bytes of memory space. The memory map, shown in Figure 2-1, includes: * 62,368 bytes of user FLASH -- MC68HC908AP64A 32,768 bytes of user FLASH -- MC68HC908AP32A 16,384 bytes of user FLASH -- MC68HC908AP16A 8,192 bytes of user FLASH -- MC68HC908AP8A * 2,048 bytes of RAM -- MC68HC908AP64A and MC68HC908AP32A 1,024 bytes of RAM -- MC68HC908AP16A and MC68HC908AP8A * 48 bytes of user-defined vectors * 959 bytes of monitor ROM
2.2 Input/Output (I/O) Section
Most of the control, status, and data registers are in the zero page area of $0000-$005F. Additional I/O registers have these addresses: * $FE00; SIM break status register, SBSR * $FE01; SIM reset status register, SRSR * $FE02; Reserved * $FE03; SIM break flag control register, SBFCR * $FE04; interrupt status register 1, INT1 * $FE05; interrupt status register 2, INT2 * $FE06; interrupt status register 3, INT3 * $FE07; Reserved * $FE08; FLASH control register, FLCR * $FE09; FLASH block protect register, FLBPR * $FE0A; Reserved * $FE0B; Reserved * $FE0C; Break address register high, BRKH * $FE0D; Break address register low, BRKL * $FE0E; Break status and control register, BRKSCR * $FE0F; LVI Status register, LVISR * $FFCF; Mask option register, MOR (FLASH register) * $FFFF; COP control register, COPCTL
2.3 Monitor ROM
The 959 bytes at addresses $FC00-$FDFF and $FE10-$FFCE are reserved ROM addresses that contain the instructions for the monitor functions. (See Chapter 8 Monitor ROM (MON).)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 29
Memory
$0000
$005F $0060 $085F $0860
I/O Registers 96 Bytes RAM 2,048 Bytes (MC68HC908AP64A)
MC68HC908AP32A $0060 RAM 2,048 Bytes $085F $0860
MC68HC908AP16A RAM 1,024 Bytes Unimplemented 1,024 Bytes FLASH Memory 16,384 Bytes $0060 $045F $0860 $485F $4860
MC68HC908AP8A RAM 1,024 Bytes Unimplemented 1,024 Bytes FLASH Memory 8,192 Bytes $0060 $045F $0860 $285F $2860
FLASH Memory 32,768 Bytes
FLASH Memory 62,368 Bytes (MC68HC908AP64A)
$885F $8860 Unimplemented 45,984 Bytes Unimplemented 29,600 Bytes
Unimplemented 54,176 Bytes
$FBFF $FC00 $FDFF $FE00 $FE01 $FE02 $FE03 $FE04 $FE05 $FE06 $FE07 $FE08 $FE09 $FE0A $FE0B $FE0C $FE0D $FE0E $FE0F $FE10 $FFCE $FFCF $FFD0 $FFFF
$FBFF Monitor ROM 2 512 Bytes SIM Break Status Register SIM Reset Status Register Reserved SIM Break Flag Control Register Interrupt Status Register 1 Interrupt Status Register 2 Interrupt Status Register 3 Reserved FLASH Control Register FLASH Block Protect Register Reserved Reserved Break Address Register High Break Address Register Low Break Status and Control Register LVI Status Register Monitor ROM 1 447 Bytes Mask Option Register FLASH Vectors 48 Bytes
$FBFF
$FBFF
Figure 2-1. Memory Map
MC68HC908AP A-Family Data Sheet, Rev. 2 30 Freescale Semiconductor
Monitor ROM
Addr. $0000
Register Name Read: Port A Data Register Write: (PTA) Reset: Read: Port B Data Register Write: (PTB) Reset: Read: Port C Data Register (PTC) Write: Reset: Read:
Bit 7 PTA7
6 PTA6
5 PTA5
4 PTA4
3 PTA3
2 PTA2
1 PTA1
Bit 0 PTA0
Unaffected by reset PTB7 PTB6 PTB5 PTB4 PTB3 PTB2 PTB1 PTB0
$0001
Unaffected by reset PTC7 PTC6 PTC5 PTC4 PTC3 PTC2 PTC1 PTC0
$0002
Unaffected by reset PTD7 PTD6 PTD5 PTD4 PTD3 PTD2 PTD1 PTD0
$0003
Port D Data Register (PTD) Write: Reset: Read: Data Direction Register A Write: (DDRA) Reset: Read: Data Direction Register B Write: (DDRB) Reset: Read: Data Direction Register C Write: (DDRC) Reset: Read: Data Direction Register D Write: (DDRD) Reset: Read: Unimplemented Write: Reset: Read:
Unaffected by reset DDRA7 0 DDRB7 0 DDRC7 0 DDRD7 0 DDRA6 0 DDRB6 0 DDRC6 0 DDRD6 0 DDRA5 0 DDRB5 0 DDRC5 0 DDRD5 0 DDRA4 0 DDRB4 0 DDRC4 0 DDRD4 0 DDRA3 0 DDRB3 0 DDRC3 0 DDRD3 0 DDRA2 0 DDRB2 0 DDRC2 0 DDRD2 0 DDRA1 0 DDRB1 0 DDRC1 0 DDRD1 0 DDRA0 0 DDRB0 0 DDRC0 0 DDRD0 0
$0004
$0005
$0006
$0007
$0008
$0009
Unimplemented Write: Reset: Read:
$000A
Unimplemented Write: Reset: Read:
$000B
Unimplemented Write: Reset: Port-A LED Control Read: Register Write: (LEDA) Reset: U = Unaffected
$000C
LEDA7 0
LEDA6 0
LEDA5 0
LEDA4 0
LEDA3 0
LEDA2 0 R
LEDA1 0 = Reserved
LEDA0 0
X = Indeterminate
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 1 of 9)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 31
Memory Addr. $000D Register Name Read: Unimplemented Write: Reset: Read: $000E Unimplemented Write: Reset: Read: $000F Unimplemented Write: Reset: $0010 Read: SPI Control Register Write: (SPCR) Reset: SPI Status and Control Read: Register Write: (SPSCR) Reset: Read: SPI Data Register Write: (SPDR) Reset: Read: $0013 SCI Control Register 1 Write: (SCC1) Reset: Read: $0014 SCI Control Register 2 Write: (SCC2) Reset: Read: $0015 SCI Control Register 3 Write: (SCC3) Reset: Read: $0016 SCI Status Register 1 (SCS1) Write: Reset: Read: $0017 SCI Status Register 2 (SCS2) Write: Reset: $0018 Read: SCI Data Register Write: (SCDR) Reset: Read: SCI Baud Rate Register Write: (SCBR) Reset: U = Unaffected 0 R7 T7 0 0 X = Indeterminate 0 R6 T6 0 0 0 R5 T5 0 R4 T4 0 R3 T3 0 R2 T2 0 R1 T1 0 R0 T0 1 0 1 0 0 0 0 0 0 0 0 0 0 BKF 0 RPF SPRIE 0 SPRF 0 R7 T7 R 0 ERRIE 0 R6 T6 SPMSTR 1 OVRF 0 R5 T5 CPOL 0 MODF 0 R4 T4 CPHA 1 SPTE 1 R3 T3 SPWOM 0 MODFEN 0 R2 T2 SPE 0 SPR1 0 R1 T1 SPTIE 0 SPR0 0 R0 T0 Bit 7 6 5 4 3 2 1 Bit 0
$0011
$0012
Unaffected by reset LOOPS 0 SCTIE 0 R8 U SCTE ENSCI 0 TCIE 0 T8 U TC TXINV 0 SCRIE 0 DMARE 0 SCRF M 0 ILIE 0 DMATE 0 IDLE WAKE 0 TE 0 ORIE 0 OR ILTY 0 RE 0 NEIE 0 NF PEN 0 RWU 0 FEIE 0 FE PTY 0 SBK 0 PEIE 0 PE
Unaffected by reset SCP1 0 SCP0 0 = Unimplemented R 0 SCR2 0 R SCR1 0 = Reserved SCR0 0
$0019
Figure 2-2. Control, Status, and Data Registers (Sheet 2 of 9)
MC68HC908AP A-Family Data Sheet, Rev. 2 32 Freescale Semiconductor
Monitor ROM Addr. $001A Register Name Keyboard Status and Control Read: Register Write: (KBSCR) Reset: Keyboard Interrupt Read: Enable Register Write: (KBIER) Reset: Bit 7 0 0 KBIE7 0 0 0 STOP_ ICLKDIS 0 0 0 COPRS 0 TOF 0 0 Bit 15 0 Bit 7 0 Bit 15 1 Bit 7 1 CH0F 0 0 X = Indeterminate 6 0 0 KBIE6 0 PUC0ENB 0 STOP_ RCLKEN 0 0 0 LVISTOP 0 5 0 0 KBIE5 0 0 0 STOP_ XCLKEN 0 0 0 LVIRSTD 0 4 0 0 KBIE4 0 0 0 3 KEYF 0 KBIE3 0 IRQ2F 0 2 0 ACK 0 KBIE2 0 0 ACK2 0 0 0 0 ACK1 0 LVIPWRD 0 0 TRST 0 12 0 4 0 12 1 4 1 MS0A 0 = Unimplemented 0 11 0 3 0 11 1 3 1 ELS0B 0 0 LVIREGD 0 0 0 SSREC 0 1 IMASK 0 KBIE1 0 IMASK2 0 0 0 Bit 0 MODE 0 KBIE0 0 MODE2 0 SCIBDSRC 0
$001B
IRQ2 Status and Control Reg- Read: $001C ister Write: (INTSCR2) Reset: $001D Read: Configuration Register 2 Write: (CONFIG2) Reset:
OSCCLK1 OSCCLK0 0 0 0 IRQ1F
One-time writable register after each reset. IRQ1 Status and Control Reg- Read: $001E ister Write: (INTSCR1) Reset: $001F Configuration Register 1 Write: (CONFIG1) Reset: Timer 1 Status and Read: Control Register Write: (T1SC) Reset: Timer 1 Counter Read: Register High Write: (T1CNTH) Reset: Timer 1 Counter Read: Register Low Write: (T1CNTL) Reset: Read: IMASK1 0 STOP 0 MODE1 0 COPD 0
One-time writable register after each reset. $0020 TOIE 0 14 0 6 0 14 1 6 1 CH0IE 0 TSTOP 1 13 0 5 0 13 1 5 1 MS0B 0 PS2 0 10 0 2 0 10 1 2 1 ELS0A 0 R PS1 0 9 0 1 0 9 1 1 1 TOV0 0 = Reserved PS0 0 Bit 8 0 Bit 0 0 Bit 8 1 Bit 0 1 CH0MAX 0
$0021
$0022
Timer 1 Counter Modulo Reg- Read: $0023 ister High Write: (T1MODH) Reset: $0024 Timer 1 Counter Modulo Read: Register Low Write: (T1MODL) Reset:
Read: Timer 1 Channel 0 Status and $0025 Write: Control Register (T1SC0) Reset: U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 3 of 9)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 33
Memory Addr. $0026 Register Name Timer 1 Channel 0 Read: Register High Write: (T1CH0H) Reset: Timer 1 Channel 0 Read: Register Low Write: (T1CH0L) Reset: Bit 7 Bit 15 6 14 5 13 4 12 3 11 2 10 1 9 Bit 0 Bit 8
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
$0027
Indeterminate after reset CH1F 0 0 Bit 15 CH1IE 0 14 0 0 13 MS1A 0 12 ELS1B 0 11 ELS1A 0 10 TOV1 0 9 CH1MAX 0 Bit 8
Read: Timer 1 Channel 1 Status and $0028 Write: Control Register (T1SC1) Reset: $0029 Timer 1 Channel 1 Read: Register High Write: (T1CH1H) Reset: Timer 1 Channel 1 Read: Register Low Write: (T1CH1L) Reset: Timer 2 Status and Read: Control Register Write: (T2SC) Reset: Timer 2 Counter Read: Register High Write: (T2CNTH) Reset: Timer 2 Counter Read: Register Low Write: (T2CNTL) Reset:
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
$002A
Indeterminate after reset TOF 0 0 Bit 15 0 Bit 7 0 Bit 15 1 Bit 7 1 CH0F 0 0 Bit 15 TOIE 0 14 0 6 0 14 1 6 1 CH0IE 0 14 TSTOP 1 13 0 5 0 13 1 5 1 MS0B 0 13 0 TRST 0 12 0 4 0 12 1 4 1 MS0A 0 12 0 11 0 3 0 11 1 3 1 ELS0B 0 11 0 PS2 0 10 0 2 0 10 1 2 1 ELS0A 0 10 PS1 0 9 0 1 0 9 1 1 1 TOV0 0 9 PS0 0 Bit 8 0 Bit 0 0 Bit 8 1 Bit 0 1 CH0MAX 0 Bit 8
$002B
$002C
$002D
Timer 2 Counter Modulo Reg- Read: $002E ister High Write: (T2MODH) Reset: $002F Timer 2 Counter Modulo Read: Register Low Write: (T2MODL) Reset:
Read: Timer 2 Channel 0 Status and $0030 Write: Control Register (T2SC0) Reset: $0031 Timer 2 Channel 0 Read: Register High Write: (T2CH0H) Reset: Timer 2 Channel 0 Read: Register Low Write: (T2CH0L) Reset: U = Unaffected
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
$0032
Indeterminate after reset X = Indeterminate = Unimplemented R = Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 4 of 9)
MC68HC908AP A-Family Data Sheet, Rev. 2 34 Freescale Semiconductor
Monitor ROM Addr. $0033 Register Name Read: Timer 2 Channel 1 Status and Write: Control Register (T2SC1) Reset: Timer 2 Channel 1 Read: Register High Write: (T2CH1H) Reset: Timer 2 Channel 1 Read: Register Low Write: (T2CH1L) Reset: Read: $0036 PLL Control Register (PCTL) Write: Reset: $0037 PLL Bandwidth Control Reg- Read: ister Write: (PBWC) Reset: PLL Multiplier Select Read: Register High Write: (PMSH) Reset: PLL Multiplier Select Read: Register Low Write: (PMSL) Reset: PLL VCO Range Select Read: Register Write: (PMRS) Reset: PLL Reference Divider Read: Select Register Write: (PMDS) Reset: Read: $003C Unimplemented Write: Reset: Read: $003D Unimplemented Write: Reset: Read: $003E Unimplemented Write: Reset: Read: $003F Unimplemented Write: Reset: U = Unaffected X = Indeterminate = Unimplemented R = Reserved Bit 7 CH1F 0 0 Bit 15 6 CH1IE 0 14 5 0 0 13 4 MS1A 0 12 3 ELS1B 0 11 2 ELS1A 0 10 1 TOV1 0 9 Bit 0 CH1MAX 0 Bit 8
$0034
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
$0035
Indeterminate after reset PLLIE 0 AUTO 0 0 0 MUL7 0 VRS7 0 0 0 PLLF 0 LOCK 0 0 0 MUL6 1 VRS6 1 0 0 PLLON 1 ACQ 0 0 0 MUL5 0 VRS5 0 0 0 BCS 0 0 0 0 0 MUL4 0 VRS4 0 0 0 PRE1 0 0 0 MUL11 0 MUL3 0 VRS3 0 RDS3 0 PRE0 0 0 0 MUL10 0 MUL2 0 VRS2 0 RDS2 0 VPR1 0 0 0 MUL9 0 MUL1 0 VRS1 0 RDS1 0 VPR0 0 R 0 MUL8 0 MUL0 0 VRS0 0 RDS0 1
$0038
$0039
$003A
$003B
Figure 2-2. Control, Status, and Data Registers (Sheet 5 of 9)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 35
Memory Addr. $0040 Register Name Read: IRSCI Control Register 1 Write: (IRSCC1) Reset: Read: IRSCI Control Register 2 Write: (IRSCC2) Reset: Read: IRSCI Control Register 3 Write: (IRSCC3) Reset: Read: IRSCI Status Register 1 Write: (IRSCS1) Reset: Read: IRSCI Status Register 2 Write: (IRSCS2) Reset: Read: IRSCI Data Register Write: (IRSCDR) Reset: Read: $0046 IRSCI Baud Rate Register Write: (IRSCBR) Reset: IRSCI Infrared Control Read: Register Write: (IRSCIRCR) Reset: MMIIC Address Register Read: (MMADR) Write: Reset: $0049 Read: MMIIC Control Register 1 Write: (MMCR1) Reset: MMIIC Control Register 2 Read: (MMCR2) Write: Reset: $004B MMIIC Status Register Read: (MMSR) Write: Reset: $004C MMIIC Data Transmit Read: Register Write: (MMDTR) Reset: U = Unaffected Bit 7 LOOPS 0 SCTIE 0 R8 U SCTE 1 6 ENSCI 0 TCIE 0 T8 U TC 1 5 0 0 SCRIE 0 DMARE 0 SCRF 0 4 M 0 ILIE 0 DMATE 0 IDLE 0 3 WAKE 0 TE 0 ORIE 0 OR 0 2 ILTY 0 RE 0 NEIE 0 NF 0 1 PEN 0 RWU 0 FEIE 0 FE 0 BKF 0 R7 T7 0 R6 T6 0 0 0 0 MMAD6 0 MMIEN 0 MMNAKIF 0 0 MMTXIF 0 0 MMTD6 0 0 MMTD5 0 0 MMTD4 0 = Unimplemented 1 MMTD3 0 0 MMTD2 0 R 1 MMTD1 0 = Reserved 0 MMTD0 0 0 MMATCH 0 R5 T5 0 R4 T4 0 R3 T3 0 R2 T2 0 R1 T1 Bit 0 PTY 0 SBK 0 PEIE 0 PE 0 RPF 0 R0 T0
$0041
$0042
$0043
$0044
$0045
Unaffected by reset CKS 0 R 0 MMAD7 1 MMEN 0 MMALIF 0 0 MMRXIF 0 0 MMTD7 0 X = Indeterminate SCP1 0 0 0 MMAD5 1 0 MMCLRBB 0 MMBB 0 MMAST 0 MMSRW SCP0 0 0 0 MMAD4 0 0 R 0 R 0 MMAD3 0 MMTXAK 0 MMRW 0 SCR2 0 TNP1 0 MMAD2 0 REPSEN 0 0 0 SCR1 0 TNP0 0 MMAD1 0 MMCRCBY TE 0 0 0 MMTXBE SCR0 0 IREN 0 MMEXTAD 0 0 0 MMCRCEF Unaffected MMRXBF
$0047
$0048
$004A
MMRXAK MMCRCBF
Figure 2-2. Control, Status, and Data Registers (Sheet 6 of 9)
MC68HC908AP A-Family Data Sheet, Rev. 2 36 Freescale Semiconductor
Monitor ROM Addr. $004D Register Name MMIIC Data Receive Read: Register Write: (MMDRR) Reset: Bit 7 MMRD7 0 6 MMRD6 0 5 MMRD5 0 4 MMRD4 0 3 MMRD3 0 2 MMRD2 0 1 MMRD1 0 Bit 0 MMRD0 0
$004E
MMIIC CRC Data Register Read: MMCRCD7 MMCRCD6 MMCRCD5 MMCRCD4 MMCRCD3 MMCRCD2 MMCRCD1 MMCRCD0 (MMCRDR) Write: Reset: 0 0 0 R 0 0 0 R 0 0 0 R 0 0 0 R 0 0 0 R 0 MMBR2 1 R 0 MMBR1 0 R 0 MMBR0 0 R MMIIC Frequency Divider Read: Register Write: (MMFDR) Reset: Read: Reserved Write: Reset: Timebase Control Register Read: (TBCR) Write: Reset: Read:
$004F
$0050
TBIF 0
$0051
TBR2 0
TBR1 0
TBR0 0
0 TACK 0
TBIE 0
TBON 0
R 0
$0052
Unimplemented Write: Reset: Read:
$0053
Unimplemented Write: Reset: Read:
$0054
Unimplemented Write: Reset: Read:
$0055
Unimplemented Write: Reset: Read:
$0056
Unimplemented Write: Reset: ADC Status and Control Read: Register Write: (ADSCR) Reset: Read: ADC Clock Control Register Write: (ADICLK) Reset: Read: ADC Data Register High 0 Write: (ADRH0) Reset: U = Unaffected COCO 0 ADIV2 0 ADx R 0 X = Indeterminate
$0057
AIEN 0 ADIV1 0 ADx R 0
ADCO 0 ADIV0 0 ADx R 0
ADCH4 1 ADICLK 0 ADx R 0
ADCH3 1 MODE1 0 ADx R 0
ADCH2 1 MODE0 0 ADx R 0 R
ADCH1 1 0 0 ADx R 0 = Reserved
ADCH0 1 0 R 0 ADx R 0
$0058
$0059
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 7 of 9)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 37
Memory Addr. $005A Register Name ADC Data Register Low 0 Read: (ADRL0) Write: Reset: $005B ADC Data Register Low 1 Read: (ADRL1) Write: Reset: $005C ADC Data Register Low 2 Read: (ADRL2) Write: Reset: $005D ADC Data Register Low 3 Read: (ADRL3) Write: Reset: $005E ADC Auto-scan Control Read: Register Write: (ADASCR) Reset: Read: $005F Unimplemented Write: Reset: Read: SIM Break Status Register Write: (SBSR) Reset: Read: SIM Reset Status Register Write: (SRSR) Reset: Read: $FE02 Reserved Write: Reset: $FE03 SIM Break Flag Control Reg- Read: ister Write: (SBFCR) Reset: Read: $FE04 Interrupt Status Register 1 Write: (INT1) Reset: Read: Interrupt Status Register 2 Write: (INT2) Reset: U = Unaffected BCFE 0 IF6 R 0 IF14 R 0 X = Indeterminate IF5 R 0 IF13 R 0 IF4 R 0 IF12 R 0 IF3 R 0 IF11 R 0 = Unimplemented IF2 R 0 IF10 R 0 IF1 R 0 IF9 R 0 R 0 R 0 IF8 R 0 = Reserved 0 R 0 IF7 R 0 R R R R R R R SBSW Note 0 POR 1 R PIN 0 R COP 0 R ILOP 0 R ILAD 0 R MODRST 0 R LVI 0 R 0 0 R Bit 7 ADx R 0 AD9 R 0 AD9 R 0 AD9 R 0 6 ADx R 0 AD8 R 0 AD8 R 0 AD8 R 0 5 ADx R 0 AD7 R 0 AD7 R 0 AD7 R 0 4 ADx R 0 AD6 R 0 AD6 R 0 AD6 R 0 3 ADx R 0 AD5 R 0 AD5 R 0 AD5 R 0 2 ADx R 0 AD4 R 0 AD4 R 0 AD4 R 0 AUTO1 0 0 0 0 0 0 1 ADx R 0 AD3 R 0 AD3 R 0 AD3 R 0 AUTO0 0 Bit 0 ADx R 0 AD2 R 0 AD2 R 0 AD2 R 0 ASCAN 0
$FE00
R
R
R
R
R
R
R
Note: Writing a logic 0 clears SBSW. $FE01
$FE05
Figure 2-2. Control, Status, and Data Registers (Sheet 8 of 9)
MC68HC908AP A-Family Data Sheet, Rev. 2 38 Freescale Semiconductor
Monitor ROM Addr. $FE06 Register Name Read: Interrupt Status Register 3 Write: (INT3) Reset: Read: $FE07 Reserved Write: Reset: $FE08 Read: FLASH Control Register Write: (FLCR) Reset: FLASH Block Protect Read: Register Write: (FLBPR) Reset: Read: $FE0A Reserved Write: Reset: Read: $FE0B Reserved Write: Reset: $FE0C Break Address Read: Register High Write: (BRKH) Reset: Break Address Read: Register Low Write: (BRKL) Reset: Break Status and Control Reset: Register Read: (BRKSCR) Write: Reset: $FE0F LVI Status Register (LVISR) Read: Write: 0 0 0 0 0 0 0 0 Bit 15 0 Bit 7 0 BRKE 0 LVIOUT 14 0 6 0 BRKA 0 0 13 0 5 0 0 0 0 12 0 4 0 0 0 0 11 0 3 0 0 0 0 10 0 2 0 0 0 0 9 0 1 0 0 0 0 Bit 8 0 Bit 0 0 0 0 0 R R R R R R R R 0 0 BPR7 0 R 0 0 BPR6 0 R 0 0 BPR5 0 R 0 0 BPR4 0 R HVEN 0 BPR3 0 R MASS 0 BPR2 0 R ERASE 0 BPR1 0 R PGM 0 BPR0 0 R Bit 7 0 R 0 R 6 IF21 R 0 R 5 IF20 R 0 R 4 IF19 R 0 R 3 IF18 R 0 R 2 IF17 R 0 R 1 IF16 R 0 R Bit 0 IF15 R 0 R
$FE09
$FE0D
$FE0E
$FFCF
Read: OSCSEL1 Mask Option Register # Write: (MOR) Erased: 1 Reset: Read: COP Control Register Write: (COPCTL) Reset: U = Unaffected U
OSCSEL0 1 U
R 1 U
R 1 U
R 1 U
R 1 U
R 1 U
R 1 U
Low byte of reset vector Writing clears COP counter (any value) Unaffected by reset X = Indeterminate = Unimplemented R = Reserved
$FFFF
# MOR is a non-volatile FLASH register; write by programming.
Figure 2-2. Control, Status, and Data Registers (Sheet 9 of 9)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 39
Memory
Table 2-1. Vector Addresses
Priority Lowest -- $FFD1 $FFD2 IF21 $FFD3 $FFD4 IF20 $FFD5 $FFD6 IF19 $FFD7 $FFD8 IF18 $FFD9 $FFDA IF17 $FFDB $FFDC IF16 $FFDD $FFDE IF15 $FFDF $FFE0 IF14 $FFE1 $FFE2 IF13 $FFE3 $FFE4 IF12 $FFE5 $FFE6 IF11 $FFE7 $FFE8 IF10 $FFE9 $FFEA IF9 $FFEB TIM2 Overflow Vector (Low) MMIIC Interrupt Vector (Low) TIM2 Overflow Vector (High) SCI Error Vector (Low) MMIIC Interrupt Vector (High) SCI Receive Vector (Low) SCI Error Vector (High) SCI Transmit Vector (Low) SCI Receive Vector (High) Keyboard Vector (Low) SCI Transmit Vector (High) ADC Conversion Complete Vector (Low) Keyboard Vector (High) SPI Receive Vector (Low) ADC Conversion Complete Vector (High) SPI Transmit Vector (Low) SPI Receive Vector (High) SCI2 (IRSCI) Error Vector (Low) SPI Transmit Vector (High) SCI2 (IRSCI) Receive Vector (Low) SCI2 (IRSCI) Error Vector (High) SCI2 (IRSCI) Transmit Vector (Low) SCI2 (IRSCI) Receive Vector (High) TBM Vector (Low) SCI2 (IRSCI) Transmit Vector (High) Reserved TBM Vector (High) INT Flag Address $FFD0 Reserved Vector
MC68HC908AP A-Family Data Sheet, Rev. 2 40 Freescale Semiconductor
Random-Access Memory (RAM)
Table 2-1. Vector Addresses (Continued)
Priority INT Flag IF8 $FFED $FFEE IF7 $FFEF $FFF0 IF6 $FFF1 $FFF2 IF5 $FFF3 $FFF4 IF4 $FFF5 $FFF6 IF3 $FFF7 $FFF8 IF2 $FFF9 $FFFA IF1 $FFFB $FFFC -- $FFFD $FFFE -- Highest $FFFF Reset Vector (Low) SWI Vector (Low) Reset Vector (High) IRQ1 Vector (Low) SWI Vector (High) IRQ2 Vector (Low) IRQ1 Vector (High) PLL Vector (Low) IRQ2 Vector (High) TIM1 Channel 0 Vector (Low) PLL Vector (High) TIM1 Channel 1 Vector (Low) TIM1 Channel 0 Vector (High) TIM1 Overflow Vector (Low) TIM1 Channel 1 Vector (High) TIM2 Channel 0 Vector (Low) TIM1 Overflow Vector (High) TIM2 Channel 1 Vector (Low) TIM2 Channel 0 Vector (High) Address $FFEC Vector TIM2 Channel 1 Vector (High)
2.4 Random-Access Memory (RAM)
Addresses $0060 through $085F (or $045F) are RAM locations. The location of the stack RAM is programmable. The 16-bit stack pointer allows the stack to be anywhere in the 64k-byte memory space. NOTE For correct operation, the stack pointer must point only to RAM locations. Within page zero are 160 bytes of RAM. Because the location of the stack RAM is programmable, all page zero RAM locations can be used for I/O control and user data or code. When the stack pointer is moved from its reset location at $00FF, direct addressing mode instructions can access efficiently all page zero RAM locations. Page zero RAM, therefore, provides ideal locations for frequently accessed global variables.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 41
Memory
Before processing an interrupt, the CPU uses five bytes of the stack to save the contents of the CPU registers. NOTE For M6805 compatibility, the H register is not stacked. During a subroutine call, the CPU uses two bytes of the stack to store the return address. The stack pointer decrements during pushes and increments during pulls. NOTE Be careful when using nested subroutines. The CPU may overwrite data in the RAM during a subroutine or during the interrupt stacking operation.
2.5 FLASH Memory
This sub-section describes the operation of the embedded FLASH memory. This memory can be read, programmed, and erased from a single external supply. The program and erase operations are enabled through the use of an internal charge pump.
Device MC68HC908AP64A MC68HC908AP32A MC68HC908AP16A MC68HC908AP8A FLASH Memory Size (Bytes) 62,368 32,768 16,384 8,192 Memory Address Range $0860-$FBFF $0860-$885F $0860-$485F $0860-$285F
2.5.1 Functional Description
The FLASH memory consists of an array of 62,368 bytes for user memory plus a block of 48 bytes for user interrupt vectors and one byte for the mask option register. An erased bit reads as logic 1 and a programmed bit reads as a logic 0. The FLASH memory page size is defined as 512 bytes, and is the minimum size that can be erased in a page erase operation. Program and erase operations are facilitated through control bits in FLASH control register (FLCR). The address ranges for the FLASH memory are: * $0860-$FBFF; user memory, 62,368 bytes * $FFD0-$FFFF; user interrupt vectors, 48 bytes * $FFCF; mask option register Programming tools are available from Freescale. Contact your local Freescale representative for more information. NOTE A security feature prevents viewing of the FLASH contents.(1)
1. No security feature is absolutely secure. However, Freescale's strategy is to make reading or copying the FLASH difficult for unauthorized users. MC68HC908AP A-Family Data Sheet, Rev. 2 42 Freescale Semiconductor
FLASH Memory
2.5.2 FLASH Control Register
The FLASH control register (FLCR) controls FLASH program and erase operation.
Address: Read: Write: Reset: 0 0 0 0 $FE08 Bit 7 0 6 0 5 0 4 0 3 HVEN 0 2 MASS 0 1 ERASE 0 Bit 0 PGM 0
Figure 2-3. FLASH Control Register (FLCR) HVEN -- High Voltage Enable Bit This read/write bit enables the charge pump to drive high voltages for program and erase operations in the array. HVEN can only be set if either PGM = 1 or ERASE = 1 and the proper sequence for program or erase is followed. 1 = High voltage enabled to array and charge pump on 0 = High voltage disabled to array and charge pump off MASS -- Mass Erase Control Bit This read/write bit configures the memory for mass erase operation or page erase operation when the ERASE bit is set. 1 = Mass erase operation selected 0 = Page erase operation selected ERASE -- Erase Control Bit This read/write bit configures the memory for erase operation. ERASE is interlocked with the PGM bit such that both bits cannot be equal to 1 or set to 1 at the same time. 1 = Erase operation selected 0 = Erase operation not selected PGM -- Program Control Bit This read/write bit configures the memory for program operation. PGM is interlocked with the ERASE bit such that both bits cannot be equal to 1 or set to 1 at the same time. 1 = Program operation selected 0 = Program operation not selected
2.5.3 FLASH Page Erase Operation
Use the following procedure to erase a page of FLASH memory. A page consists of 512 consecutive bytes starting from addresses $X000, $X200, $X400, $X600, $X800, $XA00, $XC00, or $XE00. The 48-byte user interrupt vectors cannot be erased by the page erase operation because of security reasons. Mass erase is required to erase this page. 1. Set the ERASE bit and clear the MASS bit in the FLASH control register. 2. Write any data to any FLASH location within the page address range desired. 3. Wait for a time, tnvs (5 s). 4. Set the HVEN bit. 5. Wait for a time terase (20 ms). 6. Clear the ERASE bit. 7. Wait for a time, tnvh (5 s).
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 43
Memory
8. Clear the HVEN bit. 9. After time, trcv (1 s), the memory can be accessed in read mode again. NOTE Programming and erasing of FLASH locations cannot be performed by code being executed from the FLASH memory. While these operations must be performed in the order as shown, but other unrelated operations may occur between the steps.
2.5.4 FLASH Mass Erase Operation
Use the following procedure to erase the entire FLASH memory: 1. Set both the ERASE bit and the MASS bit in the FLASH control register. 2. Write any data to any FLASH location within the FLASH memory address range. 3. Wait for a time, tnvs (5 s). 4. Set the HVEN bit. 5. Wait for a time tme (200 ms). (See NOTE below.) 6. Clear the ERASE bit. 7. Wait for a time, tnvh1 (100 s). 8. Clear the HVEN bit. 9. After time, trcv (1 s), the memory can be accessed in read mode again. NOTE Due to the relatively long mass erase time, user should take care in the code to prevent a COP reset from happening while the HVEN bit is set. Programming and erasing of FLASH locations cannot be performed by code being executed from the FLASH memory. While these operations must be performed in the order as shown, but other unrelated operations may occur between the steps.
2.5.5 FLASH Program Operation
Programming of the FLASH memory is done on a row basis. A row consists of 64 consecutive bytes starting from addresses $XX00, $XX40, $XX80 or $XXC0. Use the following procedure to program a row of FLASH memory. (Figure 2-4 shows a flowchart of the programming algorithm.) 1. Set the PGM bit. This configures the memory for program operation and enables the latching of address and data for programming. 2. Write any data to any FLASH location within the address range of the row to be programmed. 3. Wait for a time, tnvs (5 s). 4. Set the HVEN bit. 5. Wait for a time, tpgs (10 s). 6. Write data to the FLASH location to be programmed. 7. Wait for time, tprog (20 s to 40 s). 8. Repeat steps 6 and 7 until all bytes within the row are programmed. 9. Clear the PGM bit. 10. Wait for time, tnvh (5 s). 11. Clear the HVEN bit.
MC68HC908AP A-Family Data Sheet, Rev. 2 44 Freescale Semiconductor
FLASH Memory
12. After time, trcv (1 s), the memory can be accessed in read mode again. This program sequence is repeated throughout the memory until all data is programmed. NOTE The time between each FLASH address change (step 6 to step 6), or the time between the last FLASH addressed programmed to clearing the PGM bit (step 6 to step 9), must not exceed the maximum programming time, tprog max. NOTE Programming and erasing of FLASH locations cannot be performed by code being executed from the FLASH memory. While these operations must be performed in the order shown, other unrelated operations may occur between the steps.
2.5.6 FLASH Protection
Due to the ability of the on-board charge pump to erase and program the FLASH memory in the target application, provision is made to protect pages of memory from unintentional erase or program operations due to system malfunction. This protection is done by use of a FLASH block protect register (FLBPR). The FLBPR determines the range of the FLASH memory which is to be protected. The range of the protected area starts from a location defined by FLBPR and ends to the bottom of the FLASH memory ($FFFF). When the memory is protected, the HVEN bit cannot be set in either erase or program operations. NOTE The mask option register ($FFCF) and the 48 bytes of user interrupt vectors ($FFD0-$FFFF) are always protected, regardless of the value in the FLASH block protect register. A mass erase is required to erase these locations.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 45
Memory
1
Set PGM bit
Algorithm for programming a row (64 bytes) of FLASH memory
2
Write any data to any FLASH address within the row address range desired
3
Wait for a time, tnvs
4
Set HVEN bit
5
Wait for a time, tpgs
6
Write data to the FLASH address to be programmed
7
Wait for a time, tprog
Completed programming this row? N
9
Y
NOTE: The time between each FLASH address change (step 6 to step 6), or the time between the last FLASH address programmed to clearing PGM bit (step 6 to step 9) must not exceed the maximum programming time, tPROG max. This row program algorithm assumes the row/s to be programmed are initially erased.
Clear PGM bit
10
Wait for a time, tnvh
11
Clear HVEN bit
12
Wait for a time, trcv
End of Programming
Figure 2-4. FLASH Programming Flowchart
MC68HC908AP A-Family Data Sheet, Rev. 2 46 Freescale Semiconductor
FLASH Memory
2.5.7 FLASH Block Protect Register
The FLASH block protect register is implemented as an 8-bit I/O register. The value in this register determines the starting address of the protected range within the FLASH memory.
Address: Read: Write: Reset: $FE09 Bit 7 BPR7 0 6 BPR6 0 5 BPR5 0 4 BPR4 0 3 BPR3 0 2 BPR2 0 1 BPR1 0 Bit 0 BPR0 0
Figure 2-5. FLASH Block Protect Register (FLBPR) BPR[7:0] -- FLASH Block Protect Bits BPR[7:1] represent bits [15:9] of a 16-bit memory address. Bits [8:0] are logic 0's.
16-bit memory address Start address of FLASH block protect BPR[7:1] 000000000
BPR0 is used only for BPR[7:0] = $FF, for no block protection. The resultant 16-bit address is used for specifying the start address of the FLASH memory for block protection. The FLASH is protected from this start address to the end of FLASH memory, at $FFFF. With this mechanism, the protect start address can be X000, X200, X400, X0600, X800, XA00, XC00, or XE00 (at page boundaries -- 512 bytes) within the FLASH memory. Examples of protect start address: Table 2-2 FLASH Block Protect Range
BPR[7:0] $00 to $09 $0A or $0B (0000 101x) $0C or $0D (0000 110x) and so on... $FA or $FB (1111 1101x) $FC or $FD or $FE $FF $FA00 to $FFFF $FFCF to $FFFF The entire FLASH memory is NOT protected.(1) Protected Range The entire FLASH memory is protected. $0A00 to $FFFF $0C00 to $FFFF
1. Except for the mask option register ($FFCF) and the 48-byte user vectors ($FFD0-$FFFF). These FLASH locations are always protected.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 47
Memory
MC68HC908AP A-Family Data Sheet, Rev. 2 48 Freescale Semiconductor
Chapter 3 Configuration & Mask Option Registers (CONFIG & MOR)
3.1 Introduction
This section describes the configuration registers, CONFIG1 and CONFIG2; and the mask option register, MOR. The configuration registers enable or disable these options: * Computer operating properly module (COP) * COP timeout period (218 - 24 or 213 - 24 ICLK cycles) * Low-voltage inhibit (LVI) on VDD * LVI on VREG * LVI module reset * LVI module in stop mode * STOP instruction * Stop mode recovery time (32 ICLK or 4096 ICLK cycles) * Oscillator (internal, RC, and crystal) during stop mode * Serial communications interface clock source (CGMXCLK or fBUS) The mask option register selects one of the following oscillator options: * Internal oscillator * RC oscillator * Crystal oscillator
Register Name Bit 7 6 5 Configuration Register 2 Read: STOP_ STOP_ STOP_ RCLKEN XCLKEN $001D (CONFIG2) Write: ICLKDIS Reset: 0 0 0 Read: Configuration Register 1 COPRS LVISTOP LVIRSTD $001F Write: (CONFIG1) Reset: 0 0 0 Mask-Option-Register Read: OSCSEL1 OSCSEL0 R $FFCF (MOR)# Write: Erased: 1 1 1 One-time writable register after each reset. # MOR is a non-volatile FLASH register; write by programming. = Unimplemented Addr. 4 3 2 0 0 SSREC 0 R 1 1 0 0 STOP 0 R 1 Bit 0 SCIBDSRC 0 COPD 0 R 1
OSCCLK1 OSCCLK0 0 LVIPWRD 0 R 1 0 LVIREGD 0 R 1
R
= Reserved
Figure 3-1. CONFIG and MOR Registers Summary
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 49
Configuration & Mask Option Registers (CONFIG & MOR)
3.2 Functional Description
The configuration registers and the mask option register are used in the initialization of various options. These two types of registers are configured differently: * Configuration registers -- Write-once registers after reset * Mask option register -- FLASH register (write by programming) The configuration registers can be written once after each reset. All of the configuration register bits are cleared during reset. Since the various options affect the operation of the MCU, it is recommended that these registers be written immediately after reset. The configuration registers are located at $001D and $001F. The configuration registers may be read at anytime. NOTE The CONFIG registers are not in the FLASH memory but are special registers containing one-time writable latches after each reset. Upon a reset, the CONFIG registers default to predetermined settings as shown in Figure 3-2 and Figure 3-3. The mask option register (MOR) is used for selecting one of the three clock options for the MCU. The MOR is a byte located in FLASH memory, and is written to by a FLASH programming routine.
3.3 Configuration Register 1 (CONFIG1)
Address: Read: Write: Reset: $001F Bit 7 COPRS 0 6 LVISTOP 0 5 LVIRSTD 0 4 LVIPWRD 0 3 LVIREGD 0 2 SSREC 0 1 STOP 0 Bit 0 COPD 0
Figure 3-2. Configuration Register 1 (CONFIG1) COPRS -- COP Rate Select Bit COPRS selects the COP time out period. Reset clears COPRS. (See Chapter 19 Computer Operating Properly (COP).) 1 = COP time out period = 213 - 24 ICLK cycles 0 = COP time out period = 218 - 24 ICLK cycles LVISTOP -- LVI Enable in Stop Mode Bit When the LVIPWRD or LVIREGD bit is clear, setting the LVISTOP bit enables the LVI to operate during stop mode. Reset clears LVISTOP. (See Chapter 20 Low-Voltage Inhibit (LVI).) 1 = LVI enabled during stop mode 0 = LVI disabled during stop mode NOTE If LVISTOP=0, set LVIRSTD=1 before entering stop mode. LVIRSTD -- LVI Reset Disable Bit LVIRSTD disables the reset signal from the LVI module. (See Chapter 20 Low-Voltage Inhibit (LVI).) 1 = LVI module resets disabled 0 = LVI module resets enabled
MC68HC908AP A-Family Data Sheet, Rev. 2 50 Freescale Semiconductor
Configuration Register 1 (CONFIG1)
LVIPWRD -- VDD LVI Circuit Disable Bit LVIPWRD disables the VDD LVI circuit. (See Chapter 20 Low-Voltage Inhibit (LVI).) 1 = VDD LVI circuit disabled 0 = VDD LVI circuit enabled LVIREGD -- VREG LVI Circuit Disable Bit LVIREGD disables the VREG LVI circuit. (See Chapter 20 Low-Voltage Inhibit (LVI).) 1 = VREG LVI circuit disabled 0 = VREG LVI circuit enabled NOTE If LVIPWRD=1 and LVIREGD=1, set LVIRSTD=1 before entering stop mode. SSREC -- Short Stop Recovery Bit SSREC enables the CPU to exit stop mode with a delay of 32 ICLK cycles instead of a 4096 ICLK cycle delay. 1 = Stop mode recovery after 32 ICLK cycles 0 = Stop mode recovery after 4096 ICLK cycles NOTE Exiting stop mode by pulling reset will result in the long stop recovery. If using an external crystal oscillator, do not set the SSREC bit. When the LVI is disabled in stop mode (LVISTOP=0), the system stabilization time for long stop recovery (4096 ICLK cycles) gives a delay longer than the LVI's turn-on time. There is no period where the MCU is not protected from a low power condition. However, when using the short stop recovery configuration option, the 32 ICLK delay is less than the LVI's turn-on time and there exists a period in start-up where the LVI is not protecting the MCU. STOP -- STOP Instruction Enable Bit STOP enables the STOP instruction. 1 = STOP instruction enabled 0 = STOP instruction treated as illegal opcode COPD -- COP Disable Bit COPD disables the COP module. (See Chapter 19 Computer Operating Properly (COP).) 1 = COP module disabled 0 = COP module enabled
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 51
Configuration & Mask Option Registers (CONFIG & MOR)
3.4 Configuration Register 2 (CONFIG2)
Address: Read: Write: Reset: $001D Bit 7 STOP_ ICLKDIS 0 6 STOP_ RCLKEN 0 5 STOP_ XCLKEN 0 4 3 2 0 0 1 0 0 Bit 0 SCIBDSRC 0
OSCCLK1 OSCCLK0 0 0
Figure 3-3. Configuration Register 2 (CONFIG2) STOP_ICLKDIS -- Internal Oscillator Stop Mode Disable STOP_ICLKDIS disables the internal oscillator during stop mode. Setting the STOP_ICLKDIS bit disables the oscillator during stop mode. (See Chapter 5 Oscillator (OSC).) Reset clears this bit. 1 = Internal oscillator disabled during stop mode 0 = Internal oscillator enabled to operate during stop mode STOP_RCLKEN -- RC Oscillator Stop Mode Enable Bit STOP_RCLKEN enables the RC oscillator to continue operating during stop mode. Setting the STOP_RCLKEN bit allows the oscillator to operate continuously even during stop mode. This is useful for driving the timebase module to allow it to generate periodic wake up while in stop mode. (See Chapter 5 Oscillator (OSC).) Reset clears this bit. 1 = RC oscillator enabled to operate during stop mode 0 = RC oscillator disabled during stop mode STOP_XCLKEN -- X-tal Oscillator Stop Mode Enable Bit STOP_XCLKEN enables the crystal (x-tal) oscillator to continue operating during stop mode. Setting the STOP_XCLKEN bit allows the x-tal oscillator to operate continuously even during stop mode. This is useful for driving the timebase module to allow it to generate periodic wake up while in stop mode. (See Chapter 5 Oscillator (OSC).) Reset clears this bit. 1 = X-tal oscillator enabled to operate during stop mode 0 = X-tal oscillator disabled during stop mode OSCCLK1, OSCCLK0 -- Oscillator Output Control Bits OSCCLK1 and OSCCLK0 select which oscillator output to be driven out as OSCCLK to the timebase module (TBM). Reset clears these two bits.
OSCCLK1 0 0 1 1 OSCCLK0 0 1 0 1 Timebase Clock Source Internal oscillator (ICLK) RC oscillator (RCCLK) X-tal oscillator (XTAL) Not used
MC68HC908AP A-Family Data Sheet, Rev. 2 52 Freescale Semiconductor
Mask Option Register (MOR)
SCIBDSRC -- SCI Baud Rate Clock Source SCIBDSRC selects the clock source used for the standard SCI module (non-infrared SCI). The setting of this bit affects the frequency at which the SCI operates. 1 = Internal data bus clock, fBUS, is used as clock source for SCI 0 = Oscillator clock, CGMXCLK, is used as clock source for SCI
3.5 Mask Option Register (MOR)
The mask option register (MOR) is used for selecting one of the three clock options for the MCU. The MOR is a byte located in FLASH memory, and is written to by a FLASH programming routine.
Address: Read: Write: Reset: Erased:
$FFCF Bit 7 OSCSEL1 6 OSCSEL0 5 R 4 R 3 R 2 R 1 R Bit 0 R
Unaffected by reset 1 R 1 1 = Reserved 1 1 1 1 1
Figure 3-4. Mask Option Register (MOR)
OSCSEL1, OSCSEL0 -- Oscillator Selection Bits OSCSEL1 and OSCSEL0 select which oscillator is used for the MCU CGMXCLK clock. The erase state of these two bits is logic 1. These bits are unaffected by reset. (See Table 3-1). Bits 5-0 -- Should be left as 1's Table 3-1. CGMXCLK Clock Selection
OSCSEL1 0 0 OSCSEL0 0 1 CGMXCLK -- ICLK OSC2 pin -- fBUS fBUS Comments
Not used Internal oscillator generates the CGMXCLK. RC oscillator generates the CGMXCLK. Internal oscillator is available after each POR or reset. X-tal oscillator generates the CGMXCLK. Internal oscillator is available after each POR or reset.
1
0
RCCLK
1
1
X-TAL
Inverting output of XTAL
NOTE The internal oscillator is a free running oscillator and is available after each POR or reset. It is turned-off in stop mode by setting the STOP_ICLKDIS bit in CONFIG2.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 53
Configuration & Mask Option Registers (CONFIG & MOR)
MC68HC908AP A-Family Data Sheet, Rev. 2 54 Freescale Semiconductor
Chapter 4 Central Processor Unit (CPU)
4.1 Introduction
The M68HC08 CPU (central processor unit) is an enhanced and fully object-code-compatible version of the M68HC05 CPU. The CPU08 Reference Manual (Freescale document order number CPU08RM/AD) contains a description of the CPU instruction set, addressing modes, and architecture.
4.2 Features
* * * * * * * * * * * Object code fully upward-compatible with M68HC05 Family 16-bit stack pointer with stack manipulation instructions 16-Bit index register with x-register manipulation instructions 8-MHz CPU internal bus frequency 64-Kbyte program/data memory space 16 addressing modes Memory-to-memory data moves without using accumulator Fast 8-bit by 8-bit multiply and 16-bit by 8-bit divide instructions Enhanced binary-coded decimal (BCD) data handling Modular architecture with expandable internal bus definition for extension of addressing range beyond 64 Kbytes Low-power stop and wait modes
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 55
Central Processor Unit (CPU)
4.3 CPU Registers
Figure 4-1 shows the five CPU registers. CPU registers are not part of the memory map.
7 15 H 15 15 X 0 STACK POINTER (SP) 0 PROGRAM COUNTER (PC) 7 0 V11HINZC CONDITION CODE REGISTER (CCR) 0 ACCUMULATOR (A) 0 INDEX REGISTER (H:X)
CARRY/BORROW FLAG ZERO FLAG NEGATIVE FLAG INTERRUPT MASK HALF-CARRY FLAG TWO'S COMPLEMENT OVERFLOW FLAG
Figure 4-1. CPU Registers
4.3.1 Accumulator
The accumulator is a general-purpose 8-bit register. The CPU uses the accumulator to hold operands and the results of arithmetic/logic operations.
Bit 7 Read: Write: Reset: Unaffected by reset 6 5 4 3 2 1 Bit 0
Figure 4-2. Accumulator (A)
4.3.2 Index Register
The 16-bit index register allows indexed addressing of a 64-Kbyte memory space. H is the upper byte of the index register, and X is the lower byte. H:X is the concatenated 16-bit index register. In the indexed addressing modes, the CPU uses the contents of the index register to determine the conditional address of the operand. The index register can serve also as a temporary data storage location.
MC68HC908AP A-Family Data Sheet, Rev. 2 56 Freescale Semiconductor
CPU Registers
Bit 15 Read: Write: Reset: 0
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
X
X
X
X
X
X
X
X
X = Indeterminate
Figure 4-3. Index Register (H:X)
4.3.3 Stack Pointer
The stack pointer is a 16-bit register that contains the address of the next location on the stack. During a reset, the stack pointer is preset to $00FF. The reset stack pointer (RSP) instruction sets the least significant byte to $FF and does not affect the most significant byte. The stack pointer decrements as data is pushed onto the stack and increments as data is pulled from the stack. In the stack pointer 8-bit offset and 16-bit offset addressing modes, the stack pointer can function as an index register to access data on the stack. The CPU uses the contents of the stack pointer to determine the conditional address of the operand.
Bit 15 Read: Write: Reset: 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Bit 0
Figure 4-4. Stack Pointer (SP) NOTE The location of the stack is arbitrary and may be relocated anywhere in RAM. Moving the SP out of page 0 ($0000 to $00FF) frees direct address (page 0) space. For correct operation, the stack pointer must point only to RAM locations.
4.3.4 Program Counter
The program counter is a 16-bit register that contains the address of the next instruction or operand to be fetched. Normally, the program counter automatically increments to the next sequential memory location every time an instruction or operand is fetched. Jump, branch, and interrupt operations load the program counter with an address other than that of the next sequential location. During reset, the program counter is loaded with the reset vector address located at $FFFE and $FFFF. The vector address is the address of the first instruction to be executed after exiting the reset state.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 57
Central Processor Unit (CPU)
Bit 15 Read: Write: Reset:
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Bit 0
Loaded with Vector from $FFFE and $FFFF
Figure 4-5. Program Counter (PC)
4.3.5 Condition Code Register
The 8-bit condition code register contains the interrupt mask and five flags that indicate the results of the instruction just executed. Bits 6 and 5 are set permanently to logic 1. The following paragraphs describe the functions of the condition code register.
Bit 7 Read: Write: Reset: V X X = Indeterminate 6 1 1 5 1 1 4 H X 3 I 1 2 N X 1 Z X Bit 0 C X
Figure 4-6. Condition Code Register (CCR) V -- Overflow Flag The CPU sets the overflow flag when a two's complement overflow occurs. The signed branch instructions BGT, BGE, BLE, and BLT use the overflow flag. 1 = Overflow 0 = No overflow H -- Half-Carry Flag The CPU sets the half-carry flag when a carry occurs between accumulator bits 3 and 4 during an add-without-carry (ADD) or add-with-carry (ADC) operation. The half-carry flag is required for binary-coded decimal (BCD) arithmetic operations. The DAA instruction uses the states of the H and C flags to determine the appropriate correction factor. 1 = Carry between bits 3 and 4 0 = No carry between bits 3 and 4 I -- Interrupt Mask When the interrupt mask is set, all maskable CPU interrupts are disabled. CPU interrupts are enabled when the interrupt mask is cleared. When a CPU interrupt occurs, the interrupt mask is set automatically after the CPU registers are saved on the stack, but before the interrupt vector is fetched. 1 = Interrupts disabled 0 = Interrupts enabled NOTE To maintain M6805 Family compatibility, the upper byte of the index register (H) is not stacked automatically. If the interrupt service routine modifies H, then the user must stack and unstack H using the PSHH and PULH instructions.
MC68HC908AP A-Family Data Sheet, Rev. 2 58 Freescale Semiconductor
Arithmetic/Logic Unit (ALU)
After the I bit is cleared, the highest-priority interrupt request is serviced first. A return-from-interrupt (RTI) instruction pulls the CPU registers from the stack and restores the interrupt mask from the stack. After any reset, the interrupt mask is set and can be cleared only by the clear interrupt mask software instruction (CLI). N -- Negative flag The CPU sets the negative flag when an arithmetic operation, logic operation, or data manipulation produces a negative result, setting bit 7 of the result. 1 = Negative result 0 = Non-negative result Z -- Zero flag The CPU sets the zero flag when an arithmetic operation, logic operation, or data manipulation produces a result of $00. 1 = Zero result 0 = Non-zero result C -- Carry/Borrow Flag The CPU sets the carry/borrow flag when an addition operation produces a carry out of bit 7 of the accumulator or when a subtraction operation requires a borrow. Some instructions -- such as bit test and branch, shift, and rotate -- also clear or set the carry/borrow flag. 1 = Carry out of bit 7 0 = No carry out of bit 7
4.4 Arithmetic/Logic Unit (ALU)
The ALU performs the arithmetic and logic operations defined by the instruction set. Refer to the CPU08 Reference Manual (Freescale document order number CPU08RM/AD) for a description of the instructions and addressing modes and more detail about the architecture of the CPU.
4.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
4.5.1 Wait Mode
The WAIT instruction: * Clears the interrupt mask (I bit) in the condition code register, enabling interrupts. After exit from wait mode by interrupt, the I bit remains clear. After exit by reset, the I bit is set. * Disables the CPU clock
4.5.2 Stop Mode
The STOP instruction: * Clears the interrupt mask (I bit) in the condition code register, enabling external interrupts. After exit from stop mode by external interrupt, the I bit remains clear. After exit by reset, the I bit is set. * Disables the CPU clock After exiting stop mode, the CPU clock begins running after the oscillator stabilization delay.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 59
Central Processor Unit (CPU)
4.6 CPU During Break Interrupts
If a break module is present on the MCU, the CPU starts a break interrupt by: * Loading the instruction register with the SWI instruction * Loading the program counter with $FFFC:$FFFD or with $FEFC:$FEFD in monitor mode The break interrupt begins after completion of the CPU instruction in progress. If the break address register match occurs on the last cycle of a CPU instruction, the break interrupt begins immediately. A return-from-interrupt instruction (RTI) in the break routine ends the break interrupt and returns the MCU to normal operation if the break interrupt has been deasserted.
4.7 Instruction Set Summary
Table 4-1 provides a summary of the M68HC08 instruction set.
4.8 Opcode Map
The opcode map is provided in Table 4-2.
Table 4-1. Instruction Set Summary
Operand
ii dd hh ll ee ff ff ff ee ff ii dd hh ll ee ff ff ff ee ff ii ii
Address Mode
Opcode
Source Form
ADC #opr ADC opr ADC opr ADC opr,X ADC opr,X ADC ,X ADC opr,SP ADC opr,SP ADD #opr ADD opr ADD opr ADD opr,X ADD opr,X ADD ,X ADD opr,SP ADD opr,SP AIS #opr AIX #opr
Operation
Description
VH I NZC
Add with Carry
A (A) + (M) + (C)
IMM DIR EXT IX2 oo-ooo IX1 IX SP1 SP2 IMM DIR EXT IX2 oo-ooo IX1 IX SP1 SP2 - - - - - - IMM - - - - - - IMM
A9 B9 C9 D9 E9 F9 9EE9 9ED9 AB BB CB DB EB FB 9EEB 9EDB A7 AF
2 3 4 4 3 2 4 5 2 3 4 4 3 2 4 5 2 2
Add without Carry
A (A) + (M)
Add Immediate Value (Signed) to SP Add Immediate Value (Signed) to H:X
SP (SP) + (16 M) H:X (H:X) + (16 M)
MC68HC908AP A-Family Data Sheet, Rev. 2 60 Freescale Semiconductor
Cycles
Effect on CCR
Opcode Map
Table 4-1. Instruction Set Summary
Operand
ii dd hh ll ee ff ff ff ee ff dd ff ff dd ff ff rr dd dd dd dd dd dd dd dd rr rr rr rr rr rr rr rr rr rr
Address Mode
Opcode
Source Form
AND #opr AND opr AND opr AND opr,X AND opr,X AND ,X AND opr,SP AND opr,SP ASL opr ASLA ASLX ASL opr,X ASL ,X ASL opr,SP ASR opr ASRA ASRX ASR opr,X ASR opr,X ASR opr,SP BCC rel
Operation
Description
VH I NZC
Logical AND
A (A) & (M)
IMM DIR EXT IX2 0--oo- IX1 IX SP1 SP2 DIR INH INH o--ooo IX1 IX SP1 DIR INH INH o--ooo IX1 IX SP1 - - - - - - REL DIR (b0) DIR (b1) DIR (b2) DIR (b3) ------ DIR (b4) DIR (b5) DIR (b6) DIR (b7) - - - - - - REL - - - - - - REL - - - - - - REL
A4 B4 C4 D4 E4 F4 9EE4 9ED4 38 48 58 68 78 9E68 37 47 57 67 77 9E67 24 11 13 15 17 19 1B 1D 1F 25 27 90
2 3 4 4 3 2 4 5 4 1 1 4 3 5 4 1 1 4 3 5 3 4 4 4 4 4 4 4 4 3 3 3
Arithmetic Shift Left (Same as LSL)
C b7 b0
0
Arithmetic Shift Right
b7 b0
C
Branch if Carry Bit Clear
PC (PC) + 2 + rel ? (C) = 0
BCLR n, opr
Clear Bit n in M
Mn 0
BCS rel BEQ rel BGE opr
Branch if Carry Bit Set (Same as BLO) Branch if Equal Branch if Greater Than or Equal To (Signed Operands) Branch if Greater Than (Signed Operands) Branch if Half Carry Bit Clear Branch if Half Carry Bit Set Branch if Higher Branch if Higher or Same (Same as BCC) Branch if IRQ Pin High Branch if IRQ Pin Low
PC (PC) + 2 + rel ? (C) = 1 PC (PC) + 2 + rel ? (Z) = 1 PC (PC) + 2 + rel ? (N V) = 0
BGT opr BHCC rel BHCS rel BHI rel BHS rel BIH rel BIL rel
PC (PC) + 2 +rel ? (Z) | (N V)=0 - - - - - - REL PC (PC) + 2 + rel ? (H) = 0 PC (PC) + 2 + rel ? (H) = 1 PC (PC) + 2 + rel ? (C) | (Z) = 0 PC (PC) + 2 + rel ? (C) = 0 PC (PC) + 2 + rel ? IRQ = 1 PC (PC) + 2 + rel ? IRQ = 0 - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL
92 28 29 22 24 2F 2E
3 3 3 3 3 3 3
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 61
Cycles
Effect on CCR
Central Processor Unit (CPU)
Table 4-1. Instruction Set Summary
Operand
ii dd hh ll ee ff ff ff ee ff rr rr rr rr rr rr rr rr rr rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd dd dd dd dd dd dd dd
Address Mode
Opcode
Source Form
BIT #opr BIT opr BIT opr BIT opr,X BIT opr,X BIT ,X BIT opr,SP BIT opr,SP BLE opr BLO rel BLS rel BLT opr BMC rel BMI rel BMS rel BNE rel BPL rel BRA rel
Operation
Description
VH I NZC
Bit Test
(A) & (M)
IMM DIR EXT IX2 0--oo- IX1 IX SP1 SP2
A5 B5 C5 D5 E5 F5 9EE5 9ED5 93 25 23 91 2C 2B 2D 26 2A 20 01 03 05 07 09 0B 0D 0F 21 00 02 04 06 08 0A 0C 0E 10 12 14 16 18 1A 1C 1E
2 3 4 4 3 2 4 5 3 3 3 3 3 3 3 3 3 3 5 5 5 5 5 5 5 5 3 5 5 5 5 5 5 5 5 4 4 4 4 4 4 4 4
Branch if Less Than or Equal To (Signed Operands) Branch if Lower (Same as BCS) Branch if Lower or Same Branch if Less Than (Signed Operands) Branch if Interrupt Mask Clear Branch if Minus Branch if Interrupt Mask Set Branch if Not Equal Branch if Plus Branch Always
PC (PC) + 2 + rel ? (Z) | (N V)=1 - - - - - - REL PC (PC) + 2 + rel ? (C) = 1 PC (PC) + 2 + rel ? (C) | (Z) = 1 PC (PC) + 2 + rel ? (N V) = 1 PC (PC) + 2 + rel ? (I) = 0 PC (PC) + 2 + rel ? (N) = 1 PC (PC) + 2 + rel ? (I) = 1 PC (PC) + 2 + rel ? (Z) = 0 PC (PC) + 2 + rel ? (N) = 0 PC (PC) + 2 + rel - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL DIR (b0) DIR (b1) DIR (b2) DIR (b3) -----o DIR (b4) DIR (b5) DIR (b6) DIR (b7) - - - - - - REL DIR (b0) DIR (b1) DIR (b2) DIR (b3) -----o DIR (b4) DIR (b5) DIR (b6) DIR (b7) DIR (b0) DIR (b1) DIR (b2) DIR (b3) ------ DIR (b4) DIR (b5) DIR (b6) DIR (b7)
BRCLR n,opr,rel Branch if Bit n in M Clear
PC (PC) + 3 + rel ? (Mn) = 0
BRN rel
Branch Never
PC (PC) + 2
BRSET n,opr,rel Branch if Bit n in M Set
PC (PC) + 3 + rel ? (Mn) = 1
BSET n,opr
Set Bit n in M
Mn 1
MC68HC908AP A-Family Data Sheet, Rev. 2 62 Freescale Semiconductor
Cycles
Effect on CCR
Opcode Map
Table 4-1. Instruction Set Summary
Operand
rr dd rr ii rr ii rr ff rr rr ff rr dd ff ff ii dd hh ll ee ff ff ff ee ff dd ff ff ii ii+1 dd ii dd hh ll ee ff ff ff ee ff
Address Mode
Opcode
Source Form
Operation
Description
VH I NZC
PC (PC) + 2; push (PCL) SP (SP) - 1; push (PCH) SP (SP) - 1 PC (PC) + rel
BSR rel
Branch to Subroutine
- - - - - - REL
AD
4
CBEQ opr,rel CBEQA #opr,rel CBEQX #opr,rel Compare and Branch if Equal CBEQ opr,X+,rel CBEQ X+,rel CBEQ opr,SP,rel CLC CLI CLR opr CLRA CLRX CLRH CLR opr,X CLR ,X CLR opr,SP CMP #opr CMP opr CMP opr CMP opr,X CMP opr,X CMP ,X CMP opr,SP CMP opr,SP COM opr COMA COMX COM opr,X COM ,X COM opr,SP CPHX #opr CPHX opr CPX #opr CPX opr CPX opr CPX ,X CPX opr,X CPX opr,X CPX opr,SP CPX opr,SP DAA Clear Carry Bit Clear Interrupt Mask
PC (PC) + 3 + rel ? (A) - (M) = $00 DIR PC (PC) + 3 + rel ? (A) - (M) = $00 IMM PC (PC) + 3 + rel ? (X) - (M) = $00 IMM ------ PC (PC) + 3 + rel ? (A) - (M) = $00 IX1+ PC (PC) + 2 + rel ? (A) - (M) = $00 IX+ PC (PC) + 4 + rel ? (A) - (M) = $00 SP1 C0 I0 M $00 A $00 X $00 H $00 M $00 M $00 M $00 - - - - - 0 INH - - 0 - - - INH DIR INH INH 0 - - 0 1 - INH IX1 IX SP1 IMM DIR EXT IX2 o--ooo IX1 IX SP1 SP2 DIR INH INH 0--oo1 IX1 IX SP1 o--ooo IMM DIR
31 41 51 61 71 9E61 98 9A 3F 4F 5F 8C 6F 7F 9E6F A1 B1 C1 D1 E1 F1 9EE1 9ED1 33 43 53 63 73 9E63 65 75 A3 B3 C3 D3 E3 F3 9EE3 9ED3 72
5 4 4 5 4 6 1 2 3 1 1 1 3 2 4 2 3 4 4 3 2 4 5 4 1 1 4 3 5 3 4 2 3 4 4 3 2 4 5 2
Clear
Compare A with M
(A) - (M)
Complement (One's Complement)
M (M) = $FF - (M) A (A) = $FF - (M) X (X) = $FF - (M) M (M) = $FF - (M) M (M) = $FF - (M) M (M) = $FF - (M) (H:X) - (M:M + 1)
Compare H:X with M
Compare X with M
(X) - (M)
IMM DIR EXT IX2 o--ooo IX1 IX SP1 SP2 U - - o o o INH
Decimal Adjust A
(A)10
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 63
Cycles
Effect on CCR
Central Processor Unit (CPU)
Table 4-1. Instruction Set Summary
Operand
dd rr rr rr ff rr rr ff rr dd ff ff ii dd hh ll ee ff ff ff ee ff dd ff ff dd hh ll ee ff ff dd hh ll ee ff ff ii dd hh ll ee ff ff ff ee ff ii jj dd
Address Mode
Opcode
Source Form
Operation
Description
VH I NZC
DBNZ opr,rel DBNZA rel DBNZX rel Decrement and Branch if Not Zero DBNZ opr,X,rel DBNZ X,rel DBNZ opr,SP,rel DEC opr DECA DECX DEC opr,X DEC ,X DEC opr,SP DIV EOR #opr EOR opr EOR opr EOR opr,X EOR opr,X EOR ,X EOR opr,SP EOR opr,SP INC opr INCA INCX INC opr,X INC ,X INC opr,SP JMP opr JMP opr JMP opr,X JMP opr,X JMP ,X JSR opr JSR opr JSR opr,X JSR opr,X JSR ,X LDA #opr LDA opr LDA opr LDA opr,X LDA opr,X LDA ,X LDA opr,SP LDA opr,SP LDHX #opr LDHX opr
A (A)-1 or M (M)-1 or X (X)-1 PC (PC) + 3 + rel ? (result) 0 DIR PC (PC) + 2 + rel ? (result) 0 INH PC (PC) + 2 + rel ? (result) 0 - - - - - - INH PC (PC) + 3 + rel ? (result) 0 IX1 PC (PC) + 2 + rel ? (result) 0 IX PC (PC) + 4 + rel ? (result) 0 SP1 M (M) - 1 A (A) - 1 X (X) - 1 M (M) - 1 M (M) - 1 M (M) - 1 A (H:A)/(X) H Remainder DIR INH INH o--oo- IX1 IX SP1 - - - - o o INH IMM DIR EXT IX2 0--oo- IX1 IX SP1 SP2 DIR INH INH o--oo- IX1 IX SP1 DIR EXT - - - - - - IX2 IX1 IX DIR EXT - - - - - - IX2 IX1 IX IMM DIR EXT IX2 0--oo- IX1 IX SP1 SP2 0--oo- IMM DIR
3B 4B 5B 6B 7B 9E6B 3A 4A 5A 6A 7A 9E6A 52 A8 B8 C8 D8 E8 F8 9EE8 9ED8 3C 4C 5C 6C 7C 9E6C BC CC DC EC FC BD CD DD ED FD A6 B6 C6 D6 E6 F6 9EE6 9ED6 45 55
5 3 3 5 4 6 4 1 1 4 3 5 7 2 3 4 4 3 2 4 5 4 1 1 4 3 5 2 3 4 3 2 4 5 6 5 4 2 3 4 4 3 2 4 5 3 4
Decrement
Divide
Exclusive OR M with A
A (A M)
Increment
M (M) + 1 A (A) + 1 X (X) + 1 M (M) + 1 M (M) + 1 M (M) + 1
Jump
PC Jump Address
Jump to Subroutine
PC (PC) + n (n = 1, 2, or 3) Push (PCL); SP (SP) - 1 Push (PCH); SP (SP) - 1 PC Unconditional Address
Load A from M
A (M)
Load H:X from M
H:X (M:M + 1)
MC68HC908AP A-Family Data Sheet, Rev. 2 64 Freescale Semiconductor
Cycles
Effect on CCR
Opcode Map
Table 4-1. Instruction Set Summary
Operand
ii dd hh ll ee ff ff ff ee ff dd ff ff dd ff ff dd dd dd ii dd dd dd ff ff ii dd hh ll ee ff ff ff ee ff
Address Mode
Opcode
Source Form
LDX #opr LDX opr LDX opr LDX opr,X LDX opr,X LDX ,X LDX opr,SP LDX opr,SP LSL opr LSLA LSLX LSL opr,X LSL ,X LSL opr,SP LSR opr LSRA LSRX LSR opr,X LSR ,X LSR opr,SP MOV opr,opr MOV opr,X+ MOV #opr,opr MOV X+,opr MUL NEG opr NEGA NEGX NEG opr,X NEG ,X NEG opr,SP NOP NSA ORA #opr ORA opr ORA opr ORA opr,X ORA opr,X ORA ,X ORA opr,SP ORA opr,SP PSHA PSHH PSHX PULA
Operation
Description
VH I NZC
Load X from M
X (M)
IMM DIR EXT IX2 0--oo- IX1 IX SP1 SP2 DIR INH INH o--ooo IX1 IX SP1 DIR INH INH o--0oo IX1 IX SP1 DD DIX+ 0--oo- IMD IX+D - 0 - - - 0 INH DIR INH INH o--ooo IX1 IX SP1 - - - - - - INH - - - - - - INH IMM DIR EXT IX2 0--oo- IX1 IX SP1 SP2 - - - - - - INH - - - - - - INH - - - - - - INH - - - - - - INH
AE BE CE DE EE FE 9EEE 9EDE 38 48 58 68 78 9E68 34 44 54 64 74 9E64 4E 5E 6E 7E 42 30 40 50 60 70 9E60 9D 62 AA BA CA DA EA FA 9EEA 9EDA 87 8B 89 86
2 3 4 4 3 2 4 5 4 1 1 4 3 5 4 1 1 4 3 5 5 4 4 4 5 4 1 1 4 3 5 1 3 2 3 4 4 3 2 4 5 2 2 2 2
Logical Shift Left (Same as ASL)
C b7 b0
0
Logical Shift Right
0 b7 b0
C
(M)Destination (M)Source Move H:X (H:X) + 1 (IX+D, DIX+) Unsigned multiply X:A (X) x (A) M -(M) = $00 - (M) A -(A) = $00 - (A) X -(X) = $00 - (X) M -(M) = $00 - (M) M -(M) = $00 - (M) None A (A[3:0]:A[7:4])
Negate (Two's Complement)
No Operation Nibble Swap A
Inclusive OR A and M
A (A) | (M)
Push A onto Stack Push H onto Stack Push X onto Stack Pull A from Stack
Push (A); SP (SP) - 1 Push (H); SP (SP) - 1 Push (X); SP (SP) - 1 SP (SP + 1); Pull (A)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 65
Cycles
Effect on CCR
Central Processor Unit (CPU)
Table 4-1. Instruction Set Summary
Operand
dd ff ff dd ff ff ii dd hh ll ee ff ff ff ee ff dd hh ll ee ff ff ff ee ff dd
Address Mode
Opcode
Source Form
PULH PULX ROL opr ROLA ROLX ROL opr,X ROL ,X ROL opr,SP ROR opr RORA RORX ROR opr,X ROR ,X ROR opr,SP RSP
Operation
Description
VH I NZC
Pull H from Stack Pull X from Stack SP (SP + 1); Pull (H) SP (SP + 1); Pull (X)
- - - - - - INH - - - - - - INH DIR INH INH o--ooo IX1 IX SP1 DIR INH INH o--ooo IX1 IX SP1 - - - - - - INH
8A 88 39 49 59 69 79 9E69 36 46 56 66 76 9E66 9C
2 2 4 1 1 4 3 5 4 1 1 4 3 5 1
Rotate Left through Carry
C b7 b0
Rotate Right through Carry
b7 b0
C
Reset Stack Pointer
SP $FF SP (SP) + 1; Pull (CCR) SP (SP) + 1; Pull (A) SP (SP) + 1; Pull (X) SP (SP) + 1; Pull (PCH) SP (SP) + 1; Pull (PCL) SP SP + 1; Pull (PCH) SP SP + 1; Pull (PCL)
RTI
Return from Interrupt
o o o o o o INH
80
7
RTS SBC #opr SBC opr SBC opr SBC opr,X SBC opr,X SBC ,X SBC opr,SP SBC opr,SP SEC SEI STA opr STA opr STA opr,X STA opr,X STA ,X STA opr,SP STA opr,SP STHX opr STOP
Return from Subroutine
- - - - - - INH IMM DIR EXT IX2 o--ooo IX1 IX SP1 SP2 - - - - - 1 INH - - 1 - - - INH DIR EXT IX2 0 - - o o - IX1 IX SP1 SP2 0 - - o o - DIR - - 0 - - - INH
81 A2 B2 C2 D2 E2 F2 9EE2 9ED2 99 9B B7 C7 D7 E7 F7 9EE7 9ED7 35 8E
4 2 3 4 4 3 2 4 5 1 2 3 4 4 3 2 4 5 4 1
Subtract with Carry
A (A) - (M) - (C)
Set Carry Bit Set Interrupt Mask
C1 I1
Store A in M
M (A)
Store H:X in M Enable IRQ Pin; Stop Processing
(M:M + 1) (H:X) I 0; Stop Processing
MC68HC908AP A-Family Data Sheet, Rev. 2 66 Freescale Semiconductor
Cycles
Effect on CCR
Opcode Map
Table 4-1. Instruction Set Summary
Operand
dd hh ll ee ff ff ff ee ff ii dd hh ll ee ff ff ff ee ff dd ff ff
Address Mode
Opcode
Source Form
STX opr STX opr STX opr,X STX opr,X STX ,X STX opr,SP STX opr,SP SUB #opr SUB opr SUB opr SUB opr,X SUB opr,X SUB ,X SUB opr,SP SUB opr,SP
Operation
Description
VH I NZC
Store X in M
M (X)
DIR EXT IX2 0 - - o o - IX1 IX SP1 SP2 IMM DIR EXT IX2 o--ooo IX1 IX SP1 SP2
BF CF DF EF FF 9EEF 9EDF A0 B0 C0 D0 E0 F0 9EE0 9ED0
3 4 4 3 2 4 5 2 3 4 4 3 2 4 5
Subtract
A (A) - (M)
SWI
Software Interrupt
PC (PC) + 1; Push (PCL) SP (SP) - 1; Push (PCH) SP (SP) - 1; Push (X) SP (SP) - 1; Push (A) SP (SP) - 1; Push (CCR) SP (SP) - 1; I 1 PCH Interrupt Vector High Byte PCL Interrupt Vector Low Byte CCR (A) X (A) A (CCR)
- - 1 - - - INH
83
9
TAP TAX TPA TST opr TSTA TSTX TST opr,X TST ,X TST opr,SP TSX TXA TXS WAIT
Transfer A to CCR Transfer A to X Transfer CCR to A
o o o o o o INH - - - - - - INH - - - - - - INH DIR INH INH 0--oo- IX1 IX SP1 - - - - - - INH - - - - - - INH - - - - - - INH - - 0 - - - INH
84 97 85 3D 4D 5D 6D 7D 9E6D 95 9F 94 8F
2 1 1 3 1 1 3 2 4 2 1 2 1
Test for Negative or Zero
(A) - $00 or (X) - $00 or (M) - $00
Transfer SP to H:X Transfer X to A Transfer H:X to SP Enable Interrupts; Wait for Interrupt
H:X (SP) + 1 A (X) (SP) (H:X) - 1 I 0; Inhibit CPU clocking until interrupted
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 67
Cycles
Effect on CCR
Central Processor Unit (CPU)
Table 4-1. Instruction Set Summary
Operand Address Mode Opcode Cycles Effect on CCR VH I NZC
A C CCR dd dd rr DD DIR DIX+ ee ff EXT ff H H hh ll I ii IMD IMM INH IX IX+ IX+D IX1 IX1+ IX2 M N Accumulator Carry/borrow bit Condition code register Direct address of operand Direct address of operand and relative offset of branch instruction Direct to direct addressing mode Direct addressing mode Direct to indexed with post increment addressing mode High and low bytes of offset in indexed, 16-bit offset addressing Extended addressing mode Offset byte in indexed, 8-bit offset addressing Half-carry bit Index register high byte High and low bytes of operand address in extended addressing Interrupt mask Immediate operand byte Immediate source to direct destination addressing mode Immediate addressing mode Inherent addressing mode Indexed, no offset addressing mode Indexed, no offset, post increment addressing mode Indexed with post increment to direct addressing mode Indexed, 8-bit offset addressing mode Indexed, 8-bit offset, post increment addressing mode Indexed, 16-bit offset addressing mode Memory location Negative bit n opr PC PCH PCL REL rel rr SP1 SP2 SP U V X Z & |
Source Form
Operation
Description
() -( ) #
? : o --
Any bit Operand (one or two bytes) Program counter Program counter high byte Program counter low byte Relative addressing mode Relative program counter offset byte Relative program counter offset byte Stack pointer, 8-bit offset addressing mode Stack pointer 16-bit offset addressing mode Stack pointer Undefined Overflow bit Index register low byte Zero bit Logical AND Logical OR Logical EXCLUSIVE OR Contents of Negation (two's complement) Immediate value Sign extend Loaded with If Concatenated with Set or cleared Not affected
MC68HC908AP A-Family Data Sheet, Rev. 2 68 Freescale Semiconductor
Freescale Semiconductor MC68HC908AP A-Family Data Sheet, Rev. 2 69
Table 4-2. Opcode Map
Bit Manipulation DIR DIR
MSB LSB
Branch REL 2 3 BRA REL 3 BRN 2 REL 3 BHI 2 REL 3 BLS 2 REL 3 BCC 2 REL 3 BCS 2 REL 3 BNE 2 REL 3 BEQ 2 REL 3 BHCC 2 REL 3 BHCS 2 REL 3 BPL 2 REL 3 BMI 2 REL 3 BMC 2 REL 3 BMS 2 REL 3 BIL 2 REL 3 BIH 2 REL 2
DIR 3
INH 4
Read-Modify-Write INH IX1 5 1 NEGX 1 INH 4 CBEQX 3 IMM 7 DIV 1 INH 1 COMX 1 INH 1 LSRX 1 INH 4 LDHX 2 DIR 1 RORX 1 INH 1 ASRX 1 INH 1 LSLX 1 INH 1 ROLX 1 INH 1 DECX 1 INH 3 DBNZX 2 INH 1 INCX 1 INH 1 TSTX 1 INH 4 MOV 2 DIX+ 1 CLRX 1 INH 6 4 NEG IX1 5 CBEQ 3 IX1+ 3 NSA 1 INH 4 COM 2 IX1 4 LSR 2 IX1 3 CPHX 3 IMM 4 ROR 2 IX1 4 ASR 2 IX1 4 LSL 2 IX1 4 ROL 2 IX1 4 DEC 2 IX1 5 DBNZ 3 IX1 4 INC 2 IX1 3 TST 2 IX1 4 MOV 3 IMD 3 CLR 2 IX1 2
SP1 9E6
IX 7
Control INH INH 8 9
IMM A 2 SUB IMM 2 CMP 2 IMM 2 SBC 2 IMM 2 CPX 2 IMM 2 AND 2 IMM 2 BIT 2 IMM 2 LDA 2 IMM 2 AIS 2 IMM 2 EOR 2 IMM 2 ADC 2 IMM 2 ORA 2 IMM 2 ADD 2 IMM 2
DIR B
EXT C 4 SUB EXT 4 CMP 3 EXT 4 SBC 3 EXT 4 CPX 3 EXT 4 AND 3 EXT 4 BIT 3 EXT 4 LDA 3 EXT 4 STA 3 EXT 4 EOR 3 EXT 4 ADC 3 EXT 4 ORA 3 EXT 4 ADD 3 EXT 3 JMP 3 EXT 5 JSR 3 EXT 4 LDX 3 EXT 4 STX 3 EXT 3
Register/Memory IX2 SP2 D 4 SUB IX2 4 CMP 3 IX2 4 SBC 3 IX2 4 CPX 3 IX2 4 AND 3 IX2 4 BIT 3 IX2 4 LDA 3 IX2 4 STA 3 IX2 4 EOR 3 IX2 4 ADC 3 IX2 4 ORA 3 IX2 4 ADD 3 IX2 4 JMP 3 IX2 6 JSR 3 IX2 4 LDX 3 IX2 4 STX 3 IX2 3 9ED 5 SUB SP2 5 CMP 4 SP2 5 SBC 4 SP2 5 CPX 4 SP2 5 AND 4 SP2 5 BIT 4 SP2 5 LDA 4 SP2 5 STA 4 SP2 5 EOR 4 SP2 5 ADC 4 SP2 5 ORA 4 SP2 5 ADD 4 SP2 4
IX1 E
SP1 9EE 4 SUB SP1 4 CMP 3 SP1 4 SBC 3 SP1 4 CPX 3 SP1 4 AND 3 SP1 4 BIT 3 SP1 4 LDA 3 SP1 4 STA 3 SP1 4 EOR 3 SP1 4 ADC 3 SP1 4 ORA 3 SP1 4 ADD 3 SP1 3
IX F
0 5 BRSET0 3 DIR 5 BRCLR0 3 DIR 5 BRSET1 3 DIR 5 BRCLR1 3 DIR 5 BRSET2 3 DIR 5 BRCLR2 3 DIR 5 BRSET3 3 DIR 5 BRCLR3 3 DIR 5 BRSET4 3 DIR 5 BRCLR4 3 DIR 5 BRSET5 3 DIR 5 BRCLR5 3 DIR 5 BRSET6 3 DIR 5 BRCLR6 3 DIR 5 BRSET7 3 DIR 5 BRCLR7 3 DIR
1 4 BSET0 2 DIR 4 BCLR0 2 DIR 4 BSET1 2 DIR 4 BCLR1 2 DIR 4 BSET2 2 DIR 4 BCLR2 2 DIR 4 BSET3 2 DIR 4 BCLR3 2 DIR 4 BSET4 2 DIR 4 BCLR4 2 DIR 4 BSET5 2 DIR 4 BCLR5 2 DIR 4 BSET6 2 DIR 4 BCLR6 2 DIR 4 BSET7 2 DIR 4 BCLR7 2 DIR
0 1 2 3 4 5 6 7 8 9 A B C D E F
4 1 NEG NEGA DIR 1 INH 5 4 CBEQ CBEQA 3 DIR 3 IMM 5 MUL 1 INH 4 1 COM COMA 2 DIR 1 INH 4 1 LSR LSRA 2 DIR 1 INH 4 3 STHX LDHX 2 DIR 3 IMM 4 1 ROR RORA 2 DIR 1 INH 4 1 ASR ASRA 2 DIR 1 INH 4 1 LSL LSLA 2 DIR 1 INH 4 1 ROL ROLA 2 DIR 1 INH 4 1 DEC DECA 2 DIR 1 INH 5 3 DBNZ DBNZA 3 DIR 2 INH 4 1 INC INCA 2 DIR 1 INH 3 1 TST TSTA 2 DIR 1 INH 5 MOV 3 DD 3 1 CLR CLRA 2 DIR 1 INH 2
5 3 NEG NEG SP1 1 IX 6 4 CBEQ CBEQ 4 SP1 2 IX+ 2 DAA 1 INH 5 3 COM COM 3 SP1 1 IX 5 3 LSR LSR 3 SP1 1 IX 4 CPHX 2 DIR 5 3 ROR ROR 3 SP1 1 IX 5 3 ASR ASR 3 SP1 1 IX 5 3 LSL LSL 3 SP1 1 IX 5 3 ROL ROL 3 SP1 1 IX 5 3 DEC DEC 3 SP1 1 IX 6 4 DBNZ DBNZ 4 SP1 2 IX 5 3 INC INC 3 SP1 1 IX 4 2 TST TST 3 SP1 1 IX 4 MOV 2 IX+D 4 2 CLR CLR 3 SP1 1 IX 3
7 3 RTI BGE INH 2 REL 4 3 RTS BLT 1 INH 2 REL 3 BGT 2 REL 9 3 SWI BLE 1 INH 2 REL 2 2 TAP TXS 1 INH 1 INH 1 2 TPA TSX 1 INH 1 INH 2 PULA 1 INH 2 1 PSHA TAX 1 INH 1 INH 2 1 PULX CLC 1 INH 1 INH 2 1 PSHX SEC 1 INH 1 INH 2 2 PULH CLI 1 INH 1 INH 2 2 PSHH SEI 1 INH 1 INH 1 1 CLRH RSP 1 INH 1 INH 1 NOP 1 INH 1 STOP * 1 INH 1 1 WAIT TXA 1 INH 1 INH 1
3 SUB DIR 3 CMP 2 DIR 3 SBC 2 DIR 3 CPX 2 DIR 3 AND 2 DIR 3 BIT 2 DIR 3 LDA 2 DIR 3 STA 2 DIR 3 EOR 2 DIR 3 ADC 2 DIR 3 ORA 2 DIR 3 ADD 2 DIR 2 JMP 2 DIR 4 4 BSR JSR 2 REL 2 DIR 2 3 LDX LDX 2 IMM 2 DIR 2 3 AIX STX 2 IMM 2 DIR 2
MSB LSB
3 SUB IX1 3 CMP 2 IX1 3 SBC 2 IX1 3 CPX 2 IX1 3 AND 2 IX1 3 BIT 2 IX1 3 LDA 2 IX1 3 STA 2 IX1 3 EOR 2 IX1 3 ADC 2 IX1 3 ORA 2 IX1 3 ADD 2 IX1 3 JMP 2 IX1 5 JSR 2 IX1 5 3 LDX LDX 4 SP2 2 IX1 5 3 STX STX 4 SP2 2 IX1 2
2 SUB IX 2 CMP 1 IX 2 SBC 1 IX 2 CPX 1 IX 2 AND 1 IX 2 BIT 1 IX 2 LDA 1 IX 2 STA 1 IX 2 EOR 1 IX 2 ADC 1 IX 2 ORA 1 IX 2 ADD 1 IX 2 JMP 1 IX 4 JSR 1 IX 4 2 LDX LDX 3 SP1 1 IX 4 2 STX STX 3 SP1 1 IX 1
Inherent REL Relative Immediate IX Indexed, No Offset Direct IX1 Indexed, 8-Bit Offset Extended IX2 Indexed, 16-Bit Offset Direct-Direct IMD Immediate-Direct Indexed-Direct DIX+ Direct-Indexed *Pre-byte for stack pointer indexed instructions
INH IMM DIR EXT DD IX+D
SP1 Stack Pointer, 8-Bit Offset SP2 Stack Pointer, 16-Bit Offset IX+ Indexed, No Offset with Post Increment IX1+ Indexed, 1-Byte Offset with Post Increment
Opcode Map
0
High Byte of Opcode in Hexadecimal
Low Byte of Opcode in Hexadecimal
0
5 Cycles BRSET0 Opcode Mnemonic 3 DIR Number of Bytes / Addressing Mode
Central Processor Unit (CPU)
MC68HC908AP A-Family Data Sheet, Rev. 2 70 Freescale Semiconductor
Chapter 5 Oscillator (OSC)
5.1 Introduction
The oscillator module consist of three types of oscillator circuits: * Internal oscillator * RC oscillator * 1MHz to 8MHz crystal (x-tal) oscillator The reference clock for the CGM and other MCU sub-systems is selected by programming the mask option register located at $FFCF. The reference clock for the timebase module (TBM) is selected by the two bits, OSCCLK1 and OSCCLK0, in the CONFIG2 register. The internal oscillator runs continuously after a POR or reset, and is always available. The RC and crystal oscillator cannot run concurrently; one is disabled while the other is selected; because the RC and x-tal circuits share the same OSC1 pin. NOTE The oscillator circuits are powered by the on-chip VREG regulator, therefore, the output swing on OSC1 and OSC2 is from VSS to VREG. Figure 5-1. shows the block diagram of the oscillator module.
5.2 Clock Selection
Reference clocks are selectable for the following sub-systems: * CGMXCLK and CGMRCLK -- Reference clock for clock generator module (CGM) and other MCU sub-systems other than TBM and COP. This is the main reference clock for the MCU. * OSCCLK -- Reference clock for timebase module (TBM).
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 71
Oscillator (OSC)
To CGM and others To CGM PLL CGMXCLK CGMRCLK To TBM OSCCLK
MOR OSCSEL1 MUX OSCSEL0 X RC I X RC I MUX
CONFIG2 OSCCLK1 OSCCLK0
To SIM (and COP) XCLK RCCLK ICLK
X-TAL OSCILLATOR
RC OSCILLATOR
INTERNAL OSCILLATOR
BUS CLOCK
From SIM
OSC1
OSC2
Figure 5-1. Oscillator Module Block Diagram
5.2.1 CGM Reference Clock Selection
The clock generator module (CGM) reference clock (CGMXCLK) is the reference clock input to the MCU. It is selected by programming two bits in a FLASH memory location; the mask option register (MOR), at $FFCF. See 3.5 Mask Option Register (MOR).
Address: Read: Write: Reset: Erased:
$FFCF Bit 7 OSCSEL1 6 OSCSEL0 5 R 4 R 3 R 2 R 1 R Bit 0 R
Unaffected by reset 1 R 1 = Reserved 1 1 1 1 1 1
Figure 5-2. Mask Option Register (MOR)
MC68HC908AP A-Family Data Sheet, Rev. 2 72 Freescale Semiconductor
Clock Selection
Table 5-1. CGMXCLK Clock Selection
OSCSEL1 0 0 OSCSEL0 0 1 CGMXCLK -- ICLK OSC2 Pin -- fBUS fBUS Inverting output of X-TAL Not used Internal oscillator generates the CGMXCLK. RC oscillator generates the CGMXCLK. Internal oscillator is available after each POR or reset. X-tal oscillator generates the CGMXCLK. Internal oscillator is available after each POR or reset. Comments
1
0
RCCLK
1
1
XCLK
NOTE The internal oscillator is a free running oscillator and is available after each POR or reset. It is turned-off in stop mode by setting the STOP_ICLKDIS bit in CONFIG2.
5.2.2 TBM Reference Clock Selection
The timebase module reference clock (OSCCLK) is selected by configuring two bits in the CONFIG2 register, at $001D. See Chapter 3 Configuration & Mask Option Registers (CONFIG & MOR).
Address: Read: Write: Reset:
$001D Bit 7 STOP_ ICLKDIS 0 6 STOP_ RCLKEN 0 5 STOP_ XCLKEN 0 4 3 2 0 0 1 0 0 Bit 0 SCIBDSRC 0
OSCCLK1 OSCCLK0 0 0
Figure 5-3. Configuration Register 2 (CONFIG2) Table 5-2. Timebase Module Reference Clock Selection
OSCCLK1 0 0 1 1 OSCCLK0 0 1 0 1 Timebase Clock Source Internal oscillator (ICLK) RC oscillator (RCCLK) X-tal oscillator (XCLK) Not used
NOTE The RCCLK or XCLK is only available if that clock is selected as the CGM reference clock, whereas the ICLK is always available.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 73
Oscillator (OSC)
5.3 Internal Oscillator
The internal oscillator clock (ICLK), with a frequency of fICLK, is a free running clock that requires no external components. It can be selected as the CGMXCLK for the CGM and MCU sub-systems; and the OSCCLK clock for the TBM. The ICLK is also the reference clock input to the computer operating properly (COP) module. Due to the simplicity of the internal oscillator, it does not have the accuracy and stability of the RC oscillator or the x-tal oscillator. Therefore, the ICLK is not suitable where an accurate bus clock is required and it should not be used as the CGMRCLK to the CGM PLL. The internal oscillator by default is always available and is free running after POR or reset. It can be turned-off in stop mode by setting the STOP_ICLKDIS bit before executing the STOP instruction. Figure 5-4 shows the logical representation of components of the internal oscillator circuitry.
From SIM SIMOSCEN To Clock Selection MUX and COP ICLK From SIM
BUS CLOCK
CONFIG2 STOP_ICLKDIS EN INTERNAL OSCILLATOR
MCU
OSC2
Figure 5-4. Internal Oscillator
MC68HC908AP A-Family Data Sheet, Rev. 2 74 Freescale Semiconductor
RC Oscillator
5.4 RC Oscillator
The RC oscillator circuit is designed for use with an external resistor and a capacitor. In its typical configuration, the RC oscillator requires two external components, one R and one C. Component values should have a tolerance of 1% or less, to obtain a clock source with less than 10% tolerance. The oscillator configuration uses two components: * CEXT * REXT
From SIM SIMOSCEN To Clock Selection MUX RCCLK From SIM BUS CLOCK
CONFIG2 STOP_RCLKEN EN RC OSCILLATOR
MCU
OSC1 See Chapter 22 for component value requirements. VREG OSC2
REXT
CEXT
Figure 5-5. RC Oscillator
5.5 X-tal Oscillator
The crystal (x-tal) oscillator circuit is designed for use with an external 1-8MHz crystal to provide an accurate clock source. In its typical configuration, the x-tal oscillator is connected in a Pierce oscillator configuration, as shown in Figure 5-6. This figure shows only the logical representation of the internal components and may not represent actual circuitry. The oscillator configuration uses five components: * Crystal, X1 * Fixed capacitor, C1 * Tuning capacitor, C2 (can also be a fixed capacitor) * Feedback resistor, RB * Series resistor, RS (optional)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 75
Oscillator (OSC)
From SIM SIMOSCEN To Clock Selection MUX XCLK
CONFIG2 STOP_XCLKEN
MCU
OSC1 RB OSC2
RS X1 See Chapter 22 for component value requirements. C1
1-8MHz
C2
Figure 5-6. Crystal Oscillator The series resistor (RS) is included in the diagram to follow strict Pierce oscillator guidelines and may not be required for all ranges of operation, especially with high frequency crystals. Refer to the crystal manufacturer's data for more information.
5.6 I/O Signals
The following paragraphs describe the oscillator I/O signals.
5.6.1 Crystal Amplifier Input Pin (OSC1)
OSC1 pin is an input to the crystal oscillator amplifier or the input to the RC oscillator circuit.
5.6.2 Crystal Amplifier Output Pin (OSC2)
When the x-tal oscillator is selected, OSC2 pin is the output of the crystal oscillator inverting amplifier. When the RC oscillator or internal oscillator is selected, OSC2 pin is the output of the internal bus clock.
5.6.3 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal from the system integration module (SIM) enables/disables the x-tal oscillator, the RC-oscillator, or the internal oscillator circuit.
MC68HC908AP A-Family Data Sheet, Rev. 2 76 Freescale Semiconductor
Low Power Modes
5.6.4 CGM Oscillator Clock (CGMXCLK)
The CGMXCLK clock is output from the x-tal oscillator, RC oscillator or the internal oscillator. This clock drives to CGM and other MCU sub-systems.
5.6.5 CGM Reference Clock (CGMRCLK)
This is buffered signal of CGMXCLK, it is used by the CGM as the phase-locked-loop (PLL) reference clock.
5.6.6 Oscillator Clock to Time Base Module (OSCCLK)
The OSCCLK is the reference clock that drives the timebase module. See Chapter 10 Timebase Module (TBM).
5.7 Low Power Modes
The WAIT and STOP instructions put the MCU in low-power consumption standby modes.
5.7.1 Wait Mode
The WAIT instruction has no effect on the oscillator module. CGMXCLK continues to drive to the clock generator module, and OSCCLK continues to drive the timebase module.
5.7.2 Stop Mode
The STOP instruction disables the x-tal or the RC oscillator circuit, and hence the CGMXCLK clock stops running. For continuous x-tal or RC oscillator operation in stop mode, set the STOP_XCLKEN (for x-tal) or STOP_RCLKEN (for RC) bit to logic 1 before entering stop mode. The internal oscillator clock continues operation in stop mode. It can be disabled by setting the STOP_ICLKDIS bit to logic 1 before entering stop mode.
5.8 Oscillator During Break Mode
The oscillator continues to drive CGMXCLK when the device enters the break state.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 77
Oscillator (OSC)
MC68HC908AP A-Family Data Sheet, Rev. 2 78 Freescale Semiconductor
Chapter 6 Clock Generator Module (CGM)
6.1 Introduction
This section describes the clock generator module (CGM). The CGM generates the base clock signal, CGMOUT, which is based on either the oscillator clock divided by two or the divided phase-locked loop (PLL) clock, CGMPCLK, divided by two. CGMOUT is the clock from which the SIM derives the system clocks, including the bus clock, which is at a frequency of CGMOUT 2. The PLL is a frequency generator designed for use with a crystal (1 to 8 MHz) to generate a base frequency and dividing to a maximum bus frequency of 8MHz.
6.2 Features
Features of the CGM include: * Phase-locked loop with output frequency in integer multiples of an integer dividend of the crystal reference * Low-frequency crystal operation with low-power operation and high-output frequency resolution * Programmable prescaler for power-of-two increases in frequency * Programmable hardware voltage-controlled oscillator (VCO) for low-jitter operation * Automatic bandwidth control mode for low-jitter operation * Automatic frequency lock detector * CPU interrupt on entry or exit from locked condition * Configuration register bit to allow oscillator operation during stop mode
6.3 Functional Description
The CGM consists of three major sub-modules: * Oscillator module -- The oscillator module generates the constant reference frequency clock, CGMRCLK (buffered CGMXCLK). * Phase-locked loop (PLL) -- The PLL generates the programmable VCO frequency clock, CGMVCLK, and the divided VCO clock, CGMPCLK. * Base clock selector circuit -- This software-controlled circuit selects either CGMXCLK divided by two or the divided VCO clock, CGMPCLK, divided by two as the base clock, CGMOUT. The SIM derives the system clocks from either CGMOUT or CGMXCLK. Figure 6-1 shows the structure of the CGM. Figure 6-2 is a summary of the CGM registers.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 79
Clock Generator Module (CGM)
OSCILLATOR (OSC) MODULE See Chapter 5 Oscillator (OSC). INTERNAL OSCILLATOR RC OSCILLATOR CRYSTAL OSCILLATOR MUX
OSC2
ICLK OSCCLK CGMXCLK CGMRCLK
To SIM (and COP) To Timebase Module (TBM) To ADC
OSC1
OSCSEL[1:0] OSCCLK[1:0] SIMOSCEN From SIM
PHASE-LOCKED LOOP (PLL)
CGMRDV
REFERENCE DIVIDER R
CGMRCLK BCS CLOCK SELECT CIRCUIT
A
CGMOUT S* To SIM SIMDIV2 From SIM
/2
B1
RDS[3:0]
VDDA
CGMXFC
VSSA VPR[1:0] VRS[7:0] L 2E
*WHEN S = 1, CGMOUT = B
CGMPCLK
PHASE DETECTOR
LOOP FILTER
VOLTAGE CONTROLLED OSCILLATOR PLL ANALOG
LOCK DETECTOR
AUTOMATIC MODE CONTROL
INTERRUPT CONTROL
CGMINT To SIM
LOCK MUL[11:0] N CGMVDV FREQUENCY DIVIDER
AUTO
ACQ
PLLIE PRE[1:0] 2P FREQUENCY DIVIDER
PLLF
CGMVCLK
Figure 6-1. CGM Block Diagram
MC68HC908AP A-Family Data Sheet, Rev. 2 80 Freescale Semiconductor
Functional Description
Addr. $0036
Register Name PLL Control Register (PTCL) PLL Bandwidth Control Register (PBWC) PLL Multiplier Select Register High (PMSH) PLL Multiplier Select Register Low (PMSL) PLL VCO Range Select Register (PMRS) PLL Reference Divider Select Register (PMDS) Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset:
Bit 7 PLLIE 0 AUTO 0 0 0 MUL7 0 VRS7 0 0 0
6 PLLF 0 LOCK 0 0 0 MUL6 1 VRS6 1 0
5 PLLON 1 ACQ 0 0 0 MUL5 0 VRS5 0 0
4 BCS 0 0 0 0 0 MUL4 0 VRS4 0 0 0
3 PRE1 0 0 0 MUL11 0 MUL3 0 VRS3 0 RDS3 0 R
2 PRE0 0 0 0 MUL10 0 MUL2 0 VRS2 0 RDS2 0 = Reserved
1 VPR1 0 0 0 MUL9 0 MUL1 0 VRS1 0 RDS1 0
Bit 0 VPR0 0 R
$0037
$0038
MUL8 0 MUL0 0 VRS0 0 RDS0 1
$0039
$003A
$003B
0 0 = Unimplemented
NOTES: 1. When AUTO = 0, PLLIE is forced clear and is read-only. 2. When AUTO = 0, PLLF and LOCK read as clear. 3. When AUTO = 1, ACQ is read-only. 4. When PLLON = 0 or VRS7:VRS0 = $0, BCS is forced clear and is read-only. 5. When PLLON = 1, the PLL programming register is read-only. 6. When BCS = 1, PLLON is forced set and is read-only.
Figure 6-2. CGM I/O Register Summary
6.3.1 Oscillator Module
The oscillator module provides two clock outputs CGMXCLK and CGMRCLK to the CGM module. CGMXCLK when selected, is driven to SIM module to generate the system bus clock. CGMRCLK is used by the phase-lock-loop to provide a higher frequency system bus clock. The oscillator module also provides the reference clock for the timebase module (TBM). See Chapter 5 Oscillator (OSC) for detailed oscillator circuit description. See Chapter 10 Timebase Module (TBM) for detailed description on TBM.
6.3.2 Phase-Locked Loop Circuit (PLL)
The PLL is a frequency generator that can operate in either acquisition mode or tracking mode, depending on the accuracy of the output frequency. The PLL can change between acquisition and tracking modes either automatically or manually.
6.3.3 PLL Circuits
The PLL consists of these circuits: * Voltage-controlled oscillator (VCO) * Reference divider * Frequency pre-scaler * Modulo VCO frequency divider
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 81
Clock Generator Module (CGM)
* * *
Phase detector Loop filter Lock detector
The operating range of the VCO is programmable for a wide range of frequencies and for maximum immunity to external noise, including supply and CGMXFC noise. The VCO frequency is bound to a range from roughly one-half to twice the center-of-range frequency, fVRS. Modulating the voltage on the CGMXFC pin changes the frequency within this range. By design, fVRS is equal to the nominal center-of-range frequency, fNOM, (125 kHz) times a linear factor, L, and a power-of-two factor, E, or (L x 2E)fNOM. CGMRCLK is the PLL reference clock, a buffered version of CGMXCLK. CGMRCLK runs at a frequency, fRCLK, and is fed to the PLL through a programmable modulo reference divider, which divides fRCLK by a factor, R. The divider's output is the final reference clock, CGMRDV, running at a frequency, fRDV = fRCLK/R. With an external crystal (1MHz-8MHz), always set R = 1 for specified performance. With an external high-frequency clock source, use R to divide the external frequency to between 1MHz and 8MHz. The VCO's output clock, CGMVCLK, running at a frequency, fVCLK, is fed back through a programmable pre-scaler divider and a programmable modulo divider. The pre-scaler divides the VCO clock by a power-of-two factor P (the CGMPCLK) and the modulo divider reduces the VCO clock by a factor, N. The dividers' output is the VCO feedback clock, CGMVDV, running at a frequency, fVDV = fVCLK/(N x 2P). (See 6.3.6 Programming the PLL for more information.) The phase detector then compares the VCO feedback clock, CGMVDV, with the final reference clock, CGMRDV. A correction pulse is generated based on the phase difference between the two signals. The loop filter then slightly alters the DC voltage on the external capacitor connected to CGMXFC based on the width and direction of the correction pulse. The filter can make fast or slow corrections depending on its mode, described in 6.3.4 Acquisition and Tracking Modes. The value of the external capacitor and the reference frequency determines the speed of the corrections and the stability of the PLL. The lock detector compares the frequencies of the VCO feedback clock, CGMVDV, and the final reference clock, CGMRDV. Therefore, the speed of the lock detector is directly proportional to the final reference frequency, fRDV. The circuit determines the mode of the PLL and the lock condition based on this comparison.
6.3.4 Acquisition and Tracking Modes
The PLL filter is manually or automatically configurable into one of two operating modes: * Acquisition mode -- In acquisition mode, the filter can make large frequency corrections to the VCO. This mode is used at PLL start up or when the PLL has suffered a severe noise hit and the VCO frequency is far off the desired frequency. When in acquisition mode, the ACQ bit is clear in the PLL bandwidth control register. (See 6.5.2 PLL Bandwidth Control Register.) * Tracking mode -- In tracking mode, the filter makes only small corrections to the frequency of the VCO. PLL jitter is much lower in tracking mode, but the response to noise is also slower. The PLL enters tracking mode when the VCO frequency is nearly correct, such as when the PLL is selected as the base clock source. (See 6.3.8 Base Clock Selector Circuit.) The PLL is automatically in tracking mode when not in acquisition mode or when the ACQ bit is set.
MC68HC908AP A-Family Data Sheet, Rev. 2 82 Freescale Semiconductor
Functional Description
6.3.5 Manual and Automatic PLL Bandwidth Modes
The PLL can change the bandwidth or operational mode of the loop filter manually or automatically. Automatic mode is recommended for most users. In automatic bandwidth control mode (AUTO = 1), the lock detector automatically switches between acquisition and tracking modes. Automatic bandwidth control mode also is used to determine when the VCO clock, CGMVCLK, is safe to use as the source for the base clock, CGMOUT. (See 6.5.2 PLL Bandwidth Control Register.) If PLL interrupts are enabled, the software can wait for a PLL interrupt request and then check the LOCK bit. If interrupts are disabled, software can poll the LOCK bit continuously (during PLL start-up, usually) or at periodic intervals. In either case, when the LOCK bit is set, the VCO clock is safe to use as the source for the base clock. (See 6.3.8 Base Clock Selector Circuit.) If the VCO is selected as the source for the base clock and the LOCK bit is clear, the PLL has suffered a severe noise hit and the software must take appropriate action, depending on the application. (See 6.6 Interrupts for information and precautions on using interrupts.) The following conditions apply when the PLL is in automatic bandwidth control mode: * The ACQ bit (See 6.5.2 PLL Bandwidth Control Register.) is a read-only indicator of the mode of the filter. (See 6.3.4 Acquisition and Tracking Modes.) * The ACQ bit is set when the VCO frequency is within a certain tolerance and is cleared when the VCO frequency is out of a certain tolerance. (See 6.8 Acquisition/Lock Time Specifications for more information.) * The LOCK bit is a read-only indicator of the locked state of the PLL. * The LOCK bit is set when the VCO frequency is within a certain tolerance and is cleared when the VCO frequency is out of a certain tolerance. (See 6.8 Acquisition/Lock Time Specifications for more information.) * CPU interrupts can occur if enabled (PLLIE = 1) when the PLL's lock condition changes, toggling the LOCK bit. (See 6.5.1 PLL Control Register.) The PLL also may operate in manual mode (AUTO = 0). Manual mode is used by systems that do not require an indicator of the lock condition for proper operation. Such systems typically operate well below fBUSMAX. The following conditions apply when in manual mode: * ACQ is a writable control bit that controls the mode of the filter. Before turning on the PLL in manual mode, the ACQ bit must be clear. * Before entering tracking mode (ACQ = 1), software must wait a given time, tACQ (See 6.8 Acquisition/Lock Time Specifications.), after turning on the PLL by setting PLLON in the PLL control register (PCTL). * Software must wait a given time, tAL, after entering tracking mode before selecting the PLL as the clock source to CGMOUT (BCS = 1). * The LOCK bit is disabled. * CPU interrupts from the CGM are disabled.
6.3.6 Programming the PLL
The following procedure shows how to program the PLL. NOTE The round function in the following equations means that the real number should be rounded to the nearest integer number.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 83
Clock Generator Module (CGM)
1. Choose the desired bus frequency, fBUSDES, or the desired VCO frequency, fVCLKDES; and then solve for the other. The relationship between fBUS and fVCLK is governed by the equation:
f VCLK = 2 x f CGMPCLK = 2 x 4
P P
x fBUS
where P is the power of two multiplier, and can be 0, 1, 2, or 3 2. Choose a practical PLL reference frequency, fRCLK, and the reference clock divider, R. Typically, the reference is 4MHz and R = 1. Frequency errors to the PLL are corrected at a rate of fRCLK/R. For stability and lock time reduction, this rate must be as fast as possible. The VCO frequency must be an integer multiple of this rate. The relationship between the VCO frequency, fVCLK, and the reference frequency, fRCLK, is
2N f VCLK = ----------- ( f RCLK ) R
P
where N is the integer range multiplier, between 1 and 4095. In cases where desired bus frequency has some tolerance, choose fRCLK to a value determined either by other module requirements (such as modules which are clocked by CGMXCLK), cost requirements, or ideally, as high as the specified range allows. See Chapter 22 Electrical Specifications. Choose the reference divider, R = 1. When the tolerance on the bus frequency is tight, choose fRCLK to an integer divisor of fBUSDES, and R = 1. If fRCLK cannot meet this requirement, use the following equation to solve for R with practical choices of fRCLK, and choose the fRCLK that gives the lowest R.
f VCLKDES f VCLKDES R = round R MAX x ------------------------- - integer ------------------------- f RCLK f RCLK
3. Calculate N:
R x f VCLKDES N = round ------------------------------------ P f x2
RCLK
4. Calculate and verify the adequacy of the VCO and bus frequencies fVCLK and fBUS.
2N f VCLK = ----------- ( f RCLK ) R f
P
f BUS =
VCLK ---------P
2 x4
MC68HC908AP A-Family Data Sheet, Rev. 2 84 Freescale Semiconductor
Functional Description
5. Select the VCO's power-of-two range multiplier E, according to this table:
Frequency Range 0 < fVCLK < 9,830,400 9,830,400 fVCLK < 19,660,800 19,660,800 fVCLK < 39,321,600 NOTE: Do not program E to a value of 3. E 0 1 2
6. Select a VCO linear range multiplier, L, where fNOM = 125kHz
f VCLK L = round -------------------------- 2E x f
NOM
7. Calculate and verify the adequacy of the VCO programmed center-of-range frequency, fVRS. The center-of-range frequency is the midpoint between the minimum and maximum frequencies attainable by the PLL.
f VRS = ( L x 2 )f NOM
E
For proper operation,
f NOM x 2 f VRS - f VCLK -------------------------2
E
8. Verify the choice of P, R, N, E, and L by comparing fVCLK to fVRS and fVCLKDES. For proper operation, fVCLK must be within the application's tolerance of fVCLKDES, and fVRS must be as close as possible to fVCLK. NOTE Exceeding the recommended maximum bus frequency or VCO frequency can crash the MCU. 9. Program the PLL registers accordingly: a. In the PRE bits of the PLL control register (PCTL), program the binary equivalent of P. b. In the VPR bits of the PLL control register (PCTL), program the binary equivalent of E. c. In the PLL multiplier select register low (PMSL) and the PLL multiplier select register high (PMSH), program the binary equivalent of N. d. In the PLL VCO range select register (PMRS), program the binary coded equivalent of L. e. In the PLL reference divider select register (PMDS), program the binary coded equivalent of R. NOTE The values for P, E, N, L, and R can only be programmed when the PLL is off (PLLON = 0). Table 6-1 provides numeric examples (numbers are in hexadecimal notation):
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 85
Clock Generator Module (CGM)
Table 6-1. Numeric Examples
CGMVCLK 32 MHz 16 MHz 32 MHz 16 MHz 32 MHz 16 MHz 29.4912 MHz 19.6608 MHz CGMPCLK 32 MHz 16 MHz 32 MHz 16 MHz 32 MHz 16 MHz 29.4912 MHz 19.6608 MHz fBUS 8.0 MHz 4.0 MHz 8.0 MHz 4.0 MHz 8.0 MHz 4.0 MHz 7.3728 MHz 4.9152 MHz fRCLK 2 MHz 2 MHz 4 MHz 4 MHz 8 MHz 8 MHz 4.9152 MHz 4.9152 MHz R 1 1 1 1 1 1 1 1 N 10 8 8 4 4 2 6 4 P 0 0 0 0 0 0 0 0 E 2 1 2 1 2 1 2 2 L 40 40 40 40 40 40 3C 27
6.3.7 Special Programming Exceptions
The programming method described in 6.3.6 Programming the PLL does not account for three possible exceptions. A value of 0 for R, N, or L is meaningless when used in the equations given. To account for these exceptions: * A 0 value for R or N is interpreted exactly the same as a value of 1. * A 0 value for L disables the PLL and prevents its selection as the source for the base clock. (See 6.3.8 Base Clock Selector Circuit.)
6.3.8 Base Clock Selector Circuit
This circuit is used to select either the oscillator clock, CGMXCLK, or the divided VCO clock, CGMPCLK, as the source of the base clock, CGMOUT. The two input clocks go through a transition control circuit that waits up to three CGMXCLK cycles and three CGMPCLK cycles to change from one clock source to the other. During this time, CGMOUT is held in stasis. The output of the transition control circuit is then divided by two to correct the duty cycle. Therefore, the bus clock frequency, which is one-half of the base clock frequency, is one-fourth the frequency of the selected clock (CGMXCLK or CGMPCLK). The BCS bit in the PLL control register (PCTL) selects which clock drives CGMOUT. The divided VCO clock cannot be selected as the base clock source if the PLL is not turned on. The PLL cannot be turned off if the divided VCO clock is selected. The PLL cannot be turned on or off simultaneously with the selection or deselection of the divided VCO clock. The divided VCO clock also cannot be selected as the base clock source if the factor L is programmed to a 0. This value would set up a condition inconsistent with the operation of the PLL, so that the PLL would be disabled and the oscillator clock would be forced as the source of the base clock.
6.3.9 CGM External Connections
In its typical configuration, the CGM requires up to four external components. Figure 6-3 shows the external components for the PLL: * Bypass capacitor, CBYP * Filter network
MC68HC908AP A-Family Data Sheet, Rev. 2 86 Freescale Semiconductor
I/O Signals
Care should be taken with PCB routing in order to minimize signal cross talk and noise. (See 6.8 Acquisition/Lock Time Specifications for routing information, filter network and its effects on PLL performance.)
MCU
CGMXFC VSSA VDDA VDD 1 k CBYP 0.1 F
10 nF
0.22 F
Note: Filter network in box can be replaced with a 0.47F capacitor, but will degrade stability.
Figure 6-3. CGM External Connections
6.4 I/O Signals
The following paragraphs describe the CGM I/O signals.
6.4.1 External Filter Capacitor Pin (CGMXFC)
The CGMXFC pin is required by the loop filter to filter out phase corrections. An external filter network is connected to this pin. (See Figure 6-3.) NOTE To prevent noise problems, the filter network should be placed as close to the CGMXFC pin as possible, with minimum routing distances and no routing of other signals across the network.
6.4.2 PLL Analog Power Pin (VDDA)
VDDA is a power pin used by the analog portions of the PLL. Connect the VDDA pin to the same voltage potential as the VDD pin. NOTE Route VDDA carefully for maximum noise immunity and place bypass capacitors as close as possible to the package.
6.4.3 PLL Analog Ground Pin (VSSA)
VSSA is a ground pin used by the analog portions of the PLL. Connect the VSSA pin to the same voltage potential as the VSS pin.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 87
Clock Generator Module (CGM)
NOTE Route VSSA carefully for maximum noise immunity and place bypass capacitors as close as possible to the package.
6.4.4 Oscillator Output Frequency Signal (CGMXCLK)
CGMXCLK is the oscillator output signal. It runs at the full speed of the oscillator, and is generated directly from the crystal oscillator circuit, the RC oscillator circuit, or the internal oscillator circuit.
6.4.5 CGM Reference Clock (CGMRCLK)
CGMRCLK is a buffered version of CGMXCLK, this clock is the reference clock for the phase-locked-loop circuit.
6.4.6 CGM VCO Clock Output (CGMVCLK)
CGMVCLK is the clock output from the VCO.
6.4.7 CGM Base Clock Output (CGMOUT)
CGMOUT is the clock output of the CGM. This signal goes to the SIM, which generates the MCU clocks. CGMOUT is a 50 percent duty cycle clock running at twice the bus frequency. CGMOUT is software programmable to be either the oscillator output, CGMXCLK, divided by two or the divided VCO clock, CGMPCLK, divided by two.
6.4.8 CGM CPU Interrupt (CGMINT)
CGMINT is the interrupt signal generated by the PLL lock detector.
6.5 CGM Registers
The following registers control and monitor operation of the CGM: * PLL control register (PCTL) (See 6.5.1 PLL Control Register.) * PLL bandwidth control register (PBWC) (See 6.5.2 PLL Bandwidth Control Register.) * PLL multiplier select registers (PMSH and PMSL) (See 6.5.3 PLL Multiplier Select Registers.) * PLL VCO range select register (PMRS) (See 6.5.4 PLL VCO Range Select Register.) * PLL reference divider select register (PMDS) (See 6.5.5 PLL Reference Divider Select Register.)
MC68HC908AP A-Family Data Sheet, Rev. 2 88 Freescale Semiconductor
CGM Registers
6.5.1 PLL Control Register
The PLL control register (PCTL) contains the interrupt enable and flag bits, the on/off switch, the base clock selector bit, the prescaler bits, and the VCO power-of-two range selector bits.
Address: Read: Write: Reset: $0036 Bit 7 PLLIE 0 6 PLLF 0 5 PLLON 1 4 BCS 0 3 PRE1 0 2 PRE0 0 1 VPR1 0 Bit 0 VPR0 0
= Unimplemented
Figure 6-4. PLL Control Register (PCTL) PLLIE -- PLL Interrupt Enable Bit This read/write bit enables the PLL to generate an interrupt request when the LOCK bit toggles, setting the PLL flag, PLLF. When the AUTO bit in the PLL bandwidth control register (PBWC) is clear, PLLIE cannot be written and reads as logic 0. Reset clears the PLLIE bit. 1 = PLL interrupts enabled 0 = PLL interrupts disabled PLLF -- PLL Interrupt Flag Bit This read-only bit is set whenever the LOCK bit toggles. PLLF generates an interrupt request if the PLLIE bit also is set. PLLF always reads as logic 0 when the AUTO bit in the PLL bandwidth control register (PBWC) is clear. Clear the PLLF bit by reading the PLL control register. Reset clears the PLLF bit. 1 = Change in lock condition 0 = No change in lock condition NOTE Do not inadvertently clear the PLLF bit. Any read or read-modify-write operation on the PLL control register clears the PLLF bit. PLLON -- PLL On Bit This read/write bit activates the PLL and enables the VCO clock, CGMVCLK. PLLON cannot be cleared if the VCO clock is driving the base clock, CGMOUT (BCS = 1). (See 6.3.8 Base Clock Selector Circuit.) Reset sets this bit so that the loop can stabilize as the MCU is powering up. 1 = PLL on 0 = PLL off BCS -- Base Clock Select Bit This read/write bit selects either the oscillator output, CGMXCLK, or the divided VCO clock, CGMPCLK, as the source of the CGM output, CGMOUT. CGMOUT frequency is one-half the frequency of the selected clock. BCS cannot be set while the PLLON bit is clear. After toggling BCS, it may take up to three CGMXCLK and three CGMPCLK cycles to complete the transition from one source clock to the other. During the transition, CGMOUT is held in stasis. (See 6.3.8 Base Clock Selector Circuit.) Reset clears the BCS bit. 1 = CGMPCLK divided by two drives CGMOUT 0 = CGMXCLK divided by two drives CGMOUT
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 89
Clock Generator Module (CGM)
NOTE PLLON and BCS have built-in protection that prevents the base clock selector circuit from selecting the VCO clock as the source of the base clock if the PLL is off. Therefore, PLLON cannot be cleared when BCS is set, and BCS cannot be set when PLLON is clear. If the PLL is off (PLLON = 0), selecting CGMPCLK requires two writes to the PLL control register. (See 6.3.8 Base Clock Selector Circuit.) PRE1 and PRE0 -- Prescaler Program Bits These read/write bits control a prescaler that selects the prescaler power-of-two multiplier, P. (See 6.3.3 PLL Circuits and 6.3.6 Programming the PLL.) PRE1 and PRE0 cannot be written when the PLLON bit is set. Reset clears these bits. These prescaler bits affects the relationship between the VCO clock and the final system bus clock. Table 6-2. PRE1 and PRE0 Programming
PRE1 and PRE0 00 01 10 11 P 0 1 2 3 Prescaler Multiplier 1 2 4 8
VPR1 and VPR0 -- VCO Power-of-Two Range Select Bits These read/write bits control the VCO's hardware power-of-two range multiplier E that, in conjunction with L (See 6.3.3 PLL Circuits, 6.3.6 Programming the PLL, and 6.5.4 PLL VCO Range Select Register.) controls the hardware center-of-range frequency, fVRS. VPR1:VPR0 cannot be written when the PLLON bit is set. Reset clears these bits. Table 6-3. VPR1 and VPR0 Programming
VPR1 and VPR0 00 01 10 NOTE: Do not program E to a value of 3. E 0 1 2 VCO Power-of-Two Range Multiplier 1 2 4
MC68HC908AP A-Family Data Sheet, Rev. 2 90 Freescale Semiconductor
CGM Registers
6.5.2 PLL Bandwidth Control Register
The PLL bandwidth control register (PBWC): * Selects automatic or manual (software-controlled) bandwidth control mode * Indicates when the PLL is locked * In automatic bandwidth control mode, indicates when the PLL is in acquisition or tracking mode * In manual operation, forces the PLL into acquisition or tracking mode
Address: Read: Write: Reset:
$0037 Bit 7 AUTO 0 6 LOCK 0 5 ACQ 0 4 0 0 3 0 0 R 2 0 0 = Reserved 1 0 0 Bit 0 R
= Unimplemented
Figure 6-5. PLL Bandwidth Control Register (PBWCR) AUTO -- Automatic Bandwidth Control Bit This read/write bit selects automatic or manual bandwidth control. When initializing the PLL for manual operation (AUTO = 0), clear the ACQ bit before turning on the PLL. Reset clears the AUTO bit. 1 = Automatic bandwidth control 0 = Manual bandwidth control LOCK -- Lock Indicator Bit When the AUTO bit is set, LOCK is a read-only bit that becomes set when the VCO clock, CGMVCLK, is locked (running at the programmed frequency). When the AUTO bit is clear, LOCK reads as logic 0 and has no meaning. The write one function of this bit is reserved for test, so this bit must always be written a 0. Reset clears the LOCK bit. 1 = VCO frequency correct or locked 0 = VCO frequency incorrect or unlocked ACQ -- Acquisition Mode Bit When the AUTO bit is set, ACQ is a read-only bit that indicates whether the PLL is in acquisition mode or tracking mode. When the AUTO bit is clear, ACQ is a read/write bit that controls whether the PLL is in acquisition or tracking mode. In automatic bandwidth control mode (AUTO = 1), the last-written value from manual operation is stored in a temporary location and is recovered when manual operation resumes. Reset clears this bit, enabling acquisition mode. 1 = Tracking mode 0 = Acquisition mode
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 91
Clock Generator Module (CGM)
6.5.3 PLL Multiplier Select Registers
The PLL multiplier select registers (PMSH and PMSL) contain the programming information for the modulo feedback divider.
Address: Read: Write: Reset: 0 0 0 0 = Unimplemented $0038 Bit 7 0 6 0 5 0 4 0 3 MUL11 0 2 MUL10 0 1 MUL9 0 Bit 0 MUL8 0
Figure 6-6. PLL Multiplier Select Register High (PMSH)
Address: Read: Write: Reset: $0039 Bit 7 MUL7 0 6 MUL6 1 5 MUL5 0 4 MUL4 0 3 MUL3 0 2 MUL2 0 1 MUL1 0 Bit 0 MUL0 0
Figure 6-7. PLL Multiplier Select Register Low (PMSL) MUL[11:0] -- Multiplier Select Bits These read/write bits control the modulo feedback divider that selects the VCO frequency multiplier N. (See 6.3.3 PLL Circuits and 6.3.6 Programming the PLL.) A value of $0000 in the multiplier select registers configure the modulo feedback divider the same as a value of $0001. Reset initializes the registers to $0040 for a default multiply value of 64. NOTE The multiplier select bits have built-in protection such that they cannot be written when the PLL is on (PLLON = 1).
6.5.4 PLL VCO Range Select Register
The PLL VCO range select register (PMRS) contains the programming information required for the hardware configuration of the VCO.
Address: Read: Write: Reset: $003A Bit 7 VRS7 0 6 VRS6 1 5 VRS5 0 4 VRS4 0 3 VRS3 0 2 VRS2 0 1 VRS1 0 Bit 0 VRS0 0
Figure 6-8. PLL VCO Range Select Register (PMRS) VRS[7:0] -- VCO Range Select Bits These read/write bits control the hardware center-of-range linear multiplier L which, in conjunction with E (See 6.3.3 PLL Circuits, 6.3.6 Programming the PLL, and 6.5.1 PLL Control Register.), controls the hardware center-of-range frequency, fVRS. VRS[7:0] cannot be written when the PLLON bit in the PCTL is set. (See 6.3.7 Special Programming Exceptions.) A value of $00 in the VCO range select
MC68HC908AP A-Family Data Sheet, Rev. 2 92 Freescale Semiconductor
Interrupts
register disables the PLL and clears the BCS bit in the PLL control register (PCTL). (See 6.3.8 Base Clock Selector Circuit and 6.3.7 Special Programming Exceptions.). Reset initializes the register to $40 for a default range multiply value of 64. NOTE The VCO range select bits have built-in protection such that they cannot be written when the PLL is on (PLLON = 1) and such that the VCO clock cannot be selected as the source of the base clock (BCS = 1) if the VCO range select bits are all clear. The PLL VCO range select register must be programmed correctly. Incorrect programming can result in failure of the PLL to achieve lock.
6.5.5 PLL Reference Divider Select Register
The PLL reference divider select register (PMDS) contains the programming information for the modulo reference divider.
Address: Read: Write: Reset: 0 0 0 0 $003B Bit 7 0 6 0 5 0 4 0 3 RDS3 0 2 RDS2 0 1 RDS1 0 Bit 0 RDS0 1
= Unimplemented
Figure 6-9. PLL Reference Divider Select Register (PMDS) RDS[3:0] -- Reference Divider Select Bits These read/write bits control the modulo reference divider that selects the reference division factor, R. (See 6.3.3 PLL Circuits and 6.3.6 Programming the PLL.) RDS[3:0] cannot be written when the PLLON bit in the PCTL is set. A value of $00 in the reference divider select register configures the reference divider the same as a value of $01. (See 6.3.7 Special Programming Exceptions.) Reset initializes the register to $01 for a default divide value of 1. NOTE The reference divider select bits have built-in protection such that they cannot be written when the PLL is on (PLLON = 1). NOTE The default divide value of 1 is recommended for all applications.
6.6 Interrupts
When the AUTO bit is set in the PLL bandwidth control register (PBWC), the PLL can generate a CPU interrupt request every time the LOCK bit changes state. The PLLIE bit in the PLL control register (PCTL) enables CPU interrupts from the PLL. PLLF, the interrupt flag in the PCTL, becomes set whether interrupts are enabled or not. When the AUTO bit is clear, CPU interrupts from the PLL are disabled and PLLF reads as logic 0. Software should read the LOCK bit after a PLL interrupt request to see if the request was due to an entry into lock or an exit from lock. When the PLL enters lock, the divided VCO clock, CGMPCLK, divided by two can be selected as the CGMOUT source by setting BCS in the PCTL. When the PLL exits lock, the
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 93
Clock Generator Module (CGM)
VCO clock frequency is corrupt, and appropriate precautions should be taken. If the application is not frequency sensitive, interrupts should be disabled to prevent PLL interrupt service routines from impeding software performance or from exceeding stack limitations. NOTE Software can select the CGMPCLK divided by two as the CGMOUT source even if the PLL is not locked (LOCK = 0). Therefore, software should make sure the PLL is locked before setting the BCS bit.
6.7 Special Modes
The WAIT instruction puts the MCU in low power-consumption standby modes.
6.7.1 Wait Mode
The WAIT instruction does not affect the CGM. Before entering wait mode, software can disengage and turn off the PLL by clearing the BCS and PLLON bits in the PLL control register (PCTL) to save power. Less power-sensitive applications can disengage the PLL without turning it off, so that the PLL clock is immediately available at WAIT exit. This would be the case also when the PLL is to wake the MCU from wait mode, such as when the PLL is first enabled and waiting for LOCK or LOCK is lost.
6.7.2 Stop Mode
The STOP instruction disables the PLL analog circuits and no clock will be driven out of the VCO. When entering stop mode with the VCO clock (CGMPCLK) selected, before executing the STOP instruction: 1. Set the oscillator stop mode enable bit (STOP_XCLKEN in CONFIG2) if continuos clock is required in stop mode. 2. Clear the BCS bit to select CGMXCLK as CGMOUT. On exit from stop mode: 1. Set the PLLON bit if cleared before entering stop mode. 2. Wait for PLL to lock by checking the LOCK bit. 3. Set BCS bit to select CGMPCLK as CGMOUT.
6.7.3 CGM During Break Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state. (See 7.7.3 SIM Break Flag Control Register.) To allow software to clear status bits during a break interrupt, write a logic 1 to the BCFE bit. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state. To protect the PLLF bit during the break state, write a logic 0 to the BCFE bit. With BCFE at logic 0 (its default state), software can read and write the PLL control register during the break state without affecting the PLLF bit.
MC68HC908AP A-Family Data Sheet, Rev. 2 94 Freescale Semiconductor
Acquisition/Lock Time Specifications
6.8 Acquisition/Lock Time Specifications
The acquisition and lock times of the PLL are, in many applications, the most critical PLL design parameters. Proper design and use of the PLL ensures the highest stability and lowest acquisition/lock times.
6.8.1 Acquisition/Lock Time Definitions
Typical control systems refer to the acquisition time or lock time as the reaction time, within specified tolerances, of the system to a step input. In a PLL, the step input occurs when the PLL is turned on or when it suffers a noise hit. The tolerance is usually specified as a percent of the step input or when the output settles to the desired value plus or minus a percent of the frequency change. Therefore, the reaction time is constant in this definition, regardless of the size of the step input. For example, consider a system with a 5 percent acquisition time tolerance. If a command instructs the system to change from 0Hz to 1MHz, the acquisition time is the time taken for the frequency to reach 1MHz 50kHz. 50kHz = 5% of the 1MHz step input. If the system is operating at 1MHz and suffers a -100kHz noise hit, the acquisition time is the time taken to return from 900kHz to 1MHz 5kHz. 5kHz = 5% of the 100kHz step input. Other systems refer to acquisition and lock times as the time the system takes to reduce the error between the actual output and the desired output to within specified tolerances. Therefore, the acquisition or lock time varies according to the original error in the output. Minor errors may not even be registered. Typical PLL applications prefer to use this definition because the system requires the output frequency to be within a certain tolerance of the desired frequency regardless of the size of the initial error.
6.8.2 Parametric Influences on Reaction Time
Acquisition and lock times are designed to be as short as possible while still providing the highest possible stability. These reaction times are not constant, however. Many factors directly and indirectly affect the acquisition time. The most critical parameter which affects the reaction times of the PLL is the reference frequency, fRDV. This frequency is the input to the phase detector and controls how often the PLL makes corrections. For stability, the corrections must be small compared to the desired frequency, so several corrections are required to reduce the frequency error. Therefore, the slower the reference the longer it takes to make these corrections. This parameter is under user control via the choice of crystal frequency fXCLK and the R value programmed in the reference divider. (See 6.3.3 PLL Circuits, 6.3.6 Programming the PLL, and 6.5.5 PLL Reference Divider Select Register.) Another critical parameter is the external filter network. The PLL modifies the voltage on the VCO by adding or subtracting charge from capacitors in this network. Therefore, the rate at which the voltage changes for a given frequency error (thus change in charge) is proportional to the capacitance. The size of the capacitor also is related to the stability of the PLL. If the capacitor is too small, the PLL cannot make small enough adjustments to the voltage and the system cannot lock. If the capacitor is too large, the PLL may not be able to adjust the voltage in a reasonable time. (See 6.8.3 Choosing a Filter.) Also important is the operating voltage potential applied to VDDA. The power supply potential alters the characteristics of the PLL. A fixed value is best. Variable supplies, such as batteries, are acceptable if they vary within a known range at very slow speeds. Noise on the power supply is not acceptable, because it causes small frequency errors which continually change the acquisition time of the PLL.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 95
Clock Generator Module (CGM)
Temperature and processing also can affect acquisition time because the electrical characteristics of the PLL change. The part operates as specified as long as these influences stay within the specified limits. External factors, however, can cause drastic changes in the operation of the PLL. These factors include noise injected into the PLL through the filter capacitor, filter capacitor leakage, stray impedances on the circuit board, and even humidity or circuit board contamination.
6.8.3 Choosing a Filter
As described in 6.8.2 Parametric Influences on Reaction Time, the external filter network is critical to the stability and reaction time of the PLL. The PLL is also dependent on reference frequency and supply voltage. Either of the filter networks in Figure 6-10 is recommended when using a 4MHz reference clock (CGMRCLK). Figure 6-10 (a) is used for applications requiring better stability. Figure 6-10 (b) is used in low-cost applications where stability is not critical.
CGMXFC CGMXFC
1 k 10 nF 0.22 F 0.22 F
VSSA
VSSA
(a)
(b)
Figure 6-10. PLL Filter
MC68HC908AP A-Family Data Sheet, Rev. 2 96 Freescale Semiconductor
Chapter 7 System Integration Module (SIM)
7.1 Introduction
This section describes the system integration module (SIM). Together with the CPU, the SIM controls all MCU activities. A block diagram of the SIM is shown in Figure 7-1. Figure 7-2 is a summary of the SIM input/output (I/O) registers. The SIM is a system state controller that coordinates CPU and exception timing. The SIM is responsible for: * Bus clock generation and control for CPU and peripherals: - Stop/wait/reset/break entry and recovery - Internal clock control * Master reset control, including power-on reset (POR) and COP timeout * Interrupt control: - Acknowledge timing - Arbitration control timing - Vector address generation * CPU enable/disable timing * Modular architecture expandable to 128 interrupt sources Table 7-1 shows the internal signal names used in this section. Table 7-1. Signal Name Conventions
Signal Name ICLK CGMXCLK CGMVCLK, CGMPCLK CGMOUT IAB IDB PORRST IRST R/W Internal oscillator clock Selected oscillator clock from oscillator module PLL output and the divided PLL output CGMPCLK-based or oscillator-based clock output from CGM module (Bus clock = CGMOUT / 2) Internal address bus Internal data bus Signal from the power-on reset module to the SIM Internal reset signal Read/write signal Description
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 97
System Integration Module (SIM)
MODULE STOP MODULE WAIT STOP/WAIT CONTROL CPU STOP (FROM CPU) CPU WAIT (FROM CPU) SIMOSCEN (TO CGM, OSC) SIM COUNTER COP CLOCK
ICLK (FROM OSC) CGMOUT (FROM CGM) /2
VDD INTERNAL PULLUP DEVICE RESET PIN LOGIC
CLOCK CONTROL
CLOCK GENERATORS
INTERNAL CLOCKS
POR CONTROL RESET PIN CONTROL SIM RESET STATUS REGISTER MASTER RESET CONTROL
LVI (FROM LVI MODULE) ILLEGAL OPCODE (FROM CPU) ILLEGAL ADDRESS (FROM ADDRESS MAP DECODERS) COP (FROM COP MODULE)
RESET
INTERRUPT CONTROL AND PRIORITY DECODE
INTERRUPT SOURCES CPU INTERFACE
Figure 7-1. SIM Block Diagram
Addr. Register Name Bit 7 R 0 POR 1 BCFE 0 IF6 R 0 6 R 0 PIN 0 R IF5 R 0 5 R 0 COP 0 R IF4 R 0 4 R 0 ILOP 0 R IF3 R 0 3 R 0 ILAD 0 R IF2 R 0 2 R 0 MODRST 0 R IF1 R 0 Read: SIM Break Status Register $FE00 Write: (SBSR) Reset:
Note: Writing a logic 0 clears SBSW. $FE01
1 SBSW NOTE 0 LVI 0 R 0 R 0
Bit 0 R 0 0 0 R 0 R 0
Read: SIM Reset Status Register Write: (SRSR) POR: Read: SIM Break Flag Control $FE03 Write: Register (SBFCR) Reset: Read: Interrupt Status Register 1 $FE04 Write: (INT1) Reset:
Figure 7-2. SIM I/O Register Summary
MC68HC908AP A-Family Data Sheet, Rev. 2 98 Freescale Semiconductor
SIM Bus Clock Control and Generation
Read: Interrupt Status Register 2 Write: (INT2) Reset: Read: Interrupt Status Register 3 $FE06 Write: (INT3) Reset:
$FE05
IF14 R 0 0 R 0
IF13 IF12 R R 0 0 IF21 IF20 R R 0 0 = Unimplemented
IF11 R 0 IF19 R 0
IF10 R 0 IF18 R 0
IF9 R 0 IF17 R 0
IF8 R 0 IF16 R 0
IF7 R 0 IF15 R 0
Figure 7-2. SIM I/O Register Summary
7.2 SIM Bus Clock Control and Generation
The bus clock generator provides system clock signals for the CPU and peripherals on the MCU. The system clocks are generated from an incoming clock, CGMOUT, as shown in Figure 7-3. This clock can come from either an external oscillator or from the on-chip PLL. (See Chapter 6 Clock Generator Module (CGM).)
OSC2 OSCILLATOR (OSC) MODULE OSC1
OSCCLK
TO TBM
CGMXCLK
TO TIM, ADC
ICLK
SIM COUNTER SYSTEM INTEGRATION MODULE
STOP MODE CLOCK ENABLE SIGNALS FROM CONFIG2
SIMOSCEN IT12 TO REST OF MCU IT23 TO REST OF MCU
CGMRCLK CGMOUT PHASE-LOCKED LOOP (PLL)
/2
BUS CLOCK GENERATORS
SIMDIV2
PTB0 MONITOR MODE USER MODE
CGMVCLK
TO PWM
Figure 7-3. CGM Clock Signals
7.2.1 Bus Timing
In user mode, the internal bus frequency is either the oscillator output (CGMXCLK) divided by four or the divided PLL output (CGMPCLK) divided by four.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 99
System Integration Module (SIM)
7.2.2 Clock Start-up from POR or LVI Reset
When the power-on reset module or the low-voltage inhibit module generates a reset, the clocks to the CPU and peripherals are inactive and held in an inactive phase until after the 4096 ICLK cycle POR timeout has completed. The RST pin is driven low by the SIM during this entire period. The IBUS clocks start upon completion of the timeout.
7.2.3 Clocks in Stop Mode and Wait Mode
Upon exit from stop mode by an interrupt, break, or reset, the SIM allows ICLK to clock the SIM counter. The CPU and peripheral clocks do not become active until after the stop delay timeout. This timeout is selectable as 4096 or 32 ICLK cycles. (See 7.6.2 Stop Mode.) In wait mode, the CPU clocks are inactive. The SIM also produces two sets of clocks for other modules. Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode. Some modules can be programmed to be active in wait mode.
7.3 Reset and System Initialization
The MCU has these reset sources: * Power-on reset module (POR) * External reset pin (RST) * Computer operating properly module (COP) * Low-voltage inhibit module (LVI) * Illegal opcode * Illegal address All of these resets produce the vector $FFFE:$FFFF ($FEFE:$FEFF in monitor mode) and assert the internal reset signal (IRST). IRST causes all registers to be returned to their default values and all modules to be returned to their reset states. An internal reset clears the SIM counter (see 7.4 SIM Counter), but an external reset does not. Each of the resets sets a corresponding bit in the SIM reset status register (SRSR). (See 7.7 SIM Registers.)
7.3.1 External Pin Reset
The RST pin circuit includes an internal pull-up device. Pulling the asynchronous RST pin low halts all processing. The PIN bit of the SIM reset status register (SRSR) is set as long as RST is held low for a minimum of 67 ICLK cycles, assuming that neither the POR nor the LVI was the source of the reset. See Table 7-2 for details. Figure 7-4 shows the relative timing. Table 7-2. PIN Bit Set Timing
Reset Type POR/LVI All others Number of Cycles Required to Set PIN 4163 (4096 + 64 + 3) 67 (64 + 3)
MC68HC908AP A-Family Data Sheet, Rev. 2 100 Freescale Semiconductor
Reset and System Initialization
ICLK
RST
IAB
PC
VECT H VECT L
Figure 7-4. External Reset Timing
7.3.2 Active Resets from Internal Sources
All internal reset sources actively pull the RST pin low for 32 ICLK cycles to allow resetting of external peripherals. The internal reset signal IRST continues to be asserted for an additional 32 cycles (see Figure 7-5). An internal reset can be caused by an illegal address, illegal opcode, COP timeout, LVI, or POR (see Figure 7-6). NOTE For LVI or POR resets, the SIM cycles through 4096 + 32 ICLK cycles during which the SIM forces the RST pin low. The internal reset signal then follows the sequence from the falling edge of RST shown in Figure 7-5.
IRST
RST
RST PULLED LOW BY MCU 32 CYCLES 32 CYCLES
ICLK
IAB
VECTOR HIGH
Figure 7-5. Internal Reset Timing The COP reset is asynchronous to the bus clock.
ILLEGAL ADDRESS RST ILLEGAL OPCODE RST COPRST LVI POR
INTERNAL RESET
Figure 7-6. Sources of Internal Reset The active reset feature allows the part to issue a reset to peripherals and other chips within a system built around the MCU. 7.3.2.1 Power-On Reset When power is first applied to the MCU, the power-on reset module (POR) generates a pulse to indicate that power-on has occurred. The external reset pin (RST) is held low while the SIM counter counts out 4096 + 32 ICLK cycles. Thirty-two ICLK cycles later, the CPU and memories are released from reset to allow the reset vector sequence to occur.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 101
System Integration Module (SIM)
At power-on, these events occur: * A POR pulse is generated. * The internal reset signal is asserted. * The SIM enables CGMOUT. * Internal clocks to the CPU and modules are held inactive for 4096 ICLK cycles to allow stabilization of the oscillator. * The pin is driven low during the oscillator stabilization time. * The POR bit of the SIM reset status register (SRSR) is set and all other bits in the register are cleared.
OSC1
PORRST 4096 CYCLES ICLK 32 CYCLES 32 CYCLES
CGMOUT
RST IRST
IAB
$FFFE
$FFFF
Figure 7-7. POR Recovery 7.3.2.2 Computer Operating Properly (COP) Reset An input to the SIM is reserved for the COP reset signal. The overflow of the COP counter causes an internal reset and sets the COP bit in the SIM reset status register (SRSR). The SIM actively pulls down the RST pin for all internal reset sources. To prevent a COP module timeout, write any value to location $FFFF. Writing to location $FFFF clears the COP counter and bits 12 through 5 of the SIM counter. The SIM counter output, which occurs at least every 213 - 24 ICLK cycles, drives the COP counter. The COP should be serviced as soon as possible out of reset to guarantee the maximum amount of time before the first timeout. The COP module is disabled if the RST pin or the IRQ1 pin is held at VTST while the MCU is in monitor mode. The COP module can be disabled only through combinational logic conditioned with the high voltage signal on the RST or the IRQ1 pin. This prevents the COP from becoming disabled as a result of external noise. During a break state, VTST on the RST pin disables the COP module. 7.3.2.3 Illegal Opcode Reset The SIM decodes signals from the CPU to detect illegal instructions. An illegal instruction sets the ILOP bit in the SIM reset status register (SRSR) and causes a reset.
MC68HC908AP A-Family Data Sheet, Rev. 2 102 Freescale Semiconductor
SIM Counter
If the stop enable bit, STOP, in the mask option register is logic 0, the SIM treats the STOP instruction as an illegal opcode and causes an illegal opcode reset. The SIM actively pulls down the RST pin for all internal reset sources. 7.3.2.4 Illegal Address Reset An opcode fetch from an unmapped address generates an illegal address reset. The SIM verifies that the CPU is fetching an opcode prior to asserting the ILAD bit in the SIM reset status register (SRSR) and resetting the MCU. A data fetch from an unmapped address does not generate a reset. The SIM actively pulls down the RST pin for all internal reset sources. 7.3.2.5 Low-Voltage Inhibit (LVI) Reset The low-voltage inhibit module (LVI) asserts its output to the SIM when the VDD voltage falls to the LVITRIPF voltage. The LVI bit in the SIM reset status register (SRSR) is set, and the external reset pin (RST) is held low while the SIM counter counts out 4096 + 32 ICLK cycles. Thirty-two ICLK cycles later, the CPU is released from reset to allow the reset vector sequence to occur. The SIM actively pulls down the RST pin for all internal reset sources. 7.3.2.6 Monitor Mode Entry Module Reset The monitor mode entry module reset asserts its output to the SIM when monitor mode is entered in the condition where the reset vectors are blank ($FF). (See Chapter 8 Monitor ROM (MON).) When MODRST gets asserted, an internal reset occurs. The SIM actively pulls down the RST pin for all internal reset sources.
7.4 SIM Counter
The SIM counter is used by the power-on reset module (POR) and in stop mode recovery to allow the oscillator time to stabilize before enabling the internal bus (IBUS) clocks. The SIM counter also serves as a prescaler for the computer operating properly module (COP). The SIM counter overflow supplies the clock for the COP module. The SIM counter is 13 bits long and is clocked by the falling edge of CGMXCLK.
7.4.1 SIM Counter During Power-On Reset
The power-on reset module (POR) detects power applied to the MCU. At power-on, the POR circuit asserts the signal PORRST. Once the SIM is initialized, it enables the clock generation module (CGM) to drive the bus clock state machine.
7.4.2 SIM Counter During Stop Mode Recovery
The SIM counter also is used for stop mode recovery. The STOP instruction clears the SIM counter. After an interrupt, break, or reset, the SIM senses the state of the short stop recovery bit, SSREC, in the mask option register. If the SSREC bit is a logic 1, then the stop recovery is reduced from the normal delay of 4096 CGMXCLK cycles down to 32 CGMXCLK cycles. This is ideal for applications using canned oscillators that do not require long start-up times from stop mode. External crystal applications should use the full stop recovery time, that is, with SSREC cleared.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 103
System Integration Module (SIM)
7.4.3 SIM Counter and Reset States
External reset has no effect on the SIM counter. (See 7.6.2 Stop Mode for details.) The SIM counter is free-running after all reset states. (See 7.3.2 Active Resets from Internal Sources for counter control and internal reset recovery sequences.)
7.5 Exception Control
Normal, sequential program execution can be changed in three different ways: * Interrupts: - Maskable hardware CPU interrupts - Non-maskable software interrupt instruction (SWI) * Reset * Break interrupts
7.5.1 Interrupts
At the beginning of an interrupt, the CPU saves the CPU register contents on the stack and sets the interrupt mask (I bit) to prevent additional interrupts. At the end of an interrupt, the RTI instruction recovers the CPU register contents from the stack so that normal processing can resume. Figure 7-8 shows interrupt entry timing, and Figure 7-9 shows interrupt recovery timing.
MODULE INTERRUPT I-BIT IAB IDB R/W DUMMY DUMMY SP SP - 1 SP - 2 X SP - 3 A SP - 4 CCR VECT H VECT L START ADDR OPCODE
PC - 1[7:0] PC - 1[15:8]
V DATA H
V DATA L
Figure 7-8. Interrupt Entry Timing
MODULE INTERRUPT I-BIT IAB IDB R/W SP - 4 CCR SP - 3 A SP - 2 X SP - 1 SP PC PC + 1 OPCODE OPERAND
PC - 1[15:8] PC - 1[7:0]
Figure 7-9. Interrupt Recovery Timing Interrupts are latched, and arbitration is performed in the SIM at the start of interrupt processing. The arbitration result is a constant that the CPU uses to determine which vector to fetch. Once an interrupt is latched by the SIM, no other interrupt can take precedence, regardless of priority, until the latched interrupt is serviced (or the I bit is cleared). (See Figure 7-10.)
MC68HC908AP A-Family Data Sheet, Rev. 2 104 Freescale Semiconductor
Exception Control
FROM RESET
BREAK I BIT SET? INTERRUPT? NO YES
YES
I-BIT SET? NO IRQ1 INTERRUPT? NO YES
AS MANY INTERRUPTS AS EXIST ON CHIP
STACK CPU REGISTERS SET I-BIT LOAD PC WITH INTERRUPT VECTOR
FETCH NEXT INSTRUCTION
SWI INSTRUCTION? NO RTI INSTRUCTION? NO
YES
YES
UNSTACK CPU REGISTERS
EXECUTE INSTRUCTION
Figure 7-10. Interrupt Processing 7.5.1.1 Hardware Interrupts A hardware interrupt does not stop the current instruction. Processing of a hardware interrupt begins after completion of the current instruction. When the current instruction is complete, the SIM checks all pending hardware interrupts. If interrupts are not masked (I bit clear in the condition code register) and if the corresponding interrupt enable bit is set, the SIM proceeds with interrupt processing; otherwise, the next instruction is fetched and executed. If more than one interrupt is pending at the end of an instruction execution, the highest priority interrupt is serviced first. Figure 7-11 demonstrates what happens when two interrupts are pending. If an interrupt is pending upon exit from the original interrupt service routine, the pending interrupt is serviced before the LDA instruction is executed.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 105
System Integration Module (SIM)
CLI LDA #$FF BACKGROUND ROUTINE
INT1
PSHH INT1 INTERRUPT SERVICE ROUTINE PULH RTI
INT2
PSHH INT2 INTERRUPT SERVICE ROUTINE PULH RTI
Figure 7-11. Interrupt Recognition Example The LDA opcode is prefetched by both the INT1 and INT2 RTI instructions. However, in the case of the INT1 RTI prefetch, this is a redundant operation. NOTE To maintain compatibility with the M6805 Family, the H register is not pushed on the stack during interrupt entry. If the interrupt service routine modifies the H register or uses the indexed addressing mode, software should save the H register and then restore it prior to exiting the routine. 7.5.1.2 SWI Instruction The SWI instruction is a non-maskable instruction that causes an interrupt regardless of the state of the interrupt mask (I bit) in the condition code register. NOTE A software interrupt pushes PC onto the stack. A software interrupt does not push PC - 1, as a hardware interrupt does.
7.5.2 Interrupt Status Registers
The flags in the interrupt status registers identify maskable interrupt sources. Table 7-3 summarizes the interrupt sources and the interrupt status register flags that they set. The interrupt status registers can be useful for debugging.
MC68HC908AP A-Family Data Sheet, Rev. 2 106 Freescale Semiconductor
Exception Control
7.5.2.1 Interrupt Status Register 1
Address: Read: Write: Reset: $FE04 Bit 7 IF6 R 0 R 6 IF5 R 0 = Reserved 5 IF4 R 0 4 IF3 R 0 3 IF2 R 0 2 IF1 R 0 1 0 R 0 Bit 0 0 R 0
Figure 7-12. Interrupt Status Register 1 (INT1) IF6-IF1 -- Interrupt Flags 6-1 These flags indicate the presence of interrupt requests from the sources shown in Table 7-3. 1 = Interrupt request present 0 = No interrupt request present Bit 0 and Bit 1 -- Always read 0 7.5.2.2 Interrupt Status Register 2
Address: Read: Write: Reset: $FE05 Bit 7 IF14 R 0 R 6 IF13 R 0 = Reserved 5 IF12 R 0 4 IF11 R 0 3 IF10 R 0 2 IF9 R 0 1 IF8 R 0 Bit 0 IF7 R 0
Figure 7-13. Interrupt Status Register 2 (INT2) IF14-IF7 -- Interrupt Flags 14-7 These flags indicate the presence of interrupt requests from the sources shown in Table 7-3. 1 = Interrupt request present 0 = No interrupt request present 7.5.2.3 Interrupt Status Register 3
Address: Read: Write: Reset: $FE06 Bit 7 0 R 0 R 6 IF21 R 0 = Reserved 5 IF20 R 0 4 IF19 R 0 3 IF18 R 0 2 IF17 R 0 1 IF16 R 0 Bit 0 IF15 R 0
Figure 7-14. Interrupt Status Register 3 (INT3) IF21-IF15 -- Interrupt Flags 21-15 These flags indicate the presence of an interrupt request from the source shown in Table 7-3. 1 = Interrupt request present 0 = No interrupt request present
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 107
System Integration Module (SIM)
Table 7-3. Interrupt Sources
Priority Lowest INT Flag -- IF21 IF20 IF19 IF18 IF17 IF16 IF15 IF14 IF13 IF12 IF11 IF10 IF9 IF8 IF7 IF6 IF5
IF4 IF3 IF2 IF1 -- Highest --
Vector Address $FFD0 $FFD1 $FFD2 $FFD3 $FFD4 $FFD5 $FFD6 $FFD7 $FFD8 $FFD9 $FFDA $FFDB $FFDC $FFDD $FFDE $FFDF $FFE0 $FFE1 $FFE2 $FFE3 $FFE4 $FFE5 $FFE6 $FFE7 $FFE8 $FFE9 $FFEA $FFEB $FFEC $FFED $FFEE $FFEF $FFF0 $FFF1 $FFF2 $FFF3 $FFF4 $FFF5 $FFF6 $FFF7 $FFF8 $FFF9 $FFFA $FFFB $FFFC $FFFD $FFFE $FFFF
Interrupt Source Reserved Timebase Infrared SCI Transmit Infrared SCI Receive Infrared SCI Error SPI Transmit SPI Receive ADC Conversion Complete Keyboard SCI Transmit SCI Receive SCI Error MMIIC TIM2 Overflow TIM2 Channel 1 TIM2 Channel 0 TIM1 Overflow TIM1 Channel 1 TIM1 Channel 0 PLL IRQ2 IRQ1 SWI Reset
MC68HC908AP A-Family Data Sheet, Rev. 2 108 Freescale Semiconductor
Low-Power Modes
7.5.3 Reset
All reset sources always have equal and highest priority and cannot be arbitrated.
7.5.4 Break Interrupts
The break module can stop normal program flow at a software-programmable break point by asserting its break interrupt output. (See Chapter 21 Break Module (BRK).) The SIM puts the CPU into the break state by forcing it to the SWI vector location. Refer to the break interrupt subsection of each module to see how each module is affected by the break state.
7.5.5 Status Flag Protection in Break Mode
The SIM controls whether status flags contained in other modules can be cleared during break mode. The user can select whether flags are protected from being cleared by properly initializing the break clear flag enable bit (BCFE) in the SIM break flag control register (SBFCR). Protecting flags in break mode ensures that set flags will not be cleared while in break mode. This protection allows registers to be freely read and written during break mode without losing status flag information. Setting the BCFE bit enables the clearing mechanisms. Once cleared in break mode, a flag remains cleared even when break mode is exited. Status flags with a 2-step clearing mechanism -- for example, a read of one register followed by the read or write of another -- are protected, even when the first step is accomplished prior to entering break mode. Upon leaving break mode, execution of the second step will clear the flag as normal.
7.6 Low-Power Modes
Executing the WAIT or STOP instruction puts the MCU in a low power-consumption mode for standby situations. The SIM holds the CPU in a non-clocked state. The operation of each of these modes is described in the following subsections. Both STOP and WAIT clear the interrupt mask (I) in the condition code register, allowing interrupts to occur.
7.6.1 Wait Mode
In wait mode, the CPU clocks are inactive while the peripheral clocks continue to run. Figure 7-15 shows the timing for wait mode entry. A module that is active during wait mode can wake up the CPU with an interrupt if the interrupt is enabled. Stacking for the interrupt begins one cycle after the WAIT instruction during which the interrupt occurred. In wait mode, the CPU clocks are inactive. Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode. Some modules can be programmed to be active in wait mode. Wait mode also can be exited by a reset or break. A break interrupt during wait mode sets the SIM break stop/wait bit, SBSW, in the SIM break status register (SBSR). If the COP disable bit, COPD, in the mask option register is logic 0, then the computer operating properly module (COP) is enabled and remains active in wait mode.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 109
System Integration Module (SIM)
IAB WAIT ADDR WAIT ADDR + 1 SAME SAME
IDB
PREVIOUS DATA
NEXT OPCODE
SAME
SAME
R/W
NOTE: Previous data can be operand data or the WAIT opcode, depending on the last instruction.
Figure 7-15. Wait Mode Entry Timing Figure 7-16 and Figure 7-17 show the timing for WAIT recovery.
IAB $6E0B $6E0C $00FF $00FE $00FD $00FC
IDB
$A6
$A6
$A6
$01
$0B
$6E
EXITSTOPWAIT
NOTE: EXITSTOPWAIT = RST pin OR CPU interrupt OR break interrupt
Figure 7-16. Wait Recovery from Interrupt or Break
32 CYCLES IAB $6E0B 32 CYCLES RST VCT H RST VCT L
IDB
$A6
$A6
$A6
RST
ICLK
Figure 7-17. Wait Recovery from Internal Reset
7.6.2 Stop Mode
In stop mode, the SIM counter is reset and the system clocks are disabled. An interrupt request from a module can cause an exit from stop mode. Stacking for interrupts begins after the selected stop recovery time has elapsed. Reset or break also causes an exit from stop mode. The SIM disables the clock generator module output (CGMOUT) in stop mode, stopping the CPU and peripherals. Stop recovery time is selectable using the SSREC bit in the configuration register 1 (CONFIG1). If SSREC is set, stop recovery is reduced from the normal delay of 4096 ICLK cycles down to 32. This is ideal for applications using canned oscillators that do not require long start-up times from stop mode. NOTE External crystal applications should use the full stop recovery time by clearing the SSREC bit.
MC68HC908AP A-Family Data Sheet, Rev. 2 110 Freescale Semiconductor
SIM Registers
A break interrupt during stop mode sets the SIM break stop/wait bit (SBSW) in the SIM break status register (SBSR). The SIM counter is held in reset from the execution of the STOP instruction until the beginning of stop recovery. It is then used to time the recovery period. Figure 7-18 shows stop mode entry timing. NOTE To minimize stop current, all pins configured as inputs should be driven to a logic 1 or logic 0.
CPUSTOP
IAB
STOP ADDR
STOP ADDR + 1
SAME
SAME
IDB
PREVIOUS DATA
NEXT OPCODE
SAME
SAME
R/W
NOTE: Previous data can be operand data or the STOP opcode, depending on the last instruction.
Figure 7-18. Stop Mode Entry Timing
STOP RECOVERY PERIOD ICLK
INT/BREAK
IAB
STOP +1
STOP + 2
STOP + 2
SP
SP - 1
SP - 2
SP - 3
Figure 7-19. Stop Mode Recovery from Interrupt or Break
7.7 SIM Registers
The SIM has three memory-mapped registers: * SIM Break Status Register (SBSR) -- $FE00 * SIM Reset Status Register (SRSR) -- $FE01 * SIM Break Flag Control Register (SBFCR) -- $FE03
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 111
System Integration Module (SIM)
7.7.1 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a break caused an exit from stop mode or wait mode.
Address: Read: Write: Reset: Note: Writing a logic 0 clears SBSW. R = Reserved $FE00 Bit 7 R 6 R 5 R 4 R 3 R 2 R 1 SBSW Note 0 Bit 0 R
Figure 7-20. SIM Break Status Register (SBSR) SBSW -- Break Wait Bit This status bit is set when a break interrupt causes an exit from wait mode or stop mode. Clear SBSW by writing a logic 0 to it. Reset clears SBSW. 1 = Stop mode or wait mode was exited by break interrupt 0 = Stop mode or wait mode was not exited by break interrupt SBSW can be read within the break interrupt routine. The user can modify the return address on the stack by subtracting 1 from it. The following code is an example.
This code works if the H register has been pushed onto the stack in the break service routine software. This code should be executed at the end of the break service routine software. HIBYTE LOBYTE EQU EQU BRCLR TST BNE DEC DOLO RETURN DEC PULH RTI 5 6 SBSW,SBSR, RETURN LOBYTE,SP DOLO HIBYTE,SP LOBYTE,SP ; See if wait mode or stop mode was exited by ; break. ;If RETURNLO is not zero, ;then just decrement low byte. ;Else deal with high byte, too. ;Point to WAIT/STOP opcode. ;Restore H register.
If not SBSW, do RTI
MC68HC908AP A-Family Data Sheet, Rev. 2 112 Freescale Semiconductor
SIM Registers
7.7.2 SIM Reset Status Register
This register contains six flags that show the source of the last reset provided all previous reset status bits have been cleared. Clear the SIM reset status register by reading it. A power-on reset sets the POR bit and clears all other bits in the register.
Address: Read: Write: Reset: 1 0 0 0 0 0 0 0 = Unimplemented $FE01 Bit 7 POR 6 PIN 5 COP 4 ILOP 3 ILAD 2 1 LVI Bit 0 0
MODRST
Figure 7-21. SIM Reset Status Register (SRSR) POR -- Power-On Reset Bit 1 = Last reset caused by POR circuit 0 = Read of SRSR PIN -- External Reset Bit 1 = Last reset caused by external reset pin (RST) 0 = POR or read of SRSR COP -- Computer Operating Properly Reset Bit 1 = Last reset caused by COP counter 0 = POR or read of SRSR ILOP -- Illegal Opcode Reset Bit 1 = Last reset caused by an illegal opcode 0 = POR or read of SRSR ILAD -- Illegal Address Reset Bit (opcode fetches only) 1 = Last reset caused by an opcode fetch from an illegal address 0 = POR or read of SRSR MODRST -- Monitor Mode Entry Module Reset Bit 1 = Last reset caused by monitor mode entry when vector locations $FFFE and $FFFF are $FF after POR while IRQ1 = VDD 0 = POR or read of SRSR LVI -- Low-Voltage Inhibit Reset Bit 1 = Last reset caused by the LVI circuit 0 = POR or read of SRSR
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 113
System Integration Module (SIM)
7.7.3 SIM Break Flag Control Register
The SIM break control register contains a bit that enables software to clear status bits while the MCU is in a break state.
Address: Read: Write: Reset: $FE03 Bit 7 BCFE 0 R = Reserved 6 R 5 R 4 R 3 R 2 R 1 R Bit 0 R
Figure 7-22. SIM Break Flag Control Register (SBFCR) BCFE -- Break Clear Flag Enable Bit This read/write bit enables software to clear status bits by accessing status registers while the MCU is in a break state. To clear status bits during the break state, the BCFE bit must be set. 1 = Status bits clearable during break 0 = Status bits not clearable during break
MC68HC908AP A-Family Data Sheet, Rev. 2 114 Freescale Semiconductor
Chapter 8 Monitor ROM (MON)
8.1 Introduction
This section describes the monitor ROM (MON) and the monitor mode entry methods. The monitor ROM allows complete testing of the MCU through a single-wire interface with a host computer. Monitor mode entry can be achieved without use of the higher test voltage, VTST, as long as vector addresses $FFFE and $FFFF are blank, thus reducing the hardware requirements for in-circuit programming. In addition, to simplify user coding, routines are also stored in the monitor ROM area for FLASH memory program /erase.
8.2 Features
Features of the monitor ROM include: * Normal user-mode pin functionality * One pin dedicated to serial communication between monitor ROM and host computer * Standard mark/space non-return-to-zero (NRZ) communication with host computer * Execution of code in RAM or FLASH * FLASH memory security feature(1) * 959 bytes monitor ROM code size ($FC00-$FDFF and $FE10-$FFCE) * Monitor mode entry without high voltage, VTST, if reset vector is blank ($FFFE and $FFFF contain $FF) * Standard monitor mode entry if high voltage, VTST, is applied to IRQ1 * Resident routines for in-circuit programming
8.3 Functional Description
The monitor ROM receives and executes commands from a host computer. Figure 8-1 shows an example circuit used to enter monitor mode and communicate with a host computer via a standard RS-232 interface. Simple monitor commands can access any memory address. In monitor mode, the MCU can execute code downloaded into RAM by a host computer while most MCU pins retain normal operating mode functions. All communication between the host computer and the MCU is through the PTA0 pin. A level-shifting and multiplexing interface is required between PTA0 and the host computer. PTA0 is used in a wired-OR configuration and requires a pullup resistor.
1. No security feature is absolutely secure. However, Freescale's strategy is to make reading or copying the FLASH difficult for unauthorized users. MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 115
Monitor ROM (MON)
RST 0.1 F VDD
HC908AP
VDD
0.1 F
VDDA VREFH VREG VREFL
VREG
4.9152MHz/9.8304MHz (50% DUTY) OSC1 10k 0.01 F
VSS VSSA CGMXFC
MUST BE USED IF SW2 IS AT POSITION C. CONNECT TO OSC1, WITH OSC2 UNCONNECTED. EXT OSC 4.9152MHz 6-30 pF MAX232 1 1 F + 3 4 1 F + 5 C2- DB9 2 3 5 7 8 10 9 74HC125 3 2 1 10k A (SEE NOTE 2) NOTES: 1. Monitor mode entry method: SW2: Position C -- High voltage entry (VTST); must use external OSC Bus clock depends on SW1 (note 2). SW2: Position D -- Reset vector must be blank ($FFFE:$FFFF = $FF) Bus clock = 1.2288MHz. 2. Affects high voltage entry to monitor mode only (SW2 at position C): SW1: Position A -- Bus clock = OSC1 4 SW1: Position B -- Bus clock = OSC1 2 5. See Table 22-4 for VTST voltage level requirements. B 10 k V- 6 + 1 F 74HC125 5 6 4 VDD 10 k C1+ VCC 16 + 15 + 2 1 F 1 F VTST VDD 1k 8.5 V D XTAL CIRCUIT C VDD 6-30 pF 1M
0.033 F
OSC1
OSC2
C1- C2+
GND V+
SW2
(SEE NOTE 1) IRQ1 VDD
10k PTA0 VDD 10k SW1 PTA1 PTB0 PTA2 10 k
Figure 8-1. Monitor Mode Circuit
MC68HC908AP A-Family Data Sheet, Rev. 2 116 Freescale Semiconductor
Functional Description
8.3.1 Entering Monitor Mode
Table 8-1 shows the pin conditions for entering monitor mode. As specified in the table, monitor mode may be entered after a POR and will allow communication at 9600 baud provided one of the following sets of conditions is met: 1. If $FFFE and $FFFF do not contain $FF (programmed state): - The external clock is 4.9152 MHz with PTB0 low or 9.8304 MHz with PTB0 high - IRQ1 = VTST 2. If $FFFE and $FFFF both contain $FF (erased state): - The external clock is 9.8304 MHz - IRQ1 = VDD (this can be implemented through the internal IRQ1 pullup If VTST is applied to IRQ1 and PTB0 is low upon monitor mode entry (above condition set 1), the bus frequency is a divide-by-two of the input clock. If PTB0 is high with VTST applied to IRQ1 upon monitor mode entry, the bus frequency will be a divide-by-four of the input clock. Holding the PTB0 pin low when entering monitor mode causes a bypass of a divide-by-two stage at the oscillator only if VTST is applied to IRQ1. In this event, the CGMOUT frequency is equal to the CGMXCLK frequency, and the OSC1 input directly generates internal bus clocks. In this case, the OSC1 signal must have a 50% duty cycle at maximum bus frequency. If entering monitor mode without high voltage on IRQ1 (above condition set 2, where applied voltage is either VDD), then all port A pin requirements and conditions, including the PTB0 frequency divisor selection, are not in effect. This is to reduce circuit requirements when performing in-circuit programming. NOTE If the reset vector is blank and monitor mode is entered, the chip will see an additional reset cycle after the initial POR reset. Once the part has been programmed, the traditional method of applying a voltage, VTST, to IRQ1 must be used to enter monitor mode. The COP module is disabled in monitor mode based on these conditions: * If monitor mode was entered as a result of the reset vector being blank (above condition set 2), the COP is always disabled regardless of the state of IRQ1 or RST. * If monitor mode was entered with VTST on IRQ1 (condition set 1), then the COP is disabled as long as VTST is applied to either IRQ1 or RST. The second condition states that as long as VTST is maintained on the IRQ1 pin after entering monitor mode, or if VTST is applied to RST after the initial reset to get into monitor mode (when VTST was applied to IRQ1), then the COP will be disabled. In the latter situation, after VTST is applied to the RST pin, VTST can be removed from the IRQ1 pin in the interest of freeing the IRQ1 for normal functionality in monitor mode. Figure 8-2 shows a simplified diagram of the monitor mode entry when the reset vector is blank and just VDD voltage is applied to the IRQ1 pin. An external oscillator of 9.8304 MHz is required for a baud rate of 9600, as the internal bus frequency is automatically set to the external frequency divided by four. Enter monitor mode with pin configuration shown in Figure 8-1 by pulling RST low and then high. The rising edge of RST latches monitor mode. Once monitor mode is latched, the values on the specified pins can change. Once out of reset, the MCU waits for the host to send eight security bytes. (See 8.4 Security.) After the security bytes, the MCU sends a break signal (10 consecutive logic 0's) to the host, indicating that it is ready to receive a command.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 117
118
Monitor ROM (MON)
Table 8-1. Monitor Mode Signal Requirements and Options
IRQ1 RST Address $FFFE/ $FFFF X PTA2 PTA1 PTA0
(1)
PTB0
External Clock(2) X
Bus Frequency 0
PLL
COP
Baud Rate 0
Comment No operation until reset goes high PTA1 and PTA2 voltages only required if IRQ1 = VTST; PTB0 determines frequency divider PTA1 and PTA2 voltages only required if IRQ1 = VTST; PTB0 determines frequency divider External frequency always divided by 4 External frequency always divided by 4 Enters user mode -- will encounter an illegal address reset
X
GND
X
X
X
X
X
Disabled
VTST(3) MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor
VDD or VTST
X
0
1
1
0
4.9152 MHz
2.4576 MHz
OFF
Disabled
9600
VTST(3)
VDD or VTST
X
0
1
1
1
9.8304 MHz
2.4576 MHz
OFF
Disabled
9600
VDD VDD VDD or GND VDD or GND
VDD VDD
Blank "$FFFF" Blank "$FFFF" Blank "$FFFF"
X X
X X
1 1
X X
4.9152 MHz 9.8304 MHz
1.2288 MHz 2.4576 MHz
OFF OFF
Disabled Disabled
4800 9600
VTST
X
X
X
X
X
--
OFF
Enabled
--
VDD or VTST
Not Blank
X
X
X
X
X
--
OFF
Enabled
--
Enters user mode
1. PTA0 = 1 if serial communication; PTA0 = 0 if parallel communication 2. External clock is derived by a 4.9152MHz crystal/off-chip oscillator or a 9.8304MHz off-chip oscillator. 3. Monitor mode entry by IRQ1= VTST, a 4.9152/9.8304 MHz off-chip oscillator must be used. The MCU internal crystal oscillator circuit is bypassed.
Functional Description
POR RESET
IS VECTOR BLANK? YES MONITOR MODE
NO
NORMAL USER MODE
EXECUTE MONITOR CODE
POR TRIGGERED? YES
NO
Figure 8-2. Low-Voltage Monitor Mode Entry Flowchart In monitor mode, the MCU uses different vectors for reset, SWI (software interrupt), and break interrupt than those for user mode. The alternate vectors are in the $FE page instead of the $FF page and allow code execution from the internal monitor firmware instead of user code. NOTE Exiting monitor mode after it has been initiated by having a blank reset vector requires a power-on reset (POR). Pulling RST low will not exit monitor mode in this situation. Table 8-2 summarizes the differences between user mode and monitor mode vectors. Table 8-2. Mode Differences (Vectors)
Functions Modes Reset Vector High $FFFE $FEFE Reset Vector Low $FFFF $FEFF Break Vector High $FFFC $FEFC Break Vector Low $FFFD $FEFD SWI Vector High $FFFC $FEFC SWI Vector Low $FFFD $FEFD
User Monitor
8.3.2 Data Format
Communication with the monitor ROM is in standard non-return-to-zero (NRZ) mark/space data format. Transmit and receive baud rates must be identical.
START BIT NEXT START STOP BIT BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
Figure 8-3. Monitor Data Format
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 119
Monitor ROM (MON)
8.3.3 Break Signal
A start bit (logic 0) followed by nine logic 0 bits is a break signal. When the monitor receives a break signal, it drives the PTA0 pin high for the duration of two bits and then echoes back the break signal.
MISSING STOP BIT 2-STOP BIT DELAY BEFORE ZERO ECHO
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Figure 8-4. Break Transaction
8.3.4 Baud Rate
The communication baud rate is controlled by the crystal frequency and the state of the PTB0 pin (when IRQ1 is set to VTST) upon entry into monitor mode. When PTB0 is high, the divide by ratio is 1024. If the PTB0 pin is at logic 0 upon entry into monitor mode, the divide by ratio is 512. If monitor mode was entered with VDD on IRQ1, then the divide by ratio is set at 1024, regardless of PTB0. This condition for monitor mode entry requires that the reset vector is blank. Table 8-3 lists external frequencies required to achieve a standard baud rate of 9600 BPS. Other standard baud rates can be accomplished using proportionally higher or lower frequency generators. If using a crystal as the clock source, be aware of the upper frequency limit that the internal clock module can handle. Table 8-3. Monitor Baud Rate Selection
External Frequency 4.9152 MHz 9.8304 MHz 9.8304 MHz IRQ1 VTST VTST VDD PTB0 0 1 X Internal Frequency 2.4576 MHz 2.4576 MHz 2.4576 MHz Baud Rate (BPS) 9600 9600 9600
8.3.5 Commands
The monitor ROM firmware uses these commands: * READ (read memory) * WRITE (write memory) * IREAD (indexed read) * IWRITE (indexed write) * READSP (read stack pointer) * RUN (run user program) The monitor ROM firmware echoes each received byte back to the PTA0 pin for error checking. An 11-bit delay at the end of each command allows the host to send a break character to cancel the command. A delay of two bit times occurs before each echo and before READ, IREAD, or READSP data is returned. The data returned by a read command appears after the echo of the last byte of the command.
MC68HC908AP A-Family Data Sheet, Rev. 2 120 Freescale Semiconductor
Functional Description
NOTE Wait one bit time after each echo before sending the next byte.
FROM HOST
READ
READ
ADDRESS HIGH
ADDRESS HIGH
ADDRESS LOW
ADDRESS LOW
DATA
4 ECHO
1
4
1
4
1
3, 2
4 RETURN
Notes: 1 = Echo delay, 2 bit times 2 = Data return delay, 2 bit times 3 = Cancel command delay, 11 bit times 4 = Wait 1 bit time before sending next byte.
Figure 8-5. Read Transaction
FROM HOST
WRITE 3 ECHO 1
WRITE 3
ADDRESS HIGH
ADDRESS HIGH
ADDRESS LOW
ADDRESS LOW
DATA
DATA
1
3
1
3
1
2, 3
Notes: 1 = Echo delay, 2 bit times 2 = Cancel command delay, 11 bit times 3 = Wait 1 bit time before sending next byte.
Figure 8-6. Write Transaction A brief description of each monitor mode command is given in Table 8-4 through Table 8-9. Table 8-4. READ (Read Memory) Command
Description Operand Data Returned Opcode Read byte from memory 2-byte address in high-byte:low-byte order Returns contents of specified address $4A Command Sequence
SENT TO MONITOR
READ
READ
ADDRESS HIGH
ADDRESS HIGH
ADDRESS LOW
ADDRESS LOW
DATA
ECHO
RETURN
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 121
Monitor ROM (MON)
Table 8-5. WRITE (Write Memory) Command
Description Operand Data Returned Opcode Write byte to memory 2-byte address in high-byte:low-byte order; low byte followed by data byte None $49 Command Sequence
FROM HOST
WRITE
WRITE
ADDRESS HIGH
ADDRESS HIGH
ADDRESS LOW
ADDRESS LOW
DATA
DATA
ECHO
Table 8-6. IREAD (Indexed Read) Command
Description Operand Data Returned Opcode Read next 2 bytes in memory from last address accessed 2-byte address in high byte:low byte order Returns contents of next two addresses $1A Command Sequence
FROM HOST
IREAD
IREAD
DATA
DATA
ECHO
RETURN
MC68HC908AP A-Family Data Sheet, Rev. 2 122 Freescale Semiconductor
Functional Description
Table 8-7. IWRITE (Indexed Write) Command
Description Operand Data Returned Opcode Write to last address accessed + 1 Single data byte None $19 Command Sequence
FROM HOST
IWRITE
IWRITE
DATA
DATA
ECHO
A sequence of IREAD or IWRITE commands can access a block of memory sequentially over the full 64-Kbyte memory map. Table 8-8. READSP (Read Stack Pointer) Command
Description Operand Data Returned Opcode Reads stack pointer None Returns incremented stack pointer value (SP + 1) in high-byte:low-byte order $0C Command Sequence
FROM HOST
READSP
READSP
SP HIGH
SP LOW
ECHO
RETURN
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 123
Monitor ROM (MON)
Table 8-9. RUN (Run User Program) Command
Description Operand Data Returned Opcode Executes PULH and RTI instructions None None $28 Command Sequence
FROM HOST
RUN
RUN
ECHO
The MCU executes the SWI and PSHH instructions when it enters monitor mode. The RUN command tells the MCU to execute the PULH and RTI instructions. Before sending the RUN command, the host can modify the stacked CPU registers to prepare to run the host program. The READSP command returns the incremented stack pointer value, SP + 1. The high and low bytes of the program counter are at addresses SP + 5 and SP + 6.
SP HIGH BYTE OF INDEX REGISTER CONDITION CODE REGISTER ACCUMULATOR LOW BYTE OF INDEX REGISTER SP + 1 SP + 2 SP + 3 SP + 4
HIGH BYTE OF PROGRAM COUNTER SP + 5 LOW BYTE OF PROGRAM COUNTER SP + 6 SP + 7
Figure 8-7. Stack Pointer at Monitor Mode Entry
8.4 Security
A security feature discourages unauthorized reading of FLASH locations while in monitor mode. The host can bypass the security feature at monitor mode entry by sending eight security bytes that match the bytes at locations $FFF6-$FFFD. Locations $FFF6-$FFFD contain user-defined data. NOTE Do not leave locations $FFF6-$FFFD blank. For security reasons, program locations $FFF6-$FFFD even if they are not used for vectors.
MC68HC908AP A-Family Data Sheet, Rev. 2 124 Freescale Semiconductor
Security
During monitor mode entry, the MCU waits after the power-on reset for the host to send the eight security bytes on pin PTA0. If the received bytes match those at locations $FFF6-$FFFD, the host bypasses the security feature and can read all FLASH locations and execute code from FLASH. Security remains bypassed until a power-on reset occurs. If the reset was not a power-on reset, security remains bypassed and security code entry is not required. (See Figure 8-8.)
VDD 4096 + 32 ICLK CYCLES RST COMMAND 2 BYTE 8 ECHO 4 1 COMMAND ECHO BREAK 256 BUS CYCLES (MINIMUM) BYTE 1 BYTE 2 BYTE 8 1 BYTE 2 ECHO 1
FROM HOST
PTA0 1 BYTE 1 ECHO FROM MCU 4
NOTES: 1 = Echo delay, 2 bit times. 2 = Data return delay, 2 bit times. 4 = Wait 1 bit time before sending next byte.
Figure 8-8. Monitor Mode Entry Timing Upon power-on reset, if the received bytes of the security code do not match the data at locations $FFF6-$FFFD, the host fails to bypass the security feature. The MCU remains in monitor mode, but reading a FLASH location returns an invalid value and trying to execute code from FLASH causes an illegal address reset. After receiving the eight security bytes from the host, the MCU transmits a break character, signifying that it is ready to receive a command. NOTE The MCU does not transmit a break character until after the host sends the eight security bits. To determine whether the security code entered is correct, check to see if bit 6 of RAM address $60 is set. If it is, then the correct security code has been entered and FLASH can be accessed. If the security sequence fails, the device should be reset by a power-on reset and brought up in monitor mode to attempt another entry. After failing the security sequence, the FLASH module can also be mass erased by executing an erase routine that was downloaded into internal RAM. The mass erase operation clears the security code locations so that all eight security bytes become $FF (blank).
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 125
Monitor ROM (MON)
8.5 ROM-Resident Routines
Seven routines stored in the monitor ROM area (thus ROM-resident) are provided for FLASH memory manipulation. Five of the seven routines are intended to simplify FLASH program, erase, and load operations. The other two routines are intended to simplify the use of the FLASH memory as EEPROM. Table 8-10 shows a summary of the ROM-resident routines. Table 8-10. Summary of ROM-Resident Routines
Routine Name PRGRNGE ERARNGE LDRNGE MON_PRGRNGE MON_ERARNGE Routine Description Program a range of locations Erase a page or the entire array Loads data from a range of locations Program a range of locations in monitor mode Erase a page or the entire array in monitor mode Call Address $FC34 $FCE4 $FC00 $FF24 $FF28 Stack Used (bytes) 15 9 7 17 11
The routines are designed to be called as stand-alone subroutines in the user program or monitor mode. The parameters that are passed to a routine are in the form of a contiguous data block, stored in RAM. The index register (H:X) is loaded with the address of the first byte of the data block (acting as a pointer), and the subroutine is called (JSR). Using the start address as a pointer, multiple data blocks can be used, any area of RAM be used. A data block has the control and data bytes in a defined order, as shown in Figure 8-9. During the software execution, it does not consume any dedicated RAM location, the run-time heap will extend the system stack, all other RAM location will not be affected.
FILE_PTR $XXXX ADDRESS AS POINTER
R
A
M
BUS SPEED (BUS_SPD) DATA SIZE (DATASIZE) START ADDRESS HIGH (ADDRH) START ADDRESS LOW (ADDRL) DATA 0 DATA 1 DATA BLOCK
DATA ARRAY DATA N
Figure 8-9. Data Block Format for ROM-Resident Routines The control and data bytes are described below.
MC68HC908AP A-Family Data Sheet, Rev. 2 126 Freescale Semiconductor
ROM-Resident Routines
*
*
* *
Bus speed -- This one byte indicates the operating bus speed of the MCU. The value of this byte should be equal to 4 times the bus speed. E.g., for a 4MHz bus, the value is 16 ($10). This control byte is useful where the MCU clock source is switched between the PLL clock and the crystal clock. Data size -- This one byte indicates the number of bytes in the data array that are to be manipulated. The maximum data array size is 255. ERARNGE and MON_ERARNGE routines do not manipulate a data array, thus, this data size byte has no meaning. Start address -- These two bytes, high byte followed by low byte, indicate the start address of the FLASH memory to be manipulated. Data array -- This data array contains data that are to be manipulated. Data in this array are programmed to FLASH memory by the programming routines, PRGRNGE and MON_PRGRNGE. For the read routine, LDRNGE, data is read from FLASH and stored in this array.
8.5.1 PRGRNGE
PRGRNGE is used to program a range of FLASH locations with data loaded into the data array. Table 8-11. PRGRNGE Routine
Routine Name Routine Description Calling Address Stack Used PRGRNGE Program a range of locations $FC34 15 bytes Bus speed (BUS_SPD) Data size (DATASIZE) Start address high (ADDRH) Start address (ADDRL) Data 1 (DATA1) : Data N (DATAN)
Data Block Format
The start location of the FLASH to be programmed is specified by the address ADDRH:ADDRL and the number of bytes from this location is specified by DATASIZE. The maximum number of bytes that can be programmed in one routine call is 255 bytes (max. DATASIZE is 255). ADDRH:ADDRL do not need to be at a page boundary, the routine handles any boundary misalignment during programming. A check to see that all bytes in the specified range are erased is not performed by this routine prior programming. Nor does this routine do a verification after programming, so there is no return confirmation that programming was successful. User must assure that the range specified is first erased. The coding example below is to program 64 bytes of data starting at FLASH location $EE00, with a bus speed of 4.9152 MHz. The coding assumes the data block is already loaded in RAM, with the address pointer, FILE_PTR, pointing to the first byte of the data block.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 127
Monitor ROM (MON)
ORG : FILE_PTR: BUS_SPD DATASIZE START_ADDR DATAARRAY PRGRNGE FLASH_START
RAM
DS.B DS.B DS.W DS.B EQU EQU
1 1 1 64 $FC34 $EE00
; ; ; ;
Indicates 4x bus frequency Data size to be programmed FLASH start address Reserved data array
ORG FLASH INITIALISATION: MOV #20, BUS_SPD MOV #64, DATASIZE LDHX #FLASH_START STHX START_ADDR RTS MAIN: BSR INITIALISATION : : LDHX #FILE_PTR JSR PRGRNGE
8.5.2 ERARNGE
ERARNGE is used to erase a range of locations in FLASH. Table 8-12. ERARNGE Routine
Routine Name Routine Description Calling Address Stack Used ERARNGE Erase a page or the entire array $FCE4 9 bytes Bus speed (BUS_SPD) Data size (DATASIZE) Starting address (ADDRH) Starting address (ADDRL)
Data Block Format
There are two sizes of erase ranges: a page or the entire array. The ERARNGE will erase the page (512 consecutive bytes) in FLASH specified by the address ADDRH:ADDRL. This address can be any address within the page. Calling ERARNGE with ADDRH:ADDRL equal to $FFFF will erase the entire FLASH array (mass erase). Therefore, care must be taken when calling this routine to prevent an accidental mass erase. The ERARNGE routine do not use a data array. The DATASIZE byte is a dummy byte that is also not used.
MC68HC908AP A-Family Data Sheet, Rev. 2 128 Freescale Semiconductor
ROM-Resident Routines
The coding example below is to perform a page erase, from $EE00-$EFFF. The Initialization subroutine is the same as the coding example for PRGRNGE (see 8.5.1 PRGRNGE).
ERARNGE MAIN: BSR : : LDHX JSR : EQU $FCE4
INITIALISATION
#FILE_PTR ERARNGE
8.5.3 LDRNGE
LDRNGE is used to load the data array in RAM with data from a range of FLASH locations. Table 8-13. LDRNGE Routine
Routine Name Routine Description Calling Address Stack Used LDRNGE Loads data from a range of locations $FC00 7 bytes Bus speed (BUS_SPD) Data size (DATASIZE) Starting address (ADDRH) Starting address (ADDRL) Data 1 : Data N
Data Block Format
The start location of FLASH from where data is retrieved is specified by the address ADDRH:ADDRL and the number of bytes from this location is specified by DATASIZE. The maximum number of bytes that can be retrieved in one routine call is 255 bytes. The data retrieved from FLASH is loaded into the data array in RAM. Previous data in the data array will be overwritten. User can use this routine to retrieve data from FLASH that was previously programmed. The coding example below is to retrieve 64 bytes of data starting from $EE00 in FLASH. The Initialization subroutine is the same as the coding example for PRGRNGE (see 8.5.1 PRGRNGE).
LDRNGE MAIN: BSR : : LDHX JSR : EQU $FC00
INITIALIZATION
#FILE_PTR LDRNGE
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 129
Monitor ROM (MON)
8.5.4 MON_PRGRNGE
In monitor mode, MON_PRGRNGE is used to program a range of FLASH locations with data loaded into the data array. Table 8-14. MON_PRGRNGE Routine
Routine Name Routine Description Calling Address Stack Used MON_PRGRNGE Program a range of locations, in monitor mode $FF24 17 bytes Bus speed Data size Starting address (high byte) Starting address (low byte) Data 1 : Data N
Data Block Format
The MON_PRGRNGE routine is designed to be used in monitor mode. It performs the same function as the PRGRNGE routine (see 8.5.1 PRGRNGE), except that MON_PRGRNGE returns to the main program via an SWI instruction. After a MON_PRGRNGE call, the SWI instruction will return the control back to the monitor code.
8.5.5 MON_ERARNGE
In monitor mode, ERARNGE is used to erase a range of locations in FLASH. Table 8-15. MON_ERARNGE Routine
Routine Name Routine Description Calling Address Stack Used MON_ERARNGE Erase a page or the entire array, in monitor mode $FF28 11 bytes Bus speed Data size Starting address (high byte) Starting address (low byte)
Data Block Format
The MON_ERARNGE routine is designed to be used in monitor mode. It performs the same function as the ERARNGE routine (see 8.5.2 ERARNGE), except that MON_ERARNGE returns to the main program via an SWI instruction. After a MON_ERARNGE call, the SWI instruction will return the control back to the monitor code.
MC68HC908AP A-Family Data Sheet, Rev. 2 130 Freescale Semiconductor
Chapter 9 Timer Interface Module (TIM)
9.1 Introduction
This section describes the timer interface (TIM) module. The TIM is a two-channel timer that provides a timing reference with Input capture, output compare, and pulse-width-modulation functions. Figure 9-1 is a block diagram of the TIM. This particular MCU has two timer interface modules which are denoted as TIM1 and TIM2.
9.2 Features
Features of the TIM include: * Two input capture/output compare channels: - Rising-edge, falling-edge, or any-edge input capture trigger - Set, clear, or toggle output compare action * Buffered and unbuffered pulse-width-modulation (PWM) signal generation * Programmable TIM clock input with 7-frequency internal bus clock prescaler selection * Free-running or modulo up-count operation * Toggle any channel pin on overflow * TIM counter stop and reset bits
9.3 Pin Name Conventions
The text that follows describes both timers, TIM1 and TIM2. The TIM input/output (I/O) pin names are T[1,2]CH0 (timer channel 0) and T[1,2]CH1 (timer channel 1), where "1" is used to indicate TIM1 and "2" is used to indicate TIM2. The two TIMs share four I/O pins with four I/O port pins. The external clock input for TIM2 is shared with the an ADC channel pin. The full names of the TIM I/O pins are listed in Table 9-1. The generic pin names appear in the text that follows. Table 9-1. Pin Name Conventions
TIM Generic Pin Names: Full TIM Pin Names: TIM1 TIM2 T[1,2]CH0 PTB4/T1CH0 PTB6/T2CH0 T[1,2]CH1 PTB5/T1CH1 PTB7/T2CH1
NOTE References to either timer 1 or timer 2 may be made in the following text by omitting the timer number. For example, TCH0 may refer generically to T1CH0 and T2CH0, and TCH1 may refer to T1CH1 and T2CH1.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 131
Timer Interface Module (TIM)
9.4 Functional Description
Figure 9-1 shows the structure of the TIM. The central component of the TIM is the 16-bit TIM counter that can operate as a free-running counter or a modulo up-counter. The TIM counter provides the timing reference for the input capture and output compare functions. The TIM counter modulo registers, TMODH:TMODL, control the modulo value of the TIM counter. Software can read the TIM counter value at any time without affecting the counting sequence. The two TIM channels (per timer) are programmable independently as input capture or output compare channels.
PRESCALER SELECT INTERNAL BUS CLOCK TSTOP TRST 16-BIT COUNTER 16-BIT COMPARATOR TMODH:TMODL TOV0 CHANNEL 0 16-BIT COMPARATOR TCH0H:TCH0L 16-BIT LATCH MS0A MS0B TOV1 INTERNAL BUS CHANNEL 1 16-BIT COMPARATOR TCH1H:TCH1L 16-BIT LATCH MS0A CH1F CH01IE CH1IE INTERRUPT LOGIC ELS0B ELS0A CH1MAX PORT LOGIC T[1,2]CH1 CH0IE CH0F INTERRUPT LOGIC ELS0B ELS0A CH0MAX PORT LOGIC T[1,2]CH0 PRESCALER
PS2
PS1
PS0
TOF TOIE
INTERRUPT LOGIC
Figure 9-1. TIM Block Diagram Figure 9-2 summarizes the timer registers. NOTE References to either timer 1 or timer 2 may be made in the following text by omitting the timer number. For example, TSC may generically refer to both T1SC and T2SC.
MC68HC908AP A-Family Data Sheet, Rev. 2 132 Freescale Semiconductor
Functional Description Addr. $0020 Register Name Bit 7 TOF 0 0 Bit 15 0 Bit 7 0 Bit 15 1 Bit 7 1 CH0F 0 0 Bit 15 6 TOIE 0 14 0 6 0 14 1 6 1 CH0IE 0 14 5 TSTOP 1 13 0 5 0 13 1 5 1 MS0B 0 13 4 0 TRST 0 12 0 4 0 12 1 4 1 MS0A 0 12 3 0 0 11 0 3 0 11 1 3 1 ELS0B 0 11 2 PS2 0 10 0 2 0 10 1 2 1 ELS0A 0 10 1 PS1 0 9 0 1 0 9 1 1 1 TOV0 0 9 Bit 0 PS0 0 Bit 8 0 Bit 0 0 Bit 8 1 Bit 0 1 CH0MAX 0 Bit 8
$0021
$0022
$0023
$0024
$0025
$0026
$0027
$0028
$0029
$002A
$002B
$002C
$002D
$002E
TIM1 Status and Control Register (T1SC) TIM1 Counter Register High (T1CNTH) TIM1 Counter Register Low (T1CNTL) TIM Counter Modulo Register High (TMODH) TIM1 Counter Modulo Register Low (T1MODL) TIM1 Channel 0 Status and Control Register (T1SC0) TIM1 Channel 0 Register High (T1CH0H) TIM1 Channel 0 Register Low (T1CH0L) TIM1 Channel 1 Status and Control Register (T1SC1) TIM1 Channel 1 Register High (T1CH1H) TIM1 Channel 1 Register Low (T1CH1L) TIM2 Status and Control Register (T2SC) TIM2 Counter Register High (T2CNTH) TIM2 Counter Register Low (T2CNTL) TIM2 Counter Modulo Register High (T2MODH)
Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset:
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
Indeterminate after reset CH1F 0 0 Bit 15 CH1IE 0 14 0 0 13 MS1A 0 12 ELS1B 0 11 ELS1A 0 10 TOV1 0 9 CH1MAX 0 Bit 8
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
TOF 0 0 Bit 15 0 Bit 7 0 Bit 15 1
TOIE 0 14 0 6 0 14
TSTOP 1 13 0 5 0 13
Indeterminate after reset 0 0 TRST 0 0 12 11 0 4 0 12 1 0 3 0 11 1
PS2 0 10 0 2 0 10 1
PS1 0 9 0 1 0 9 1
PS0 0 Bit 8 0 Bit 0 0 Bit 8 1
1 1 = Unimplemented
Figure 9-2. TIM I/O Register Summary (Sheet 1 of 2)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 133
Timer Interface Module (TIM) Addr. $002F Register Name Bit 7 Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Bit 7 1 CH0F 0 0 Bit 15 6 6 1 CH0IE 0 14 5 5 1 MS0B 0 13 4 4 1 MS0A 0 12 3 3 1 ELS0B 0 11 2 2 1 ELS0A 0 10 1 1 1 TOV0 0 9 Bit 0 Bit 0 1 CH0MAX 0 Bit 8
$0030
$0031
$0032
$0033
$0034
$0035
TIM2 Counter Modulo Register Low (T2MODL) TIM2 Channel 0 Status and Control Register (T2SC0) TIM2 Channel 0 Register High (T2CH0H) TIM2 Channel 0 Register Low (T2CH0L) TIM2 Channel 1 Status and Control Register (T2SC1) TIM2 Channel 1 Register High (T2CH1H) TIM2 Channel 1 Register Low (T2CH1L)
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
Indeterminate after reset CH1F 0 0 Bit 15 CH1IE 0 14 0 0 13 MS1A 0 12 ELS1B 0 11 ELS1A 0 10 TOV1 0 9 CH1MAX 0 Bit 8
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
Indeterminate after reset = Unimplemented
Figure 9-2. TIM I/O Register Summary (Sheet 2 of 2) 9.4.1 TIM Counter Prescaler
The TIM clock source can be one of the seven prescaler outputs. The prescaler generates seven clock rates from the internal bus clock. The prescaler select bits, PS[2:0], in the TIM status and control register select the TIM clock source.
9.4.2 Input Capture
With the input capture function, the TIM can capture the time at which an external event occurs. When an active edge occurs on the pin of an input capture channel, the TIM latches the contents of the TIM counter into the TIM channel registers, TCHxH:TCHxL. The polarity of the active edge is programmable. Input captures can generate TIM CPU interrupt requests.
9.4.3 Output Compare
With the output compare function, the TIM can generate a periodic pulse with a programmable polarity, duration, and frequency. When the counter reaches the value in the registers of an output compare channel, the TIM can set, clear, or toggle the channel pin. Output compares can generate TIM CPU interrupt requests. 9.4.3.1 Unbuffered Output Compare Any output compare channel can generate unbuffered output compare pulses as described in 9.4.3 Output Compare. The pulses are unbuffered because changing the output compare value requires writing the new value over the old value currently in the TIM channel registers.
MC68HC908AP A-Family Data Sheet, Rev. 2 134 Freescale Semiconductor
Functional Description
An unsynchronized write to the TIM channel registers to change an output compare value could cause incorrect operation for up to two counter overflow periods. For example, writing a new value before the counter reaches the old value but after the counter reaches the new value prevents any compare during that counter overflow period. Also, using a TIM overflow interrupt routine to write a new, smaller output compare value may cause the compare to be missed. The TIM may pass the new value before it is written. Use the following methods to synchronize unbuffered changes in the output compare value on channel x: * When changing to a smaller value, enable channel x output compare interrupts and write the new value in the output compare interrupt routine. The output compare interrupt occurs at the end of the current output compare pulse. The interrupt routine has until the end of the counter overflow period to write the new value. * When changing to a larger output compare value, enable TIM overflow interrupts and write the new value in the TIM overflow interrupt routine. The TIM overflow interrupt occurs at the end of the current counter overflow period. Writing a larger value in an output compare interrupt routine (at the end of the current pulse) could cause two output compares to occur in the same counter overflow period. 9.4.3.2 Buffered Output Compare Channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the TCH0 pin. The TIM channel registers of the linked pair alternately control the output. Setting the MS0B bit in TIM channel 0 status and control register (TSC0) links channel 0 and channel 1. The output compare value in the TIM channel 0 registers initially controls the output on the TCH0 pin. Writing to the TIM channel 1 registers enables the TIM channel 1 registers to synchronously control the output after the TIM overflows. At each subsequent overflow, the TIM channel registers (0 or 1) that control the output are the ones written to last. TSC0 controls and monitors the buffered output compare function, and TIM channel 1 status and control register (TSC1) is unused. While the MS0B bit is set, the channel 1 pin, TCH1, is available as a general-purpose I/O pin. NOTE In buffered output compare operation, do not write new output compare values to the currently active channel registers. User software should track the currently active channel to prevent writing a new value to the active channel. Writing to the active channel registers is the same as generating unbuffered output compares.
9.4.4 Pulse Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel, the TIM can generate a PWM signal. The value in the TIM counter modulo registers determines the period of the PWM signal. The channel pin toggles when the counter reaches the value in the TIM counter modulo registers. The time between overflows is the period of the PWM signal. As Figure 9-3 shows, the output compare value in the TIM channel registers determines the pulse width of the PWM signal. The time between overflow and output compare is the pulse width. Program the TIM to clear the channel pin on output compare if the state of the PWM pulse is logic 1. Program the TIM to set the pin if the state of the PWM pulse is logic 0. The value in the TIM counter modulo registers and the selected prescaler output determines the frequency of the PWM output. The frequency of an 8-bit PWM signal is variable in 256 increments. Writing
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 135
Timer Interface Module (TIM)
$00FF (255) to the TIM counter modulo registers produces a PWM period of 256 times the internal bus clock period if the prescaler select value is $000. See 9.9.1 TIM Status and Control Register.
OVERFLOW OVERFLOW OVERFLOW
PERIOD
PULSE WIDTH TCHx
OUTPUT COMPARE
OUTPUT COMPARE
OUTPUT COMPARE
Figure 9-3. PWM Period and Pulse Width The value in the TIM channel registers determines the pulse width of the PWM output. The pulse width of an 8-bit PWM signal is variable in 256 increments. Writing $0080 (128) to the TIM channel registers produces a duty cycle of 128/256 or 50%. 9.4.4.1 Unbuffered PWM Signal Generation Any output compare channel can generate unbuffered PWM pulses as described in 9.4.4 Pulse Width Modulation (PWM). The pulses are unbuffered because changing the pulse width requires writing the new pulse width value over the old value currently in the TIM channel registers. An unsynchronized write to the TIM channel registers to change a pulse width value could cause incorrect operation for up to two PWM periods. For example, writing a new value before the counter reaches the old value but after the counter reaches the new value prevents any compare during that PWM period. Also, using a TIM overflow interrupt routine to write a new, smaller pulse width value may cause the compare to be missed. The TIM may pass the new value before it is written. Use the following methods to synchronize unbuffered changes in the PWM pulse width on channel x: * When changing to a shorter pulse width, enable channel x output compare interrupts and write the new value in the output compare interrupt routine. The output compare interrupt occurs at the end of the current pulse. The interrupt routine has until the end of the PWM period to write the new value. * When changing to a longer pulse width, enable TIM overflow interrupts and write the new value in the TIM overflow interrupt routine. The TIM overflow interrupt occurs at the end of the current PWM period. Writing a larger value in an output compare interrupt routine (at the end of the current pulse) could cause two output compares to occur in the same PWM period. NOTE In PWM signal generation, do not program the PWM channel to toggle on output compare. Toggling on output compare prevents reliable 0% duty cycle generation and removes the ability of the channel to self-correct in the event of software error or noise. Toggling on output compare also can cause incorrect PWM signal generation when changing the PWM pulse width to a new, much larger value.
MC68HC908AP A-Family Data Sheet, Rev. 2 136 Freescale Semiconductor
Functional Description
9.4.4.2 Buffered PWM Signal Generation Channels 0 and 1 can be linked to form a buffered PWM channel whose output appears on the TCH0 pin. The TIM channel registers of the linked pair alternately control the pulse width of the output. Setting the MS0B bit in TIM channel 0 status and control register (TSC0) links channel 0 and channel 1. The TIM channel 0 registers initially control the pulse width on the TCH0 pin. Writing to the TIM channel 1 registers enables the TIM channel 1 registers to synchronously control the pulse width at the beginning of the next PWM period. At each subsequent overflow, the TIM channel registers (0 or 1) that control the pulse width are the ones written to last. TSC0 controls and monitors the buffered PWM function, and TIM channel 1 status and control register (TSC1) is unused. While the MS0B bit is set, the channel 1 pin, TCH1, is available as a general-purpose I/O pin. NOTE In buffered PWM signal generation, do not write new pulse width values to the currently active channel registers. User software should track the currently active channel to prevent writing a new value to the active channel. Writing to the active channel registers is the same as generating unbuffered PWM signals. 9.4.4.3 PWM Initialization To ensure correct operation when generating unbuffered or buffered PWM signals, use the following initialization procedure: 1. In the TIM status and control register (TSC): a. Stop the TIM counter by setting the TIM stop bit, TSTOP. b. Reset the TIM counter and prescaler by setting the TIM reset bit, TRST. 2. In the TIM counter modulo registers (TMODH:TMODL), write the value for the required PWM period. 3. In the TIM channel x registers (TCHxH:TCHxL), write the value for the required pulse width. 4. In TIM channel x status and control register (TSCx): a. Write 0:1 (for unbuffered output compare or PWM signals) or 1:0 (for buffered output compare or PWM signals) to the mode select bits, MSxB:MSxA. (See Table 9-3.) b. Write 1 to the toggle-on-overflow bit, TOVx. c. Write 1:0 (to clear output on compare) or 1:1 (to set output on compare) to the edge/level select bits, ELSxB:ELSxA. The output action on compare must force the output to the complement of the pulse width level. (See Table 9-3.) NOTE In PWM signal generation, do not program the PWM channel to toggle on output compare. Toggling on output compare prevents reliable 0% duty cycle generation and removes the ability of the channel to self-correct in the event of software error or noise. Toggling on output compare can also cause incorrect PWM signal generation when changing the PWM pulse width to a new, much larger value. 5. In the TIM status control register (TSC), clear the TIM stop bit, TSTOP.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 137
Timer Interface Module (TIM)
Setting MS0B links channels 0 and 1 and configures them for buffered PWM operation. The TIM channel 0 registers (TCH0H:TCH0L) initially control the buffered PWM output. TIM status control register 0 (TSCR0) controls and monitors the PWM signal from the linked channels. Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on TIM overflows. Subsequent output compares try to force the output to a state it is already in and have no effect. The result is a 0% duty cycle output. Setting the channel x maximum duty cycle bit (CHxMAX) and setting the TOVx bit generates a 100% duty cycle output. (See 9.9.4 TIM Channel Status and Control Registers.)
9.5 Interrupts
The following TIM sources can generate interrupt requests: * TIM overflow flag (TOF) -- The TOF bit is set when the TIM counter reaches the modulo value programmed in the TIM counter modulo registers. The TIM overflow interrupt enable bit, TOIE, enables TIM overflow CPU interrupt requests. TOF and TOIE are in the TIM status and control register. * TIM channel flags (CH1F:CH0F) -- The CHxF bit is set when an input capture or output compare occurs on channel x. Channel x TIM CPU interrupt requests are controlled by the channel x interrupt enable bit, CHxIE. Channel x TIM CPU interrupt requests are enabled when CHxIE = 1. CHxF and CHxIE are in the TIM channel x status and control register.
9.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power- consumption standby modes.
9.6.1 Wait Mode
The TIM remains active after the execution of a WAIT instruction. In wait mode, the TIM registers are not accessible by the CPU. Any enabled CPU interrupt request from the TIM can bring the MCU out of wait mode. If TIM functions are not required during wait mode, reduce power consumption by stopping the TIM before executing the WAIT instruction.
9.6.2 Stop Mode
The TIM is inactive after the execution of a STOP instruction. The STOP instruction does not affect register conditions or the state of the TIM counter. TIM operation resumes when the MCU exits stop mode after an external interrupt.
9.7 TIM During Break Interrupts
A break interrupt stops the TIM counter. The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. The BCFE bit in the break flag control register (BFCR) enables software to clear status bits during the break state. (See 21.5.4 SIM Break Flag Control Register.)
MC68HC908AP A-Family Data Sheet, Rev. 2 138 Freescale Semiconductor
I/O Signals
To allow software to clear status bits during a break interrupt, write a logic 1 to the BCFE bit. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state. To protect status bits during the break state, write a logic 0 to the BCFE bit. With BCFE at logic 0 (its default state), software can read and write I/O registers during the break state without affecting status bits. Some status bits have a 2-step read/write clearing procedure. If software does the first step on such a bit before the break, the bit cannot change during the break state as long as BCFE is at logic 0. After the break, doing the second step clears the status bit.
9.8 I/O Signals
Port B shares four of its pins with the TIM. The four TIM channel I/O pins are T1CH0, T1CH1, T2CH0, and T2CH1 as described in 9.3 Pin Name Conventions. Each channel I/O pin is programmable independently as an input capture pin or an output compare pin. T1CH0 and T2CH0 can be configured as buffered output compare or buffered PWM pins.
9.9 I/O Registers
NOTE References to either timer 1 or timer 2 may be made in the following text by omitting the timer number. For example, TSC may generically refer to both T1SC AND T2SC. These I/O registers control and monitor operation of the TIM: * TIM status and control register (TSC) * TIM counter registers (TCNTH:TCNTL) * TIM counter modulo registers (TMODH:TMODL) * TIM channel status and control registers (TSC0, TSC1) * TIM channel registers (TCH0H:TCH0L, TCH1H:TCH1L)
9.9.1 TIM Status and Control Register
The TIM status and control register (TSC): * Enables TIM overflow interrupts * Flags TIM overflows * Stops the TIM counter * Resets the TIM counter * Prescales the TIM counter clock
Address: T1SC, $0020 and T2SC, $002B Bit 7 Read: Write: Reset: TOF 0 0 6 TOIE 0 5 TSTOP 1 4 0 TRST 0 0 3 0 2 PS2 0 1 PS1 0 Bit 0 PS0 0
= Unimplemented
Figure 9-4. TIM Status and Control Register (TSC)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 139
Timer Interface Module (TIM)
TOF -- TIM Overflow Flag Bit This read/write flag is set when the TIM counter reaches the modulo value programmed in the TIM counter modulo registers. Clear TOF by reading the TIM status and control register when TOF is set and then writing a logic 0 to TOF. If another TIM overflow occurs before the clearing sequence is complete, then writing logic 0 to TOF has no effect. Therefore, a TOF interrupt request cannot be lost due to inadvertent clearing of TOF. Reset clears the TOF bit. Writing a logic 1 to TOF has no effect. 1 = TIM counter has reached modulo value 0 = TIM counter has not reached modulo value TOIE -- TIM Overflow Interrupt Enable Bit This read/write bit enables TIM overflow interrupts when the TOF bit becomes set. Reset clears the TOIE bit. 1 = TIM overflow interrupts enabled 0 = TIM overflow interrupts disabled TSTOP -- TIM Stop Bit This read/write bit stops the TIM counter. Counting resumes when TSTOP is cleared. Reset sets the TSTOP bit, stopping the TIM counter until software clears the TSTOP bit. 1 = TIM counter stopped 0 = TIM counter active NOTE Do not set the TSTOP bit before entering wait mode if the TIM is required to exit wait mode. TRST -- TIM Reset Bit Setting this write-only bit resets the TIM counter and the TIM prescaler. Setting TRST has no effect on any other registers. Counting resumes from $0000. TRST is cleared automatically after the TIM counter is reset and always reads as logic 0. Reset clears the TRST bit. 1 = Prescaler and TIM counter cleared 0 = No effect NOTE Setting the TSTOP and TRST bits simultaneously stops the TIM counter at a value of $0000. PS[2:0] -- Prescaler Select Bits These read/write bits select one of the seven prescaler outputs as the input to the TIM counter as Table 9-2 shows. Reset clears the PS[2:0] bits. Table 9-2. Prescaler Selection
PS2 0 0 0 0 1 1 1 1 PS1 0 0 1 1 0 0 1 1 PS0 0 1 0 1 0 1 0 1 TIM Clock Source Internal bus clock / 1 Internal bus clock / 2 Internal bus clock / 4 Internal bus clock / 8 Internal bus clock / 16 Internal bus clock / 32 Internal bus clock / 64 Not available
MC68HC908AP A-Family Data Sheet, Rev. 2 140 Freescale Semiconductor
I/O Registers
9.9.2 TIM Counter Registers
The two read-only TIM counter registers contain the high and low bytes of the value in the TIM counter. Reading the high byte (TCNTH) latches the contents of the low byte (TCNTL) into a buffer. Subsequent reads of TCNTH do not affect the latched TCNTL value until TCNTL is read. Reset clears the TIM counter registers. Setting the TIM reset bit (TRST) also clears the TIM counter registers. NOTE If you read TCNTH during a break interrupt, be sure to unlatch TCNTL by reading TCNTL before exiting the break interrupt. Otherwise, TCNTL retains the value latched during the break.
Address: T1CNTH, $0021 and T2CNTH, $002C Bit 7 Read: Write: Reset: 0 0 0 0 0 0 0 0 Bit 15 6 14 5 13 4 12 3 11 2 10 1 9 Bit 0 Bit 8
Figure 9-5. TIM Counter Registers High (TCNTH)
Address: T1CNTL, $0022 and T2CNTL, $002D Bit 7 Read: Write: Reset: 0 0 0 0 0 0 0 0 Bit 7 6 6 5 5 4 4 3 3 2 2 1 1 Bit 0 Bit 0
Figure 9-6. TIM Counter Registers Low (TCNTL)
9.9.3 TIM Counter Modulo Registers
The read/write TIM modulo registers contain the modulo value for the TIM counter. When the TIM counter reaches the modulo value, the overflow flag (TOF) becomes set, and the TIM counter resumes counting from $0000 at the next timer clock. Writing to the high byte (TMODH) inhibits the TOF bit and overflow interrupts until the low byte (TMODL) is written. Reset sets the TIM counter modulo registers.
Address: T1MODH, $0023 and T2MODH, $002E Bit 7 Read: Write: Reset: Bit 15 1 6 14 1 5 13 1 4 12 1 3 11 1 2 10 1 1 9 1 Bit 0 Bit 8 1
Figure 9-7. TIM Counter Modulo Register High (TMODH)
Address: T1MODL, $0024 and T2MODL, $002F Bit 7 Read: Write: Reset: Bit 7 1 6 6 1 5 5 1 4 4 1 3 3 1 2 2 1 1 1 1 Bit 0 Bit 0 1
Figure 9-8. TIM Counter Modulo Register Low (TMODL) NOTE Reset the TIM counter before writing to the TIM counter modulo registers.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 141
Timer Interface Module (TIM)
9.9.4 TIM Channel Status and Control Registers
Each of the TIM channel status and control registers: * Flags input captures and output compares * Enables input capture and output compare interrupts * Selects input capture, output compare, or PWM operation * Selects high, low, or toggling output on output compare * Selects rising edge, falling edge, or any edge as the active input capture trigger * Selects output toggling on TIM overflow * Selects 0% and 100% PWM duty cycle * Selects buffered or unbuffered output compare/PWM operation
Address: T1SC0, $0025 and T2SC0, $0030 Bit 7 Read: Write: Reset: CH0F 0 0 6 CH0IE 0 5 MS0B 0 4 MS0A 0 3 ELS0B 0 2 ELS0A 0 1 TOV0 0 Bit 0 CH0MAX 0
Figure 9-9. TIM Channel 0 Status and Control Register (TSC0)
Address: T1SC1, $0028 and T2SC1, $0033 Bit 7 Read: Write: Reset: CH1F 0 0 6 CH1IE 0 5 0 0 4 MS1A 0 3 ELS1B 0 2 ELS1A 0 1 TOV1 0 Bit 0 CH1MAX 0
Figure 9-10. TIM Channel 1 Status and Control Register (TSC1) CHxF -- Channel x Flag Bit When channel x is an input capture channel, this read/write bit is set when an active edge occurs on the channel x pin. When channel x is an output compare channel, CHxF is set when the value in the TIM counter registers matches the value in the TIM channel x registers. When TIM CPU interrupt requests are enabled (CHxIE = 1), clear CHxF by reading TIM channel x status and control register with CHxF set and then writing a logic 0 to CHxF. If another interrupt request occurs before the clearing sequence is complete, then writing logic 0 to CHxF has no effect. Therefore, an interrupt request cannot be lost due to inadvertent clearing of CHxF. Reset clears the CHxF bit. Writing a logic 1 to CHxF has no effect. 1 = Input capture or output compare on channel x 0 = No input capture or output compare on channel x CHxIE -- Channel x Interrupt Enable Bit This read/write bit enables TIM CPU interrupt service requests on channel x. Reset clears the CHxIE bit. 1 = Channel x CPU interrupt requests enabled 0 = Channel x CPU interrupt requests disabled MSxB -- Mode Select Bit B This read/write bit selects buffered output compare/PWM operation. MSxB exists only in the TIM1 channel 0 and TIM2 channel 0 status and control registers.
MC68HC908AP A-Family Data Sheet, Rev. 2 142 Freescale Semiconductor
I/O Registers
Setting MS0B disables the channel 1 status and control register and reverts TCH1 to general-purpose I/O. Reset clears the MSxB bit. 1 = Buffered output compare/PWM operation enabled 0 = Buffered output compare/PWM operation disabled MSxA -- Mode Select Bit A When ELSxB:ELSxA 0:0, this read/write bit selects either input capture operation or unbuffered output compare/PWM operation. See Table 9-3. 1 = Unbuffered output compare/PWM operation 0 = Input capture operation When ELSxB:ELSxA = 0:0, this read/write bit selects the initial output level of the TCHx pin. See Table 9-3. Reset clears the MSxA bit. 1 = Initial output level low 0 = Initial output level high NOTE Before changing a channel function by writing to the MSxB or MSxA bit, set the TSTOP and TRST bits in the TIM status and control register (TSC). ELSxB and ELSxA -- Edge/Level Select Bits When channel x is an input capture channel, these read/write bits control the active edge-sensing logic on channel x. When channel x is an output compare channel, ELSxB and ELSxA control the channel x output behavior when an output compare occurs. When ELSxB and ELSxA are both clear, channel x is not connected to an I/O port, and pin TCHx is available as a general-purpose I/O pin. Table 9-3 shows how ELSxB and ELSxA work. Reset clears the ELSxB and ELSxA bits. Table 9-3. Mode, Edge, and Level Selection
MSxB:MSxA X0 X1 00 00 00 01 01 01 1X 1X 1X ELSxB:ELSxA 00 Output preset 00 01 10 11 01 10 11 01 10 11 Buffered output compare or buffered PWM Output compare or PWM Input capture Pin under port control; initial output level low Capture on rising edge only Capture on falling edge only Capture on rising or falling edge Toggle output on compare Clear output on compare Set output on compare Toggle output on compare Clear output on compare Set output on compare Mode Configuration Pin under port control; initial output level high
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 143
Timer Interface Module (TIM)
NOTE Before enabling a TIM channel register for input capture operation, make sure that the TCHx pin is stable for at least two bus clocks. TOVx -- Toggle On Overflow Bit When channel x is an output compare channel, this read/write bit controls the behavior of the channel x output when the TIM counter overflows. When channel x is an input capture channel, TOVx has no effect. Reset clears the TOVx bit. 1 = Channel x pin toggles on TIM counter overflow 0 = Channel x pin does not toggle on TIM counter overflow NOTE When TOVx is set, a TIM counter overflow takes precedence over a channel x output compare if both occur at the same time. CHxMAX -- Channel x Maximum Duty Cycle Bit When the TOVx bit is at logic 1, setting the CHxMAX bit forces the duty cycle of buffered and unbuffered PWM signals to 100%. As Figure 9-11 shows, the CHxMAX bit takes effect in the cycle after it is set or cleared. The output stays at the 100% duty cycle level until the cycle after CHxMAX is cleared.
OVERFLOW OVERFLOW OVERFLOW OVERFLOW OVERFLOW
PERIOD TCHx
OUTPUT COMPARE CHxMAX
OUTPUT COMPARE
OUTPUT COMPARE
OUTPUT COMPARE
Figure 9-11. CHxMAX Latency
9.9.5 TIM Channel Registers
These read/write registers contain the captured TIM counter value of the input capture function or the output compare value of the output compare function. The state of the TIM channel registers after reset is unknown. In input capture mode (MSxB:MSxA = 0:0), reading the high byte of the TIM channel x registers (TCHxH) inhibits input captures until the low byte (TCHxL) is read. In output compare mode (MSxB:MSxA 0:0), writing to the high byte of the TIM channel x registers (TCHxH) inhibits output compares until the low byte (TCHxL) is written.
MC68HC908AP A-Family Data Sheet, Rev. 2 144 Freescale Semiconductor
I/O Registers
Address: T1CH0H, $0026 and T2CH0H, $0031 Bit 7 Read: Write: Reset: Bit 15 6 14 5 13 4 12 3 11 2 10 1 9 Bit 0 Bit 8
Indeterminate after reset
Figure 9-12. TIM Channel 0 Register High (TCH0H)
Address: T1CH0L, $0027 and T2CH0L $0032 Bit 7 Read: Write: Reset: Bit 7 6 6 5 5 4 4 3 3 2 2 1 1 Bit 0 Bit 0
Indeterminate after reset
Figure 9-13. TIM Channel 0 Register Low (TCH0L)
Address: T1CH1H, $0029 and T2CH1H, $0034 Bit 7 Read: Write: Reset: Bit 15 6 14 5 13 4 12 3 11 2 10 1 9 Bit 0 Bit 8
Indeterminate after reset
Figure 9-14. TIM Channel 1 Register High (TCH1H)
Address: T1CH1L, $002A and T2CH1L, $0035 Bit 7 Read: Write: Reset: Bit 7 6 6 5 5 4 4 3 3 2 2 1 1 Bit 0 Bit 0
Indeterminate after reset
Figure 9-15. TIM Channel 1 Register Low (TCH1L)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 145
Timer Interface Module (TIM)
MC68HC908AP A-Family Data Sheet, Rev. 2 146 Freescale Semiconductor
Chapter 10 Timebase Module (TBM)
10.1 Introduction
This section describes the timebase module (TBM). The TBM will generate periodic interrupts at user selectable rates using a counter clocked by the selected OSCCLK clock from the oscillator module. This TBM version uses 18 divider stages, eight of which are user selectable.
10.2 Features
Features of the TBM module include: * Eight user selectable periodic interrupts * User selectable oscillator clock source enable during stop mode to allow periodic wake-up from stop
10.3 Functional Description
This module can generate a periodic interrupt by dividing the oscillator clock frequency, OSCCLK. The counter is initialized to all 0s when TBON bit is cleared. The counter, shown in Figure 10-1, starts counting when the TBON bit is set. When the counter overflows at the tap selected by TBR[2:0], the TBIF bit gets set. If the TBIE bit is set, an interrupt request is sent to the CPU. The TBIF flag is cleared by writing a 1 to the TACK bit. The first time the TBIF flag is set after enabling the timebase module, the interrupt is generated at approximately half of the overflow period. Subsequent events occur at the exact period. The reference clock OSCCLK is derived from the oscillator module, see 5.2.2 TBM Reference Clock Selection.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 147
Timebase Module (TBM)
TBON
OSCCLK From OSC module
/2
/2
/2 /8
/2
/2 / 16
/2 / 32
/2 / 64
/2
/2
/2
/2 / 2048
(See Chapter 5 Oscillator (OSC).)
TBMINT
/2
/2
/2
/2
/2 / 32768
/2 / 65536
/2 / 131072 / 262144
TACK
TBR2
TBR1
TBR0
TBIF 000 001 010 011 100 101 110 111 SEL R
TBIE
Figure 10-1. Timebase Block Diagram
10.4 Timebase Register Description
The timebase has one register, the TBCR, which is used to enable the timebase interrupts and set the rate.
Address: Read: Write: Reset: 0 $0051 Bit 7 TBIF 6 TBR2 0 5 TBR1 0 4 TBR0 0 3 0 TACK 0 R 2 TBIE 0 = Reserved 1 TBON 0 Bit 0 R 0
= Unimplemented
Figure 10-2. Timebase Control Register (TBCR) TBIF -- Timebase Interrupt Flag This read-only flag bit is set when the timebase counter has rolled over. 1 = Timebase interrupt pending 0 = Timebase interrupt not pending
MC68HC908AP A-Family Data Sheet, Rev. 2 148 Freescale Semiconductor
Timebase Register Description
TBR[2:0] -- Timebase Rate Selection These read/write bits are used to select the rate of timebase interrupts as shown in Table 10-1. NOTE Do not change TBR[2:0] bits while the timebase is enabled (TBON = 1). Table 10-1. Timebase Rate Selection for OSCCLK = 4 MHz
TBR2 0 0 0 0 1 1 1 1 TBR1 0 0 1 1 0 0 1 1 TBR0 0 1 0 1 0 1 0 1 Divider 262144 131072 65536 32768 64 32 16 8 Timebase Interrupt Rate(1) Hz 15.259 30.518 61.035 122.07 62,500 125,000 250,000 500,000 ms 65.536 32.768 16.384 8.192 0.016 0.008 0.004 0.002
1. If user selects one of the shaded timebase settings, ensure that the operating bus frequency is fast enough to service the periodic interrupts.
TACK -- Timebase ACKnowledge The TACK bit is a write-only bit and always reads as 0. Writing a logic 1 to this bit clears TBIF, the timebase interrupt flag bit. Writing a logic 0 to this bit has no effect. 1 = Clear timebase interrupt flag 0 = No effect TBIE -- Timebase Interrupt Enabled This read/write bit enables the timebase interrupt when the TBIF bit becomes set. Reset clears the TBIE bit. 1 = Timebase interrupt enabled 0 = Timebase interrupt disabled TBON -- Timebase Enabled This read/write bit enables the timebase. Timebase may be turned off to reduce power consumption when its function is not necessary. The counter can be initialized by clearing and then setting this bit. Reset clears the TBON bit. 1 = Timebase enabled 0 = Timebase disabled and the counter initialized to 0's
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 149
Timebase Module (TBM)
10.5 Interrupts
The timebase module can interrupt the CPU on a regular basis with a rate defined by TBR[2:0]. When the timebase counter chain rolls over, the TBIF flag is set. If the TBIE bit is set, enabling the timebase interrupt, the counter chain overflow will generate a CPU interrupt request. The interrupt vector is defined in Table 2-1 . Vector Addresses. Interrupts must be acknowledged by writing a logic 1 to the TACK bit.
10.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power- consumption standby modes.
10.6.1 Wait Mode
The timebase module remains active after execution of the WAIT instruction. In wait mode, the timebase register is not accessible by the CPU. If the timebase functions are not required during wait mode, reduce the power consumption by stopping the timebase before enabling the WAIT instruction.
10.6.2 Stop Mode
The timebase module may remain active after execution of the STOP instruction if the oscillator has been enabled to operate during stop mode through the stop mode oscillator enable bit (STOP_ICLKDIS, STOP_RCLKEN, or STOP_XCLKEN) for the selected oscillator in the CONFIG2 register. The timebase module can be used in this mode to generate a periodic walk-up from stop mode. If the oscillator has not been enabled to operate in stop mode, the timebase module will not be active during stop mode. In stop mode the timebase register is not accessible by the CPU. If the timebase functions are not required during stop mode, reduce the power consumption by stopping the timebase before enabling the STOP instruction.
MC68HC908AP A-Family Data Sheet, Rev. 2 150 Freescale Semiconductor
Chapter 11 Serial Communications Interface Module (SCI)
11.1 Introduction
The MC68HC908AP64A has two SCI modules: * SCI1 is a standard SCI module, and * SCI2 is an infrared SCI module. This section describes SCI1, the serial communications interface (SCI) module, which allows high-speed asynchronous communications with peripheral devices and other MCUs. NOTE When the SCI is enabled, the TxD pin is an open-drain output and requires a pullup resistor to be connected for proper SCI operation.
11.2 Features
Features of the SCI module include the following: * Full-duplex operation * Standard mark/space non-return-to-zero (NRZ) format * 32 programmable baud rates * Programmable 8-bit or 9-bit character length * Separately enabled transmitter and receiver * Separate receiver and transmitter CPU interrupt requests * Programmable transmitter output polarity * Two receiver wakeup methods: - Idle line wakeup - Address mark wakeup * Interrupt-driven operation with eight interrupt flags: - Transmitter empty - Transmission complete - Receiver full - Idle receiver input - Receiver overrun - Noise error - Framing error - Parity error * Receiver framing error detection * Hardware parity checking * 1/16 bit-time noise detection * Configuration register bit, SCIBDSRC, to allow selection of baud rate clock source
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 151
Serial Communications Interface Module (SCI)
11.3 Pin Name Conventions
The generic names of the SCI I/O pins are: * RxD (receive data) * TxD (transmit data) SCI I/O (input/output) lines are implemented by sharing parallel I/O port pins. The full name of an SCI input or output reflects the name of the shared port pin. Table 11-1 shows the full names and the generic names of the SCI I/O pins. The generic pin names appear in the text of this section. Table 11-1. Pin Name Conventions
Generic Pin Names: Full Pin Names: RxD PTB3/RxD TxD PTB2/TxD
NOTE When the SCI is enabled, the TxD pin is an open-drain output and requires a pullup resistor to be connected for proper SCI operation.
Addr. $0013 Register Name SCI Control Register 1 (SCC1) SCI Control Register 2 (SCC2) SCI Control Register 3 (SCC3) Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Bit 7 LOOPS 0 SCTIE 0 R8 U SCTE 1 6 ENSCI 0 TCIE 0 T8 U TC 1 5 TXINV 0 SCRIE 0 DMARE 0 SCRF 0 4 M 0 ILIE 0 DMATE 0 IDLE 0 3 WAKE 0 TE 0 ORIE 0 OR 0 2 ILTY 0 RE 0 NEIE 0 NF 0 1 PEN 0 RWU 0 FEIE 0 FE 0 BKF 0 R1 T1 SCR1 0 Bit 0 PTY 0 SBK 0 PEIE 0 PE 0 RPF 0 R0 T0 SCR0 0
$0014
$0015
$0016 SCI Status Register 1 (SCS1)
$0017 SCI Status Register 2 (SCS2) SCI Data Register (SCDR) SCI Baud Rate Register (SCBR)
$0018
0 R7 T7 0 0
0 R6 T6 0
0 R5 T5 SCP1
0 0 R4 R3 T4 T3 Unaffected by reset SCP0 0 R 0
0 R2 T2 SCR2 0
$0019
0 0 = Unimplemented
R = Reserved
U = Unaffected
Figure 11-1. SCI I/O Register Summary
MC68HC908AP A-Family Data Sheet, Rev. 2 152 Freescale Semiconductor
Functional Description
11.4 Functional Description
Figure 11-2 shows the structure of the SCI module. The SCI allows full-duplex, asynchronous, NRZ serial communication among the MCU and remote devices, including other MCUs. The transmitter and receiver of the SCI operate independently, although they use the same baud rate generator. During normal operation, the CPU monitors the status of the SCI, writes the data to be transmitted, and processes received data. The baud rate clock source for the SCI can be selected via the configuration bit, SCIBDSRC, of the CONFIG2 register ($001D).
INTERNAL BUS
SCI DATA REGISTER TRANSMITTER INTERRUPT CONTROL RECEIVER INTERRUPT CONTROL RECEIVE SHIFT REGISTER DMA INTERRUPT CONTROL ERROR INTERRUPT CONTROL
SCI DATA REGISTER TRANSMIT SHIFT REGISTER
RxD
TxD
TXINV SCTIE TCIE SCRIE ILIE TE RE RWU SBK SCTE TC SCRF IDLE OR NF FE PE LOOPS LOOPS WAKEUP CONTROL SCIBDSRC FROM CONFIG RECEIVE CONTROL FLAG CONTROL M WAKE ILTY SL CGMXCLK A X B IT12 SL = 0 => X = A SL = 1 => X = B /4 PRESCALER BAUD DIVIDER PEN PTY DATA SELECTION CONTROL ENSCI TRANSMIT CONTROL ORIE NEIE FEIE PEIE
R8 T8
DMARE DMATE
ENSCI
BKF RPF
CGMXCLK is from CGM module IT12 = fBUS
/ 16
Figure 11-2. SCI Module Block Diagram
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 153
Serial Communications Interface Module (SCI)
11.4.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format illustrated in Figure 11-3.
8-BIT DATA FORMAT BIT M IN SCC1 CLEAR START BIT BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 PARITY BIT BIT 7 STOP BIT
NEXT START BIT
9-BIT DATA FORMAT BIT M IN SCC1 SET START BIT BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 BIT 7
PARITY BIT BIT 8 STOP BIT
NEXT START BIT
Figure 11-3. SCI Data Formats
11.4.2 Transmitter
Figure 11-4 shows the structure of the SCI transmitter. The baud rate clock source for the SCI can be selected via the configuration bit, SCIBDSRC. Source selection values are shown in Figure 11-4.
INTERNAL BUS
/4 SCIBDSRC FROM CONFIG2
PRESCALER
BAUD DIVIDER
/ 16
SCI DATA REGISTER
SCP0 SCR1 SCR2 SCR0 TRANSMITTER CPU INTERRUPT REQUEST TRANSMITTER DMA SERVICE REQUEST TXINV
SL CGMXCLK A X B IT12 SL = 0 => X = A SL = 1 => X = B
H
8 MSB
7
6
5
4
3
2
1
0
START L
SCP1 STOP
11-BIT TRANSMIT SHIFT REGISTER
TxD
M SHIFT ENABLE PEN PTY PARITY GENERATION LOAD FROM SCDR
PREAMBLE ALL 1s
T8 DMATE DMATE SCTIE SCTE DMATE SCTE SCTIE TC TCIE
TRANSMITTER CONTROL LOGIC
SCTE
LOOPS SCTIE TC TCIE ENSCI TE
Figure 11-4. SCI Transmitter
MC68HC908AP A-Family Data Sheet, Rev. 2 154 Freescale Semiconductor
BREAK ALL 0s SBK
Functional Description
11.4.2.1 Character Length The transmitter can accommodate either 8-bit or 9-bit data. The state of the M bit in SCI control register 1 (SCC1) determines character length. When transmitting 9-bit data, bit T8 in SCI control register 3 (SCC3) is the ninth bit (bit 8). 11.4.2.2 Character Transmission During an SCI transmission, the transmit shift register shifts a character out to the TxD pin. The SCI data register (SCDR) is the write-only buffer between the internal data bus and the transmit shift register. To initiate an SCI transmission: 1. Enable the SCI by writing a logic 1 to the enable SCI bit (ENSCI) in SCI control register 1 (SCC1). 2. Enable the transmitter by writing a logic 1 to the transmitter enable bit (TE) in SCI control register 2 (SCC2). 3. Clear the SCI transmitter empty bit by first reading SCI status register 1 (SCS1) and then writing to the SCDR. 4. Repeat step 3 for each subsequent transmission. At the start of a transmission, transmitter control logic automatically loads the transmit shift register with a preamble of logic 1s. After the preamble shifts out, control logic transfers the SCDR data into the transmit shift register. A logic 0 start bit automatically goes into the least significant bit position of the transmit shift register. A logic 1 stop bit goes into the most significant bit position. The SCI transmitter empty bit, SCTE, in SCS1 becomes set when the SCDR transfers a byte to the transmit shift register. The SCTE bit indicates that the SCDR can accept new data from the internal data bus. If the SCI transmit interrupt enable bit, SCTIE, in SCC2 is also set, the SCTE bit generates a transmitter CPU interrupt request. When the transmit shift register is not transmitting a character, the TxD pin goes to the idle condition, logic 1. If at any time software clears the ENSCI bit in SCI control register 1 (SCC1), the transmitter and receiver relinquish control of the port pin. 11.4.2.3 Break Characters Writing a logic 1 to the send break bit, SBK, in SCC2 loads the transmit shift register with a break character. A break character contains all logic 0s and has no start, stop, or parity bit. Break character length depends on the M bit in SCC1. As long as SBK is at logic 1, transmitter logic continuously loads break characters into the transmit shift register. After software clears the SBK bit, the shift register finishes transmitting the last break character and then transmits at least one logic 1. The automatic logic 1 at the end of a break character guarantees the recognition of the start bit of the next character. The SCI recognizes a break character when a start bit is followed by eight or nine logic 0 data bits and a logic 0 where the stop bit should be. Receiving a break character has these effects on SCI registers: * Sets the framing error bit (FE) in SCS1 * Sets the SCI receiver full bit (SCRF) in SCS1 * Clears the SCI data register (SCDR) * Clears the R8 bit in SCC3 * Sets the break flag bit (BKF) in SCS2 * May set the overrun (OR), noise flag (NF), parity error (PE), or reception in progress flag (RPF) bits
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 155
Serial Communications Interface Module (SCI)
11.4.2.4 Idle Characters An idle character contains all logic 1s and has no start, stop, or parity bit. Idle character length depends on the M bit in SCC1. The preamble is a synchronizing idle character that begins every transmission. If the TE bit is cleared during a transmission, the TxD pin becomes idle after completion of the transmission in progress. Clearing and then setting the TE bit during a transmission queues an idle character to be sent after the character currently being transmitted. NOTE When queueing an idle character, return the TE bit to logic 1 before the stop bit of the current character shifts out to the TxD pin. Setting TE after the stop bit appears on TxD causes data previously written to the SCDR to be lost. Toggle the TE bit for a queued idle character when the SCTE bit becomes set and just before writing the next byte to the SCDR. 11.4.2.5 Inversion of Transmitted Output The transmit inversion bit (TXINV) in SCI control register 1 (SCC1) reverses the polarity of transmitted data. All transmitted values, including idle, break, start, and stop bits, are inverted when TXINV is at logic 1. (See 11.8.1 SCI Control Register 1.) 11.4.2.6 Transmitter Interrupts These conditions can generate CPU interrupt requests from the SCI transmitter: * SCI transmitter empty (SCTE) -- The SCTE bit in SCS1 indicates that the SCDR has transferred a character to the transmit shift register. SCTE can generate a transmitter CPU interrupt request. Setting the SCI transmit interrupt enable bit, SCTIE, in SCC2 enables the SCTE bit to generate transmitter CPU interrupt requests. * Transmission complete (TC) -- The TC bit in SCS1 indicates that the transmit shift register and the SCDR are empty and that no break or idle character has been generated. The transmission complete interrupt enable bit, TCIE, in SCC2 enables the TC bit to generate transmitter CPU interrupt requests.
11.4.3 Receiver
Figure 11-5 shows the structure of the SCI receiver. 11.4.3.1 Character Length The receiver can accommodate either 8-bit or 9-bit data. The state of the M bit in SCI control register 1 (SCC1) determines character length. When receiving 9-bit data, bit R8 in SCI control register 2 (SCC2) is the ninth bit (bit 8). When receiving 8-bit data, bit R8 is a copy of the eighth bit (bit 7). 11.4.3.2 Character Reception During an SCI reception, the receive shift register shifts characters in from the RxD pin. The SCI data register (SCDR) is the read-only buffer between the internal data bus and the receive shift register. After a complete character shifts into the receive shift register, the data portion of the character transfers to the SCDR. The SCI receiver full bit, SCRF, in SCI status register 1 (SCS1) becomes set, indicating that
MC68HC908AP A-Family Data Sheet, Rev. 2 156 Freescale Semiconductor
Functional Description
the received byte can be read. If the SCI receive interrupt enable bit, SCRIE, in SCC2 is also set, the SCRF bit generates a receiver CPU interrupt request.
INTERNAL BUS
SCIBDSRC FROM CONFIG2
SCR1 SCP1 SCP0 SCR2 SCR0 START 0 L RWU PRESCALER BAUD DIVIDER / 16 DATA RECOVERY ALL 0s ALL 1s MSB SCI DATA REGISTER
SL CGMXCLK A X B IT12 SL = 0 => X = A SL = 1 => X = B
STOP
/4
11-BIT RECEIVE SHIFT REGISTER 8 7 6 5 4 3 2 1
RxD
H
BKF RPF ERROR CPU INTERRUPT REQUEST DMA SERVICE REQUEST
CPU INTERRUPT REQUEST
M WAKE ILTY PEN PTY WAKEUP LOGIC PARITY CHECKING IDLE ILIE DMARE SCRF SCRIE DMARE SCRF SCRIE DMARE OR ORIE NF NEIE FE FEIE PE PEIE
SCRF IDLE
R8
ILIE
SCRIE
DMARE OR ORIE NF NEIE FE FEIE PE PEIE
Figure 11-5. SCI Receiver Block Diagram
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 157
Serial Communications Interface Module (SCI)
11.4.3.3 Data Sampling The receiver samples the RxD pin at the RT clock rate. The RT clock is an internal signal with a frequency 16 times the baud rate. To adjust for baud rate mismatch, the RT clock is resynchronized at the following times (see Figure 11-6): * After every start bit * After the receiver detects a data bit change from logic 1 to logic 0 (after the majority of data bit samples at RT8, RT9, and RT10 returns a valid logic 1 and the majority of the next RT8, RT9, and RT10 samples returns a valid logic 0) To locate the start bit, data recovery logic does an asynchronous search for a logic 0 preceded by three logic 1s. When the falling edge of a possible start bit occurs, the RT clock begins to count to 16.
START BIT RxD LSB
SAMPLES
START BIT QUALIFICATION
START BIT VERIFICATION
DATA SAMPLING
RT CLOCK RT10 RT11 RT12 RT13 RT14 RT15 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT2 RT3 RT4 RT5 RT6 RT7 RT8 RT9 RT1 RT2 RT3 RT4 RT CLOCK STATE RT CLOCK RESET RT16
Figure 11-6. Receiver Data Sampling To verify the start bit and to detect noise, data recovery logic takes samples at RT3, RT5, and RT7. Table 11-2 summarizes the results of the start bit verification samples. Table 11-2. Start Bit Verification
RT3, RT5, and RT7 Samples 000 001 010 011 100 101 110 111 Start Bit Verification Yes Yes Yes No Yes No No No Noise Flag 0 1 1 0 1 0 0 0
MC68HC908AP A-Family Data Sheet, Rev. 2 158 Freescale Semiconductor
Functional Description
Start bit verification is not successful if any two of the three verification samples are logic 1s. If start bit verification is not successful, the RT clock is reset and a new search for a start bit begins. To determine the value of a data bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10. Table 11-3 summarizes the results of the data bit samples. Table 11-3. Data Bit Recovery
RT8, RT9, and RT10 Samples 000 001 010 011 100 101 110 111 Data Bit Determination 0 0 0 1 0 1 1 1 Noise Flag 0 1 1 1 1 1 1 0
NOTE The RT8, RT9, and RT10 samples do not affect start bit verification. If any or all of the RT8, RT9, and RT10 start bit samples are logic 1s following a successful start bit verification, the noise flag (NF) is set and the receiver assumes that the bit is a start bit. To verify a stop bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10. Table 11-4 summarizes the results of the stop bit samples. Table 11-4. Stop Bit Recovery
RT8, RT9, and RT10 Samples 000 001 010 011 100 101 110 111 Framing Error Flag 1 1 1 0 1 0 0 0 Noise Flag 0 1 1 1 1 1 1 0
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 159
Serial Communications Interface Module (SCI)
11.4.3.4 Framing Errors If the data recovery logic does not detect a logic 1 where the stop bit should be in an incoming character, it sets the framing error bit, FE, in SCS1. A break character also sets the FE bit because a break character has no stop bit. The FE bit is set at the same time that the SCRF bit is set. 11.4.3.5 Baud Rate Tolerance A transmitting device may be operating at a baud rate below or above the receiver baud rate. Accumulated bit time misalignment can cause one of the three stop bit data samples to fall outside the actual stop bit. Then a noise error occurs. If more than one of the samples is outside the stop bit, a framing error occurs. In most applications, the baud rate tolerance is much more than the degree of misalignment that is likely to occur. As the receiver samples an incoming character, it resynchronizes the RT clock on any valid falling edge within the character. Resynchronization within characters corrects misalignments between transmitter bit times and receiver bit times. Slow Data Tolerance Figure 11-7 shows how much a slow received character can be misaligned without causing a noise error or a framing error. The slow stop bit begins at RT8 instead of RT1 but arrives in time for the stop bit data samples at RT8, RT9, and RT10.
MSB STOP
RT10
RT11
RT12
RT13
RT14
RT15
DATA SAMPLES
Figure 11-7. Slow Data For an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times x 16 RT cycles + 10 RT cycles = 154 RT cycles. With the misaligned character shown in Figure 11-7, the receiver counts 154 RT cycles at the point when the count of the transmitting device is 9 bit times x 16 RT cycles + 3 RT cycles = 147 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a slow 8-bit character with no errors is
154 - 147 x 100 = 4.54% ------------------------154
For a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times x 16 RT cycles + 10 RT cycles = 170 RT cycles. With the misaligned character shown in Figure 11-7, the receiver counts 170 RT cycles at the point when the count of the transmitting device is 10 bit times x 16 RT cycles + 3 RT cycles = 163 RT cycles.
MC68HC908AP A-Family Data Sheet, Rev. 2 160 Freescale Semiconductor
RT16
RT1
RT2
RT3
RT4
RT5
RT6
RT7
RT8
RT9
RECEIVER RT CLOCK
Functional Description
The maximum percent difference between the receiver count and the transmitter count of a slow 9-bit character with no errors is
170 - 163 x 100 = 4.12% ------------------------170
Fast Data Tolerance Figure 11-8 shows how much a fast received character can be misaligned without causing a noise error or a framing error. The fast stop bit ends at RT10 instead of RT16 but is still there for the stop bit data samples at RT8, RT9, and RT10.
STOP IDLE OR NEXT CHARACTER
RT10
RT11
RT12
RT13
RT14
RT15
DATA SAMPLES
Figure 11-8. Fast Data For an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times x 16 RT cycles + 10 RT cycles = 154 RT cycles. With the misaligned character shown in Figure 11-8, the receiver counts 154 RT cycles at the point when the count of the transmitting device is 10 bit times x 16 RT cycles = 160 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a fast 8-bit character with no errors is
154 - 160 x 100 = 3.90% ------------------------154
For a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times x 16 RT cycles + 10 RT cycles = 170 RT cycles. With the misaligned character shown in Figure 11-8, the receiver counts 170 RT cycles at the point when the count of the transmitting device is 11 bit times x 16 RT cycles = 176 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a fast 9-bit character with no errors is
170 - 176 x 100 = 3.53% ------------------------170
11.4.3.6 Receiver Wakeup So that the MCU can ignore transmissions intended only for other receivers in multiple-receiver systems, the receiver can be put into a standby state. Setting the receiver wakeup bit, RWU, in SCC2 puts the receiver into a standby state during which receiver interrupts are disabled.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 161
RT16
RT1
RT2
RT3
RT4
RT5
RT6
RT7
RT8
RT9
RECEIVER RT CLOCK
Serial Communications Interface Module (SCI)
Depending on the state of the WAKE bit in SCC1, either of two conditions on the RxD pin can bring the receiver out of the standby state: * Address mark -- An address mark is a logic 1 in the most significant bit position of a received character. When the WAKE bit is set, an address mark wakes the receiver from the standby state by clearing the RWU bit. The address mark also sets the SCI receiver full bit, SCRF. Software can then compare the character containing the address mark to the user-defined address of the receiver. If they are the same, the receiver remains awake and processes the characters that follow. If they are not the same, software can set the RWU bit and put the receiver back into the standby state. * Idle input line condition -- When the WAKE bit is clear, an idle character on the RxD pin wakes the receiver from the standby state by clearing the RWU bit. The idle character that wakes the receiver does not set the receiver idle bit, IDLE, or the SCI receiver full bit, SCRF. The idle line type bit, ILTY, determines whether the receiver begins counting logic 1s as idle character bits after the start bit or after the stop bit. NOTE With the WAKE bit clear, setting the RWU bit after the RxD pin has been idle may cause the receiver to wake up immediately. 11.4.3.7 Receiver Interrupts The following sources can generate CPU interrupt requests from the SCI receiver: * SCI receiver full (SCRF) -- The SCRF bit in SCS1 indicates that the receive shift register has transferred a character to the SCDR. SCRF can generate a receiver CPU interrupt request. Setting the SCI receive interrupt enable bit, SCRIE, in SCC2 enables the SCRF bit to generate receiver CPU interrupts. * Idle input (IDLE) -- The IDLE bit in SCS1 indicates that 10 or 11 consecutive logic 1s shifted in from the RxD pin. The idle line interrupt enable bit, ILIE, in SCC2 enables the IDLE bit to generate CPU interrupt requests. 11.4.3.8 Error Interrupts The following receiver error flags in SCS1 can generate CPU interrupt requests: * Receiver overrun (OR) -- The OR bit indicates that the receive shift register shifted in a new character before the previous character was read from the SCDR. The previous character remains in the SCDR, and the new character is lost. The overrun interrupt enable bit, ORIE, in SCC3 enables OR to generate SCI error CPU interrupt requests. * Noise flag (NF) -- The NF bit is set when the SCI detects noise on incoming data or break characters, including start, data, and stop bits. The noise error interrupt enable bit, NEIE, in SCC3 enables NF to generate SCI error CPU interrupt requests. * Framing error (FE) -- The FE bit in SCS1 is set when a logic 0 occurs where the receiver expects a stop bit. The framing error interrupt enable bit, FEIE, in SCC3 enables FE to generate SCI error CPU interrupt requests. * Parity error (PE) -- The PE bit in SCS1 is set when the SCI detects a parity error in incoming data. The parity error interrupt enable bit, PEIE, in SCC3 enables PE to generate SCI error CPU interrupt requests.
MC68HC908AP A-Family Data Sheet, Rev. 2 162 Freescale Semiconductor
Low-Power Modes
11.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power- consumption standby modes.
11.5.1 Wait Mode
The SCI module remains active after the execution of a WAIT instruction. In wait mode, the SCI module registers are not accessible by the CPU. Any enabled CPU interrupt request from the SCI module can bring the MCU out of wait mode. If SCI module functions are not required during wait mode, reduce power consumption by disabling the module before executing the WAIT instruction. Refer to 7.6 Low-Power Modes for information on exiting wait mode.
11.5.2 Stop Mode
The SCI module is inactive after the execution of a STOP instruction. The STOP instruction does not affect SCI register states. SCI module operation resumes after an external interrupt. Because the internal clock is inactive during stop mode, entering stop mode during an SCI transmission or reception results in invalid data. Refer to 7.6 Low-Power Modes for information on exiting stop mode.
11.6 SCI During Break Module Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state. To allow software to clear status bits during a break interrupt, write a logic 1 to the BCFE bit. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state. To protect status bits during the break state, write a logic 0 to the BCFE bit. With BCFE at logic 0 (its default state), software can read and write I/O registers during the break state without affecting status bits. Some status bits have a 2-step read/write clearing procedure. If software does the first step on such a bit before the break, the bit cannot change during the break state as long as BCFE is at logic 0. After the break, doing the second step clears the status bit.
11.7 I/O Signals
Port B shares two of its pins with the SCI module. The two SCI I/O pins are: * PTB2/TxD -- Transmit data * PTB3/RxD -- Receive data
11.7.1 TxD (Transmit Data)
When the SCI is enabled (ENSCI=1), the PTB2/TxD pin becomes the serial data output, TxD, from the SCI transmitter regardless of the state of the DDRB2 bit in data direction register B (DDRB). The TxD pin is an open-drain output and requires a pullup resistor to be connected for proper SCI operation.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 163
Serial Communications Interface Module (SCI)
NOTE The PTB2/TxD pin is an open-drain pin when configured as an output. Therefore, when configured as a general purpose output pin (PTB2), a pullup resistor must be connected to this pin.
11.7.2 RxD (Receive Data)
When the SCI is enabled (ENSCI=1), the PTB3/RxD pin becomes the serial data input, RxD, to the SCI receiver regardless of the state of the DDRB3 bit in data direction register B (DDRB). NOTE The PTB3/RxD pin is an open-drain pin when configured as an output. Therefore, when configured as a general purpose output pin (PTB3), a pullup resistor must be connected to this pin.
11.8 I/O Registers
These I/O registers control and monitor SCI operation: * SCI control register 1 (SCC1) * SCI control register 2 (SCC2) * SCI control register 3 (SCC3) * SCI status register 1 (SCS1) * SCI status register 2 (SCS2) * SCI data register (SCDR) * SCI baud rate register (SCBR)
MC68HC908AP A-Family Data Sheet, Rev. 2 164 Freescale Semiconductor
I/O Registers
11.8.1 SCI Control Register 1
SCI control register 1: * Enables loop mode operation * Enables the SCI * Controls output polarity * Controls character length * Controls SCI wakeup method * Controls idle character detection * Enables parity function * Controls parity type
Address: Read: Write: Reset: $0013 Bit 7 LOOPS 0 6 ENSCI 0 5 TXINV 0 4 M 0 3 WAKE 0 2 ILTY 0 1 PEN 0 Bit 0 PTY 0
Figure 11-9. SCI Control Register 1 (SCC1) LOOPS -- Loop Mode Select Bit This read/write bit enables loop mode operation. In loop mode the RxD pin is disconnected from the SCI, and the transmitter output goes into the receiver input. Both the transmitter and the receiver must be enabled to use loop mode. Reset clears the LOOPS bit. 1 = Loop mode enabled 0 = Normal operation enabled ENSCI -- Enable SCI Bit This read/write bit enables the SCI and the SCI baud rate generator. Clearing ENSCI sets the SCTE and TC bits in SCI status register 1 and disables transmitter interrupts. Reset clears the ENSCI bit. 1 = SCI enabled 0 = SCI disabled TXINV -- Transmit Inversion Bit This read/write bit reverses the polarity of transmitted data. Reset clears the TXINV bit. 1 = Transmitter output inverted 0 = Transmitter output not inverted NOTE Setting the TXINV bit inverts all transmitted values, including idle, break, start, and stop bits. M -- Mode (Character Length) Bit This read/write bit determines whether SCI characters are eight or nine bits long. (See Table 11-5.) The ninth bit can serve as an extra stop bit, as a receiver wakeup signal, or as a parity bit. Reset clears the M bit. 1 = 9-bit SCI characters 0 = 8-bit SCI characters
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 165
Serial Communications Interface Module (SCI)
WAKE -- Wakeup Condition Bit This read/write bit determines which condition wakes up the SCI: a logic 1 (address mark) in the most significant bit position of a received character or an idle condition on the RxD pin. Reset clears the WAKE bit. 1 = Address mark wakeup 0 = Idle line wakeup ILTY -- Idle Line Type Bit This read/write bit determines when the SCI starts counting logic 1s as idle character bits. The counting begins either after the start bit or after the stop bit. If the count begins after the start bit, then a string of logic 1s preceding the stop bit may cause false recognition of an idle character. Beginning the count after the stop bit avoids false idle character recognition, but requires properly synchronized transmissions. Reset clears the ILTY bit. 1 = Idle character bit count begins after stop bit 0 = Idle character bit count begins after start bit PEN -- Parity Enable Bit This read/write bit enables the SCI parity function. (See Table 11-5.) When enabled, the parity function inserts a parity bit in the most significant bit position. (See Figure 11-3.) Reset clears the PEN bit. 1 = Parity function enabled 0 = Parity function disabled PTY -- Parity Bit This read/write bit determines whether the SCI generates and checks for odd parity or even parity. (See Table 11-5.) Reset clears the PTY bit. 1 = Odd parity 0 = Even parity NOTE Changing the PTY bit in the middle of a transmission or reception can generate a parity error. Table 11-5. Character Format Selection
Control Bits M 0 1 0 0 1 1 PEN:PTY 0X 0X 10 11 10 11 Start Bits 1 1 1 1 1 1 Data Bits 8 9 7 7 8 8 Character Format Parity None None Even Odd Even Odd Stop Bits 1 1 1 1 1 1 Character Length 10 bits 11 bits 10 bits 10 bits 11 bits 11 bits
MC68HC908AP A-Family Data Sheet, Rev. 2 166 Freescale Semiconductor
I/O Registers
11.8.2 SCI Control Register 2
SCI control register 2: * Enables the following CPU interrupt requests: - Enables the SCTE bit to generate transmitter CPU interrupt requests - Enables the TC bit to generate transmitter CPU interrupt requests - Enables the SCRF bit to generate receiver CPU interrupt requests - Enables the IDLE bit to generate receiver CPU interrupt requests * Enables the transmitter * Enables the receiver * Enables SCI wakeup * Transmits SCI break characters
Address: Read: Write: Reset: $0014 Bit 7 SCTIE 0 6 TCIE 0 5 SCRIE 0 4 ILIE 0 3 TE 0 2 RE 0 1 RWU 0 Bit 0 SBK 0
Figure 11-10. SCI Control Register 2 (SCC2) SCTIE -- SCI Transmit Interrupt Enable Bit This read/write bit enables the SCTE bit to generate SCI transmitter CPU interrupt requests. Reset clears the SCTIE bit. 1 = SCTE enabled to generate CPU interrupt 0 = SCTE not enabled to generate CPU interrupt TCIE -- Transmission Complete Interrupt Enable Bit This read/write bit enables the TC bit to generate SCI transmitter CPU interrupt requests. Reset clears the TCIE bit. 1 = TC enabled to generate CPU interrupt requests 0 = TC not enabled to generate CPU interrupt requests SCRIE -- SCI Receive Interrupt Enable Bit This read/write bit enables the SCRF bit to generate SCI receiver CPU interrupt requests. Reset clears the SCRIE bit. 1 = SCRF enabled to generate CPU interrupt 0 = SCRF not enabled to generate CPU interrupt ILIE -- Idle Line Interrupt Enable Bit This read/write bit enables the IDLE bit to generate SCI receiver CPU interrupt requests. Reset clears the ILIE bit. 1 = IDLE enabled to generate CPU interrupt requests 0 = IDLE not enabled to generate CPU interrupt requests
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 167
Serial Communications Interface Module (SCI)
TE -- Transmitter Enable Bit Setting this read/write bit begins the transmission by sending a preamble of 10 or 11 logic 1s from the transmit shift register to the TxD pin. If software clears the TE bit, the transmitter completes any transmission in progress before the TxD returns to the idle condition (logic 1). Clearing and then setting TE during a transmission queues an idle character to be sent after the character currently being transmitted. Reset clears the TE bit. 1 = Transmitter enabled 0 = Transmitter disabled NOTE Writing to the TE bit is not allowed when the enable SCI bit (ENSCI) is clear. ENSCI is in SCI control register 1. RE -- Receiver Enable Bit Setting this read/write bit enables the receiver. Clearing the RE bit disables the receiver but does not affect receiver interrupt flag bits. Reset clears the RE bit. 1 = Receiver enabled 0 = Receiver disabled NOTE Writing to the RE bit is not allowed when the enable SCI bit (ENSCI) is clear. ENSCI is in SCI control register 1. RWU -- Receiver Wakeup Bit This read/write bit puts the receiver in a standby state during which receiver interrupts are disabled. The WAKE bit in SCC1 determines whether an idle input or an address mark brings the receiver out of the standby state and clears the RWU bit. Reset clears the RWU bit. 1 = Standby state 0 = Normal operation SBK -- Send Break Bit Setting and then clearing this read/write bit transmits a break character followed by a logic 1. The logic 1 after the break character guarantees recognition of a valid start bit. If SBK remains set, the transmitter continuously transmits break characters with no logic 1s between them. Reset clears the SBK bit. 1 = Transmit break characters 0 = No break characters being transmitted NOTE Do not toggle the SBK bit immediately after setting the SCTE bit. Toggling SBK before the preamble begins causes the SCI to send a break character instead of a preamble.
MC68HC908AP A-Family Data Sheet, Rev. 2 168 Freescale Semiconductor
I/O Registers
11.8.3 SCI Control Register 3
SCI control register 3: * Stores the ninth SCI data bit received and the ninth SCI data bit to be transmitted * Enables these interrupts: - Receiver overrun interrupts - Noise error interrupts - Framing error interrupts * Parity error interrupts
Address: Read: Write: Reset: U $0015 Bit 7 R8 6 T8 U 5 DMARE 0 4 DMATE 0 3 ORIE 0 U = Unaffected 2 NEIE 0 1 FEIE 0 Bit 0 PEIE 0
= Unimplemented
Figure 11-11. SCI Control Register 3 (SCC3) R8 -- Received Bit 8 When the SCI is receiving 9-bit characters, R8 is the read-only ninth bit (bit 8) of the received character. R8 is received at the same time that the SCDR receives the other 8 bits. When the SCI is receiving 8-bit characters, R8 is a copy of the eighth bit (bit 7). Reset has no effect on the R8 bit. T8 -- Transmitted Bit 8 When the SCI is transmitting 9-bit characters, T8 is the read/write ninth bit (bit 8) of the transmitted character. T8 is loaded into the transmit shift register at the same time that the SCDR is loaded into the transmit shift register. Reset has no effect on the T8 bit. DMARE -- DMA Receive Enable Bit CAUTION The DMA module is not included on this MCU. Writing a logic 1 to DMARE or DMATE may adversely affect MCU performance. 1 = DMA not enabled to service SCI receiver DMA service requests generated by the SCRF bit (SCI receiver CPU interrupt requests enabled) 0 = DMA not enabled to service SCI receiver DMA service requests generated by the SCRF bit (SCI receiver CPU interrupt requests enabled) DMATE -- DMA Transfer Enable Bit CAUTION The DMA module is not included on this MCU. Writing a logic 1 to DMARE or DMATE may adversely affect MCU performance. 1 = SCTE DMA service requests enabled; SCTE CPU interrupt requests disabled 0 = SCTE DMA service requests disabled; SCTE CPU interrupt requests enabled ORIE -- Receiver Overrun Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the receiver overrun bit, OR. 1 = SCI error CPU interrupt requests from OR bit enabled 0 = SCI error CPU interrupt requests from OR bit disabled
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 169
Serial Communications Interface Module (SCI)
NEIE -- Receiver Noise Error Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the noise error bit, NE. Reset clears NEIE. 1 = SCI error CPU interrupt requests from NE bit enabled 0 = SCI error CPU interrupt requests from NE bit disabled FEIE -- Receiver Framing Error Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the framing error bit, FE. Reset clears FEIE. 1 = SCI error CPU interrupt requests from FE bit enabled 0 = SCI error CPU interrupt requests from FE bit disabled PEIE -- Receiver Parity Error Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the parity error bit, PE. (See 11.8.4 SCI Status Register 1.) Reset clears PEIE. 1 = SCI error CPU interrupt requests from PE bit enabled 0 = SCI error CPU interrupt requests from PE bit disabled
11.8.4 SCI Status Register 1
SCI status register 1 (SCS1) contains flags to signal these conditions: * Transfer of SCDR data to transmit shift register complete * Transmission complete * Transfer of receive shift register data to SCDR complete * Receiver input idle * Receiver overrun * Noisy data * Framing error * Parity error
Address: Read: Write: Reset: 1 1 0 0 0 0 0 0 = Unimplemented $0016 Bit 7 SCTE 6 TC 5 SCRF 4 IDLE 3 OR 2 NF 1 FE Bit 0 PE
Figure 11-12. SCI Status Register 1 (SCS1) SCTE -- SCI Transmitter Empty Bit This clearable, read-only bit is set when the SCDR transfers a character to the transmit shift register. SCTE can generate an SCI transmitter CPU interrupt request. When the SCTIE bit in SCC2 is set, SCTE generates an SCI transmitter CPU interrupt request. In normal operation, clear the SCTE bit by reading SCS1 with SCTE set and then writing to SCDR. Reset sets the SCTE bit. 1 = SCDR data transferred to transmit shift register 0 = SCDR data not transferred to transmit shift register
MC68HC908AP A-Family Data Sheet, Rev. 2 170 Freescale Semiconductor
I/O Registers
TC -- Transmission Complete Bit This read-only bit is set when the SCTE bit is set, and no data, preamble, or break character is being transmitted. TC generates an SCI transmitter CPU interrupt request if the TCIE bit in SCC2 is also set. TC is automatically cleared when data, preamble or break is queued and ready to be sent. There may be up to 1.5 transmitter clocks of latency between queueing data, preamble, and break and the transmission actually starting. Reset sets the TC bit. 1 = No transmission in progress 0 = Transmission in progress SCRF -- SCI Receiver Full Bit This clearable, read-only bit is set when the data in the receive shift register transfers to the SCI data register. SCRF can generate an SCI receiver CPU interrupt request. When the SCRIE bit in SCC2 is set, SCRF generates a CPU interrupt request. In normal operation, clear the SCRF bit by reading SCS1 with SCRF set and then reading the SCDR. Reset clears SCRF. 1 = Received data available in SCDR 0 = Data not available in SCDR IDLE -- Receiver Idle Bit This clearable, read-only bit is set when 10 or 11 consecutive logic 1s appear on the receiver input. IDLE generates an SCI receiver CPU interrupt request if the ILIE bit in SCC2 is also set. Clear the IDLE bit by reading SCS1 with IDLE set and then reading the SCDR. After the receiver is enabled, it must receive a valid character that sets the SCRF bit before an idle condition can set the IDLE bit. Also, after the IDLE bit has been cleared, a valid character must again set the SCRF bit before an idle condition can set the IDLE bit. Reset clears the IDLE bit. 1 = Receiver input idle 0 = Receiver input active (or idle since the IDLE bit was cleared) OR -- Receiver Overrun Bit This clearable, read-only bit is set when software fails to read the SCDR before the receive shift register receives the next character. The OR bit generates an SCI error CPU interrupt request if the ORIE bit in SCC3 is also set. The data in the shift register is lost, but the data already in the SCDR is not affected. Clear the OR bit by reading SCS1 with OR set and then reading the SCDR. Reset clears the OR bit. 1 = Receive shift register full and SCRF = 1 0 = No receiver overrun Software latency may allow an overrun to occur between reads of SCS1 and SCDR in the flag-clearing sequence. Figure 11-13 shows the normal flag-clearing sequence and an example of an overrun caused by a delayed flag-clearing sequence. The delayed read of SCDR does not clear the OR bit because OR was not set when SCS1 was read. Byte 2 caused the overrun and is lost. The next flag-clearing sequence reads byte 3 in the SCDR instead of byte 2. In applications that are subject to software latency or in which it is important to know which byte is lost due to an overrun, the flag-clearing routine can check the OR bit in a second read of SCS1 after reading the data register. NF -- Receiver Noise Flag Bit This clearable, read-only bit is set when the SCI detects noise on the RxD pin. NF generates an SCI error CPU interrupt request if the NEIE bit in SCC3 is also set. Clear the NF bit by reading SCS1 and then reading the SCDR. Reset clears the NF bit. 1 = Noise detected 0 = No noise detected
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 171
Serial Communications Interface Module (SCI)
FE -- Receiver Framing Error Bit This clearable, read-only bit is set when a logic 0 is accepted as the stop bit. FE generates an SCI error CPU interrupt request if the FEIE bit in SCC3 also is set. Clear the FE bit by reading SCS1 with FE set and then reading the SCDR. Reset clears the FE bit. 1 = Framing error detected 0 = No framing error detected
NORMAL FLAG CLEARING SEQUENCE SCRF = 1 SCRF = 0 SCRF = 1 SCRF = 0 SCRF = 1 SCRF = 0 BYTE 4 READ SCS1 SCRF = 1 OR = 0 READ SCDR BYTE 3 BYTE 4 READ SCS1 SCRF = 1 OR = 1 READ SCDR BYTE 3
BYTE 1 READ SCS1 SCRF = 1 OR = 0 READ SCDR BYTE 1
BYTE 2 READ SCS1 SCRF = 1 OR = 0 READ SCDR BYTE 2
BYTE 3
DELAYED FLAG CLEARING SEQUENCE SCRF = 1 OR = 1 SCRF = 0 OR = 1 SCRF = 1 SCRF = 1 OR = 1 SCRF = 0 OR = 0
BYTE 1
BYTE 2 READ SCS1 SCRF = 1 OR = 0 READ SCDR BYTE 1
BYTE 3
Figure 11-13. Flag Clearing Sequence PE -- Receiver Parity Error Bit This clearable, read-only bit is set when the SCI detects a parity error in incoming data. PE generates an SCI error CPU interrupt request if the PEIE bit in SCC3 is also set. Clear the PE bit by reading SCS1 with PE set and then reading the SCDR. Reset clears the PE bit. 1 = Parity error detected 0 = No parity error detected
MC68HC908AP A-Family Data Sheet, Rev. 2 172 Freescale Semiconductor
I/O Registers
11.8.5 SCI Status Register 2
SCI status register 2 contains flags to signal the following conditions: * Break character detected * Incoming data
Address: Read: Write: Reset: 0 0 0 0 0 0 0 0 = Unimplemented $0017 Bit 7 6 5 4 3 2 1 BKF Bit 0 RPF
Figure 11-14. SCI Status Register 2 (SCS2) BKF -- Break Flag Bit This clearable, read-only bit is set when the SCI detects a break character on the RxD pin. In SCS1, the FE and SCRF bits are also set. In 9-bit character transmissions, the R8 bit in SCC3 is cleared. BKF does not generate a CPU interrupt request. Clear BKF by reading SCS2 with BKF set and then reading the SCDR. Once cleared, BKF can become set again only after logic 1s again appear on the RxD pin followed by another break character. Reset clears the BKF bit. 1 = Break character detected 0 = No break character detected RPF -- Reception in Progress Flag Bit This read-only bit is set when the receiver detects a logic 0 during the RT1 time period of the start bit search. RPF does not generate an interrupt request. RPF is reset after the receiver detects false start bits (usually from noise or a baud rate mismatch) or when the receiver detects an idle character. Polling RPF before disabling the SCI module or entering stop mode can show whether a reception is in progress. 1 = Reception in progress 0 = No reception in progress
11.8.6 SCI Data Register
The SCI data register (SCDR) is the buffer between the internal data bus and the receive and transmit shift registers. Reset has no effect on data in the SCI data register.
Address: Read: Write: Reset: $0018 Bit 7 R7 T7 6 R6 T6 5 R5 T5 4 R4 T4 3 R3 T3 2 R2 T2 1 R1 T1 Bit 0 R0 T0
Unaffected by reset
Figure 11-15. SCI Data Register (SCDR) R7/T7-R0/T0 -- Receive/Transmit Data Bits Reading the SCDR accesses the read-only received data bits, R7-R0. Writing to the SCDR writes the data to be transmitted, T7-T0. Reset has no effect on the SCDR. NOTE Do not use read/modify/write instructions on the SCI data register.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 173
Serial Communications Interface Module (SCI)
11.8.7 SCI Baud Rate Register
The baud rate register (SCBR) selects the baud rate for both the receiver and the transmitter.
Address: Read: Write: Reset: 0 0 $0019 0 6 0 5 SCP1 0 4 SCP0 0 3 R 0 R 2 SCR2 0 = Reserved 1 SCR1 0 Bit 0 SCR0 0
= Unimplemented
Figure 11-16. SCI Baud Rate Register (SCBR) SCP1 and SCP0 -- SCI Baud Rate Prescaler Bits These read/write bits select the baud rate prescaler divisor as shown in Table 11-6. Reset clears SCP1 and SCP0. Table 11-6. SCI Baud Rate Prescaling
SCP1 and SCP0 00 01 10 11 Prescaler Divisor (PD) 1 3 4 13
SCR2-SCR0 -- SCI Baud Rate Select Bits These read/write bits select the SCI baud rate divisor as shown in Table 11-7. Reset clears SCR2-SCR0. Table 11-7. SCI Baud Rate Selection
SCR2, SCR1, and SCR0 000 001 010 011 100 101 110 111 Baud Rate Divisor (BD) 1 2 4 8 16 32 64 128
Use this formula to calculate the SCI baud rate:
SCI clock source baud rate = -------------------------------------------64 x PD x BD
where: SCI clock source = fBUS or CGMXCLK (selected by SCIBDSRC bit in CONFIG2 register) PD = prescaler divisor BD = baud rate divisor
MC68HC908AP A-Family Data Sheet, Rev. 2 174 Freescale Semiconductor
I/O Registers
Table 11-8 shows the SCI baud rates that can be generated with a 4.9152-MHz bus clock when fBUS is selected as SCI clock source. Table 11-8. SCI Baud Rate Selection Examples
SCP1 and SCP0 00 00 00 00 00 00 00 00 01 01 01 01 01 01 01 01 10 10 10 10 10 10 10 10 11 11 11 11 11 11 11 11 Prescaler Divisor (PD) 1 1 1 1 1 1 1 1 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 13 13 13 13 13 13 13 13 SCR2, SCR1, and SCR0 000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111 Baud Rate Divisor (BD) 1 2 4 8 16 32 64 128 1 2 4 8 16 32 64 128 1 2 4 8 16 32 64 128 1 2 4 8 16 32 64 128 Baud Rate (fBUS = 4.9152 MHz) 76,800 38,400 19,200 9600 4800 2400 1200 600 25,600 12,800 6400 3200 1600 800 400 200 19,200 9600 4800 2400 1200 600 300 150 5908 2954 1477 739 369 185 92 46
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 175
Serial Communications Interface Module (SCI)
MC68HC908AP A-Family Data Sheet, Rev. 2 176 Freescale Semiconductor
Chapter 12 Infrared Serial Communications Interface Module (IRSCI)
12.1 Introduction
The MC68HC908AP64A has two SCI modules: * SCI1 is a standard SCI module, and * SCI2 is an infrared SCI module. This section describes SCI2, the infrared serial communications interface (IRSCI) module which allows high-speed asynchronous communications with peripheral devices and other MCUs. This IRSCI consists of an SCI module for conventional SCI functions and a software programmable infrared encoder/decoder sub-module for encoding/decoding the serial data for connection to infrared LEDs in remote control applications. NOTE When the IRSCI is enabled, the SCTxD pin is an open-drain output and requires a pullup resistor to be connected for proper SCI operation. Features of the SCI module include the following: * Full duplex operation * Standard mark/space non-return-to-zero (NRZ) format * Programmable 8-bit or 9-bit character length * Separately enabled transmitter and receiver * Separate receiver and transmitter CPU interrupt requests * Two receiver wakeup methods: - Idle line wakeup - Address mark wakeup * Interrupt-driven operation with eight interrupt flags: - Transmitter empty - Transmission complete - Receiver full - Idle receiver input - Receiver overrun - Noise error - Framing error - Parity error * Receiver framing error detection * Hardware parity checking * 1/16 bit-time noise detection Features of the infrared (IR) sub-module include the following: * IR sub-module enable/disable for infrared SCI or conventional SCI on SCTxD and SCRxD pins * Software selectable infrared modulation/demodulation (3/16, 1/16 or 1/32 width pulses)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 177
Infrared Serial Communications Interface Module (IRSCI)
12.2 Pin Name Conventions
The generic names of the IRSCI I/O pins are: * RxD (receive data) * TxD (transmit data) IRSCI I/O (input/output) lines are implemented by sharing parallel I/O port pins. The full name of an IRSCI input or output reflects the name of the shared port pin. Table 12-1 shows the full names and the generic names of the IRSCI I/O pins. The generic pin names appear in the text of this section. Table 12-1. Pin Name Conventions
Generic Pin Names: Full Pin Names: RxD PTC7/SCRxD TxD PTC6/SCTxD
NOTE When the IRSCI is enabled, the SCTxD pin is an open-drain output and requires a pullup resistor to be connected for proper SCI operation.
Addr. $0040 Register Name IRSCI Control Register 1 (IRSCC1) IRSCI Control Register 2 (IRSCC2) IRSCI Control Register 3 (IRSCC3) IRSCI Status Register 1 (IRSCS1) IRSCI Status Register 2 (IRSCS2) IRSCI Data Register (IRSCDR) IRSCI Baud Rate Register (IRSCBR) IRSCI Infrared Control Register (IRSCIRCR) Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Bit 7 LOOPS 0 SCTIE 0 R8 U SCTE 1 6 ENSCI 0 TCIE 0 T8 U TC 1 5 0 0 SCRIE 0 DMARE 0 SCRF 0 4 M 0 ILIE 0 DMATE 0 IDLE 0 3 WAKE 0 TE 0 ORIE 0 OR 0 2 ILTY 0 RE 0 NEIE 0 NF 0 1 PEN 0 RWU 0 FEIE 0 FE 0 BKF 0 R1 T1 SCR1 0 TNP0 0 Bit 0 PTY 0 SBK 0 PEIE 0 PE 0 RPF 0 R0 T0 SCR0 0 IREN 0
$0041
$0042
$0043
$0044
$0045
0 R7 T7 CKS 0 R 0
0 R6 T6 0 0 0
0 R5 T5 SCP1 0 0
0 0 R4 R3 T4 T3 Unaffected by reset SCP0 0 0 0 R = Reserved R 0 R 0
0 R2 T2 SCR2 0 TNP1 0 U = Unaffected
$0046
$0047
0 0 = Unimplemented
Figure 12-1. IRSCI I/O Registers Summary
MC68HC908AP A-Family Data Sheet, Rev. 2 178 Freescale Semiconductor
IRSCI Module Overview
12.3 IRSCI Module Overview
The IRSCI consists of a serial communications interface (SCI) and a infrared interface sub-module as shown in Figure 12-2.
INTERNAL BUS
SCI_TxD CGMXCLK SERIAL COMMUNICATIONS INTERFACE MODULE (SCI) SCI_R32XCLK SCI_R16XCLK SCI_RxD INFRARED SUB-MODULE
SCTxD
BUS CLOCK
SCRxD
Figure 12-2. IRSCI Block Diagram The SCI module provides serial data transmission and reception, with a programmable baud rate clock based on the bus clock or the CGMXCLK. The infrared sub-module receives two clock sources from the SCI module: SCI_R16XCLK and SCI_R32XCLK. Both reference clocks are used to generate the narrow pulses during data transmission. The SCI_R16XCLK and SCI_R32XCLK are internal clocks with frequencies that are 16 and 32 times the baud rate respectively. Both SCI_R16XCLK and SCI_R32XCLK clocks are used for transmitting data. The SCI_R16XCLK clock is used only for receiving data. NOTE For proper SCI function (transmit or receive), the bus clock MUST be programmed to at least 32 times that of the selected baud rate. When the infrared sub-module is disabled, signals on the TxD and RxD pins pass through unchanged to the SCI module.
12.4 Infrared Functional Description
Figure 12-3 shows the structure of the infrared sub-module. The infrared sub-module provides the capability of transmitting narrow pulses to an infrared LED and receiving narrow pulses and transforming them to serial bits, which are sent to the SCI module. The infrared sub-module receives two clocks from the SCI. One of these two clocks is selected as the base clock to generate the 3/16, 1/16, or 1/32 bit width narrow pulses during transmission. The sub-module consists of two main blocks: the transmit encoder and the receive decoder. When transmitting data, the SCI data stream is encoded by the infrared sub-module. For every "0" bit, a narrow "low" pulse is transmitted; no pulse is transmitted for "1" bits. When receiving data, the infrared pulses should be detected using an infrared photo diode for conversion to CMOS voltage levels before connecting to the RxD pin for the infrared decoder. The SCI data stream is reconstructed by stretching the "0" pulses.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 179
Infrared Serial Communications Interface Module (IRSCI)
TNP[1:0] IREN
SCI_TxD
TRANSMIT ENCODER
IR_TxD MUX SCTxD
SCI_R32XCLK SCI_R16XCLK
IR_RxD SCI_RxD MUX
RECEIVE DECODER
SCRxD
Figure 12-3. Infrared Sub-Module Diagram
12.4.1 Infrared Transmit Encoder
The infrared transmit encoder converts the "0" bits in the serial data stream from the SCI module to narrow "low" pulses, to the TxD pin. The narrow pulse is sent with a duration of 1/32, 1/16, or 3/16 of a data bit width. When two consecutive zeros are sent, the two consecutive narrow pulses will be separated by a time equal to a data bit width.
DATA BIT WIDTH DETERMINED BY BAUD RATE
SCI DATA
INFRARED SCI DATA
PULSE WIDTH = 1/32, 1/16, OR 3/16 DATA BIT WIDTH
Figure 12-4. Infrared SCI Data Example
12.4.2 Infrared Receive Decoder
The infrared receive decoder converts low narrow pulses from the RxD pin to standard SCI data bits. The reference clock, SCI_R16XCLK, clocks a four bit internal counter which counts from 0 to 15. An incoming pulse starts the internal counter and a "0" is sent out to the IR_RxD output. Subsequent incoming pulses are ignored when the counter count is between 0 and 7; IR_RxD remains "0". Once the counter passes 7, an incoming pulse will reset the counter; IR_RxD remains "0". When the counter reaches 15, the IR_RxD output returns to "1", the counter stops and waits for further pulses. A pulse is interpreted as jitter if it arrives shortly after the counter reaches 15; IR_RxD remains "1".
MC68HC908AP A-Family Data Sheet, Rev. 2 180 Freescale Semiconductor
SCI Functional Description
12.5 SCI Functional Description
Figure 12-5 shows the structure of the SCI.
INTERNAL BUS
SCI DATA REGISTER TRANSMITTER INTERRUPT CONTROL DMA INTERRUPT CONTROL RECEIVER INTERRUPT CONTROL RECEIVE SHIFT REGISTER ERROR INTERRUPT CONTROL
SCI DATA REGISTER TRANSMIT SHIFT REGISTER
SCI_RxD
SCI_TxD
SCTIE TCIE SCRIE ILIE TE RE RWU SBK SCTE TC SCRF IDLE OR NF FE PE LOOPS LOOPS WAKEUP CONTROL RECEIVE CONTROL FLAG CONTROL M WAKE ILTY
CGMXCLK BUS CLOCK
R8 T8
DMARE DMATE
ORIE NEIE FEIE PEIE
ENSCI TRANSMIT CONTROL
CKS
ENSCI
BKF RPF
A SL X B SL = 0 => X = A SL = 1 => X = B
BAUD RATE GENERATOR
PEN PTY DATA SELECTION CONTROL
SCI_R32XCLK SCI_R16XCLK
/16
Figure 12-5. SCI Module Block Diagram
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 181
Infrared Serial Communications Interface Module (IRSCI)
The SCI allows full-duplex, asynchronous, NRZ serial communication between the MCU and remote devices, including other MCUs. The transmitter and receiver of the SCI operate independently, although they use the same baud rate generator. During normal operation, the CPU monitors the status of the SCI, writes the data to be transmitted, and processes received data. NOTE For SCI operations, the IR sub-module is transparent to the SCI module. Data at going out of the SCI transmitter and data going into the SCI receiver is always in SCI format. It makes no difference to the SCI module whether the IR sub-module is enabled or disabled. NOTE This SCI module is a standard HC08 SCI module with the following modifications: * * A control bit, CKS, is added to the SCI baud rate control register to select between two input clocks for baud rate clock generation The TXINV bit is removed from the SCI control register 1
12.5.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format illustrated in Figure 12-6.
8-BIT DATA FORMAT BIT M IN IRSCC1 CLEAR START BIT BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 PARITY BIT BIT 7 STOP BIT
NEXT START BIT
9-BIT DATA FORMAT BIT M IN IRSCC1 SET START BIT BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 BIT 7
PARITY BIT BIT 8 STOP BIT
NEXT START BIT
Figure 12-6. SCI Data Formats
12.5.2 Transmitter
Figure 12-7 shows the structure of the SCI transmitter. The baud rate clock source for the SCI can be selected by the CKS bit, in the SCI baud rate register (see 12.9.7 IRSCI Baud Rate Register). 12.5.2.1 Character Length The transmitter can accommodate either 8-bit or 9-bit data. The state of the M bit in IRSCI control register 1 (IRSCC1) determines character length. When transmitting 9-bit data, bit T8 in IRSCI control register 3 (IRSCC3) is the ninth bit (bit 8).
MC68HC908AP A-Family Data Sheet, Rev. 2 182 Freescale Semiconductor
SCI Functional Description
CKS
INTERNAL BUS
CGMXCLK BUS CLOCK
A SL X B SCP1 SCP0 SCR1 SCR2 SCR0 TRANSMITTER CPU INTERRUPT REQUEST
PRESCALER
BAUD DIVIDER
/ 16
SCI DATA REGISTER
SL = 0 => X = A SL = 1 => X = B
H
8 MSB
7
6
5
4
3
2
1
0
START L
STOP
11-BIT TRANSMIT SHIFT REGISTER
SCI_TxD
TRANSMITTER DMA SERVICE REQUEST
SHIFT ENABLE
PEN PTY
PREAMBLE ALL 1s
T8 DMATE DMATE SCTIE SCTE DMATE SCTE SCTIE TC TCIE
TRANSMITTER CONTROL LOGIC
SCTE
LOOPS SCTIE TC TCIE ENSCI TE
Figure 12-7. SCI Transmitter 12.5.2.2 Character Transmission During an SCI transmission, the transmit shift register shifts a character out to the TxD pin. The IRSCI data register (IRSCDR) is the write-only buffer between the internal data bus and the transmit shift register. To initiate an SCI transmission: 1. Enable the SCI by writing a logic 1 to the enable SCI bit (ENSCI) in IRSCI control register 1 (IRSCC1). 2. Enable the transmitter by writing a logic 1 to the transmitter enable bit (TE) in IRSCI control register 2 (IRSCC2). 3. Clear the SCI transmitter empty bit by first reading IRSCI status register 1 (IRSCS1) and then writing to the IRSCDR. 4. Repeat step 3 for each subsequent transmission. At the start of a transmission, transmitter control logic automatically loads the transmit shift register with a preamble of logic 1s. After the preamble shifts out, control logic transfers the IRSCDR data into the transmit shift register. A logic 0 start bit automatically goes into the least significant bit position of the transmit shift register. A logic 1 stop bit goes into the most significant bit position.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 183
BREAK ALL 0s SBK
PARITY GENERATION
LOAD FROM IRSCDR
M
Infrared Serial Communications Interface Module (IRSCI)
The SCI transmitter empty bit, SCTE, in IRSCS1 becomes set when the IRSCDR transfers a byte to the transmit shift register. The SCTE bit indicates that the IRSCDR can accept new data from the internal data bus. If the SCI transmit interrupt enable bit, SCTIE, in IRSCC2 is also set, the SCTE bit generates a transmitter interrupt request. When the transmit shift register is not transmitting a character, the TxD pin goes to the idle condition, logic 1. If at any time software clears the ENSCI bit in IRSCI control register 1 (IRSCC1), the transmitter and receiver relinquish control of the port pins. 12.5.2.3 Break Characters Writing a logic 1 to the send break bit, SBK, in IRSCC2 loads the transmit shift register with a break character. A break character contains all logic 0s and has no start, stop, or parity bit. Break character length depends on the M bit in IRSCC1. As long as SBK is at logic 1, transmitter logic continuously loads break characters into the transmit shift register. After software clears the SBK bit, the shift register finishes transmitting the last break character and then transmits at least one logic 1. The automatic logic 1 at the end of a break character guarantees the recognition of the start bit of the next character. The SCI recognizes a break character when a start bit is followed by eight or nine logic 0 data bits and a logic 0 where the stop bit should be. Receiving a break character has the following effects on SCI registers: * Sets the framing error bit (FE) in IRSCS1 * Sets the SCI receiver full bit (SCRF) in IRSCS1 * Clears the SCI data register (IRSCDR) * Clears the R8 bit in IRSCC3 * Sets the break flag bit (BKF) in IRSCS2 * May set the overrun (OR), noise flag (NF), parity error (PE), or reception in progress flag (RPF) bits 12.5.2.4 Idle Characters An idle character contains all logic 1s and has no start, stop, or parity bit. Idle character length depends on the M bit in IRSCC1. The preamble is a synchronizing idle character that begins every transmission. If the TE bit is cleared during a transmission, the TxD pin becomes idle after completion of the transmission in progress. Clearing and then setting the TE bit during a transmission queues an idle character to be sent after the character currently being transmitted. NOTE When queueing an idle character, return the TE bit to logic 1 before the stop bit of the current character shifts out to the TxD pin. Setting TE after the stop bit appears on TxD causes data previously written to the IRSCDR to be lost. Toggle the TE bit for a queued idle character when the SCTE bit becomes set and just before writing the next byte to the IRSCDR. 12.5.2.5 Transmitter Interrupts The following conditions can generate CPU interrupt requests from the SCI transmitter:
MC68HC908AP A-Family Data Sheet, Rev. 2 184 Freescale Semiconductor
SCI Functional Description
*
*
SCI transmitter empty (SCTE) -- The SCTE bit in IRSCS1 indicates that the IRSCDR has transferred a character to the transmit shift register. SCTE can generate a transmitter CPU interrupt request. Setting the SCI transmit interrupt enable bit, SCTIE, in IRSCC2 enables the SCTE bit to generate transmitter CPU interrupt requests. Transmission complete (TC) -- The TC bit in IRSCS1 indicates that the transmit shift register and the IRSCDR are empty and that no break or idle character has been generated. The transmission complete interrupt enable bit, TCIE, in IRSCC2 enables the TC bit to generate transmitter CPU interrupt requests.
12.5.3 Receiver
Figure 12-8 shows the structure of the SCI receiver.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 185
Infrared Serial Communications Interface Module (IRSCI)
INTERNAL BUS
SCR1 CKS SCP1 SCP0 CGMXCLK BUS CLOCK A SL X B PRESCALER BAUD DIVIDER SCR2 SCR0 START 0 L RWU / 16 DATA RECOVERY ALL 0s ALL 1s MSB SCI DATA REGISTER
STOP
SL = 0 => X = A SL = 1 => X = B
11-BIT RECEIVE SHIFT REGISTER 8 7 6 5 4 3 2 1
SCI_RxD
H
BKF RPF ERROR CPU INTERRUPT REQUEST DMA SERVICE REQUEST
CPU INTERRUPT REQUEST
M WAKE ILTY PEN PTY WAKEUP LOGIC PARITY CHECKING IDLE ILIE DMARE SCRF SCRIE DMARE SCRF SCRIE DMARE OR ORIE NF NEIE FE FEIE PE PEIE
SCRF IDLE
R8
ILIE
SCRIE
DMARE OR ORIE NF NEIE FE FEIE PE PEIE
Figure 12-8. SCI Receiver Block Diagram 12.5.3.1 Character Length The receiver can accommodate either 8-bit or 9-bit data. The state of the M bit in IRSCI control register 1 (IRSCC1) determines character length. When receiving 9-bit data, bit R8 in IRSCI control register 2 (IRSCC2) is the ninth bit (bit 8). When receiving 8-bit data, bit R8 is a copy of the eighth bit (bit 7).
MC68HC908AP A-Family Data Sheet, Rev. 2 186 Freescale Semiconductor
SCI Functional Description
12.5.3.2 Character Reception During an SCI reception, the receive shift register shifts characters in from the RxD pin. The SCI data register (IRSCDR) is the read-only buffer between the internal data bus and the receive shift register. After a complete character shifts into the receive shift register, the data portion of the character transfers to the IRSCDR. The SCI receiver full bit, SCRF, in IRSCI status register 1 (IRSCS1) becomes set, indicating that the received byte can be read. If the SCI receive interrupt enable bit, SCRIE, in IRSCC2 is also set, the SCRF bit generates a receiver CPU interrupt request. 12.5.3.3 Data Sampling The receiver samples the RxD pin at the RT clock rate. The RT clock is an internal signal with a frequency 16 times the baud rate. To adjust for baud rate mismatch, the RT clock is resynchronized at the following times (see Figure 12-9): * After every start bit * After the receiver detects a data bit change from logic 1 to logic 0 (after the majority of data bit samples at RT8, RT9, and RT10 returns a valid logic 1 and the majority of the next RT8, RT9, and RT10 samples returns a valid logic 0)
START BIT SCI_RxD LSB
SAMPLES
START BIT QUALIFICATION
START BIT VERIFICATION
DATA SAMPLING
RT CLOCK RT10 RT11 RT12 RT13 RT14 RT15 RT CLOCK STATE RT CLOCK RESET RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT2 RT3 RT4 RT5 RT6 RT7 RT8 RT9 RT16 RT1 RT2 RT3 RT4
Figure 12-9. Receiver Data Sampling To locate the start bit, data recovery logic does an asynchronous search for a logic 0 preceded by three logic 1s. When the falling edge of a possible start bit occurs, the RT clock begins to count to 16. To verify the start bit and to detect noise, data recovery logic takes samples at RT3, RT5, and RT7. Table 12-2 summarizes the results of the start bit verification samples. Table 12-2. Start Bit Verification
RT3, RT5, and RT7 Samples 000 001 010 Start Bit Verification Yes Yes Yes Noise Flag 0 1 1
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 187
Infrared Serial Communications Interface Module (IRSCI)
Table 12-2. Start Bit Verification
RT3, RT5, and RT7 Samples 011 100 101 110 111 Start Bit Verification No Yes No No No Noise Flag 0 1 0 0 0
If start bit verification is not successful, the RT clock is reset and a new search for a start bit begins. To determine the value of a data bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10. Table 12-3 summarizes the results of the data bit samples. Table 12-3. Data Bit Recovery
RT8, RT9, and RT10 Samples 000 001 010 011 100 101 110 111 Data Bit Determination 0 0 0 1 0 1 1 1 Noise Flag 0 1 1 1 1 1 1 0
NOTE The RT8, RT9, and RT10 samples do not affect start bit verification. If any or all of the RT8, RT9, and RT10 start bit samples are logic 1s following a successful start bit verification, the noise flag (NF) is set and the receiver assumes that the bit is a start bit. To verify a stop bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10. Table 12-4 summarizes the results of the stop bit samples. Table 12-4. Stop Bit Recovery
RT8, RT9, and RT10 Samples 000 001 Framing Error Flag 1 1 Noise Flag 0 1
MC68HC908AP A-Family Data Sheet, Rev. 2 188 Freescale Semiconductor
SCI Functional Description
Table 12-4. Stop Bit Recovery
RT8, RT9, and RT10 Samples 010 011 100 101 110 111 Framing Error Flag 1 0 1 0 0 0 Noise Flag 1 1 1 1 1 0
12.5.3.4 Framing Errors If the data recovery logic does not detect a logic 1 where the stop bit should be in an incoming character, it sets the framing error bit, FE, in IRSCS1. The FE flag is set at the same time that the SCRF bit is set. A break character that has no stop bit also sets the FE bit. 12.5.3.5 Baud Rate Tolerance A transmitting device may be operating at a baud rate below or above the receiver baud rate. Accumulated bit time misalignment can cause one of the three stop bit data samples to fall outside the actual stop bit. Then a noise error occurs. If more than one of the samples is outside the stop bit, a framing error occurs. In most applications, the baud rate tolerance is much more than the degree of misalignment that is likely to occur. As the receiver samples an incoming character, it resynchronizes the RT clock on any valid falling edge within the character. Resynchronization within characters corrects misalignments between transmitter bit times and receiver bit times. Slow Data Tolerance Figure 12-10 shows how much a slow received character can be misaligned without causing a noise error or a framing error. The slow stop bit begins at RT8 instead of RT1 but arrives in time for the stop bit data samples at RT8, RT9, and RT10.
MSB STOP
RT10
RT11
RT12
RT13
RT14
RT15
DATA SAMPLES
Figure 12-10. Slow Data For an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times x 16 RT cycles + 10 RT cycles = 154 RT cycles. With the misaligned character shown in Figure 12-10, the receiver counts 154 RT cycles at the point when the count of the transmitting device is 9 bit times x 16 RT cycles + 3 RT cycles = 147 RT cycles.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 189
RT16
RT1
RT2
RT3
RT4
RT5
RT6
RT7
RT8
RT9
RECEIVER RT CLOCK
Infrared Serial Communications Interface Module (IRSCI)
The maximum percent difference between the receiver count and the transmitter count of a slow 8-bit character with no errors is
154 - 147 x 100 = 4.54% ------------------------154
For a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times x 16 RT cycles + 10 RT cycles = 170 RT cycles. With the misaligned character shown in Figure 12-10, the receiver counts 170 RT cycles at the point when the count of the transmitting device is 10 bit times x 16 RT cycles + 3 RT cycles = 163 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a slow 9-bit character with no errors is
170 - 163 x 100 = 4.12% ------------------------170
Fast Data Tolerance Figure 12-11 shows how much a fast received character can be misaligned without causing a noise error or a framing error. The fast stop bit ends at RT10 instead of RT16 but is still there for the stop bit data samples at RT8, RT9, and RT10.
STOP IDLE OR NEXT CHARACTER
RT10
RT11
RT12
RT13
RT14
RT15
DATA SAMPLES
Figure 12-11. Fast Data For an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times x 16 RT cycles + 10 RT cycles = 154 RT cycles. With the misaligned character shown in Figure 12-11, the receiver counts 154 RT cycles at the point when the count of the transmitting device is 10 bit times x 16 RT cycles = 160 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a fast 8-bit character with no errors is
154 - 160 x 100 = 3.90% ------------------------154
For a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times x 16 RT cycles + 10 RT cycles = 170 RT cycles. With the misaligned character shown in Figure 12-11, the receiver counts 170 RT cycles at the point when the count of the transmitting device is 11 bit times x 16 RT cycles = 176 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a fast 9-bit character with no errors is
MC68HC908AP A-Family Data Sheet, Rev. 2 190 Freescale Semiconductor
RT16
RT1
RT2
RT3
RT4
RT5
RT6
RT7
RT8
RT9
RECEIVER RT CLOCK
SCI Functional Description
170 - 176 x 100 = 3.53% ------------------------170
12.5.3.6 Receiver Wakeup So that the MCU can ignore transmissions intended only for other receivers in multiple-receiver systems, the receiver can be put into a standby state. Setting the receiver wakeup bit, RWU, in IRSCC2 puts the receiver into a standby state during which receiver interrupts are disabled. Depending on the state of the WAKE bit in IRSCC1, either of two conditions on the RxD pin can bring the receiver out of the standby state: * Address mark -- An address mark is a logic 1 in the most significant bit position of a received character. When the WAKE bit is set, an address mark wakes the receiver from the standby state by clearing the RWU bit. The address mark also sets the SCI receiver full bit, SCRF. Software can then compare the character containing the address mark to the user-defined address of the receiver. If they are the same, the receiver remains awake and processes the characters that follow. If they are not the same, software can set the RWU bit and put the receiver back into the standby state. * Idle input line condition -- When the WAKE bit is clear, an idle character on the RxD pin wakes the receiver from the standby state by clearing the RWU bit. The idle character that wakes the receiver does not set the receiver idle bit, IDLE, or the SCI receiver full bit, SCRF. The idle line type bit, ILTY, determines whether the receiver begins counting logic 1s as idle character bits after the start bit or after the stop bit. NOTE Clearing the WAKE bit after the RxD pin has been idle may cause the receiver to wake up immediately. 12.5.3.7 Receiver Interrupts The following sources can generate CPU interrupt requests from the SCI receiver: * SCI receiver full (SCRF) -- The SCRF bit in IRSCS1 indicates that the receive shift register has transferred a character to the IRSCDR. SCRF can generate a receiver interrupt request. Setting the SCI receive interrupt enable bit, SCRIE, in IRSCC2 enables the SCRF bit to generate receiver CPU interrupts. * Idle input (IDLE) -- The IDLE bit in IRSCS1 indicates that 10 or 11 consecutive logic 1s shifted in from the RxD pin. The idle line interrupt enable bit, ILIE, in IRSCC2 enables the IDLE bit to generate CPU interrupt requests. 12.5.3.8 Error Interrupts The following receiver error flags in IRSCS1 can generate CPU interrupt requests: * Receiver overrun (OR) -- The OR bit indicates that the receive shift register shifted in a new character before the previous character was read from the IRSCDR. The previous character remains in the IRSCDR, and the new character is lost. The overrun interrupt enable bit, ORIE, in IRSCC3 enables OR to generate SCI error CPU interrupt requests. * Noise flag (NF) -- The NF bit is set when the SCI detects noise on incoming data or break characters, including start, data, and stop bits. The noise error interrupt enable bit, NEIE, in IRSCC3 enables NF to generate SCI error CPU interrupt requests.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 191
Infrared Serial Communications Interface Module (IRSCI)
*
*
Framing error (FE) -- The FE bit in IRSCS1 is set when a logic 0 occurs where the receiver expects a stop bit. The framing error interrupt enable bit, FEIE, in IRSCC3 enables FE to generate SCI error CPU interrupt requests. Parity error (PE) -- The PE bit in IRSCS1 is set when the SCI detects a parity error in incoming data. The parity error interrupt enable bit, PEIE, in IRSCC3 enables PE to generate SCI error CPU interrupt requests.
12.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power- consumption standby modes.
12.6.1 Wait Mode
The SCI module remains active after the execution of a WAIT instruction. In wait mode, the SCI module registers are not accessible by the CPU. Any enabled CPU interrupt request from the SCI module can bring the MCU out of wait mode. If SCI module functions are not required during wait mode, reduce power consumption by disabling the module before executing the WAIT instruction. Refer to 7.6 Low-Power Modes for information on exiting wait mode.
12.6.2 Stop Mode
The SCI module is inactive after the execution of a STOP instruction. The STOP instruction does not affect SCI register states. SCI module operation resumes after an external interrupt. Because the internal clock is inactive during stop mode, entering stop mode during an SCI transmission or reception results in invalid data. Refer to 7.6 Low-Power Modes for information on exiting stop mode.
12.7 SCI During Break Module Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during interrupts generated by the break module. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state. To allow software to clear status bits during a break interrupt, write a logic 1 to the BCFE bit. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state. To protect status bits during the break state, write a logic 0 to the BCFE bit. With BCFE at logic 0 (its default state), software can read and write I/O registers during the break state without affecting status bits. Some status bits have a two-step read/write clearing procedure. If software does the first step on such a bit before the break, the bit cannot change during the break state as long as BCFE is at logic 0. After the break, doing the second step clears the status bit.
12.8 I/O Signals
The two IRSCI I/O pins are: * PTC6/SCTxD -- Transmit data * PTC7/SCRxD -- Receive data
MC68HC908AP A-Family Data Sheet, Rev. 2 192 Freescale Semiconductor
I/O Registers
12.8.1 PTC6/SCTxD (Transmit Data)
The PTC6/SCTxD pin is the serial data (standard or infrared) output from the SCI transmitter. The IRSCI shares the PTC6/SCTxD pin with port C. When the IRSCI is enabled, the PTC6/SCTxD pin is an output regardless of the state of the DDRC6 bit in data direction register C (DDRC). NOTE The PTC6/SCTxD pin is an open-drain pin when configured as an output. Therefore, when configured as SCTxD or a general purpose output pin (PTC6), a pullup resistor must be connected to this pin.
12.8.2 PTC7/SCRxD (Receive Data)
The PTC7/SCRxD pin is the serial data input to the IRSCI receiver. The IRSCI shares the PTC7/SCRxD pin with port C. When the IRSCI is enabled, the PTC7/SCRxD pin is an input regardless of the state of the DDRC7 bit in data direction register C (DDRC). NOTE The PTC7/SCRxD pin is an open-drain pin when configured as an output. Therefore, when configured as a general purpose output pin (PTC7), a pullup resistor must be connected to this pin. Table 12-5 shows a summary of I/O pin functions when the SCI is enabled. Table 12-5. SCI Pin Functions (Standard and Infrared)
IRSCC1 [ENSCI] 1 1 1 1 1 1 1 1 0 IRSCIRCR [IREN] 0 0 0 0 1 1 1 1 X IRSCC2 [TE] 0 0 1 1 0 0 1 1 X IRSCC2 [RE] 0 1 0 1 0 1 0 1 X Hi-Z(1) Hi-Z(1) Output SCI (idle high) Output SCI (idle high) Hi-Z(1) Hi-Z(1) Output IR SCI (idle high) Output IR SCI (idle high) TxD Pin RxD Pin Input ignored (terminate externally) Input sampled, pin should idle high Input ignored (terminate externally) Input sampled, pin should idle high Input ignored (terminate externally) Input sampled, pin should idle high Input ignored (terminate externally) Input sampled, pin should idle high
Pins under port control (standard I/O port)
1. After completion of transmission in progress.
12.9 I/O Registers
The following I/O registers control and monitor SCI operation: * IRSCI control register 1 (IRSCC1) * IRSCI control register 2 (IRSCC2) * IRSCI control register 3 (IRSCC3)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 193
Infrared Serial Communications Interface Module (IRSCI)
* * * * *
IRSCI status register 1 (IRSCS1) IRSCI status register 2 (IRSCS2) IRSCI data register (IRSCDR) IRSCI baud rate register (IRSCBR) IRSCI infrared control register (IRSCIRCR)
12.9.1 IRSCI Control Register 1
SCI control register 1: * Enables loop mode operation * Enables the SCI * Controls output polarity * Controls character length * Controls SCI wakeup method * Controls idle character detection * Enables parity function * Controls parity type
Address: Read: Write: Reset: $0040 Bit 7 LOOPS 0 6 ENSCI 0 5 0 0 4 M 0 3 WAKE 0 2 ILTY 0 1 PEN 0 Bit 0 PTY 0
Figure 12-12. IRSCI Control Register 1 (IRSCC1) LOOPS -- Loop Mode Select Bit This read/write bit enables loop mode operation for the SCI only. In loop mode the RxD pin is disconnected from the SCI, and the transmitter output goes into the receiver input. Both the transmitter and the receiver must be enabled to use loop mode. The infrared encoder/decoder is not in the loop. Reset clears the LOOPS bit. 1 = Loop mode enabled 0 = Normal operation enabled ENSCI -- Enable SCI Bit This read/write bit enables the SCI and the SCI baud rate generator. Clearing ENSCI sets the SCTE and TC bits in SCI status register 1 and disables transmitter interrupts. Reset clears the ENSCI bit. 1 = SCI enabled 0 = SCI disabled
MC68HC908AP A-Family Data Sheet, Rev. 2 194 Freescale Semiconductor
I/O Registers
M -- Mode (Character Length) Bit This read/write bit determines whether SCI characters are eight or nine bits long. (See Table 12-6.) The ninth bit can serve as an extra stop bit, as a receiver wakeup signal, or as a parity bit. Reset clears the M bit. 1 = 9-bit SCI characters 0 = 8-bit SCI characters WAKE -- Wakeup Condition Bit This read/write bit determines which condition wakes up the SCI: a logic 1 (address mark) in the most significant bit position of a received character or an idle condition on the RxD pin. Reset clears the WAKE bit. 1 = Address mark wakeup 0 = Idle line wakeup ILTY -- Idle Line Type Bit This read/write bit determines when the SCI starts counting logic 1s as idle character bits. The counting begins either after the start bit or after the stop bit. If the count begins after the start bit, then a string of logic 1s preceding the stop bit may cause false recognition of an idle character. Beginning the count after the stop bit avoids false idle character recognition, but requires properly synchronized transmissions. Reset clears the ILTY bit. 1 = Idle character bit count begins after stop bit 0 = Idle character bit count begins after start bit PEN -- Parity Enable Bit This read/write bit enables the SCI parity function. (See Table 12-6.) When enabled, the parity function inserts a parity bit in the most significant bit position. (See Figure 12-6.) Reset clears the PEN bit. 1 = Parity function enabled 0 = Parity function disabled PTY -- Parity Bit This read/write bit determines whether the SCI generates and checks for odd parity or even parity. (See Table 12-6.) Reset clears the PTY bit. 1 = Odd parity 0 = Even parity NOTE Changing the PTY bit in the middle of a transmission or reception can generate a parity error. Table 12-6. Character Format Selection
Control Bits M 0 1 0 0 1 1 PEN:PTY 0X 0X 10 11 10 11 Start Bits 1 1 1 1 1 1 Data Bits 8 9 7 7 8 8 Character Format Parity None None Even Odd Even Odd Stop Bits 1 1 1 1 1 1 Character Length 10 bits 11 bits 10 bits 10 bits 11 bits 11 bits
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 195
Infrared Serial Communications Interface Module (IRSCI)
12.9.2 IRSCI Control Register 2
IRSCI control register 2: * Enables the following CPU interrupt requests: - Enables the SCTE bit to generate transmitter CPU interrupt requests - Enables the TC bit to generate transmitter CPU interrupt requests - Enables the SCRF bit to generate receiver CPU interrupt requests - Enables the IDLE bit to generate receiver CPU interrupt requests * Enables the transmitter * Enables the receiver * Enables SCI wakeup * Transmits SCI break characters
Address: Read: Write: Reset: $0041 Bit 7 SCTIE 0 6 TCIE 0 5 SCRIE 0 4 ILIE 0 3 TE 0 2 RE 0 1 RWU 0 Bit 0 SBK 0
Figure 12-13. IRSCI Control Register 2 (IRSCC2) SCTIE -- SCI Transmit Interrupt Enable Bit This read/write bit enables the SCTE bit to generate SCI transmitter CPU interrupt requests. Reset clears the SCTIE bit. 1 = SCTE enabled to generate CPU interrupt 0 = SCTE not enabled to generate CPU interrupt TCIE -- Transmission Complete Interrupt Enable Bit This read/write bit enables the TC bit to generate SCI transmitter CPU interrupt requests. Reset clears the TCIE bit. 1 = TC enabled to generate CPU interrupt requests 0 = TC not enabled to generate CPU interrupt requests SCRIE -- SCI Receive Interrupt Enable Bit This read/write bit enables the SCRF bit to generate SCI receiver CPU interrupt requests. Reset clears the SCRIE bit. 1 = SCRF enabled to generate CPU interrupt 0 = SCRF not enabled to generate CPU interrupt ILIE -- Idle Line Interrupt Enable Bit This read/write bit enables the IDLE bit to generate SCI receiver CPU interrupt requests. Reset clears the ILIE bit. 1 = IDLE enabled to generate CPU interrupt requests 0 = IDLE not enabled to generate CPU interrupt requests TE -- Transmitter Enable Bit Setting this read/write bit begins the transmission by sending a preamble of 10 or 11 logic 1s from the transmit shift register to the TxD pin. If software clears the TE bit, the transmitter completes any transmission in progress before the TxD returns to the idle condition (logic 1). Clearing and then setting TE during a transmission queues an idle character to be sent after the character currently being transmitted. Reset clears the TE bit. 1 = Transmitter enabled 0 = Transmitter disabled
MC68HC908AP A-Family Data Sheet, Rev. 2 196 Freescale Semiconductor
I/O Registers
NOTE Writing to the TE bit is not allowed when the enable SCI bit (ENSCI) is clear. ENSCI is in SCI control register 1. RE -- Receiver Enable Bit Setting this read/write bit enables the receiver. Clearing the RE bit disables the receiver but does not affect receiver interrupt flag bits. Reset clears the RE bit. 1 = Receiver enabled 0 = Receiver disabled NOTE Writing to the RE bit is not allowed when the enable SCI bit (ENSCI) is clear. ENSCI is in SCI control register 1. RWU -- Receiver Wakeup Bit This read/write bit puts the receiver in a standby state during which receiver interrupts are disabled. The WAKE bit in IRSCC1 determines whether an idle input or an address mark brings the receiver out of the standby state and clears the RWU bit. Reset clears the RWU bit. 1 = Standby state 0 = Normal operation SBK -- Send Break Bit Setting and then clearing this read/write bit transmits a break character followed by a logic 1. The logic 1 after the break character guarantees recognition of a valid start bit. If SBK remains set, the transmitter continuously transmits break characters with no logic 1s between them. Reset clears the SBK bit. 1 = Transmit break characters 0 = No break characters being transmitted NOTE Do not toggle the SBK bit immediately after setting the SCTE bit. Toggling SBK before the preamble begins causes the SCI to send a break character instead of a preamble.
12.9.3 IRSCI Control Register 3
IRSCI control register 3: * Stores the ninth SCI data bit received and the ninth SCI data bit to be transmitted * Enables the following interrupts: - Receiver overrun interrupts - Noise error interrupts - Framing error interrupts - Parity error interrupts
Address: Read: Write: Reset: U $0042 Bit 7 R8 6 T8 U = Unimplemented 5 DMARE 0 4 DMATE 0 3 ORIE 0 U = Unaffected 2 NEIE 0 1 FEIE 0 Bit 0 PEIE 0
Figure 12-14. IRSCI Control Register 3 (IRSCC3)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 197
Infrared Serial Communications Interface Module (IRSCI)
R8 -- Received Bit 8 When the SCI is receiving 9-bit characters, R8 is the read-only ninth bit (bit 8) of the received character. R8 is received at the same time that the IRSCDR receives the other 8 bits. When the SCI is receiving 8-bit characters, R8 is a copy of the eighth bit (bit 7). Reset has no effect on the R8 bit. T8 -- Transmitted Bit 8 When the SCI is transmitting 9-bit characters, T8 is the read/write ninth bit (bit 8) of the transmitted character. T8 is loaded into the transmit shift register at the same time that the IRSCDR is loaded into the transmit shift register. Reset has no effect on the T8 bit. DMARE -- DMA Receive Enable Bit CAUTION The DMA module is not included on this MCU. Writing a logic 1 to DMARE or DMATE may adversely affect MCU performance. 1 = DMA not enabled to service SCI receiver DMA service requests generated by the SCRF bit (SCI receiver CPU interrupt requests enabled) 0 = DMA not enabled to service SCI receiver DMA service requests generated by the SCRF bit (SCI receiver CPU interrupt requests enabled) DMATE -- DMA Transfer Enable Bit CAUTION The DMA module is not included on this MCU. Writing a logic 1 to DMARE or DMATE may adversely affect MCU performance. 1 = SCTE DMA service requests enabled; SCTE CPU interrupt requests disabled 0 = SCTE DMA service requests disabled; SCTE CPU interrupt requests enabled ORIE -- Receiver Overrun Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the receiver overrun bit, OR. Reset clears ORIE. 1 = SCI error CPU interrupt requests from OR bit enabled 0 = SCI error CPU interrupt requests from OR bit disabled NEIE -- Receiver Noise Error Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the noise error bit, NE. Reset clears NEIE. 1 = SCI error CPU interrupt requests from NE bit enabled 0 = SCI error CPU interrupt requests from NE bit disabled FEIE -- Receiver Framing Error Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the framing error bit, FE. Reset clears FEIE. 1 = SCI error CPU interrupt requests from FE bit enabled 0 = SCI error CPU interrupt requests from FE bit disabled PEIE -- Receiver Parity Error Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the parity error bit, PE. (See 12.9.4 IRSCI Status Register 1.) Reset clears PEIE. 1 = SCI error CPU interrupt requests from PE bit enabled 0 = SCI error CPU interrupt requests from PE bit disabled
MC68HC908AP A-Family Data Sheet, Rev. 2 198 Freescale Semiconductor
I/O Registers
12.9.4 IRSCI Status Register 1
SCI status register 1 contains flags to signal these conditions: * Transfer of IRSCDR data to transmit shift register complete * Transmission complete * Transfer of receive shift register data to IRSCDR complete * Receiver input idle * Receiver overrun * Noisy data * Framing error * Parity error
Address: Read: Write: Reset: 1 1 0 0 0 0 0 0 = Unimplemented $0043 Bit 7 SCTE 6 TC 5 SCRF 4 IDLE 3 OR 2 NF 1 FE Bit 0 PE
Figure 12-15. IRSCI Status Register 1 (IRSCS1) SCTE -- SCI Transmitter Empty Bit This clearable, read-only bit is set when the IRSCDR transfers a character to the transmit shift register. SCTE can generate an SCI transmitter CPU interrupt request. When the SCTIE bit in IRSCC2 is set, SCTE generates an SCI transmitter CPU interrupt request. In normal operation, clear the SCTE bit by reading IRSCS1 with SCTE set and then writing to IRSCDR. Reset sets the SCTE bit. 1 = IRSCDR data transferred to transmit shift register 0 = IRSCDR data not transferred to transmit shift register TC -- Transmission Complete Bit This read-only bit is set when the SCTE bit is set, and no data, preamble, or break character is being transmitted. TC generates an SCI transmitter CPU interrupt request if the TCIE bit in IRSCC2 is also set. TC is automatically cleared when data, preamble or break is queued and ready to be sent. There may be up to 1.5 transmitter clocks of latency between queueing data, preamble, and break and the transmission actually starting. Reset sets the TC bit. 1 = No transmission in progress 0 = Transmission in progress SCRF -- SCI Receiver Full Bit This clearable, read-only bit is set when the data in the receive shift register transfers to the SCI data register. SCRF can generate an SCI receiver CPU interrupt request. When the SCRIE bit in IRSCC2 is set, SCRF generates a CPU interrupt request. In normal operation, clear the SCRF bit by reading IRSCS1 with SCRF set and then reading the IRSCDR. Reset clears SCRF. 1 = Received data available in IRSCDR 0 = Data not available in IRSCDR IDLE -- Receiver Idle Bit This clearable, read-only bit is set when 10 or 11 consecutive logic 1s appear on the receiver input. IDLE generates an SCI receiver CPU interrupt request if the ILIE bit in IRSCC2 is also set. Clear the IDLE bit by reading IRSCS1 with IDLE set and then reading the IRSCDR. After the receiver is enabled,
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 199
Infrared Serial Communications Interface Module (IRSCI)
it must receive a valid character that sets the SCRF bit before an idle condition can set the IDLE bit. Also, after the IDLE bit has been cleared, a valid character must again set the SCRF bit before an idle condition can set the IDLE bit. Reset clears the IDLE bit. 1 = Receiver input idle 0 = Receiver input active (or idle since the IDLE bit was cleared) OR -- Receiver Overrun Bit This clearable, read-only bit is set when software fails to read the IRSCDR before the receive shift register receives the next character. The OR bit generates an SCI error CPU interrupt request if the ORIE bit in IRSCC3 is also set. The data in the shift register is lost, but the data already in the IRSCDR is not affected. Clear the OR bit by reading IRSCS1 with OR set and then reading the IRSCDR. Reset clears the OR bit. 1 = Receive shift register full and SCRF = 1 0 = No receiver overrun Software latency may allow an overrun to occur between reads of IRSCS1 and IRSCDR in the flag-clearing sequence. Figure 12-16 shows the normal flag-clearing sequence and an example of an overrun caused by a delayed flag-clearing sequence. The delayed read of IRSCDR does not clear the OR bit because OR was not set when IRSCS1 was read. Byte 2 caused the overrun and is lost. The next flag-clearing sequence reads byte 3 in the IRSCDR instead of byte 2. In applications that are subject to software latency or in which it is important to know which byte is lost due to an overrun, the flag-clearing routine can check the OR bit in a second read of IRSCS1 after reading the data register.
NORMAL FLAG CLEARING SEQUENCE SCRF = 1 SCRF = 0 SCRF = 1 SCRF = 0 SCRF = 1 SCRF = 0 BYTE 4 READ IRSCS1 SCRF = 1 OR = 0 READ IRSCDR BYTE 3 BYTE 4 READ IRSCS1 SCRF = 1 OR = 1 READ IRSCDR BYTE 3
BYTE 1 READ IRSCS1 SCRF = 1 OR = 0 READ IRSCDR BYTE 1
BYTE 2 READ IRSCS1 SCRF = 1 OR = 0 READ IRSCDR BYTE 2
BYTE 3
DELAYED FLAG CLEARING SEQUENCE SCRF = 1 OR = 1 SCRF = 0 OR = 1 SCRF = 1 SCRF = 1 OR = 1 SCRF = 0 OR = 0
BYTE 1
BYTE 2 READ IRSCS1 SCRF = 1 OR = 0 READ IRSCDR BYTE 1
BYTE 3
Figure 12-16. Flag Clearing Sequence
MC68HC908AP A-Family Data Sheet, Rev. 2 200 Freescale Semiconductor
I/O Registers
NF -- Receiver Noise Flag Bit This clearable, read-only bit is set when the SCI detects noise on the RxD pin. NF generates an SCI error CPU interrupt request if the NEIE bit in IRSCC3 is also set. Clear the NF bit by reading IRSCS1 and then reading the IRSCDR. Reset clears the NF bit. 1 = Noise detected 0 = No noise detected FE -- Receiver Framing Error Bit This clearable, read-only bit is set when a logic 0 is accepted as the stop bit. FE generates an SCI error CPU interrupt request if the FEIE bit in IRSCC3 also is set. Clear the FE bit by reading IRSCS1 with FE set and then reading the IRSCDR. Reset clears the FE bit. 1 = Framing error detected 0 = No framing error detected PE -- Receiver Parity Error Bit This clearable, read-only bit is set when the SCI detects a parity error in incoming data. PE generates an SCI error CPU interrupt request if the PEIE bit in IRSCC3 is also set. Clear the PE bit by reading IRSCS1 with PE set and then reading the IRSCDR. Reset clears the PE bit. 1 = Parity error detected 0 = No parity error detected
12.9.5 IRSCI Status Register 2
IRSCI status register 2 contains flags to signal the following conditions: * Break character detected * Incoming data
Address: Read: Write: Reset: 0 0 0 0 0 0 0 0 = Unimplemented $0044 Bit 7 6 5 4 3 2 1 BKF Bit 0 RPF
Figure 12-17. IRSCI Status Register 2 (IRSCS2) BKF -- Break Flag Bit This clearable, read-only bit is set when the SCI detects a break character on the RxD pin. In IRSCS1, the FE and SCRF bits are also set. In 9-bit character transmissions, the R8 bit in IRSCC3 is cleared. BKF does not generate a CPU interrupt request. Clear BKF by reading IRSCS2 with BKF set and then reading the IRSCDR. Once cleared, BKF can become set again only after logic 1s again appear on the RxD pin followed by another break character. Reset clears the BKF bit. 1 = Break character detected 0 = No break character detected
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 201
Infrared Serial Communications Interface Module (IRSCI)
RPF -- Reception in Progress Flag Bit This read-only bit is set when the receiver detects a logic 0 during the RT1 time period of the start bit search. RPF does not generate an interrupt request. RPF is reset after the receiver detects false start bits (usually from noise or a baud rate mismatch) or when the receiver detects an idle character. Polling RPF before disabling the SCI module or entering stop mode can show whether a reception is in progress. 1 = Reception in progress 0 = No reception in progress
12.9.6 IRSCI Data Register
The IRSCI data register is the buffer between the internal data bus and the receive and transmit shift registers. Reset has no effect on data in the IRSCI data register.
Address: Read: Write: Reset: $0045 Bit 7 R7 T7 6 R6 T6 5 R5 T5 4 R4 T4 3 R3 T3 2 R2 T2 1 R1 T1 Bit 0 R0 T0
Unaffected by reset
Figure 12-18. IRSCI Data Register (IRSCDR) R7/T7-R0/T0 -- Receive/Transmit Data Bits Reading the IRSCDR accesses the read-only received data bits, R7-R0. Writing to the IRSCDR writes the data to be transmitted, T7-T0. Reset has no effect on the IRSCDR. NOTE Do not use read/modify/write instructions on the IRSCI data register.
12.9.7 IRSCI Baud Rate Register
The baud rate register selects the baud rate for both the receiver and the transmitter.
Address: Read: Write: Reset: $0046 Bit 7 CKS 0 6 0 0 5 SCP1 0 4 SCP0 0 3 R 0 R 2 SCR2 0 = Reserved 1 SCR1 0 Bit 0 SCR0 0
= Unimplemented
Figure 12-19. IRSCI Baud Rate Register (IRSCBR) CKS -- Baud Clock Input Select This read/write bit selects the source clock for the baud rate generator. Reset clears the CKS bit, selecting CGMXCLK. 1 = Bus clock drives the baud rate generator 0 = CGMXCLK drives the baud rate generator SCP1 and SCP0 -- SCI Baud Rate Prescaler Bits These read/write bits select the baud rate prescaler divisor as shown in Table 12-7. Reset clears SCP1 and SCP0.
MC68HC908AP A-Family Data Sheet, Rev. 2 202 Freescale Semiconductor
I/O Registers
Table 12-7. SCI Baud Rate Prescaling
SCP1 and SCP0 00 01 10 11 Prescaler Divisor (PD) 1 3 4 13
SCR2-SCR0 -- SCI Baud Rate Select Bits These read/write bits select the SCI baud rate divisor as shown in Table 12-8. Reset clears SCR2-SCR0. Table 12-8. IRSCI Baud Rate Selection
SCR2, SCR1, and SCR0 000 001 010 011 100 101 110 111 Baud Rate Divisor (BD) 1 2 4 8 16 32 64 128
Use this formula to calculate the SCI baud rate:
SCI clock source baud rate = -------------------------------------------16 x PD x BD
where: SCI clock source = fBUS or CGMXCLK (selected by CKS bit) PD = prescaler divisor BD = baud rate divisor Table 12-9 shows the SCI baud rates that can be generated with a 4.9152-MHz bus clock when fBUS is selected as SCI clock source.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 203
Infrared Serial Communications Interface Module (IRSCI)
Table 12-9. IRSCI Baud Rate Selection Examples
SCP1 and SCP0 00 00 00 00 00 00 00 00 01 01 01 01 01 01 01 01 10 10 10 10 10 10 10 10 11 11 11 11 11 11 11 11 Prescaler Divisor (PD) 1 1 1 1 1 1 1 1 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 13 13 13 13 13 13 13 13 SCR2, SCR1, and SCR0 000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111 Baud Rate Divisor (BD) 1 2 4 8 16 32 64 128 1 2 4 8 16 32 64 128 1 2 4 8 16 32 64 128 1 2 4 8 16 32 64 128 Baud Rate (fBUS = 4.9152 MHz) -- -- 76800 38400 19200 9600 4800 2400 -- 51200 25600 12800 6400 3200 1600 800 76800 38400 19200 9600 4800 2400 1200 600 23632 11816 5908 2954 1477 739 369 185
MC68HC908AP A-Family Data Sheet, Rev. 2 204 Freescale Semiconductor
I/O Registers
12.9.8 IRSCI Infrared Control Register
The infrared control register contains the control bits for the infrared sub-module. * Enables the infrared sub-module * Selects the infrared transmitter narrow pulse width
Address: Read: Write: Reset: $0047 Bit 7 R 0 6 0 0 5 0 0 4 0 0 3 R 0 R 2 TNP1 0 = Reserved 1 TNP0 0 Bit 0 IREN 0
= Unimplemented
Figure 12-20. IRSCI Infrared Control Register (IRSCIRCR) TNP1 and TNP0 -- Transmitter Narrow Pulse Bits These read/write bits select the infrared transmitter narrow pulse width as shown in Table 12-10. Reset clears TNP1 and TNP0. Table 12-10. Infrared Narrow Pulse Selection
TNP1 and TNP0 00 01 10 SCI transmits a 1/32 narrow pulse 11 Prescaler Divisor (PD) SCI transmits a 3/16 narrow pulse SCI transmits a 1/16 narrow pulse
IREN -- Infrared Enable Bit This read/write bit enables the infrared sub-module for encoding and decoding the SCI data stream. When this bit is clear, the infrared sub-module is disabled. Reset clears the IREN bit. 1 = infrared sub-module enabled 0 = infrared sub-module disabled
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 205
Infrared Serial Communications Interface Module (IRSCI)
MC68HC908AP A-Family Data Sheet, Rev. 2 206 Freescale Semiconductor
Chapter 13 Serial Peripheral Interface Module (SPI)
13.1 Introduction
This section describes the serial peripheral interface (SPI) module, which allows full-duplex, synchronous, serial communications with peripheral devices.
13.2 Features
Features of the SPI module include the following: * Full-duplex operation * Master and slave modes * Double-buffered operation with separate transmit and receive registers * Four master mode frequencies (maximum = bus frequency / 2) * Maximum slave mode frequency = bus frequency * Serial clock with programmable polarity and phase * Two separately enabled interrupts: - SPRF (SPI receiver full) - SPTE (SPI transmitter empty) * Mode fault error flag with CPU interrupt capability * Overflow error flag with CPU interrupt capability * Programmable wired-OR mode
13.3 Pin Name Conventions and I/O Register Addresses
The text that follows describes the SPI. The SPI I/O pin names are SS (slave select), SPSCK (SPI serial clock), CGND (clock ground), MOSI (master out slave in), and MISO (master in/slave out). The SPI shares four I/O pins with four parallel I/O ports. The full names of the SPI I/O pins are shown in Table 13-1. The generic pin names appear in the text that follows. Table 13-1. Pin Name Conventions
SPI Generic Pin Names: Full SPI Pin Names: SPI MISO PTC2/MISO MOSI PTC3/MOSI SS PTC4/SS SPSCK PTC5/SPSCK CGND VSS
Figure 13-1 summarizes the SPI I/O registers.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 205
Serial Peripheral Interface Module (SPI)
=
Addr.
Register Name Read: Write: Reset: Read: Write: Reset: Read: Write: Reset:
Bit 7 SPRIE 0 SPRF 0 R7 T7
6 R 0 ERRIE 0 R6 T6
5 SPMSTR 1 OVRF 0 R5 T5
4 CPOL 0 MODF
3 CPHA 1 SPTE
2 SPWOM 0 MODFEN 0 R2 T2 = Reserved
1 SPE 0 SPR1 0 R1 T1
Bit 0 SPTIE 0 SPR0 0 R0 T0
$0010 SPI Control Register (SPCR) SPI Status and Control Register (SPSCR) SPI Data Register (SPDR)
$0011
$0012
= Unimplemented
0 1 R4 R3 T4 T3 Unaffected by reset R
Figure 13-1. SPI I/O Register Summary
13.4 Functional Description
Figure 13-2 shows the structure of the SPI module. The SPI module allows full-duplex, synchronous, serial communication between the MCU and peripheral devices, including other MCUs. Software can poll the SPI status flags or SPI operation can be interrupt-driven. The following paragraphs describe the operation of the SPI module.
13.4.1 Master Mode
The SPI operates in master mode when the SPI master bit, SPMSTR, is set. NOTE Configure the SPI modules as master or slave before enabling them. Enable the master SPI before enabling the slave SPI. Disable the slave SPI before disabling the master SPI. (See 13.13.1 SPI Control Register.) Only a master SPI module can initiate transmissions. Software begins the transmission from a master SPI module by writing to the transmit data register. If the shift register is empty, the byte immediately transfers to the shift register, setting the SPI transmitter empty bit, SPTE. The byte begins shifting out on the MOSI pin under the control of the serial clock. (See Figure 13-3.) The SPR1 and SPR0 bits control the baud rate generator and determine the speed of the shift register. (See 13.13.2 SPI Status and Control Register.) Through the SPSCK pin, the baud rate generator of the master also controls the shift register of the slave peripheral. As the byte shifts out on the MOSI pin of the master, another byte shifts in from the slave on the master's MISO pin. The transmission ends when the receiver full bit, SPRF, becomes set. At the same time that SPRF becomes set, the byte from the slave transfers to the receive data register. In normal operation, SPRF signals the end of a transmission. Software clears SPRF by reading the SPI status and control register with SPRF set and then reading the SPI data register. Writing to the SPI data register clears the SPTE bit.
MC68HC908AP A-Family Data Sheet, Rev. 2 206 Freescale Semiconductor
Functional Description
INTERNAL BUS
TRANSMIT DATA REGISTER CGMOUT / 2 FROM SIM 7 /2 /8 CLOCK DIVIDER / 32 / 128 CLOCK SELECT RECEIVE DATA REGISTER PIN CONTROL LOGIC SPSCK CLOCK LOGIC M S SS 6
SHIFT REGISTER 5 4 3 2 1 0 MISO
MOSI
SPMSTR
SPE
SPR1
SPR0
SPMSTR
CPHA
CPOL
RESERVED TRANSMITTER CPU INTERRUPT REQUEST RESERVED RECEIVER/ERROR CPU INTERRUPT REQUEST SPI CONTROL
MODFEN ERRIE SPTIE SPRIE R SPE SPRF SPTE OVRF MODF
SPWOM
Figure 13-2. SPI Module Block Diagram
MASTER MCU SLAVE MCU
SHIFT REGISTER
MISO MOSI SPSCK
MISO MOSI SPSCK SS
SHIFT REGISTER
BAUD RATE GENERATOR
SS
VDD
Figure 13-3. Full-Duplex Master-Slave Connections
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 207
Serial Peripheral Interface Module (SPI)
13.4.2 Slave Mode
The SPI operates in slave mode when the SPMSTR bit is clear. In slave mode, the SPSCK pin is the input for the serial clock from the master MCU. Before a data transmission occurs, the SS pin of the slave SPI must be at logic 0. SS must remain low until the transmission is complete. (See 13.7.2 Mode Fault Error.) In a slave SPI module, data enters the shift register under the control of the serial clock from the master SPI module. After a byte enters the shift register of a slave SPI, it transfers to the receive data register, and the SPRF bit is set. To prevent an overflow condition, slave software then must read the receive data register before another full byte enters the shift register. The maximum frequency of the SPSCK for an SPI configured as a slave is the bus clock speed (which is twice as fast as the fastest master SPSCK clock that can be generated). The frequency of the SPSCK for an SPI configured as a slave does not have to correspond to any SPI baud rate. The baud rate only controls the speed of the SPSCK generated by an SPI configured as a master. Therefore, the frequency of the SPSCK for an SPI configured as a slave can be any frequency less than or equal to the bus speed. When the master SPI starts a transmission, the data in the slave shift register begins shifting out on the MISO pin. The slave can load its shift register with a new byte for the next transmission by writing to its transmit data register. The slave must write to its transmit data register at least one bus cycle before the master starts the next transmission. Otherwise, the byte already in the slave shift register shifts out on the MISO pin. Data written to the slave shift register during a transmission remains in a buffer until the end of the transmission. When the clock phase bit (CPHA) is set, the first edge of SPSCK starts a transmission. When CPHA is clear, the falling edge of SS starts a transmission. (See 13.5 Transmission Formats.) NOTE SPSCK must be in the proper idle state before the slave is enabled to prevent SPSCK from appearing as a clock edge.
13.5 Transmission Formats
During an SPI transmission, data is simultaneously transmitted (shifted out serially) and received (shifted in serially). A serial clock synchronizes shifting and sampling on the two serial data lines. A slave select line allows selection of an individual slave SPI device; slave devices that are not selected do not interfere with SPI bus activities. On a master SPI device, the slave select line can optionally be used to indicate multiple-master bus contention.
13.5.1 Clock Phase and Polarity Controls
Software can select any of four combinations of serial clock (SPSCK) phase and polarity using two bits in the SPI control register (SPCR). The clock polarity is specified by the CPOL control bit, which selects an active high or low clock and has no significant effect on the transmission format. The clock phase (CPHA) control bit selects one of two fundamentally different transmission formats. The clock phase and polarity should be identical for the master SPI device and the communicating slave device. In some cases, the phase and polarity are changed between transmissions to allow a master device to communicate with peripheral slaves having different requirements. NOTE Before writing to the CPOL bit or the CPHA bit, disable the SPI by clearing the SPI enable bit (SPE).
MC68HC908AP A-Family Data Sheet, Rev. 2 208 Freescale Semiconductor
Transmission Formats
13.5.2 Transmission Format When CPHA = 0
Figure 13-4 shows an SPI transmission in which CPHA is logic 0. The figure should not be used as a replacement for data sheet parametric information. Two waveforms are shown for SPSCK: one for CPOL = 0 and another for CPOL = 1. The diagram may be interpreted as a master or slave timing diagram since the serial clock (SPSCK), master in/slave out (MISO), and master out/slave in (MOSI) pins are directly connected between the master and the slave. The MISO signal is the output from the slave, and the MOSI signal is the output from the master. The SS line is the slave select input to the slave. The slave SPI drives its MISO output only when its slave select input (SS) is at logic 0, so that only the selected slave drives to the master. The SS pin of the master is not shown but is assumed to be inactive. The SS pin of the master must be high or must be reconfigured as general-purpose I/O not affecting the SPI. (See 13.7.2 Mode Fault Error.) When CPHA = 0, the first SPSCK edge is the MSB capture strobe. Therefore, the slave must begin driving its data before the first SPSCK edge, and a falling edge on the SS pin is used to start the slave data transmission. The slave's SS pin must be toggled back to high and then low again between each byte transmitted as shown in Figure 13-5.
SPSCK CYCLE # FOR REFERENCE SPSCK; CPOL = 0 SPSCK; CPOL =1 MOSI FROM MASTER MISO FROM SLAVE SS; TO SLAVE CAPTURE STROBE MSB MSB BIT 6 BIT 6 BIT 5 BIT 5 BIT 4 BIT 4 BIT 3 BIT 3 BIT 2 BIT 2 BIT 1 BIT 1 LSB LSB 1 2 3 4 5 6 7 8
Figure 13-4. Transmission Format (CPHA = 0)
MISO/MOSI MASTER SS SLAVE SS CPHA = 0 SLAVE SS CPHA = 1 BYTE 1 BYTE 2 BYTE 3
Figure 13-5. CPHA/SS Timing When CPHA = 0 for a slave, the falling edge of SS indicates the beginning of the transmission. This causes the SPI to leave its idle state and begin driving the MISO pin with the MSB of its data. Once the transmission begins, no new data is allowed into the shift register from the transmit data register. Therefore, the SPI data register of the slave must be loaded with transmit data before the falling edge of SS. Any data written after the falling edge is stored in the transmit data register and transferred to the shift register after the current transmission.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 209
Serial Peripheral Interface Module (SPI)
13.5.3 Transmission Format When CPHA = 1
Figure 13-6 shows an SPI transmission in which CPHA is logic 1. The figure should not be used as a replacement for data sheet parametric information. Two waveforms are shown for SPSCK: one for CPOL = 0 and another for CPOL = 1. The diagram may be interpreted as a master or slave timing diagram since the serial clock (SPSCK), master in/slave out (MISO), and master out/slave in (MOSI) pins are directly connected between the master and the slave. The MISO signal is the output from the slave, and the MOSI signal is the output from the master. The SS line is the slave select input to the slave. The slave SPI drives its MISO output only when its slave select input (SS) is at logic 0, so that only the selected slave drives to the master. The SS pin of the master is not shown but is assumed to be inactive. The SS pin of the master must be high or must be reconfigured as general-purpose I/O not affecting the SPI. (See 13.7.2 Mode Fault Error.) When CPHA = 1, the master begins driving its MOSI pin on the first SPSCK edge. Therefore, the slave uses the first SPSCK edge as a start transmission signal. The SS pin can remain low between transmissions. This format may be preferable in systems having only one master and only one slave driving the MISO data line.
SPSCK CYCLE # FOR REFERENCE SPSCK; CPOL = 0 SPSCK; CPOL =1 MOSI FROM MASTER MISO FROM SLAVE SS; TO SLAVE CAPTURE STROBE MSB MSB BIT 6 BIT 6 BIT 5 BIT 5 BIT 4 BIT 4 BIT 3 BIT 3 BIT 2 BIT 2 BIT 1 BIT 1 LSB LSB 1 2 3 4 5 6 7 8
Figure 13-6. Transmission Format (CPHA = 1) When CPHA = 1 for a slave, the first edge of the SPSCK indicates the beginning of the transmission. This causes the SPI to leave its idle state and begin driving the MISO pin with the MSB of its data. Once the transmission begins, no new data is allowed into the shift register from the transmit data register. Therefore, the SPI data register of the slave must be loaded with transmit data before the first edge of SPSCK. Any data written after the first edge is stored in the transmit data register and transferred to the shift register after the current transmission.
13.5.4 Transmission Initiation Latency
When the SPI is configured as a master (SPMSTR = 1), writing to the SPDR starts a transmission. CPHA has no effect on the delay to the start of the transmission, but it does affect the initial state of the SPSCK signal. When CPHA = 0, the SPSCK signal remains inactive for the first half of the first SPSCK cycle. When CPHA = 1, the first SPSCK cycle begins with an edge on the SPSCK line from its inactive to its active level. The SPI clock rate (selected by SPR1:SPR0) affects the delay from the write to SPDR and the start of the SPI transmission. (See Figure 13-7.) The internal SPI clock in the master is a free-running derivative of the internal MCU clock. To conserve power, it is enabled only when both the SPE and SPMSTR bits are set. SPSCK edges occur halfway through the low time of the internal MCU clock. Since the SPI clock is free-running, it is uncertain where the write to the SPDR occurs relative to the slower SPSCK. This uncertainty causes the variation in the initiation delay shown in Figure 13-7. This delay is no longer than a single SPI bit time. That is, the maximum delay is two MCU bus cycles for DIV2, eight MCU bus cycles for DIV8, 32 MCU bus cycles for DIV32, and 128 MCU bus cycles for DIV128.
MC68HC908AP A-Family Data Sheet, Rev. 2 210 Freescale Semiconductor
Queuing Transmission Data
WRITE TO SPDR BUS CLOCK MOSI SPSCK CPHA = 1 SPSCK CPHA = 0 SPSCK CYCLE NUMBER
INITIATION DELAY
MSB
BIT 6
BIT 5
1
2
3
INITIATION DELAY FROM WRITE SPDR TO TRANSFER BEGIN
WRITE TO SPDR BUS CLOCK EARLIEST LATEST WRITE TO SPDR BUS CLOCK EARLIEST WRITE TO SPDR BUS CLOCK EARLIEST WRITE TO SPDR BUS CLOCK EARLIEST SPSCK = INTERNAL CLOCK / 128; 128 POSSIBLE START POINTS LATEST SPSCK = INTERNAL CLOCK / 32; 32 POSSIBLE START POINTS LATEST SPSCK = INTERNAL CLOCK / 8; 8 POSSIBLE START POINTS LATEST SPSCK = INTERNAL CLOCK / 2; 2 POSSIBLE START POINTS
Figure 13-7. Transmission Start Delay (Master)
13.6 Queuing Transmission Data
The double-buffered transmit data register allows a data byte to be queued and transmitted. For an SPI configured as a master, a queued data byte is transmitted immediately after the previous transmission has completed. The SPI transmitter empty flag (SPTE) indicates when the transmit data buffer is ready to accept new data. Write to the transmit data register only when the SPTE bit is high. Figure 13-8 shows the timing associated with doing back-to-back transmissions with the SPI (SPSCK has CPHA: CPOL = 1:0).
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 211
Serial Peripheral Interface Module (SPI)
WRITE TO SPDR SPTE SPSCK CPHA:CPOL = 1:0 MOSI MSB BIT BIT BIT BIT BIT BIT LSB MSB BIT BIT BIT BIT BIT BIT LSB MSB BIT BIT BIT 654321 654321 654 BYTE 1 BYTE 2 BYTE 3 4 6 7 7 CPU READS SPDR, CLEARING SPRF BIT. 8 CPU WRITES BYTE 3 TO SPDR, QUEUEING BYTE 3 AND CLEARING SPTE BIT. 9 SECOND INCOMING BYTE TRANSFERS FROM SHIFT REGISTER TO RECEIVE DATA REGISTER, SETTING SPRF BIT. 10 BYTE 3 TRANSFERS FROM TRANSMIT DATA REGISTER TO SHIFT REGISTER, SETTING SPTE BIT. 11 CPU READS SPSCR WITH SPRF BIT SET. 12 CPU READS SPDR, CLEARING SPRF BIT. 9 11 12 1 2 3 5 8 10
SPRF READ SPSCR READ SPDR 1 CPU WRITES BYTE 1 TO SPDR, CLEARING SPTE BIT. 2 BYTE 1 TRANSFERS FROM TRANSMIT DATA REGISTER TO SHIFT REGISTER, SETTING SPTE BIT. 3 CPU WRITES BYTE 2 TO SPDR, QUEUEING BYTE 2 AND CLEARING SPTE BIT. 4 FIRST INCOMING BYTE TRANSFERS FROM SHIFT REGISTER TO RECEIVE DATA REGISTER, SETTING SPRF BIT. 5 BYTE 2 TRANSFERS FROM TRANSMIT DATA REGISTER TO SHIFT REGISTER, SETTING SPTE BIT. 6 CPU READS SPSCR WITH SPRF BIT SET.
Figure 13-8. SPRF/SPTE CPU Interrupt Timing The transmit data buffer allows back-to-back transmissions without the slave precisely timing its writes between transmissions as in a system with a single data buffer. Also, if no new data is written to the data buffer, the last value contained in the shift register is the next data word to be transmitted. For an idle master or idle slave that has no data loaded into its transmit buffer, the SPTE is set again no more than two bus cycles after the transmit buffer empties into the shift register. This allows the user to queue up a 16-bit value to send. For an already active slave, the load of the shift register cannot occur until the transmission is completed. This implies that a back-to-back write to the transmit data register is not possible. The SPTE indicates when the next write can occur.
13.7 Error Conditions
The following flags signal SPI error conditions: * Overflow (OVRF) -- Failing to read the SPI data register before the next full byte enters the shift register sets the OVRF bit. The new byte does not transfer to the receive data register, and the unread byte still can be read. OVRF is in the SPI status and control register. * Mode fault error (MODF) -- The MODF bit indicates that the voltage on the slave select pin (SS) is inconsistent with the mode of the SPI. MODF is in the SPI status and control register.
MC68HC908AP A-Family Data Sheet, Rev. 2 212 Freescale Semiconductor
Error Conditions
13.7.1 Overflow Error
The overflow flag (OVRF) becomes set if the receive data register still has unread data from a previous transmission when the capture strobe of bit 1 of the next transmission occurs. The bit 1 capture strobe occurs in the middle of SPSCK cycle 7. (See Figure 13-4 and Figure 13-6.) If an overflow occurs, all data received after the overflow and before the OVRF bit is cleared does not transfer to the receive data register and does not set the SPI receiver full bit (SPRF). The unread data that transferred to the receive data register before the overflow occurred can still be read. Therefore, an overflow error always indicates the loss of data. Clear the overflow flag by reading the SPI status and control register and then reading the SPI data register. OVRF generates a receiver/error CPU interrupt request if the error interrupt enable bit (ERRIE) is also set. The SPRF, MODF, and OVRF interrupts share the same CPU interrupt vector. (See Figure 13-11.) It is not possible to enable MODF or OVRF individually to generate a receiver/error CPU interrupt request. However, leaving MODFEN low prevents MODF from being set. If the CPU SPRF interrupt is enabled and the OVRF interrupt is not, watch for an overflow condition. Figure 13-9 shows how it is possible to miss an overflow. The first part of Figure 13-9 shows how it is possible to read the SPSCR and SPDR to clear the SPRF without problems. However, as illustrated by the second transmission example, the OVRF bit can be set in between the time that SPSCR and SPDR are read.
BYTE 1 1 BYTE 2 4 BYTE 3 6 BYTE 4 8
SPRF
OVRF READ SPSCR READ SPDR 1 2 3 4 2 5
3 BYTE 1 SETS SPRF BIT. CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. CPU READS BYTE 1 IN SPDR, CLEARING SPRF BIT. BYTE 2 SETS SPRF BIT. 5 6 7 8
7 CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST. CPU READS BYTE 2 IN SPDR, CLEARING SPRF BIT, BUT NOT OVRF BIT. BYTE 4 FAILS TO SET SPRF BIT BECAUSE OVRF BIT IS NOT CLEARED. BYTE 4 IS LOST.
Figure 13-9. Missed Read of Overflow Condition In this case, an overflow can be missed easily. Since no more SPRF interrupts can be generated until this OVRF is serviced, it is not obvious that bytes are being lost as more transmissions are completed. To prevent this, either enable the OVRF interrupt or do another read of the SPSCR following the read of the SPDR. This ensures that the OVRF was not set before the SPRF was cleared and that future transmissions can set the SPRF bit. Figure 13-10 illustrates this process. Generally, to avoid this second SPSCR read, enable the OVRF to the CPU by setting the ERRIE bit.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 213
Serial Peripheral Interface Module (SPI)
BYTE 1 SPI RECEIVE COMPLETE SPRF OVRF READ SPSCR READ SPDR 1 2 3 4 5 6 7 2 3 BYTE 1 SETS SPRF BIT. CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. CPU READS BYTE 1 IN SPDR, CLEARING SPRF BIT. CPU READS SPSCR AGAIN TO CHECK OVRF BIT. BYTE 2 SETS SPRF BIT. CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST. 4 6 8 8 9 9 10 12 13 14 1 BYTE 2 5 BYTE 3 7 BYTE 4 11
CPU READS BYTE 2 IN SPDR, CLEARING SPRF BIT. CPU READS SPSCR AGAIN TO CHECK OVRF BIT.
10 CPU READS BYTE 2 SPDR, CLEARING OVRF BIT. 11 BYTE 4 SETS SPRF BIT. 12 CPU READS SPSCR. 13 CPU READS BYTE 4 IN SPDR, CLEARING SPRF BIT. 14 CPU READS SPSCR AGAIN TO CHECK OVRF BIT.
Figure 13-10. Clearing SPRF When OVRF Interrupt Is Not Enabled
13.7.2 Mode Fault Error
Setting the SPMSTR bit selects master mode and configures the SPSCK and MOSI pins as outputs and the MISO pin as an input. Clearing SPMSTR selects slave mode and configures the SPSCK and MOSI pins as inputs and the MISO pin as an output. The mode fault bit, MODF, becomes set any time the state of the slave select pin, SS, is inconsistent with the mode selected by SPMSTR. To prevent SPI pin contention and damage to the MCU, a mode fault error occurs if: * The SS pin of a slave SPI goes high during a transmission * The SS pin of a master SPI goes low at any time For the MODF flag to be set, the mode fault error enable bit (MODFEN) must be set. Clearing the MODFEN bit does not clear the MODF flag but does prevent MODF from being set again after MODF is cleared. MODF generates a receiver/error CPU interrupt request if the error interrupt enable bit (ERRIE) is also set. The SPRF, MODF, and OVRF interrupts share the same CPU interrupt vector. (See Figure 13-11.) It is not possible to enable MODF or OVRF individually to generate a receiver/error CPU interrupt request. However, leaving MODFEN low prevents MODF from being set. In a master SPI with the mode fault enable bit (MODFEN) set, the mode fault flag (MODF) is set if SS goes to logic 0. A mode fault in a master SPI causes the following events to occur: * If ERRIE = 1, the SPI generates an SPI receiver/error CPU interrupt request. * The SPE bit is cleared. * The SPTE bit is set. * The SPI state counter is cleared. * The data direction register of the shared I/O port regains control of port drivers.
MC68HC908AP A-Family Data Sheet, Rev. 2 214 Freescale Semiconductor
Interrupts
NOTE To prevent bus contention with another master SPI after a mode fault error, clear all SPI bits of the data direction register of the shared I/O port before enabling the SPI. When configured as a slave (SPMSTR = 0), the MODF flag is set if SS goes high during a transmission. When CPHA = 0, a transmission begins when SS goes low and ends once the incoming SPSCK goes back to its idle level following the shift of the eighth data bit. When CPHA = 1, the transmission begins when the SPSCK leaves its idle level and SS is already low. The transmission continues until the SPSCK returns to its idle level following the shift of the last data bit. (See 13.5 Transmission Formats.) NOTE Setting the MODF flag does not clear the SPMSTR bit. The SPMSTR bit has no function when SPE = 0. Reading SPMSTR when MODF = 1 shows the difference between a MODF occurring when the SPI is a master and when it is a slave. When CPHA = 0, a MODF occurs if a slave is selected (SS is at logic 0) and later unselected (SS is at logic 1) even if no SPSCK is sent to that slave. This happens because SS at logic 0 indicates the start of the transmission (MISO driven out with the value of MSB) for CPHA = 0. When CPHA = 1, a slave can be selected and then later unselected with no transmission occurring. Therefore, MODF does not occur since a transmission was never begun. In a slave SPI (MSTR = 0), the MODF bit generates an SPI receiver/error CPU interrupt request if the ERRIE bit is set. The MODF bit does not clear the SPE bit or reset the SPI in any way. Software can abort the SPI transmission by clearing the SPE bit of the slave. NOTE A logic 1 voltage on the SS pin of a slave SPI puts the MISO pin in a high impedance state. Also, the slave SPI ignores all incoming SPSCK clocks, even if it was already in the middle of a transmission. To clear the MODF flag, read the SPSCR with the MODF bit set and then write to the SPCR register. This entire clearing mechanism must occur with no MODF condition existing or else the flag is not cleared.
13.8 Interrupts
Four SPI status flags can be enabled to generate CPU interrupt requests. Table 13-2. SPI Interrupts
Flag SPTE Transmitter empty SPRF Receiver full OVRF Overflow MODF Mode fault Request SPI transmitter CPU interrupt request (SPTIE = 1, SPE = 1) SPI receiver CPU interrupt request (SPRIE = 1) SPI receiver/error interrupt request (ERRIE = 1) SPI receiver/error interrupt request (ERRIE = 1)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 215
Serial Peripheral Interface Module (SPI)
Reading the SPI status and control register with SPRF set and then reading the receive data register clears SPRF. The clearing mechanism for the SPTE flag is always just a write to the transmit data register. The SPI transmitter interrupt enable bit (SPTIE) enables the SPTE flag to generate transmitter CPU interrupt requests, provided that the SPI is enabled (SPE = 1). The SPI receiver interrupt enable bit (SPRIE) enables the SPRF bit to generate receiver CPU interrupt requests, regardless of the state of the SPE bit. (See Figure 13-11.) The error interrupt enable bit (ERRIE) enables both the MODF and OVRF bits to generate a receiver/error CPU interrupt request. The mode fault enable bit (MODFEN) can prevent the MODF flag from being set so that only the OVRF bit is enabled by the ERRIE bit to generate receiver/error CPU interrupt requests.
NOT AVAILABLE
SPTE
SPTIE
SPE SPI TRANSMITTER CPU INTERRUPT REQUEST
R
NOT AVAILABLE
SPRIE
SPRF
SPI RECEIVER/ERROR ERRIE MODF OVRF CPU INTERRUPT REQUEST
Figure 13-11. SPI Interrupt Request Generation The following sources in the SPI status and control register can generate CPU interrupt requests: * SPI receiver full bit (SPRF) -- The SPRF bit becomes set every time a byte transfers from the shift register to the receive data register. If the SPI receiver interrupt enable bit, SPRIE, is also set, SPRF generates an SPI receiver/error CPU interrupt request. * SPI transmitter empty (SPTE) -- The SPTE bit becomes set every time a byte transfers from the transmit data register to the shift register. If the SPI transmit interrupt enable bit, SPTIE, is also set, SPTE generates an SPTE CPU interrupt request.
13.9 Resetting the SPI
Any system reset completely resets the SPI. Partial resets occur whenever the SPI enable bit (SPE) is low. Whenever SPE is low, the following occurs: * The SPTE flag is set. * Any transmission currently in progress is aborted.
MC68HC908AP A-Family Data Sheet, Rev. 2 216 Freescale Semiconductor
Low-Power Modes
* * *
The shift register is cleared. The SPI state counter is cleared, making it ready for a new complete transmission. All the SPI port logic is defaulted back to being general-purpose I/O.
These items are reset only by a system reset: * All control bits in the SPCR register * All control bits in the SPSCR register (MODFEN, ERRIE, SPR1, and SPR0) * The status flags SPRF, OVRF, and MODF By not resetting the control bits when SPE is low, the user can clear SPE between transmissions without having to set all control bits again when SPE is set back high for the next transmission. By not resetting the SPRF, OVRF, and MODF flags, the user can still service these interrupts after the SPI has been disabled. The user can disable the SPI by writing 0 to the SPE bit. The SPI can also be disabled by a mode fault occurring in an SPI that was configured as a master with the MODFEN bit set.
13.10 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
13.10.1 Wait Mode
The SPI module remains active after the execution of a WAIT instruction. In wait mode the SPI module registers are not accessible by the CPU. Any enabled CPU interrupt request from the SPI module can bring the MCU out of wait mode. If SPI module functions are not required during wait mode, reduce power consumption by disabling the SPI module before executing the WAIT instruction. To exit wait mode when an overflow condition occurs, enable the OVRF bit to generate CPU interrupt requests by setting the error interrupt enable bit (ERRIE). (See 13.8 Interrupts.)
13.10.2 Stop Mode
The SPI module is inactive after the execution of a STOP instruction. The STOP instruction does not affect register conditions. SPI operation resumes after an external interrupt. If stop mode is exited by reset, any transfer in progress is aborted, and the SPI is reset.
13.11 SPI During Break Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state. (See Chapter 7 System Integration Module (SIM).) To allow software to clear status bits during a break interrupt, write a logic 1 to the BCFE bit. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state. To protect status bits during the break state, write a logic 0 to the BCFE bit. With BCFE at logic 0 (its default state), software can read and write I/O registers during the break state without affecting status bits. Some status bits have a 2-step read/write clearing procedure. If software does the first step on such a bit before the break, the bit cannot change during the break state as long as BCFE is at logic 0. After the break, doing the second step clears the status bit.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 217
Serial Peripheral Interface Module (SPI)
Since the SPTE bit cannot be cleared during a break with the BCFE bit cleared, a write to the transmit data register in break mode does not initiate a transmission nor is this data transferred into the shift register. Therefore, a write to the SPDR in break mode with the BCFE bit cleared has no effect.
13.12 I/O Signals
The SPI module has five I/O pins and shares four of them with a parallel I/O port. They are: * MISO -- Data received * MOSI -- Data transmitted * SPSCK -- Serial clock * SS -- Slave select * CGND -- Clock ground (internally connected to VSS) The SPI has limited inter-integrated circuit (I2C) capability (requiring software support) as a master in a single-master environment. To communicate with I2C peripherals, MOSI becomes an open-drain output when the SPWOM bit in the SPI control register is set. In I2C communication, the MOSI and MISO pins are connected to a bidirectional pin from the I2C peripheral and through a pullup resistor to VDD.
13.12.1 MISO (Master In/Slave Out)
MISO is one of the two SPI module pins that transmits serial data. In full duplex operation, the MISO pin of the master SPI module is connected to the MISO pin of the slave SPI module. The master SPI simultaneously receives data on its MISO pin and transmits data from its MOSI pin. Slave output data on the MISO pin is enabled only when the SPI is configured as a slave. The SPI is configured as a slave when its SPMSTR bit is logic 0 and its SS pin is at logic 0. To support a multiple-slave system, a logic 1 on the SS pin puts the MISO pin in a high-impedance state. When enabled, the SPI controls data direction of the MISO pin regardless of the state of the data direction register of the shared I/O port.
13.12.2 MOSI (Master Out/Slave In)
MOSI is one of the two SPI module pins that transmits serial data. In full-duplex operation, the MOSI pin of the master SPI module is connected to the MOSI pin of the slave SPI module. The master SPI simultaneously transmits data from its MOSI pin and receives data on its MISO pin. When enabled, the SPI controls data direction of the MOSI pin regardless of the state of the data direction register of the shared I/O port.
13.12.3 SPSCK (Serial Clock)
The serial clock synchronizes data transmission between master and slave devices. In a master MCU, the SPSCK pin is the clock output. In a slave MCU, the SPSCK pin is the clock input. In full-duplex operation, the master and slave MCUs exchange a byte of data in eight serial clock cycles. When enabled, the SPI controls data direction of the SPSCK pin regardless of the state of the data direction register of the shared I/O port.
MC68HC908AP A-Family Data Sheet, Rev. 2 218 Freescale Semiconductor
I/O Signals
13.12.4 SS (Slave Select)
The SS pin has various functions depending on the current state of the SPI. For an SPI configured as a slave, the SS is used to select a slave. For CPHA = 0, the SS is used to define the start of a transmission. (See 13.5 Transmission Formats.) Since it is used to indicate the start of a transmission, the SS must be toggled high and low between each byte transmitted for the CPHA = 0 format. However, it can remain low between transmissions for the CPHA = 1 format. See Figure 13-12.
MISO/MOSI MASTER SS SLAVE SS CPHA = 0 SLAVE SS CPHA = 1 BYTE 1 BYTE 2 BYTE 3
Figure 13-12. CPHA/SS Timing When an SPI is configured as a slave, the SS pin is always configured as an input. It cannot be used as a general-purpose I/O regardless of the state of the MODFEN control bit. However, the MODFEN bit can still prevent the state of the SS from creating a MODF error. (See 13.13.2 SPI Status and Control Register.) NOTE A logic 1 voltage on the SS pin of a slave SPI puts the MISO pin in a high-impedance state. The slave SPI ignores all incoming SPSCK clocks, even if it was already in the middle of a transmission. When an SPI is configured as a master, the SS input can be used in conjunction with the MODF flag to prevent multiple masters from driving MOSI and SPSCK. (See 13.7.2 Mode Fault Error.) For the state of the SS pin to set the MODF flag, the MODFEN bit in the SPSCK register must be set. If the MODFEN bit is low for an SPI master, the SS pin can be used as a general-purpose I/O under the control of the data direction register of the shared I/O port. With MODFEN high, it is an input-only pin to the SPI regardless of the state of the data direction register of the shared I/O port. The CPU can always read the state of the SS pin by configuring the appropriate pin as an input and reading the port data register. (See Table 13-3.) Table 13-3. SPI Configuration
SPE 0 1 1 1 SPMSTR X(1) 0 1 1 MODFEN X X 0 1 SPI Configuration Not enabled Slave Master without MODF Master with MODF State of SS Logic General-purpose I/O; SS ignored by SPI Input-only to SPI General-purpose I/O; SS ignored by SPI Input-only to SPI
Note 1. X = Don't care
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 219
Serial Peripheral Interface Module (SPI)
13.12.5 CGND (Clock Ground)
CGND is the ground return for the serial clock pin, SPSCK, and the ground for the port output buffers. It is internally connected to VSS as shown in Table 13-1.
13.13 I/O Registers
Three registers control and monitor SPI operation: * SPI control register (SPCR) * SPI status and control register (SPSCR) * SPI data register (SPDR)
13.13.1 SPI Control Register
The SPI control register: * Enables SPI module interrupt requests * Configures the SPI module as master or slave * Selects serial clock polarity and phase * Configures the SPSCK, MOSI, and MISO pins as open-drain outputs * Enables the SPI module
Address: Read: Write: Reset: $0010 Bit 7 SPRIE 0 6 R 0 5 SPMSTR 1 4 CPOL 0 3 CPHA 1 R 2 SPWOM 0 = Reserved 1 SPE 0 Bit 0 SPTIE 0
= Unimplemented
Figure 13-13. SPI Control Register (SPCR) SPRIE -- SPI Receiver Interrupt Enable Bit This read/write bit enables CPU interrupt requests generated by the SPRF bit. The SPRF bit is set when a byte transfers from the shift register to the receive data register. Reset clears the SPRIE bit. 1 = SPRF CPU interrupt requests enabled 0 = SPRF CPU interrupt requests disabled SPMSTR -- SPI Master Bit This read/write bit selects master mode operation or slave mode operation. Reset sets the SPMSTR bit. 1 = Master mode 0 = Slave mode CPOL -- Clock Polarity Bit This read/write bit determines the logic state of the SPSCK pin between transmissions. (See Figure 13-4 and Figure 13-6.) To transmit data between SPI modules, the SPI modules must have identical CPOL values. Reset clears the CPOL bit. CPHA -- Clock Phase Bit
MC68HC908AP A-Family Data Sheet, Rev. 2 220 Freescale Semiconductor
I/O Registers
This read/write bit controls the timing relationship between the serial clock and SPI data. (See Figure 13-4 and Figure 13-6.) To transmit data between SPI modules, the SPI modules must have identical CPHA values. When CPHA = 0, the SS pin of the slave SPI module must be set to logic 1 between bytes. (See Figure 13-12.) Reset sets the CPHA bit.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 221
Serial Peripheral Interface Module (SPI)
SPWOM -- SPI Wired-OR Mode Bit This read/write bit disables the pullup devices on pins SPSCK, MOSI, and MISO so that those pins become open-drain outputs. 1 = Wired-OR SPSCK, MOSI, and MISO pins 0 = Normal push-pull SPSCK, MOSI, and MISO pins SPE -- SPI Enable This read/write bit enables the SPI module. Clearing SPE causes a partial reset of the SPI. (See 13.9 Resetting the SPI.) Reset clears the SPE bit. 1 = SPI module enabled 0 = SPI module disabled SPTIE-- SPI Transmit Interrupt Enable This read/write bit enables CPU interrupt requests generated by the SPTE bit. SPTE is set when a byte transfers from the transmit data register to the shift register. Reset clears the SPTIE bit. 1 = SPTE CPU interrupt requests enabled 0 = SPTE CPU interrupt requests disabled
13.13.2 SPI Status and Control Register
The SPI status and control register contains flags to signal these conditions: * Receive data register full * Failure to clear SPRF bit before next byte is received (overflow error) * Inconsistent logic level on SS pin (mode fault error) * Transmit data register empty The SPI status and control register also contains bits that perform these functions: * Enable error interrupts * Enable mode fault error detection * Select master SPI baud rate
Address Read: Write: Reset: 0 $0011 Bit 7 SPRF 6 ERRIE 0 5 OVRF 0 4 MODF 0 3 SPTE 1 2 MODFEN 0 1 SPR1 0 Bit 0 SPR0 0
= Unimplemented
Figure 13-14. SPI Status and Control Register (SPSCR) SPRF -- SPI Receiver Full Bit This clearable, read-only flag is set each time a byte transfers from the shift register to the receive data register. SPRF generates a CPU interrupt request if the SPRIE bit in the SPI control register is set also. During an SPRF CPU interrupt, the CPU clears SPRF by reading the SPI status and control register with SPRF set and then reading the SPI data register. Reset clears the SPRF bit. 1 = Receive data register full 0 = Receive data register not full
MC68HC908AP A-Family Data Sheet, Rev. 2 222 Freescale Semiconductor
I/O Registers
ERRIE -- Error Interrupt Enable Bit This read/write bit enables the MODF and OVRF bits to generate CPU interrupt requests. Reset clears the ERRIE bit. 1 = MODF and OVRF can generate CPU interrupt requests 0 = MODF and OVRF cannot generate CPU interrupt requests OVRF -- Overflow Bit This clearable, read-only flag is set if software does not read the byte in the receive data register before the next full byte enters the shift register. In an overflow condition, the byte already in the receive data register is unaffected, and the byte that shifted in last is lost. Clear the OVRF bit by reading the SPI status and control register with OVRF set and then reading the receive data register. Reset clears the OVRF bit. 1 = Overflow 0 = No overflow MODF -- Mode Fault Bit This clearable, read-only flag is set in a slave SPI if the SS pin goes high during a transmission with the MODFEN bit set. In a master SPI, the MODF flag is set if the SS pin goes low at any time with the MODFEN bit set. Clear the MODF bit by reading the SPI status and control register (SPSCR) with MODF set and then writing to the SPI control register (SPCR). Reset clears the MODF bit. 1 = SS pin at inappropriate logic level 0 = SS pin at appropriate logic level SPTE -- SPI Transmitter Empty Bit This clearable, read-only flag is set each time the transmit data register transfers a byte into the shift register. SPTE generates an SPTE CPU interrupt request if the SPTIE bit in the SPI control register is set also. NOTE Do not write to the SPI data register unless the SPTE bit is high. During an SPTE CPU interrupt, the CPU clears the SPTE bit by writing to the transmit data register. Reset sets the SPTE bit. 1 = Transmit data register empty 0 = Transmit data register not empty MODFEN -- Mode Fault Enable Bit This read/write bit, when set to 1, allows the MODF flag to be set. If the MODF flag is set, clearing the MODFEN does not clear the MODF flag. If the SPI is enabled as a master and the MODFEN bit is low, then the SS pin is available as a general-purpose I/O. If the MODFEN bit is set, then this pin is not available as a general-purpose I/O. When the SPI is enabled as a slave, the SS pin is not available as a general-purpose I/O regardless of the value of MODFEN. (See 13.12.4 SS (Slave Select).) If the MODFEN bit is low, the level of the SS pin does not affect the operation of an enabled SPI configured as a master. For an enabled SPI configured as a slave, having MODFEN low only prevents the MODF flag from being set. It does not affect any other part of SPI operation. (See 13.7.2 Mode Fault Error.) SPR1 and SPR0 -- SPI Baud Rate Select Bits In master mode, these read/write bits select one of four baud rates as shown in Table 13-4. SPR1 and SPR0 have no effect in slave mode. Reset clears SPR1 and SPR0.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 223
Serial Peripheral Interface Module (SPI)
Table 13-4. SPI Master Baud Rate Selection
SPR1 and SPR0 00 01 10 11 Baud Rate Divisor (BD) 2 8 32 128
Use this formula to calculate the SPI baud rate:
CGMOUT Baud rate = ------------------------2 x BD
where: CGMOUT = base clock output of the clock generator module (CGM) BD = baud rate divisor
13.13.3 SPI Data Register
The SPI data register consists of the read-only receive data register and the write-only transmit data register. Writing to the SPI data register writes data into the transmit data register. Reading the SPI data register reads data from the receive data register. The transmit data and receive data registers are separate registers that can contain different values. (See Figure 13-2.)
Address: Read: Write: Reset: $0012 Bit 7 R7 T7 6 R6 T6 5 R5 T5 4 R4 T4 3 R3 T3 2 R2 T2 1 R1 T1 Bit 0 R0 T0
Unaffected by reset
Figure 13-15. SPI Data Register (SPDR) R7-R0/T7-T0 -- Receive/Transmit Data Bits NOTE Do not use read-modify-write instructions on the SPI data register since the register read is not the same as the register written.
MC68HC908AP A-Family Data Sheet, Rev. 2 224 Freescale Semiconductor
Chapter 14 Multi-Master IIC Interface (MMIIC)
14.1 Introduction
The multi-master IIC (MMIIC) interface is a two wire, bidirectional serial bus which provides a simple, efficient way for data exchange between devices. The interface is designed for internal serial communication between the MCU and other IIC devices. It has hardware generated START and STOP signals; and byte by byte interrupt driven software algorithm. This bus is suitable for applications which need frequent communications over a short distance between a number of devices. It also provides a flexibility that allows additional devices to be connected to the bus. The maximum data rate is 100k-bps, and the maximum communication distance and number of devices that can be connected is limited by a maximum bus capacitance of 400pF. This MMIIC interface is also SMBus (System Management Bus) version 1.0 and 1.1 compatible, with hardware cyclic redundancy code (CRC) generation, making it suitable for smart battery applications.
14.2 Features
Features of the MMIC module include: * Full SMBus version 1.0/1.1 compliance * Multi-master IIC bus standard * Software programmable for one of eight different serial clock frequencies * Software controllable acknowledge bit generation * Interrupt driven byte by byte data transfer * Calling address identification interrupt * Arbitration loss detection and no-ACK awareness in master mode and automatic mode switching from master to slave * Auto detection of R/W bit and switching of transmit or receive mode accordingly * Detection of START, repeated START, and STOP signals * Auto generation of START and STOP condition in master mode * Repeated start generation * Master clock generator with eight selectable baud rates * Automatic recognition of the received acknowledge bit * Busy detection * Software enabled 8-bit CRC generation/decoding
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 225
Multi-Master IIC Interface (MMIIC)
14.3 I/O Pins
The MMIIC module uses two I/O pins, shared with standard port I/O pins. The full name of the MMIIC I/O pins are listed in Table 14-1. The generic pin name appear in the text that follows. The SDA and SDL pins are open-drain. When configured as general purpose output pins (PTB0 and PTB1), pullup resistors must be connected to these pins. Table 14-1. Pin Name Conventions
MMIIC Generic Pin Names: SDA SCL Full MCU Pin Names: PTB0/SDA MMEN bit in MMCR1 ($0049) PTB1/SCL Pin Selected for MMIIC Function By:
Addr. $0048
Register Name MMIIC Address Register (MMADR) MMIIC Control Register 1 (MMCR1) MMIIC Control Register 2 (MMCR2) MMIIC Status Register (MMSR) MMIIC Data Transmit Register (MMDTR) MMIIC Data Receive Register (MDDRR) MMIIC CRC Data Register (MMCRDR) MMIIC Frequency Divider Register (MMFDR)
$0049
$004A
$004B
$004C
$004D
$004E
$004F
Bit 7 6 5 4 3 2 1 Read: MMAD7 MMAD6 MMAD5 MMAD4 MMAD3 MMAD2 MMAD1 Write: Reset: 1 0 1 0 0 0 0 Read: 0 0 MMEN MMIEN MMTXAK REPSEN MMCRCBYTE Write: MMCLRBB Reset: 0 0 0 0 0 0 0 Read: MMALIF MMNAKIF MMBB 0 0 MMAST MMRW Write: 0 0 Reset: 0 0 0 0 0 0 0 Read: MMRXIF MMTXIF MMATCH MMSRW MMRXAK MMCRCBF MMTXBE Write: 0 0 Reset: 0 0 0 0 1 0 1 Read: MMTD7 MMTD6 MMTD5 MMTD4 MMTD3 MMTD2 MMTD1 Write: Reset: 0 0 0 0 0 0 0 Read: MMRD7 MMRD6 MMRD5 MMRD4 MMRD3 MMRD2 MMRD1 Write: Reset: 0 0 0 0 0 0 0 Read: MMCRCD7 MMCRCD6 MMCRCD5 MMCRCD4 MMCRCD3 MMCRCD2 MMCRCD1 Write: Reset: 0 0 0 0 0 0 0 Read: 0 0 0 0 0 MMBR2 MMBR1 Write: Reset: 0 0 0 0 0 1 0 = Unimplemented
Bit 0 MMEXTAD 0 0 0 MMCRCEF Unaffected MMRXBF 0 MMTD0 0 MMRD0 0 MMCRCD0 0 MMBR0 0
Figure 14-1. MMIIC I/O Register Summary
14.4 Multi-Master IIC System Configuration
The multi-master IIC system uses a serial data line SDA and a serial clock line SCL for data transfer. All devices connected to it must have open collector (drain) outputs and the logical-AND function is performed on both lines by two pull-up resistors.
MC68HC908AP A-Family Data Sheet, Rev. 2 226 Freescale Semiconductor
Multi-Master IIC Bus Protocol
14.5 Multi-Master IIC Bus Protocol
Normally a standard communication is composed of four parts: 1. START signal, 2. slave address transmission, 3. data transfer, and 4. STOP signal. These are described briefly in the following sections and illustrated in Figure 14-2.
9th clock pulse MSB SCL 1 1 0 0 0 0 1 LSB 1 MSB 1 1 0 1 0 0 1 9th clock pulse LSB 1
SDA ACK START signal MSB SCL 1 1 0 0 0 0 1 LSB 1 MSB 1 1 0 1 0 0 1 Data must be stable when SCL is HIGH No ACK STOP signal LSB 1
SDA ACK START signal Repeated START signal No ACK STOP signal
Figure 14-2. Multi-Master IIC Bus Transmission Signal Diagram
14.5.1 START Signal
When the bus is free, (i.e. no master device is engaging the bus -- both SCL and SDA lines are at logic high) a master may initiate communication by sending a START signal. As shown in Figure 14-2, a START signal is defined as a high to low transition of SDA while SCL is high. This signal denotes the beginning of a new data transfer (each data transfer may contain several bytes of data) and wakes up all slaves.
14.5.2 Slave Address Transmission
The first byte transferred immediately after the START signal is the slave address transmitted by the master. This is a 7-bit calling address followed by a R/W-bit. The R/W-bit dictates to the slave the desired direction of the data transfer. A logic 0 indicates that the master wishes to transmit data to the slave; a logic 1 indicates that the master wishes to receive data from the slave.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 227
Multi-Master IIC Interface (MMIIC)
Only the slave with a matched address will respond by sending back an acknowledge bit by pulling SDA low on the 9th clock cycle. (See Figure 14-2.)
14.5.3 Data Transfer
Once a successful slave addressing is achieved, the data transfer can proceed byte by byte in the direction specified by the R/W-bit sent by the calling master. Each data byte is 8 bits. Data can be changed only when SCL is low and must be held stable when SCL is high as shown in Figure 14-2. The MSB is transmitted first and each byte has to be followed by an acknowledge bit. This is signalled by the receiving device by pulling the SDA low on the 9th clock cycle. Therefore, one complete data byte transfer requires 9 clock cycles. If the slave receiver does not acknowledge the master, the SDA line should be left high by the slave. The master can then generate a STOP signal to abort the data transfer or a START signal (repeated START) to commence a new transfer. If the master receiver does not acknowledge the slave transmitter after a byte has been transmitted, it means an "end of data" to the slave. The slave should release the SDA line for the master to generate a STOP or START signal.
14.5.4 Repeated START Signal
As shown in Figure 14-2, a repeated START signal is used to generate START signal without first generating a STOP to terminate the communication. This is used by the master to communicate with another slave or with the same slave in a different mode (transmit/receive mode) without releasing the bus.
14.5.5 STOP Signal
The master can terminate the communication by generating a STOP signal to free the bus. However, the master may generate a START signal followed by a calling command without first generating a STOP signal. This is called repeat START. A STOP signal is defined as a low to high transition of SDA while SCL is at logic high (see Figure 14-2).
14.5.6 Arbitration Procedure
The interface circuit is a multi-master system which allows more than one master to be connected. If two or more masters try to control the bus at the same time, a clock synchronization procedure determines the bus clock. The clock low period is equal to the longest clock low period and the clock high period is equal to the shortest one among the masters. A data arbitration procedure determines the priority. A master will lose arbitration if it transmits a logic 1 while another transmits a logic 0. The losing master will immediately switch over to slave receive mode and stops its data and clock outputs. The transition from master to slave will not generate a STOP condition. Meanwhile a software bit will be set by hardware to indicates loss of arbitration.
14.5.7 Clock Synchronization
Since wired-AND logic is performed on SCL line, a high to low transition on the SCL line will affect the devices connected to the bus. The devices start counting their low period once a device's clock has gone low, it will hold the SCL line low until the clock high state is reached. However, the change of low to high
MC68HC908AP A-Family Data Sheet, Rev. 2 228 Freescale Semiconductor
MMIIC I/O Registers
in this device clock may not change the state of the SCL line if another device clock is still in its low period. Therefore the synchronized clock SCL will be held low by the device which last releases SCL to logic high. Devices with shorter low periods enter a high wait state during this time. When all devices concerned have counted off their low period, the synchronized SCL line will be released and go high, and all devices will start counting their high periods. The first device to complete its high period will again pull the SCL line low. Figure 14-3 illustrates the clock synchronization waveforms.
WAIT Start counting high period
SCL1
SCL2
SCL
Internal counter reset
Figure 14-3. Clock Synchronization
14.5.8 Handshaking
The clock synchronization mechanism can be used as a handshake in data transfer. A slave device may hold the SCL low after completion of one byte data transfer and will halt the bus clock, forcing the master clock into a wait state until the slave releases the SCL line.
14.5.9 Packet Error Code
The packet error code (PEC) for the MMIIC interface is in the form a cyclic redundancy code (CRC). The PEC is generated by hardware for every transmitted and received byte of data. The transmission of the generated PEC is controlled by user software. The CRC data register, MMCRCDR, contains the generated PEC byte, with three other bits in the MMIIC control registers and status register monitoring and controlling the PEC byte.
14.6 MMIIC I/O Registers
These I/O registers control and monitor MMIIC operation: * MMIIC address register (MMADR) -- $0048 * MMIIC control register 1 (MMCR1) -- $0049 * MMIIC control register 2 (MMCR2) -- $004A * MMIIC status register (MMSR) -- $004B * MMIIC data transmit register (MMDTR) -- $004C * MMIIC data receive register (MMDRR) -- $004D * MMIIC CRC data register (MMCRCDR) -- $004E * MMIIC frequency divide register (MMFDR) -- $004F
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 229
Multi-Master IIC Interface (MMIIC)
14.6.1 MMIIC Address Register (MMADR)
Address: $0048 Bit 7 6 MMAD6 0 5 MMAD5 1 4 MMAD4 0 3 MMAD3 0 2 MMAD2 0 1 MMAD1 0 Bit 0 MMEXTAD 0
Read: Write: Reset:
MMAD7 1
Figure 14-4. MMIIC Address Register (MMADR) MMAD[7:1] -- Multi-Master Address These seven bits represent the MMIIC interface's own specific slave address when in slave mode, and the calling address when in master mode. Software must update MMAD[7:1] as the calling address while entering master mode and restore its own slave address after master mode is relinquished. This register is cleared as $A0 upon reset. MMEXTAD -- Multi-Master Expanded Address This bit is set to expand the address of the MMIIC in slave mode. When set, the MMIIC will acknowledge the following addresses from a calling master: $MMAD[7:1], 0000000, and 0001100. Reset clears this bit. 1 = MMIIC responds to the following calling addresses: $MMAD[7:1], 0000000, and 0001100. 0 = MMIIC responds to address $MMAD[7:1] For example, when MMADR is configured as:
MMAD7 1 MMAD6 1 MMAD5 0 MMAD4 1 MMAD3 0 MMAD2 1 MMAD1 0 MMEXTAD 1
The MMIIC module will respond to the calling address:
Bit 7 1 6 1 5 0 4 1 3 0 2 1 Bit 1 0
or the general calling address:
0 0 0 0 0 0 0
or the calling address:
Bit 7 0 6 0 5 0 4 1 3 1 2 0 Bit 1 0
Note that bit-0 of the 8-bit calling address is the MMRW bit from the calling master.
MC68HC908AP A-Family Data Sheet, Rev. 2 230 Freescale Semiconductor
MMIIC I/O Registers
14.6.2 MMIIC Control Register 1 (MMCR1)
Address: Read: Write: Reset: $0049 Bit 7 6 5 4 3 2 1
MMCRCBYTE
Bit 0
MMEN
0
MMIEN
0
0
MMCLRBB 0
0
0
MMTXAK REPSEN
0 0
0
0 0
= Unimplemented
Figure 14-5. MMIIC Control Register 1 (MMCR1) MMEN -- MMIIC Enable This bit is set to enable the Multi-master IIC module. When MMEN = 0, module is disabled and all flags will restore to its power-on default states. Reset clears this bit. 1 = MMIIC module enabled 0 = MMIIC module disabled MMIEN -- MMIIC Interrupt Enable When this bit is set, the MMTXIF, MMRXIF, MMALIF, and MMNAKIF flags are enabled to generate an interrupt request to the CPU. When MMIEN is cleared, the these flags are prevented from generating an interrupt request. Reset clears this bit. 1 = MMTXIF, MMRXIF, MMALIF, and/or MMNAKIF bit set will generate interrupt request to CPU 0 = MMTXIF, MMRXIF, MMALIF, and/or MMNAKIF bit set will not generate interrupt request to CPU MMCLRBB -- MMIIC Clear Busy Flag Writing a logic 1 to this write-only bit clears the MMBB flag. MMCLRBB always reads as a logic 0. Reset clears this bit. 1 = Clear MMBB flag 0 = No affect on MMBB flag MMTXAK -- MMIIC Transmit Acknowledge Enable This bit is set to disable the MMIIC from sending out an acknowledge signal to the bus at the 9th clock bit after receiving 8 data bits. When MMTXAK is cleared, an acknowledge signal will be sent at the 9th clock bit. Reset clears this bit. 1 = MMIIC does not send acknowledge signals at 9th clock bit 0 = MMIIC sends acknowledge signal at 9th clock bit REPSEN -- Repeated Start Enable This bit is set to enable repeated START signal to be generated when in master mode transfer (MMAST = 1). The REPSEN bit is cleared by hardware after the completion of repeated START signal or when the MMAST bit is cleared. Reset clears this bit. 1 = Repeated START signal will be generated if MMAST bit is set 0 = No repeated START signal will be generated MMCRCBYTE -- MMIIC CRC Byte In receive mode, this bit is set by software to indicate that the next receiving byte will be the packet error checking (PEC) data. In master receive mode, after completion of CRC generation on the received PEC data, an acknowledge signal is sent if MMTXAK = 0; no acknowledge is sent If MMTXAK = 1. In slave receive mode, no acknowledge signal is sent if a CRC error is detected on the received PEC data. If no CRC error is detected, an acknowledge signal is sent if MMTXAK = 0; no acknowledge is sent If MMTXAK = 1.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 231
Multi-Master IIC Interface (MMIIC)
Under normal operation, the user software should clear MMTXAK bit before setting MMCRCBYTE bit to ensure that an acknowledge signal is sent when no CRC error is detected. The MMCRCBYTE bit should not be set in transmit mode. This bit is cleared by the next START signal. Reset also clears this bit. 1 = Next receiving byte is the packet error checking (PEC) data 0 = Next receiving byte is not PEC data
14.6.3 MMIIC Control Register 2 (MMCR2)
Address: Read: Write: Reset: $004A Bit 7 MMALIF 0 0 6 MMNAKIF 0 0 0 = Unimplemented 5 MMBB 4 MMAST 0 3 MMRW 0 2 0 0 1 0 0 Bit 0
MMCRCEF
Unaffected
Figure 14-6. MMIIC Control Register 2 (MMCR2) MMALIF -- Arbitration Loss Interrupt Flag This flag is set when software attempt to set MMAST but the MMBB has been set by detecting the start condition on the lines or when the MMIIC is transmitting a "1" to SDA line but detected a "0" from SDA line in master mode -- an arbitration loss. This bit generates an interrupt request to the CPU if the MMIEN bit in MMCR1 is set. This bit is cleared by writing "0" to it or by reset. 1 = Lost arbitration in master mode 0 = No arbitration lost MMNAKIF -- No AcKnowledge Interrupt Flag (Master Mode) This flag is only set in master mode (MMAST = 1) when there is no acknowledge bit detected after one data byte or calling address is transferred. This flag also clears MMAST. MMNAKIF generates an interrupt request to CPU if the MMIEN bit in MMCR1 is set. This bit is cleared by writing "0" to it or by reset. 1 = No acknowledge bit detected 0 = Acknowledge bit detected MMBB -- MMIIC Bus Busy Flag This flag is set after a start condition is detected (bus busy), and is cleared when a stop condition (bus idle) is detected or the MMIIC is disabled. Reset clears this bit. 1 = Start condition detected 0 = Stop condition detected or MMIIC is disabled MMAST -- MMIIC Master Control This bit is set to initiate a master mode transfer. In master mode, the module generates a start condition to the SDA and SCL lines, followed by sending the calling address stored in MMADR. When the MMAST bit is cleared by MMNAKIF set (no acknowledge) or by software, the module generates the stop condition to the lines after the current byte is transmitted. If an arbitration loss occurs (MMALIF = 1), the module reverts to slave mode by clearing MMAST, and releasing SDA and SCL lines immediately. This bit is cleared by writing "0" to it or by reset. 1 = Master mode operation 0 = Slave mode operation
MC68HC908AP A-Family Data Sheet, Rev. 2 232 Freescale Semiconductor
MMIIC I/O Registers
MMRW -- MMIIC Master Read/Write This bit is transmitted out as bit 0 of the calling address when the module sets the MMAST bit to enter master mode. The MMRW bit determines the transfer direction of the data bytes that follows. When it is "1", the module is in master receive mode. When it is "0", the module is in master transmit mode. Reset clears this bit. 1 = Master mode receive 0 = Master mode transmit MMCRCEF -- MMIIC CRC Error Flag This flag is set when a CRC error is detected, and cleared when no CRC error is detected. The MMCRCEF is only meaningful after receiving a PEC data. This flag is unaffected by reset. 1 = CRC error detected on PEC byte 0 = No CRC error detected on PEC byte
14.6.4 MMIIC Status Register (MMSR)
Address: Read: Write: Reset: $004B Bit 7 MMRXIF 6 MMTXIF 5 MMATCH 4 MMSRW 3 MMRXAK 2
MMCRCBF
1 MMTXBE
Bit 0 MMRXBF
0 0
0 0 0 0 1 0 1 0 = Unimplemented
Figure 14-7. MMIIC Status Register (MMSR) MMRXIF -- MMIIC Receive Interrupt Flag This flag is set after the data receive register (MMDRR) is loaded with a new received data. Once the MMDRR is loaded with received data, no more received data can be loaded to the MMDRR register until the CPU reads the data from the MMDRR to clear MMRXBF flag. MMRXIF generates an interrupt request to CPU if the MMIEN bit in MMCR is also set. This bit is cleared by writing "0" to it or by reset; or when the MMEN = 0. 1 = New data in data receive register (MMDRR) 0 = No data received MMTXIF -- MMIIC Transmit Interrupt Flag This flag is set when data in the data transmit register (MMDTR) is downloaded to the output circuit, and that new data can be written to the MMDTR. MMTXIF generates an interrupt request to CPU if the MMIEN bit in MMCR is also set. This bit is cleared by writing "0" to it or when the MMEN = 0. 1 = Data transfer completed 0 = Data transfer in progress MMATCH -- MMIIC Address Match Flag This flag is set when the received data in the data receive register (MMDRR) is a calling address which matches with the address or its extended addresses (MMEXTAD = 1) specified in the address register (MMADR). The MMATCH flag is set at the 9th clock of the calling address and will be cleared on the 9th clock of the next receiving data. Note: slave transmits do not clear MMATCH. 1 = Received address matches MMADR 0 = Received address does not match
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 233
Multi-Master IIC Interface (MMIIC)
MMSRW -- MMIIC Slave Read/Write Select This bit indicates the data direction when the module is in slave mode. It is updated after the calling address is received from a master device. MMSRW = 1 when the calling master is reading data from the module (slave transmit mode). MMSRW = 0 when the master is writing data to the module (receive mode). 1 = Slave mode transmit 0 = Slave mode receive MMRXAK -- MMIIC Receive Acknowledge When this bit is cleared, it indicates an acknowledge signal has been received after the completion of eight data bits transmission on the bus. When MMRXAK is set, it indicates no acknowledge signal has been detected at the 9th clock; the module will release the SDA line for the master to generate STOP or repeated START condition. Reset sets this bit. 1 = No acknowledge signal received at 9th clock 0 = Acknowledge signal received at 9th clock MMCRCBF -- CRC Data Buffer Full Flag This flag is set when the CRC data register (MMCRCDR) is loaded with a CRC byte for the current received or transmitted data. In transmit mode, after a byte of data has been sent (MMTXIF = 1), the MMCRCBF will be set when the CRC byte has been generated and ready in the MMCRCDR. The content of the MMCRCDR should be copied to the MMDTR for transmission. In receive mode, the MMCRCBF is set when the CRC byte has been generated and ready in MMCRCDR, for the current byte of received data. The MMCRCBF bit is cleared when the CRC data register is read. Reset also clears this bit. 1 = Data ready in CRC data register (MMCRCDR) 0 = Data not ready in CRC data register (MMCRCDR) MMTXBE -- MMIIC Transmit Buffer Empty This flag indicates the status of the data transmit register (MMDTR). When the CPU writes the data to the MMDTR, the MMTXBE flag will be cleared. MMTXBE is set when MMDTR is emptied by a transfer of its data to the output circuit. Reset sets this bit. 1 = Data transmit register empty 0 = Data transmit register full MMRXBF -- MMIIC Receive Buffer Full This flag indicates the status of the data receive register (MMDRR). When the CPU reads the data from the MMDRR, the MMRXBF flag will be cleared. MMRXBF is set when MMDRR is full by a transfer of data from the input circuit to the MMDRR. Reset clears this bit. 1 = Data receive register full 0 = Data receive register empty
14.6.5 MMIIC Data Transmit Register (MMDTR)
Address: Read: Write: Reset: $004C Bit 7 MMTD7 0 6 MMTD6 0 5 MMTD5 0 4 MMTD4 0 3 MMTD3 0 2 MMTD2 0 1 MMTD1 0 Bit 0 MMTD0 0
Figure 14-8. MMIIC Data Transmit Register (MMDTR)
MC68HC908AP A-Family Data Sheet, Rev. 2 234 Freescale Semiconductor
MMIIC I/O Registers
When the MMIIC module is enabled, MMEN = 1, data written into this register depends on whether module is in master or slave mode. In slave mode, the data in MMDTR will be transferred to the output circuit when: * the module detects a matched calling address (MMATCH = 1), with the calling master requesting data (MMSRW = 1); or * the previous data in the output circuit has be transmitted and the receiving master returns an acknowledge bit, indicated by a received acknowledge bit (MMRXAK = 0). If the calling master does not return an acknowledge bit (MMRXAK = 1), the module will release the SDA line for master to generate a STOP or repeated START condition. The data in the MMDTR will not be transferred to the output circuit until the next calling from a master. The transmit buffer empty flag remains cleared (MMTXBE = 0). In master mode, the data in MMDTR will be transferred to the output circuit when: * the module receives an acknowledge bit (MMRXAK = 0), after setting master transmit mode (MMRW = 0), and the calling address has been transmitted; or * the previous data in the output circuit has be transmitted and the receiving slave returns an acknowledge bit, indicated by a received acknowledge bit (MMRXAK = 0). If the slave does not return an acknowledge bit (MMRXAK = 1), the master will generate a STOP or repeated START condition. The data in the MMDTR will not be transferred to the output circuit. The transmit buffer empty flag remains cleared (MMTXBE = 0). The sequence of events for slave transmit and master transmit are illustrated in Figure 14-12.
14.6.6 MMIIC Data Receive Register (MMDRR)
Address: Read: Write: Reset: 0 0 0 0 0 0 0 0 = Unimplemented $004D Bit 7 MMRD7 6 MMRD6 5 MMRD5 4 MMRD4 3 MMRD3 2 MMRD2 1 MMRD1 Bit 0 MMRD0
Figure 14-9. MMIIC Data Receive Register (MMDRR) When the MMIIC module is enabled, MMEN = 1, data in this read-only register depends on whether module is in master or slave mode. In slave mode, the data in MMDRR is: * the calling address from the master when the address match flag is set (MMATCH = 1); or * the last data received when MMATCH = 0. In master mode, the data in the MMDRR is: * the last data received. When the MMDRR is read by the CPU, the receive buffer full flag is cleared (MMRXBF = 0), and the next received data is loaded to the MMDRR. Each time when new data is loaded to the MMDRR, the MMRXIF interrupt flag is set, indicating that new data is available in MMDRR. The sequence of events for slave receive and master receive are illustrated in Figure 14-12.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 235
Multi-Master IIC Interface (MMIIC)
14.6.7 MMIIC CRC Data Register (MMCRCDR)
Address: $004E Bit 7 Write: Reset: 0 0 0 0 0 0 0 0 6 5 4 3 2 1 Bit 0
Read: MMCRCD7 MMCRCD6 MMCRCD5 MMCRCD4 MMCRCD3 MMCRCD2 MMCRCD1 MMCRCD0
= Unimplemented
Figure 14-10. MMIIC CRC Data Register (MMCRCDR) When the MMIIC module is enabled, MMEN = 1, and the CRC buffer full flag is set (MMCRCBF = 1), data in this read-only register contains the generated CRC byte for the last byte of received or transmitted data. A CRC byte is generated for each received and transmitted data byte and loaded to the CRC data register. The MMCRCBF bit will be set to indicate the CRC byte is ready in the CRC data register. Reading the CRC data register clears the MMCRCBF bit. If the CRC data register is not read, the MMCRCBF bit will be cleared by hardware before the next CRC byte is loaded.
14.6.8 MMIIC Frequency Divider Register (MMFDR)
Address: Read: Write: Reset: 0 0 0 0 0 $004F Bit 7 0 6 0 5 0 4 0 3 0 2 MMBR2 1 1 MMBR1 0 Bit 0 MMBR0 0
= Unimplemented
Figure 14-11. MMIIC Frequency Divider Register (MMFDR) The three bits in the frequency divider register (MMFDR) selects the divider to divide the bus clock to the desired baud rate for the MMIIC data transfer. Table 14-2 shows the divider values for MMBR[2:0].
MC68HC908AP A-Family Data Sheet, Rev. 2 236 Freescale Semiconductor
Program Algorithm
Table 14-2. MMIIC Baud Rate Selection
MMIIC Baud Rates for Bus Clocks: MMBR2 0 0 0 0 1 1 1 1 MMBR1 0 0 1 1 0 0 1 1 MMBR0 0 1 0 1 0 1 0 1 Divider 8MHz 20 40 80 160 320 640 1280 2560 400kHz 200kHz 100kHz 50kHz 25kHz 12.5kHz 6.25kHz 3.125kHz 4MHz 200kHz 100kHz 50kHz 25kHz 12.5kHz 6.25kHz 3.125kHz 1.5625kHz 2MHz 100kHz 50kHz 25kHz 12.5kHz 6.25kHz 3.125kHz 1.5625kHz 0.78125kHz 1MHz 50kHz 25kHz 12.5kHz 6.25kHz 3.125kHz 1.5625kHz 0.78125kHz 0.3906kHz
NOTE The frequency of the MMIIC baud rate is only guaranteed for 100kHz to 10kHz. The divider is available for the flexibility on bus frequency selection.
14.7 Program Algorithm
When the MMIIC module detects an arbitration loss in master mode, it releases both SDA and SCL lines immediately. But if there are no further STOP conditions detected, the module will hang up. Therefore, it is recommended to have time-out software to recover from this condition. The software can start the time-out counter by looking at the MMBB (bus busy) flag and reset the counter on the completion of one byte transmission. If a time-out has occurred, software can clear the MMEN bit (disable MMIIC module) to release the bus, and hence clear the MMBB flag. This is the only way to clear the MMBB flag by software if the module hangs up due to a no STOP condition received. The MMIIC can resume operation again by setting the MMEN bit.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 237
Multi-Master IIC Interface (MMIIC)
14.7.1 Data Sequence
(a) Master Transmit Mode
START Address 0 ACK TX Data1 ACK TX DataN ACK STOP
MMTXBE=0 MMRW=0 MMAST=1 Data1 MMDTR
MMTXBE=1 MMTXIF=1 Data2 MMDTR
MMTXBE=1 MMTXIF=1 Data3 MMDTR
MMTXBE=1 MMNAKIF=1 MMTXIF=1 MMAST=0 DataN+2 MMDTR MMTXBE=0
(b) Master Receive Mode
START Address 1 ACK RX Data1 ACK RX DataN NAK STOP
MMRXBF=0 MMRW=1 MMAST=1 MMTXBE=0 (dummy data MMDTR)
Data1 MMDRR MMRXIF=1 MMRXBF=1
DataN MMDRR MMNAKIF=1 MMRXIF=1 MMAST=0 MMRXBF=1
(c) Slave Transmit Mode
START Address 1 ACK TX Data1 ACK TX DataN NAK STOP
MMTXBE=1 MMRXBF=0
MMRXIF=1 MMRXBF=1 MMATCH=1 MMSRW=1 Data1 MMDTR
MMTXBE=1 MMTXIF=1 Data2 MMDTR
MMTXBE=1 MMNAKIF=1 MMTXIF=1 MMTXBE=0 DataN+2 MMDTR
(d) Slave Receive Mode
START Address 0 ACK RX Data1 ACK RX DataN ACK STOP
MMTXBE=0 MMRXBF=0
MMRXIF=1 MMRXBF=1 MMATCH=1 MMSRW=0
Data1 MMDRR MMRXIF=1 MMRXBF=1
DataN MMDRR MMRXIF=1 MMRXBF=1
Shaded data packets indicate transmissions by the MCU
Figure 14-12. Data Transfer Sequences for Master/Slave Transmit/Receive Modes
MC68HC908AP A-Family Data Sheet, Rev. 2 238 Freescale Semiconductor
SMBus Protocols with PEC and without PEC
14.8 SMBus Protocols with PEC and without PEC
Following is a description of the various MMIIC bus protocols with and without a packet error code (PEC).
14.8.1 Quick Command
1 START 7 1 1 1 STOP Stop Condition Master to Slave Slave to Master
Slave Address RW ACK Start Condition Command Bit Acknowledge
Figure 14-13. Quick Command
14.8.2 Send Byte
START Slave Address W ACK Command Code ACK STOP
(a) Send Byte Protocol START Slave Address W ACK Command Code ACK
PEC
ACK
STOP
(b) Send Byte Protocol with PEC
Figure 14-14. Send Byte
14.8.3 Receive Byte
START Slave Address R ACK Data Byte NAK STOP
(a) Receive Byte Protocol START Slave Address R ACK Data Byte ACK
PEC
NAK
STOP
(b) Receive Byte Protocol with PEC
Figure 14-15. Receive Byte
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 239
Multi-Master IIC Interface (MMIIC)
14.8.4 Write Byte/Word
START Slave Address W ACK
Command Code
ACK
Data Byte
ACK
STOP
(a) Write Byte Protocol START Slave Address W ACK
Command Code
ACK
Data Byte
ACK
PEC
ACK
STOP
(b) Write Byte Protocol with PEC START Slave Address W ACK
Command Code
ACK
Data Byte Low
ACK
Data Byte High
ACK
STOP
(c) Write Word Protocol START Slave Address W ACK
Command Code
ACK
Data Byte Low
ACK
Data Byte High
ACK
PEC
ACK
STOP
(d) Write Word Protocol with PEC
Figure 14-16. Write Byte/Word
14.8.5 Read Byte/Word
START Slave Address W ACK
Command Code
ACK
START
Slave Address
R
ACK
Data Byte
NAK
STOP
(a) Read Byte Protocol START Slave Address W ACK
Command Code
ACK
START
Slave Address
R
ACK
Data Byte
ACK
PEC
NAK
STOP
(b) Read Byte Protocol with PEC START Slave Address W ACK
Command Code
ACK
START
Slave Address
R
ACK
Data Byte Low
ACK
Data Byte High
(c) Read Word Protocol START
NAK
STOP
Slave Address
W ACK
Command Code NAK
ACK
START
Slave Address
R
ACK
Data Byte Low
ACK
Data Byte High
ACK
PEC
STOP
(d) Read Word Protocol with PEC
Figure 14-17. Read Byte/Word
MC68HC908AP A-Family Data Sheet, Rev. 2 240 Freescale Semiconductor
SMBus Protocols with PEC and without PEC
14.8.6 Process Call
START START (a) Process Call START START Slave Address Slave Address W ACK R Slave Address Slave Address W ACK R
Command Code Data Byte Low
ACK ACK
Data Byte Low Data Byte High
ACK NAK
Data Byte High STOP
ACK
ACK
Command Code Data Byte Low
ACK ACK
Data Byte Low Data Byte High
ACK ACK
Data Byte High STOP
ACK PEC NAK STOP
ACK
(b) Process Call with PEC
Figure 14-18. Process Call
14.8.7 Block Read/Write
START Slave Address W ACK
Command Code ACK
ACK
Byte Count = N
ACK
Data Byte 1
ACK
Data Byte 2
(a) Block Read START
ACK
Data Byte N
STOP
Slave Address
W ACK
Command Code ACK
ACK
Byte Count = N PEC ACK
ACK STOP
Data Byte 1
ACK
Data Byte 2
ACK
Data Byte N
(b) Block Read with PEC START Slave Address W ACK
Command Code ACK
ACK
START
Slave Address
R
ACK
Byte Count = N
ACK
Data Byte 1
(c) Block Write START
ACK
Data Byte 2
Data Byte N
NAK
STOP
Slave Address
W ACK
Command Code ACK
ACK
START
Slave Address
R
ACK
Byte Count = N NAK STOP
ACK
Data Byte 1
ACK
Data Byte 2
Data Byte N
ACK
PEC
(d) Block Write with PEC
Figure 14-19. Block Read/Write
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 241
Multi-Master IIC Interface (MMIIC)
14.9 SMBus Protocol Implementation
Shaded data packets indicate transmissions by the MCU
MASTER MODE
START Address 0 ACK Command ACK START Address 1 ACK RX Data1 ACK ACK RX DataN NAK STOP
OPERATION: Prepare for repeated START FLAGS: MMTXIF set MMRXAK clear ACTION: 1. Set MMRW 2. Set REPSEN 3. Clear MMTXAK 4. Load dummy ($FF) to MMDTR OPERATION: Prepare for Master mode ACTION: 1. Load slave address to MMADR 2. Clear MMRW 3. Load command to MMDTR 4. Set MMAST
OPERATION: Get ready to receive data FLAGS: MMTXIF set MMRXAK clear ACTION: Load dummy ($FF) to MMDTR
OPERATION: Read received data FLAGS: MMRXIF set ACTION: Read Data1 from MMDRR
OPERATION: Generate STOP FLAGS: MMRXIF set ACTION: Read DataN from MMDRR
OPERATION: Read received data and prepare for STOP FLAGS: MMRXIF set ACTION: 1. Set MMTXAK 2. Read Data(N-1) from MMDRR 3. Clear MMAST
SLAVE MODE
START Address 0 ACK Command ACK START Address 1 ACK TX Data1 ACK ACK TX DataN NAK STOP
OPERATION: Slave address match and check for data direction FLAGS: MMRXIF set MMATCH set MMSRW depends on 8th bit of calling address byte ACTION: 1. Check MMSRW 2. Read Slave address
OPERATION: Slave address match and get ready to transmit data FLAGS: MMRXIF set MMATCH set MMSRW depends on 8th bit of calling address byte ACTION: Check MMSRW
OPERATION: Transmit data FLAGS: MMTXIF set MMRXAK clear ACTION: Load Data3 to MMDTR
OPERATION: Last data sent FLAGS: MMTXIF set MMRXAK set ACTION: Load dummy ($FF) to MMDTR
OPERATION: Prepare for Slave mode ACTION: 1. Load slave address to MMADR 2. Clear MMTXAK 3. Clear MMAST
OPERATION: Read and decode received command FLAGS: MMRXIF set MMATCH clear ACTION: Load Data1 to MMDTR
OPERATION: Transmit data FLAGS: MMTXIF set ACTION: Load Data2 to MMDTR
OPERATION: Last data is going to be sent FLAGS: MMTXIF set MMRXAK clear ACTION: Load dummy ($FF) to MMDTR
Figure 14-20. SMBus Protocol Implementation
MC68HC908AP A-Family Data Sheet, Rev. 2 242 Freescale Semiconductor
Chapter 15 Analog-to-Digital Converter (ADC)
15.1 Introduction
This section describes the analog-to-digital converter (ADC). The ADC is a 8-channel 10-bit linear successive approximation ADC.
15.2 Features
Features of the ADC module include: * Eight channels with multiplexed input * High impedance buffered input * Linear successive approximation with monotonicity * 10-bit resolution * Single or continuous conversion * Auto-scan conversion on four channels * Conversion complete flag or conversion complete interrupt * Selectable ADC clock * Conversion result justification - 8-bit truncated mode - Right justified mode - Left justified mode - Left justified sign mode
Addr. $0057 Register Name ADC Status and Control Read: Register Write: (ADSCR) Reset: ADC Clock Control Read: Register Write: (ADICLK) Reset: Read: ADC Data Register High 0 Write: (ADRH0) Reset: Read: ADC Data Register Low 0 Write: (ADRL0) Reset: Read: ADC Data Register Low 1 Write: (ADRL1) Reset: Bit 7 COCO 0 ADIV2 0 ADx R 0 ADx R 0 AD9 R 0 6 AIEN 0 ADIV1 0 ADx R 0 ADx R 0 AD8 R 0 5 ADCO 0 ADIV0 0 ADx R 0 ADx R 0 AD7 R 0 4 ADCH4 1 ADICLK 0 ADx R 0 ADx R 0 AD6 R 0 3 ADCH3 1 MODE1 0 ADx R 0 ADx R 0 AD5 R 0 2 ADCH2 1 MODE0 1 ADx R 0 ADx R 0 AD4 R 0 1 ADCH1 1 0 0 ADx R 0 ADx R 0 AD3 R 0 Bit 0 ADCH0 1 0 R 0 ADx R 0 ADx R 0 AD2 R 0
$0058
$0059
$005A
$005B
Figure 15-1. ADC I/O Register Summary
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 243
Analog-to-Digital Converter (ADC) Read: ADC Data Register Low 2 Write: (ADRL3) Reset: Read: ADC Data Register Low 3 Write: (ADRL3) Reset: ADC Auto-scan Control Read: Register Write: (ADASCR) Reset: AD9 R 0 AD9 R 0 0 0 AD8 R 0 AD8 R 0 0 AD7 R 0 AD7 R 0 0 AD6 R 0 AD6 R 0 0 0 AD5 R 0 AD5 R 0 0 0 AD4 R 0 AD4 R 0 AUTO1 0 = Reserved AD3 R 0 AD3 R 0 AUTO0 0 AD2 R 0 AD2 R 0 ASCAN 0
$005C
$005D
$005E
0 0 = Unimplemented
R
Figure 15-1. ADC I/O Register Summary
15.3 Functional Description
The ADC provides eight pins for sampling external sources at pins PTA0/ADC0-PTA7/ADC7. An analog multiplexer allows the single ADC converter to select one of eight ADC channels as ADC voltage in (VADIN). VADIN is converted by the successive approximation register-based analog-to-digital converter. When the conversion is completed, ADC places the result in the ADC data register, high and low byte (ADRH0 and ADRL0), and sets a flag or generates an interrupt. An additional three ADC data registers (ADRL1-ADRL3) are available to store the individual converted data for ADC channels ADC1-ADC3 when the auto-scan mode is enabled. Data from channel ADC0 is stored in ADRL0 in the auto-scan mode. Figure 15-2 shows the structure of the ADC module.
15.3.1 ADC Port I/O Pins
PTA0-PTA7 are general-purpose I/O pins that are shared with the ADC channels. The channel select bits, ADCH[4:0], define which ADC channel/port pin will be used as the input signal. The ADC overrides the port I/O logic by forcing that pin as input to the ADC. The remaining ADC channels/port pins are controlled by the port I/O logic and can be used as general-purpose I/O. Writes to the port data register or data direction register will not have any affect on the port pin that is selected by the ADC. Read of a port pin which is in use by the ADC will return the pin condition if the corresponding DDR bit is at logic 0. If the DDR bit is at logic 1, the value in the port data latch is read.
15.3.2 Voltage Conversion
When the input voltage to the ADC equals VREFH, the ADC converts the signal to $3FF (full scale). If the input voltage equals VREFL, the ADC converts it to $000. Input voltages between VREFH and VREFL are a straight-line linear conversion. All other input voltages will result in $3FF if greater than VREFH and $000 if less than VREFL. NOTE Input voltage should not exceed the analog supply voltages.
MC68HC908AP A-Family Data Sheet, Rev. 2 244 Freescale Semiconductor
Functional Description
INTERNAL DATA BUS READ DDRAx WRITE DDRAx RESET WRITE PTAx DDRAx PTAx PTAx/ADCx DISABLE
READ PTAx ADC0-ADC7 (8 CHANNELS) ADC DATA REGISTERS ADRH0 ADRL0 ADRL1 ADRL2 ADRL3 VREFH VREFL DISABLE
INTERRUPT LOGIC
CONVERSION COMPLETE 10-BIT ADC
ADC VOLTAGE IN (VADIN)
CHANNEL SELECT
AIEN
COCO CGMXCLK BUS CLOCK
ADCICLK MUX CLOCK GENERATOR ADCH[4:0] ADIV[2:0] ADICLK
ASCAN
2-BIT UP-COUNTER
AUTO[1:0]
Figure 15-2. ADC Block Diagram
15.3.3 Conversion Time
Conversion starts after a write to the ADSCR. One conversion will take between 16 and 17 ADC clock cycles, therefore:
16 to17 ADC cycles ADC frequency
Conversion time =
Number of bus cycles = conversion time x bus frequency
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 245
Analog-to-Digital Converter (ADC)
The ADC conversion time is determined by the clock source chosen and the divide ratio selected. The clock source is either the bus clock or CGMXCLK and is selectable by the ADICLK bit located in the ADC clock register. The divide ratio is selected by the ADIV[2:0] bits. For example, if a 4MHz CGMXCLK is selected as the ADC input clock source, with a divide-by-four prescale, and the bus speed is set at 2MHz:
16 to17 ADC cycles 4MHz / 4 = 16 to 17 s
Conversion time =
Number of bus cycles = 16 s x 2MHz = 32 to 34 cycles
NOTE The ADC frequency must be between fADIC minimum and fADIC maximum to meet A/D specifications. (See 22.5 5V DC Electrical Characteristics.). Since an ADC cycle may be comprised of several bus cycles (four in the previous example) and the start of a conversion is initiated by a bus cycle write to the ADSCR, from zero to four additional bus cycles may occur before the start of the initial ADC cycle. This results in a fractional ADC cycle and is represented as the 17th cycle.
15.3.4 Continuous Conversion
In the continuous conversion mode, the ADC continuously converts the selected channel, filling the ADC data register with new data after each conversion. Data from the previous conversion will be overwritten whether that data has been read or not. Conversions will continue until the ADCO bit is cleared. The COCO bit is set after each conversion and can be cleared by writing to the ADC status and control register or reading of the ADRL0 data register.
15.3.5 Auto-Scan Mode
In auto-scan mode, the ADC input channel is selected by the value of the 2-bit up-counter, instead of the channel select bits, ADCH[4:0]. The value of the counter also defines the data register ADRLx to be used to store the conversion result. When ASCAN bit is set, a write to ADC status and control register (ADSCR) will reset the auto-scan up-counter and ADC conversion will start on the channel 0 up to the channel number defined by the integer value of AUTO[1:0]. After a channel conversion is completed, data is stored in ADRLx and the COCO-bit will be set. The counter value will be incremented by 1 and a new conversion will start. This process will continue until the counter value reaches the value of AUTO[1:0]. When this happens, it indicates that the current channel is the last channel to be converted. Upon the completion on the last channel, the counter value will not be incremented and no further conversion will be performed. To start another auto-scan cycle, a write to ADSCR must be performed. NOTE The system only provides 8-bit data storage in auto-scan code, user must clear MODE[1:0] bits to select 8-bit truncation mode before entering auto-scan mode. It is recommended that user should disable the auto-scan function before switching channel and also before entering STOP mode.
MC68HC908AP A-Family Data Sheet, Rev. 2 246 Freescale Semiconductor
Interrupts
15.3.6 Result Justification
The conversion result may be formatted in four different ways. * Left justified * Right justified * Left justified sign data mode * 8-bit truncation All four of these modes are controlled using MODE0 and MODE1 bits located in the ADC clock control register (ADICLK). Left justification will place the eight most significant bits (MSB) in the corresponding ADC data register high (ADRH). This may be useful if the result is to be treated as an 8-bit result where the least significant two bits, located in the ADC data register low (ADRL) can be ignored. However, you must read ADRL after ADRH or else the interlocking will prevent all new conversions from being stored. Right justification will place only the two MSBs in the corresponding ADC data register high (ADRH) and the eight LSB bits in ADC data register low (ADRL). This mode of operation typically is used when a 10-bit unsigned result is desired. Left justified sign data mode is similar to left justified mode with one exception. The MSB of the 10-bit result, AD9 located in ADRH is complemented. This mode of operation is useful when a result, represented as a signed magnitude from mid-scale, is needed. Finally, 8-bit truncation mode will place the eight MSBs in ADC data register low (ADRL). The two LSBs are dropped. This mode of operation is used when compatibility with 8-bit ADC designs are required. No interlocking between ADRH and ADRL is present.
15.3.7 Data Register Interlocking
Reading ADRH in any 10-bit mode latches the contents of ADRL until ADRL is read. Until ADRL is read all subsequent ADC results will be lost. This register interlocking can also be reset by a write to the ADC status and control register, or ADC clock control register. A power-on reset or reset will also clear the interlocking. Note that an external conversion request will not reset the lock.
15.3.8 Monotonicity
The conversion process is monotonic and has no missing codes.
15.4 Interrupts
When the AIEN bit is set, the ADC module is capable of generating a CPU interrupt after each ADC conversion or after an auto-scan conversion cycle. A CPU interrupt is generated if the COCO bit is at logic 0. The COCO bit is not used as a conversion complete flag when interrupts are enabled. The interrupt vector is defined in Table 2-1 . Vector Addresses.
15.5 Low-Power Modes
The STOP and WAIT instructions put the MCU in low power-consumption standby modes.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 247
Analog-to-Digital Converter (ADC)
15.5.1 Wait Mode
The ADC continues normal operation in wait mode. Any enabled CPU interrupt request from the ADC can bring the MCU out of wait mode. If the ADC is not required to bring the MCU out of wait mode, power down the ADC by setting the ADCH[4:0] bits to logic 1's before executing the WAIT instruction.
15.5.2 Stop Mode
The ADC module is inactive after the execution of a STOP instruction. Any pending conversion is aborted. ADC conversions resume when the MCU exits stop mode. Allow one conversion cycle to stabilize the analog circuitry before attempting a new ADC conversion after exiting stop mode.
15.6 I/O Signals
The ADC module has eight channels shared with port A I/O pins.
15.6.1 ADC Voltage In (VADIN)
VADIN is the input voltage signal from one of the eight ADC channels to the ADC module.
15.6.2 ADC Analog Power Pin (VDDA)
The ADC analog portion uses VDDA as its power pin. Connect the VDDA pin to the same voltage potential as VDD. External filtering may be necessary to ensure clean VDDA for good results. NOTE Route VDDA carefully for maximum noise immunity and place bypass capacitors as close as possible to the package.
15.6.3 ADC Analog Ground Pin (VSSA)
The ADC analog portion uses VSSA as its ground pin. Connect the VSSA pin to the same voltage potential as VSS.
15.6.4 ADC Voltage Reference High Pin (VREFH)
VREFH is the power supply for setting the reference voltage VREFH. Connect the VREFH pin to the same voltage potential as VDDA. There will be a finite current associated with VREFH (see Chapter 22 Electrical Specifications). NOTE Route VREFH carefully for maximum noise immunity and place bypass capacitors as close as possible to the package.
15.6.5 ADC Voltage Reference Low Pin (VREFL)
VREFL is the lower reference supply for the ADC. Connect the VREFL pin to the same voltage potential as VSSA. There will be a finite current associated with VREFL (see Chapter 22 Electrical Specifications).
MC68HC908AP A-Family Data Sheet, Rev. 2 248 Freescale Semiconductor
I/O Registers
15.7 I/O Registers
These I/O registers control and monitor ADC operation: * ADC status and control register (ADSCR) -- $0057 * ADC clock control register (ADICLK) -- $0058 * ADC data register high:low 0 (ADRH0:ADRL0) -- $0059:$005A * ADC data register low 1-3 (ADRL1-ADRL3) -- $005B-$005D * ADC auto-scan control register (ADASCR) -- $005E
15.7.1 ADC Status and Control Register
Function of the ADC status and control register is described here.
Address: Read: Write: Reset: 0 $0057 COCO AIEN 0 ADCO 0 ADCH4 1 ADCH3 1 ADCH2 1 ADCH1 1 ADCH0 1
Figure 15-3. ADC Status and Control Register (ADSCR) COCO -- Conversions Complete Bit When the AIEN bit is a logic 0, the COCO is a read-only bit which is set each time a conversion is completed. This bit is cleared whenever the ADSCR is written, or whenever the ADC clock control register is written, or whenever the ADC data register low, ADRLx, is read. If the AIEN bit is logic 1, the COCO bit always read as logic 0. ADC interrupt will be generated at the end if an ADC conversion. Reset clears the COCO bit. 1 = Conversion completed (AIEN = 0) 0 = Conversion not completed (AIEN = 0)/CPU interrupt (AIEN=1) AIEN -- ADC Interrupt Enable Bit When this bit is set, an interrupt is generated at the end of an ADC conversion. The interrupt signal is cleared when the data register, ADR0, is read or the ADSCR is written. Reset clears the AIEN bit. 1 = ADC interrupt enabled 0 = ADC interrupt disabled ADCO -- ADC Continuous Conversion Bit When set, the ADC will convert samples continuously and update the ADC data register at the end of each conversion. Only one conversion is allowed when this bit is cleared. Reset clears the ADCO bit. 1 = Continuous ADC conversion 0 = One ADC conversion This bit should not be set when auto-scan mode is enabled; i.e. when ASCAN=1. ADCH[4:0] -- ADC Channel Select Bits ADCH[4:0] form a 5-bit field which is used to select one of the ADC channels when not in auto-scan mode. The five channel select bits are detailed in Table 15-1. NOTE Care should be taken when using a port pin as both an analog and a digital input simultaneously to prevent switching noise from corrupting the analog signal. Recovery from the disabled state requires one conversion cycle to stabilize.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 249
Analog-to-Digital Converter (ADC)
Table 15-1. MUX Channel Select
ADCH4 0 0 0 0 0 0 0 0 0 1 1 1 1 ADCH3 0 0 0 0 0 0 0 0 1 1 1 1 1 ADCH2 0 0 0 0 1 1 1 1 0 1 1 1 1 ADCH1 0 0 1 1 0 0 1 1 0 0 0 1 1 ADCH0 0 1 0 1 0 1 0 1 0 0 1 0 1 ADC Channel ADC0 ADC1 ADC2 ADC3 ADC4 ADC5 ADC6 ADC7 ADC8 ADC28 ADC29 ADC30 ADC powered-off Input Select PTA0 PTA1 PTA2 PTA3 PTA4 PTA5 PTA6 PTA7 Reserved VREFH (see Note 2) VREFL (see Note 2) --
NOTES: 1. If any unused channels are selected, the resulting ADC conversion will be unknown. 2. The voltage levels supplied from internal reference nodes as specified in the table are used to verify the operation of the ADC converter both in production test and for user applications.
15.7.2 ADC Clock Control Register
The ADC clock control register (ADICLK) selects the clock frequency for the ADC.
Address: Read: Write: Reset: $0058 ADIV2 0 ADIV1 0 ADIV0 0 ADICLK 0 MODE1 0 R MODE0 1 = Reserved 0 0 0 R 0
= Unimplemented
Figure 15-4. ADC Clock Control Register (ADICLK) ADIV[2:0] -- ADC Clock Prescaler Bits ADIV2, ADIV1, and ADIV0 form a 3-bit field which selects the divide ratio used by the ADC to generate the internal ADC clock. Table 15-2 shows the available clock configurations. The ADC clock should be set to between 500kHz and 1MHz.
MC68HC908AP A-Family Data Sheet, Rev. 2 250 Freescale Semiconductor
I/O Registers
Table 15-2. ADC Clock Divide Ratio
ADIV2 0 0 0 0 1 X = don't care ADIV1 0 0 1 1 X ADIV0 0 1 0 1 X ADC Clock Rate ADC input clock / 1 ADC input clock / 2 ADC input clock / 4 ADC input clock / 8 ADC input clock / 16
ADICLK -- ADC Input Clock Select Bit ADICLK selects either bus clock or CGMXCLK as the input clock source to generate the internal ADC clock. Reset selects CGMXCLK as the ADC clock source. If the external clock (CGMXCLK) is equal to or greater than 1MHz, CGMXCLK can be used as the clock source for the ADC. If CGMXCLK is less than 1MHz, use the PLL-generated bus clock as the clock source. As long as the internal ADC clock is at fADIC, correct operation can be guaranteed. 1 = Internal bus clock 0 = External clock, CGMXCLK
fADIC = CGMXCLK or bus frequency ADIV[2:0]
MODE1 and MODE0 -- Modes of Result Justification MODE1 and MODE0 selects between four modes of operation. The manner in which the ADC conversion results will be placed in the ADC data registers is controlled by these modes of operation. Reset returns right-justified mode. Table 15-3. ADC Mode Select
MODE1 0 0 1 1 MODE0 0 1 0 1 Justification Mode 8-bit truncated mode Right justified mode Left justified mode Left justified sign data mode
15.7.3 ADC Data Register 0 (ADRH0 and ADRL0)
The ADC data register 0 consist of a pair of 8-bit registers: high byte (ADRH0), and low byte (ADRL0). This pair form a 16-bit register to store the 10-bit ADC result for the selected ADC result justification mode. In 8-bit truncated mode, the ADRL0 holds the eight most significant bits (MSBs) of the 10-bit result. The ADRL0 is updated each time an ADC conversion completes. In 8-bit truncated mode, ADRL0 contains no interlocking with ADRH0. (See Figure 15-5 . ADRH0 and ADRL0 in 8-Bit Truncated Mode.)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 251
Analog-to-Digital Converter (ADC)
Addr. $0059
Register Name ADC Data Register High 0 (ADRH0) ADC Data Register Low 0 (ADRL0) Read: Write: Reset: Read: Write: Reset:
$005A
Bit 7 0 R 0 AD9 R 0
6 0 R 0 AD8 R 0
5 0 R 0 AD7 R 0
4 0 R 0 AD6 R 0
3 0 R 0 AD5 R 0
2 0 R 0 AD4 R 0
1 0 R 0 AD3 R 0
Bit 0 0 R 0 AD2 R 0
Figure 15-5. ADRH0 and ADRL0 in 8-Bit Truncated Mode In right justified mode the ADRH0 holds the two MSBs, and the ADRL0 holds the eight least significant bits (LSBs), of the 10-bit result. ADRH0 and ADRL0 are updated each time a single channel ADC conversion completes. Reading ADRH0 latches the contents of ADRL0. Until ADRL0 is read all subsequent ADC results will be lost. (See Figure 15-6 . ADRH0 and ADRL0 in Right Justified Mode.)
Addr. $0059 Register Name ADC Data Register High 0 (ADRH0) ADC Data Register Low 0 (ADRL0) Read: Write: Reset: Read: Write: Reset: Bit 7 0 R 0 AD7 R 0 6 0 R 0 AD6 R 0 5 0 R 0 AD5 R 0 4 0 R 0 AD4 R 0 3 0 R 0 AD3 R 0 2 0 R 0 AD2 R 0 1 AD9 R 0 AD1 R 0 Bit 0 AD8 R 0 AD0 R 0
$005A
Figure 15-6. ADRH0 and ADRL0 in Right Justified Mode In left justified mode the ADRH0 holds the eight most significant bits (MSBs), and the ADRL0 holds the two least significant bits (LSBs), of the 10-bit result. The ADRH0 and ADRL0 are updated each time a single channel ADC conversion completes. Reading ADRH0 latches the contents of ADRL0. Until ADRL0 is read all subsequent ADC results will be lost. (See Figure 15-7 . ADRH0 and ADRL0 in Left Justified Mode.)
Addr. $0059 Register Name ADC Data Register High 0 (ADRH0) ADC Data Register Low 0 (ADRL0) Read: Write: Reset: Read: Write: Reset: Bit 7 AD9 R 0 AD1 R 0 6 AD8 R 0 AD0 R 0 5 AD7 R 0 0 R 0 4 AD6 R 0 0 R 0 3 AD5 R 0 0 R 0 2 AD4 R 0 0 R 0 1 AD3 R 0 0 R 0 Bit 0 AD2 R 0 0 R 0
$005A
Figure 15-7. ADRH0 and ADRL0 in Left Justified Mode In left justified sign mode the ADRH0 holds the eight MSBs with the MSB complemented, and the ADRL0 holds the two least significant bits (LSBs), of the 10-bit result. The ADRH0 and ADRL0 are updated each time a single channel ADC conversion completes. Reading ADRH0 latches the contents of ADRL0. Until ADRL0 is read all subsequent ADC results will be lost. (See Figure 15-8 ADRH0 and ADRL0 in Left Justified Sign Data Mode.)
MC68HC908AP A-Family Data Sheet, Rev. 2 252 Freescale Semiconductor
I/O Registers
Addr. $0059
Register Name ADC Data Register High 0 (ADRH0) ADC Data Register Low 0 (ADRL0) Read: Write: Reset: Read: Write: Reset:
$005A
Bit 7 AD9 R 0 AD1 R 0
6 AD8 R 0 AD0 R 0
5 AD7 R 0 0 R 0
4 AD6 R 0 0 R 0
3 AD5 R 0 0 R 0
2 AD4 R 0 0 R 0
1 AD3 R 0 0 R 0
Bit 0 AD2 R 0 0 R 0
Figure 15-8 ADRH0 and ADRL0 in Left Justified Sign Data Mode
15.7.4 ADC Auto-Scan Mode Data Registers (ADRL1-ADRL3)
The ADC data registers 1 to 3 (ADRL1-ADRL3), are 8-bit registers for conversion results in 8-bit truncated mode, for channels ADC1 to ADC3, when the ADC is operating in auto-scan mode (MODE[1:0] = 00).
Address: ADRL1, $005B; ADRL2, $005C; and ADRL3, $005D Read: Write: Reset: AD9 R 0 R AD8 R 0 = Reserved AD7 R 0 AD6 R 0 AD5 R 0 AD4 R 0 AD3 R 0 AD2 R 0
Figure 15-9. ADC Data Register Low 1 to 3 (ADRL1-ADRL3)
15.7.5 ADC Auto-Scan Control Register (ADASCR)
The ADC auto-scan control register (ADASCR) enables and controls the ADC auto-scan function.
Address: Read: Write: Reset: 0 0 0 0 0 R = Unimplemented $005E 0 0 0 0 0 AUTO1 0 = Reserved AUTO0 0 ASCAN 0
Figure 15-10. ADC Scan Control Register (ADASCR) AUTO[1:0] -- Auto-Scan Mode Channel Select Bits AUTO1 and AUTO0 form a 2-bit field which is used to define the number of auto-scan channels used when in auto-scan mode. Reset clears these bits. Table 15-4. Auto-scan Mode Channel Select
AUTO1 0 0 1 1 AUTO0 0 1 0 1 Auto-Scan Channels ADC0 only ADC0 to ADC1 ADC0 to ADC2 ADC0 to ADC3
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 253
Analog-to-Digital Converter (ADC)
ASCAN -- Auto-scan Mode Enable Bit This bit enable/disable the auto-scan mode. Reset clears this bit. 1 = Auto-scan mode is enabled 0 = Auto-scan mode is disabled Auto-scan mode should not be enabled when ADC continuous conversion is enabled; i.e. when ADCO=1.
MC68HC908AP A-Family Data Sheet, Rev. 2 254 Freescale Semiconductor
Chapter 16 Input/Output (I/O) Ports
16.1 Introduction
Thirty-two (32) bidirectional input-output (I/O) pins form four parallel ports. All I/O pins are programmable as inputs or outputs. NOTE Connect any unused I/O pins to an appropriate logic level, either VDD or VSS. Although the I/O ports do not require termination for proper operation, termination reduces excess current consumption and the possibility of electrostatic damage.
Addr. $0000 Register Name Port A Data Register (PTA) Port B Data Register (PTB) Port C Data Register (PTC) Bit 7 6 PTA6 5 PTA5 4 PTA4 3 PTA3 2 PTA2 1 PTA1 Bit 0 PTA0
$0001
$0002
$0003
Port D Data Register (PTD) Data Direction Register A (DDRA) Data Direction Register B (DDRB) Data Direction Register C (DDRC) Data Direction Register D (DDRD) Port-A LED Control Register (LEDA)
$0004
$0005
$0006
$0007
$000C
Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset:
PTA7
Unaffected by reset PTB7 PTB6 PTB5 PTB4 PTB3 PTB2 PTB1 PTB0
Unaffected by reset PTC7 PTC6 PTC5 PTC4 PTC3 PTC2 PTC1 PTC0
Unaffected by reset PTD7 PTD6 PTD5 PTD4 PTD3 PTD2 PTD1 PTD0
Unaffected by reset DDRA7 0 DDRB7 0 DDRC7 0 DDRD7 0 LEDA7 0 DDRA6 0 DDRB6 0 DDRC6 0 DDRD6 0 LEDA6 0 DDRA5 0 DDRB5 0 DDRC5 0 DDRD5 0 LEDA5 0 DDRA4 0 DDRB4 0 DDRC4 0 DDRD4 0 LEDA4 0 DDRA3 0 DDRB3 0 DDRC3 0 DDRD3 0 LEDA3 0 DDRA2 0 DDRB2 0 DDRC2 0 DDRD2 0 LEDA2 0 DDRA1 0 DDRB1 0 DDRC1 0 DDRD1 0 LEDA1 0 DDRA0 0 DDRB0 0 DDRC0 0 DDRD0 0 LEDA0 0
Figure 16-1. I/O Port Register Summary
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 255
Input/Output (I/O) Ports
Table 16-1. Port Control Register Bits Summary
Port Bit 0 1 2 A 3 4 5 6 7 0 1 2 3 B 4 5 6 7 0 1 2 3 C 4 5 6 7 0 1 2 D 3 4 5 6 7 DDRB4 TIM1 DDRB5 DDRB6 TIM2 DDRB7 DDRC0 DDRC1 DDRC2 DDRC3 DDRC4 DDRC5 DDRC6 IRSCI DDRC7 DDRD0 DDRD1 DDRD2 DDRD3 DDRD4 DDRD5 DDRD6 DDRD7 KBI KBIER ($001B) KBIE0 KBIE1 KBIE2 KBIE3 KBIE4 KBIE5 KBIE6 KBIE7 IRSCC1 ($0040) ENSCI SPI SPCR ($0010) SPE IRQ2 -- T2SC1 ($0033) INTSCR2 ($001C) -- ELS1B:ELS1A IMASK2 -- T1SC1 ($0028) T2SC0 ($0030) ELS1B:ELS1A ELS0B:ELS0A T1SC0 ($0025) ELS0B:ELS0A DDR DDRA0 DDRA1 DDRA2 DDRA3 DDRA4 DDRA5 DDRA6 DDRA7 DDRB0 MBUS DDRB1 DDRB2 SCI DDRB3 SCC1 ($0013) ENSCI MMCR1 ($0049) MMEN ADC ADSCR ($0057) ADCH[4:0] Module Control Module Register Control Bit Pin PTA0/ADC0 PTA1/ADC1 PTA2/ADC2 PTA3/ADC3 PTA4/ADC4 PTA5/ADC5 PTA6/ADC6 PTA7/ADC7 PTB0/SDA(1) PTB1/SCL(1) PTB2/TxD(1) PTB3/RxD(1) PTB4/T1CH0(2) PTB5/T1CH1(2) PTB6/T2CH0(2) PTB7/T2CH1(2) PTC0/IRQ2(2) PTC1 PTC2/MISO PTC3/MOSI PTC4/SS PTC5/SPSCK PTC6/SCTxD(1) PTC7/SCRxD(1) PTD0/KBI0(2) PTD1/KBI1(2) PTD2/KBI2(2) PTD3/KBI3(2) PTD4/KBI4(2) PTD5/KBI5(2) PTD6/KBI6(2) PTD7/KBI7(2)
1. Pin is open-drain when configured as output. Pullup resistor must be connected when configured as output. 2. Pin has schmitt trigger when configured as input.
MC68HC908AP A-Family Data Sheet, Rev. 2 256 Freescale Semiconductor
Port A
16.2 Port A
Port A is an 8-bit special-function port that shares all of its pins with the analog-to-digital converter (ADC) module. Port A pins also have LED direct drive capability.
16.2.1 Port A Data Register (PTA)
The port A data register contains a data latch for each of the eight port A pins.
Address: Read: Write: Reset: Alternative Function: Additional Function: ADC7 LED drive ADC6 LED drive ADC5 LED drive $0000 Bit 7 PTA7 6 PTA6 5 PTA5 4 PTA4 3 PTA3 2 PTA2 1 PTA1 Bit 0 PTA0
Unaffected by reset ADC4 LED drive ADC3 LED drive ADC2 LED drive ADC1 LED drive ADC0 LED drive
Figure 16-2. Port A Data Register (PTA) PTA[7:0] -- Port A Data Bits These read/write bits are software-programmable. Data direction of each port A pin is under the control of the corresponding bit in data direction register A. Reset has no effect on port A data. ADC7-ADC0 -- ADC Channels 7 to 0 ADC7-ADC0 are pins used for the input channels to the analog-to-digital converter module. The channel select bits, ADCH[4:0], in the ADC status and control register define which port pin will be used as an ADC input and overrides any control from the port I/O logic. NOTE Care must be taken when reading port A while applying analog voltages to ADC7-ADC0 pins. If the appropriate ADC channel is not enabled, excessive current drain may occur if analog voltages are applied to the PTAx/ADCx pin, while PTA is read as a digital input. Those ports not selected as analog input channels are considered digital I/O ports. LED drive -- Direct LED drive pins PTA7-PTA0 pins can be configured for direct LED drive. See 16.2.3 Port-A LED Control Register (LEDA).
16.2.2 Data Direction Register (DDRA)
Data direction register A determines whether each port A pin is an input or an output. Writing a logic 1 to a DDRA bit enables the output buffer for the corresponding port A pin; a logic 0 disables the output buffer.
Address: Read: Write: Reset: $0004 Bit 7 DDRA7 0 6 DDRA6 0 5 DDRA5 0 4 DDRA4 0 3 DDRA3 0 2 DDRA2 0 1 DDRA1 0 Bit 0 DDRA0 0
Figure 16-3. Data Direction Register A (DDRA)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 257
Input/Output (I/O) Ports
DDRA[7:0] -- Data Direction Register A Bits These read/write bits control port A data direction. Reset clears DDRA[7:0], configuring all port A pins as inputs. 1 = Corresponding port A pin configured as output 0 = Corresponding port A pin configured as input NOTE Avoid glitches on port A pins by writing to the port A data register before changing data direction register A bits from 0 to 1. Figure 16-4 shows the port A I/O logic.
READ DDRA ($0004)
WRITE DDRA ($0004) INTERNAL DATA BUS RESET WRITE PTA ($0000) PTAx PTAx DDRAx
READ PTA ($0000)
Figure 16-4. Port A I/O Circuit When DDRAx is a logic 1, reading address $0000 reads the PTAx data latch. When DDRAx is a logic 0, reading address $0000 reads the voltage level on the pin. The data latch can always be written, regardless of the state of its data direction bit. Table 16-2 summarizes the operation of the port A pins. Table 16-2. Port A Pin Functions
DDRA Bit 0 1 Accesses to DDRA PTA Bit X(1) X I/O Pin Mode Read/Write Input, Hi-Z(2) Output DDRA[7:0] DDRA[7:0] Read Pin PTA[7:0] Write PTA[7:0](3) PTA[7:0] Accesses to PTA
1. X = don't care. 2. Hi-Z = high impedance. 3. Writing affects data register, but does not affect input.
MC68HC908AP A-Family Data Sheet, Rev. 2 258 Freescale Semiconductor
Port B
16.2.3 Port-A LED Control Register (LEDA)
The port-A LED control register (LEDA) controls the direct LED drive capability on PTA7-PTA0 pins. Each bit is individually configurable and requires that the data direction register, DDRA, bit be configured as an output.
Address: Read: Write: Reset: $000C Bit 7 LEDA7 0 6 LEDA6 0 5 LEDA5 0 4 LEDA4 0 3 LEDA3 0 2 LEDA2 0 1 LEDA1 0 Bit 0 LEDA0 0
Figure 16-5. Port A LED Control Register (LEDA) LEDA[7:0] -- Port A LED Drive Enable Bits These read/write bits are software programmable to enable the direct LED drive on an output port pin. 1 = Corresponding port A pin is configured for direct LED drive, with 15mA current sinking capability 0 = Corresponding port A pin is configured for standard drive
16.3 Port B
Port B is an 8-bit special-function port that shares two of its pins with the multi-master IIC (MMIIC) module, two of its pins with SCI module, and four of its pins with two timer interface (TIM1 and TIM2) modules. NOTE PTB3-PTB0 are open-drain pins when configured as outputs regardless whether the pins are used as general purpose I/O pins, MMIIC pins, or SCI pins. Therefore, when configured as general purpose output pins, MMIIC pins, or SCI pins (the TxD pin), pullup resistors must be connected to these pins.
16.3.1 Port B Data Register (PTB)
The port B data register contains a data latch for each of the eight port B pins.
Address: $0001 Bit 7 6 PTB6 5 PTB5 4 PTB4 3 PTB3 2 PTB2 1 PTB1 Bit 0 PTB0
Read: Write: Reset: Alternative Function:
PTB7
Unaffected by reset T2CH1 T2CH0 T1CH1 T1CH0 RxD TxD SCL SDA
Figure 16-6. Port B Data Register (PTB) PTB[7:0] -- Port B Data Bits These read/write bits are software-programmable. Data direction of each port B pin is under the control of the corresponding bit in data direction register B. Reset has no effect on port B data.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 259
Input/Output (I/O) Ports
SDA and SCL -- Multi-Master IIC Data and Clock The SDA and SCL pins are multi-master IIC data and clock pins. Setting the MMEN bit in the MMIIC control register 1 (MMCR1) configures the PTB0/SDA and PTB1/SCL pins for MMIIC function and overrides any control from the port I/O logic. TxD and RxD -- SCI Transmit and Receive Data The TxD and RxD pins are SCI transmit and receive data pins. Setting the ENSCI bit in the SCI control register 1 (SCC1) configures the PTB2/TxD and PTB3/RxD pins for SCI function and overrides any control from the port I/O logic. T1CH0 and T1CH1 -- Timer 1 Channel I/O The T1CH0 and T1CH1 pins are the TIM1 input capture/output compare pins. The edge/level select bits, ELSxB:ELSxA, determine whether the PTB4/T1CH0-PTB5/T1CH1 pins are timer channel I/O pins or general-purpose I/O pins. T2CH0 and T2CH1 -- Timer 2 Channel I/O The T2CH0 and T2CH1 pins are the TIM2 input capture/output compare pins. The edge/level select bits, ELSxB:ELSxA, determine whether the PTB6/T2CH0-PTB7/T2CH1 pins are timer channel I/O pins or general-purpose I/O pins.
16.3.2 Data Direction Register B (DDRB)
Data direction register B determines whether each port B pin is an input or an output. Writing a logic 1 to a DDRB bit enables the output buffer for the corresponding port B pin; a logic 0 disables the output buffer.
Address: Read: Write: Reset: $0005 Bit 7 DDRB7 0 6 DDRB6 0 5 DDRB5 0 4 DDRB4 0 3 DDRB3 0 2 DDRB2 0 1 DDRB1 0 Bit 0 DDRB0 0
Figure 16-7. Data Direction Register B (DDRB) DDRB[7:0] -- Data Direction Register B Bits These read/write bits control port B data direction. Reset clears DDRB[7:0], configuring all port B pins as inputs. 1 = Corresponding port B pin configured as output 0 = Corresponding port B pin configured as input NOTE Avoid glitches on port B pins by writing to the port B data register before changing data direction register B bits from 0 to 1. Figure 16-8 shows the port B I/O logic.
MC68HC908AP A-Family Data Sheet, Rev. 2 260 Freescale Semiconductor
Port C
READ DDRB ($0005)
WRITE DDRB ($0005) INTERNAL DATA BUS RESET WRITE PTB ($0001) PTBx DDRBx
PTBx #
READ PTB ($0001)
# PTB3-PTB0 are open-drain pins when configured as outputs. PTB7-PTB4 have schmitt trigger inputs.
Figure 16-8. Port B I/O Circuit When DDRBx is a logic 1, reading address $0001 reads the PTBx data latch. When DDRBx is a logic 0, reading address $0001 reads the voltage level on the pin. The data latch can always be written, regardless of the state of its data direction bit. Table 16-3 summarizes the operation of the port B pins. Table 16-3. Port B Pin Functions
DDRB Bit 0 1 Accesses to DDRB PTB Bit X(1) X I/O Pin Mode Read/Write Input, Hi-Z(2) Output DDRB[7:0] DDRB[7:0] Read Pin PTB[7:0] Write PTB[7:0](3) PTB[7:0] Accesses to PTB
1. X = don't care. 2. Hi-Z = high impedance. 3. Writing affects data register, but does not affect input.
16.4 Port C
Port C is an 8-bit special-function port that shares one of its pins with the IRQ2, four of its pins with the SPI module, and two of its pins with the IRSCI module.
16.4.1 Port C Data Register (PTC)
The port C data register contains a data latch for each of the eight port C pins.
Address: Read: Write: Reset: Alternative Function: SCRxD SCTxD SPSCK $0002 Bit 7 PTC7 6 PTC6 5 PTC5 4 PTC4 3 PTC3 2 PTC2 1 PTC1 Bit 0 PTC0
Unaffected by reset SS MOSI MISO IRQ2
Figure 16-9. Port C Data Register (PTC)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 261
Input/Output (I/O) Ports
PTC[7:0] -- Port C Data Bits These read/write bits are software-programmable. Data direction of each port C pin is under the control of the corresponding bit in data direction register C. Reset has no effect on port C data. IRQ2 -- IRQ2 input pin The PTC0/IRQ2 pin is always available as input pin to the IRQ2 module. Care must be taken to available unwanted interrupts when this pin is used as general purpose I/O. PTC0/IRQ2 pin has an internal pullup, and can be disabled by setting the PUC0ENB bit in the IRQ2 status and control register (INTSCR2). MISO, MOSI, SS, and SPSCK -- SPI Data I/O, Select, and Clock Pins These pins are the SPI data in/out, select, and clock pins. Setting the SPE bit in the SPI control register (SPCR) configures PTC2/MISO, PTC3/MOSI, PTC4/SS, and PTC5/SPSCK pins for SPI function and overrides any control from the port I/O logic. SCTxD and SCRxD -- IrSCI Transmit and Receive Data The SCTxD and SCRxD pins are IRSCI transmit and receive data pins. Setting the ENSCI bit in the IRSCI control register 1 (IRSCC1) configures the PTC6/SCTxD and PTC7/SCRxD pins for IRSCI function and overrides any control from the port I/O logic.
16.4.2 Data Direction Register C (DDRC)
Data direction register C determines whether each port C pin is an input or an output. Writing a logic 1 to a DDRC bit enables the output buffer for the corresponding port C pin; a logic 0 disables the output buffer.
Address: Read: Write: Reset: $0006 Bit 7 DDRC7 0 6 DDRC6 0 5 DDRC5 0 4 DDRC4 0 3 DDRC3 0 2 DDRC2 0 1 DDRC1 0 Bit 0 DDRC0 0
Figure 16-10. Data Direction Register C (DDRC) DDRC[7:0] -- Data Direction Register C Bits These read/write bits control port C data direction. Reset clears DDRC[7:0], configuring all port C pins as inputs. 1 = Corresponding port C pin configured as output 0 = Corresponding port C pin configured as input NOTE Avoid glitches on port C pins by writing to the port C data register before changing data direction register C bits from 0 to 1. Figure 16-11 shows the port C I/O logic. NOTE For those devices packaged in a 42-pin shrink dual in-line package, PTC0 and PTC1 are not connected. DDRC0 and DDRC1 should be set to a 1 to configure PTC0 and PTC1 as outputs.
MC68HC908AP A-Family Data Sheet, Rev. 2 262 Freescale Semiconductor
Port D
READ DDRC ($0006)
WRITE DDRC ($0006) INTERNAL DATA BUS RESET WRITE PTC ($0002) PTCx DDRCx
PTCx #
READ PTC ($0002)
# PTC0 has schmitt trigger input.
Figure 16-11. Port C I/O Circuit When DDRCx is a logic 1, reading address $0002 reads the PTCx data latch. When DDRCx is a logic 0, reading address $0002 reads the voltage level on the pin. The data latch can always be written, regardless of the state of its data direction bit. Table 16-4 summarizes the operation of the port C pins. Table 16-4. Port C Pin Functions
DDRC Bit 0 1 Accesses to DDRC PTC Bit X(1) X I/O Pin Mode Read/Write Input, Hi-Z(2) Output DDRC[7:0] DDRC[7:0] Read Pin PTC[7:0] Write PTC[7:0](3) PTC[7:0] Accesses to PTC
1. X = don't care. 2. Hi-Z = high impedance. 3. Writing affects data register, but does not affect input.
16.5 Port D
Port D is an 8-bit special function port that shares all of its pins with the keyboard interrupt module.
16.5.1 Port D Data Register (PTD)
The port D data register contains a data latch for each of the eight port D pins.
Address: Read: Write: Reset: Alternative Function: KBI7 KBI6 KBI5 $0003 Bit 7 PTD7 6 PTD6 5 PTD5 4 PTD4 3 PTD3 2 PTD2 1 PTD1 Bit 0 PTD0
Unaffected by reset KBI4 KBI3 KBI2 KBI1 KBI0
Figure 16-12. Port D Data Register (PTD)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 263
Input/Output (I/O) Ports
PTD[7:0] -- Port D Data Bits These read/write bits are software programmable. Data direction of each port D pin is under the control of the corresponding bit in data direction register D. Reset has no effect on port D data. KBI7-KBI0 -- Keyboard Interrupt Inputs The keyboard interrupt enable bits, KBIE[7:0], in the keyboard interrupt enable register (KBIER), enable the port D pins as external interrupt pins. See Chapter 18 Keyboard Interrupt Module (KBI).
16.5.2 Data Direction Register D (DDRD)
Data direction register D determines whether each port D pin is an input or an output. Writing a logic 1 to a DDRD bit enables the output buffer for the corresponding port D pin; a logic 0 disables the output buffer.
Address: Read: Write: Reset: $0007 Bit 7 DDRD7 0 6 DDRD6 0 5 DDRD5 0 4 DDRD4 0 3 DDRD3 0 2 DDRD2 0 1 DDRD1 0 Bit 0 DDRD0 0
Figure 16-13. Data Direction Register D (DDRD) DDRD[7:0] -- Data Direction Register D Bits These read/write bits control port D data direction. Reset clears DDRD[7:0], configuring all port D pins as inputs. 1 = Corresponding port D pin configured as output 0 = Corresponding port D pin configured as input NOTE Avoid glitches on port D pins by writing to the port D data register before changing data direction register D bits from 0 to 1. Figure 16-14 shows the port D I/O logic.
READ DDRD ($0007) KBIEx WRITE DDRD ($0007) INTERNAL DATA BUS RESET WRITE PTD ($0003) PTDx DDRDx
PTDx #
READ PTD ($0003)
# PTD7-PTD0 have schmitt trigger inputs.
Figure 16-14. Port D I/O Circuit When bit DDRDx is a logic 1, reading address $0003 reads the PTDx data latch. When bit DDRDx is a logic 0, reading address $0003 reads the voltage level on the pin. The data latch can always be written, regardless of the state of its data direction bit.
MC68HC908AP A-Family Data Sheet, Rev. 2 264 Freescale Semiconductor
Port D
Table 16-5 summarizes the operation of the port D pins. Table 16-5. Port D Pin Functions
DDRD Bit 0 1 Accesses to DDRD PTD Bit X(1) X I/O Pin Mode Read/Write Input, Hi-Z(2) Output DDRD[7:0] DDRD[7:0] Read Pin PTD[7:0] Write PTD[7:0](3) PTD[7:0] Accesses to PTD
1. X = don't care. 2. Hi-Z = high impedance. 3. Writing affects data register, but does not affect input.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 265
Input/Output (I/O) Ports
MC68HC908AP A-Family Data Sheet, Rev. 2 266 Freescale Semiconductor
Chapter 17 External Interrupt (IRQ)
17.1 Introduction
The external interrupt (IRQ) module provides two maskable interrupt inputs: IRQ1 and IRQ2.
17.2 Features
Features of the IRQ module include: * A dedicated external interrupt pin, IRQ1 * An external interrupt pin shared with a port pin, PTC0/IRQ2 * Separate IRQ interrupt control bits for IRQ1 and IRQ2 * Hysteresis buffers * Programmable edge-only or edge and level interrupt sensitivity * Automatic interrupt acknowledge * Internal pullup resistor, with disable option on IRQ2 NOTE References to either IRQ1 or IRQ2 may be made in the following text by omitting the IRQ number. For example, IRQF may refer generically to IRQ1F and IRQ2F, and IMASK may refer to IMASK1 and IMASK2.
Addr. $001C Register Name IRQ2 Status and Control Read: Register Write: (INTSCR2) Reset: IRQ1 Status and Control Read: Register Write: (INTSCR1) Reset: Bit 7 0 0 0 0 6 PUC0ENB 0 0 5 0 0 0 4 0 0 0 0 3 IRQ2F 0 IRQ1F 0 2 0 ACK2 0 0 ACK1 0 1 IMASK2 0 IMASK1 0 Bit 0 MODE2 0 MODE1 0
$001E
0 0 = Unimplemented
Figure 17-1. External Interrupt I/O Register Summary
17.3 Functional Description
A logic 0 applied to the external interrupt pin can latch a CPU interrupt request. Figure 17-2 and Figure 17-3 shows the structure of the IRQ module. Interrupt signals on the IRQ pin are latched into the IRQ latch. An interrupt latch remains set until one of the following actions occurs: * Vector fetch -- A vector fetch automatically generates an interrupt acknowledge signal that clears the latch that caused the vector fetch.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 267
External Interrupt (IRQ)
*
*
Software clear -- Software can clear an interrupt latch by writing to the appropriate acknowledge bit in the interrupt status and control register (INTSCR). Writing a logic 1 to the ACK bit clears the IRQ latch. Reset -- A reset automatically clears the interrupt latch.
The external interrupt pin is falling-edge-triggered and is software-configurable to be either falling-edge or falling-edge and low-level-triggered. The MODE bit in the INTSCR controls the triggering sensitivity of the IRQ pin. When an interrupt pin is edge-triggered only, the interrupt remains set until a vector fetch, software clear, or reset occurs. When an interrupt pin is both falling-edge and low-level-triggered, the interrupt remains set until both of the following occur: * Vector fetch or software clear * Return of the interrupt pin to logic 1 The vector fetch or software clear may occur before or after the interrupt pin returns to logic 1. As long as the pin is low, the interrupt request remains pending. A reset will clear the latch and the MODE1 control bit, thereby clearing the interrupt even if the pin stays low. When set, the IMASK bit in the INTSCR mask all external interrupt requests. A latched interrupt request is not presented to the interrupt priority logic unless the IMASK bit is clear. NOTE The interrupt mask (I) in the condition code register (CCR) masks all interrupt requests, including external interrupt requests.
RESET ACK1 INTERNAL ADDRESS BUS VECTOR FETCH DECODER VDD INTERNAL PULLUP DEVICE IRQ1 VDD D CLR Q IRQ1F IRQ1 INTERRUPT REQUEST TO CPU FOR BIL/BIH INSTRUCTIONS
SYNCHRONIZER
CK
IMASK1
MODE1 HIGH VOLTAGE DETECT TO MODE SELECT LOGIC
Figure 17-2. IRQ1 Block Diagram
MC68HC908AP A-Family Data Sheet, Rev. 2 268 Freescale Semiconductor
IRQ1 and IRQ2 Pins
RESET ACK2 INTERNAL ADDRESS BUS VECTOR FETCH DECODER VDD INTERNAL PULLUP DEVICE PUC0ENB D IRQ2
VDD CLR Q
IRQ2F IRQ2 INTERRUPT REQUEST
SYNCHRONIZER
CK
IMASK2
MODE2
Figure 17-3. IRQ2 Block Diagram
17.4 IRQ1 and IRQ2 Pins
A logic 0 on the IRQ pin can latch an interrupt request into the IRQ latch. A vector fetch, software clear, or reset clears the IRQ latch. If the MODE bit is set, the IRQ pin is both falling-edge-sensitive and low-level-sensitive. With MODE set, both of the following actions must occur to clear IRQ: * Vector fetch or software clear -- A vector fetch generates an interrupt acknowledge signal to clear the latch. Software may generate the interrupt acknowledge signal by writing a logic 1 to the ACK bit in the interrupt status and control register (INTSCR). The ACK bit is useful in applications that poll the IRQ pin and require software to clear the IRQ latch. Writing to the ACK bit prior to leaving an interrupt service routine can also prevent spurious interrupts due to noise. Setting ACK does not affect subsequent transitions on the IRQ pin. A falling edge that occurs after writing to the ACK bit another interrupt request. If the IRQ mask bit, IMASK, is clear, the CPU loads the program counter with the vector address at location defined in Table 2-1 . Vector Addresses. * Return of the IRQ pin to logic 1 -- As long as the IRQ pin is at logic 0, IRQ remains active. The vector fetch or software clear and the return of the IRQ pin to logic 1 may occur in any order. The interrupt request remains pending as long as the IRQ pin is at logic 0. A reset will clear the latch and the MODE control bit, thereby clearing the interrupt even if the pin stays low. If the MODE bit is clear, the IRQ pin is falling-edge-sensitive only. With MODE clear, a vector fetch or software clear immediately clears the IRQ latch. The IRQF bit in the INTSCR register can be used to check for pending interrupts. The IRQF bit is not affected by the IMASK bit, which makes it useful in applications where polling is preferred. Use the BIH or BIL instruction to read the logic level on the IRQ1 pin. NOTE The BIH and BIL instructions do not read the logic level on the IRQ2 pin.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 269
External Interrupt (IRQ)
NOTE When using the level-sensitive interrupt trigger, avoid false interrupts by masking interrupt requests in the interrupt routine. The IRQ1 pin has a permanent internal pullup device connected, while the IRQ2 pin has an optional pullup device that can be enabled or disabled by the PUC0ENB bit in the INTSCR2 register.
17.5 IRQ Module During Break Interrupts
The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear the latch during the break state. (See Chapter 21 Break Module (BRK).) To allow software to clear the IRQ latch during a break interrupt, write a logic 1 to the BCFE bit. If a latch is cleared during the break state, it remains cleared when the MCU exits the break state. To protect CPU interrupt flags during the break state, write a logic 0 to the BCFE bit. With BCFE at logic 0 (its default state), writing to the ACK bit in the IRQ status and control register during the break state has no effect on the IRQ interrupt flags.
17.6 IRQ Registers
Each IRQ is controlled and monitored by an status and control register. * IRQ1 Status and Control Register -- $001E * IRQ2 Status and Control Register -- $001C
17.6.1 IRQ1 Status and Control Register
The IRQ1 status and control register (INTSCR1) controls and monitors operation of IRQ1. The INTSCR1 has the following functions: * Shows the state of the IRQ1 flag * Clears the IRQ1 latch * Masks IRQ1 interrupt request * Controls triggering sensitivity of the IRQ1 interrupt pin
Address: Read: Write: Reset: 0 0 0 0 0 = Unimplemented $001E Bit 7 0 6 0 5 0 4 0 3 IRQ1F 2 0 ACK1 0 1 IMASK1 0 Bit 0 MODE1 0
Figure 17-4. IRQ1 Status and Control Register (INTSCR1) IRQ1F -- IRQ1 Flag Bit This read-only status bit is high when the IRQ1 interrupt is pending. 1 = IRQ1 interrupt pending 0 = IRQ1 interrupt not pending ACK1 -- IRQ1 Interrupt Request Acknowledge Bit Writing a logic 1 to this write-only bit clears the IRQ1 latch. ACK1 always reads as logic 0. Reset clears ACK1.
MC68HC908AP A-Family Data Sheet, Rev. 2 270 Freescale Semiconductor
IRQ Registers
IMASK1 -- IRQ1 Interrupt Mask Bit Writing a logic 1 to this read/write bit disables IRQ1 interrupt requests. Reset clears IMASK1. 1 = IRQ1 interrupt requests disabled 0 = IRQ1 interrupt requests enabled MODE1 -- IRQ1 Edge/Level Select Bit This read/write bit controls the triggering sensitivity of the IRQ1 pin. Reset clears MODE1. 1 = IRQ1 interrupt requests on falling edges and low levels 0 = IRQ1 interrupt requests on falling edges only
17.6.2 IRQ2 Status and Control Register
The IRQ2 status and control register (INTSCR2) controls and monitors operation of IRQ2. The INTSCR2 has the following functions: * Enables/disables the internal pullup device on IRQ2 pin * Shows the state of the IRQ2 flag * Clears the IRQ2 latch * Masks IRQ2 interrupt request * Controls triggering sensitivity of the IRQ2 interrupt pin
Address: Read: Write: Reset: 0 $001C Bit 7 0 6 PUC0ENB 0 5 0 0 4 0 0 3 IRQ2F 0 2 0 ACK2 0 1 IMASK2 0 Bit 0 MODE2 0
= Unimplemented
Figure 17-5. IRQ2 Status and Control Register (INTSCR2) PUC0ENB -- IRQ2 Pin Pullup Enable Bit. Setting this bit to logic 1 disables the pullup on PTC0/IRQ2 pin. Reset clears this bit. 1 = IRQ2 pin internal pullup is disabled 0 = IRQ2 pin internal pullup is enabled IRQ2F -- IRQ2 Flag Bit This read-only status bit is high when the IRQ2 interrupt is pending. 1 = IRQ2 interrupt pending 0 = IRQ2 interrupt not pending ACK2 -- IRQ2 Interrupt Request Acknowledge Bit Writing a logic 1 to this write-only bit clears the IRQ2 latch. ACK2 always reads as logic 0. Reset clears ACK2. IMASK2 -- IRQ2 Interrupt Mask Bit Writing a logic 1 to this read/write bit disables IRQ2 interrupt requests. Reset clears IMASK2. 1 = IRQ2 interrupt requests disabled 0 = IRQ2 interrupt requests enabled MODE2 -- IRQ2 Edge/Level Select Bit This read/write bit controls the triggering sensitivity of the IRQ2 pin. Reset clears MODE2. 1 = IRQ2 interrupt requests on falling edges and low levels 0 = IRQ2 interrupt requests on falling edges only
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 271
External Interrupt (IRQ)
MC68HC908AP A-Family Data Sheet, Rev. 2 272 Freescale Semiconductor
Chapter 18 Keyboard Interrupt Module (KBI)
18.1 Introduction
The keyboard interrupt module (KBI) provides eight independently maskable external interrupts which are accessible via PTD0-PTD7. When a port pin is enabled for keyboard interrupt function, an internal 30k pullup device is also enabled on the pin.
18.2 Features
Features of the keyboard interrupt module include the following: * Eight keyboard interrupt pins with pullup devices * Separate keyboard interrupt enable bits and one keyboard interrupt mask * Programmable edge-only or edge- and level- interrupt sensitivity * Exit from low-lower modes
Addr. $001A Register Name Keyboard Status Read: and Control Register Write: (KBSCR) Reset: Keyboard Interrupt Enable Read: Register Write: (KBIER) Reset: Bit 7 0 0 KBIE7 0 6 0 0 KBIE6 5 0 0 KBIE5 4 0 0 KBIE4 0 3 KEYF 0 KBIE3 0 2 0 ACKK 0 KBIE2 0 1 IMASKK 0 KBIE1 0 Bit 0 MODEK 0 KBIE0 0
$001B
0 0 = Unimplemented
Figure 18-1. KBI I/O Register Summary
18.3 I/O Pins
The eight keyboard interrupt pins are shared with standard port I/O pins. The full name of the KBI pins are listed in Table 18-1. The generic pin name appear in the text that follows. Table 18-1. Pin Name Conventions
KBI Generic Pin Name KBI0-KBI7 Full MCU Pin Name PTD0/KBI0-PTD7/KBI7 Pin Selected for KBI Function by KBIEx Bit in KBIER KBIE0-KBIE7
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 273
Keyboard Interrupt Module (KBI)
18.4 Functional Description
INTERNAL BUS
KBI0 VDD . KBIE0 TO PULLUP ENABLE . KBI7 . D CLR Q
ACKK RESET
VECTOR FETCH DECODER KEYF SYNCHRONIZER Keyboard Interrupt Request
CK
KEYBOARD INTERRUPT FF
IMASKK
MODEK KBIE7 TO PULLUP ENABLE
Figure 18-2. Keyboard Interrupt Block Diagram Writing to the KBIE7-KBIE0 bits in the keyboard interrupt enable register independently enables or disables each port D pin as a keyboard interrupt pin. Enabling a keyboard interrupt pin in port D also enables its internal pull-up device. A logic 0 applied to an enabled keyboard interrupt pin latches a keyboard interrupt request. A keyboard interrupt is latched when one or more keyboard pins goes low after all were high. The MODEK bit in the keyboard status and control register controls the triggering mode of the keyboard interrupt. * If the keyboard interrupt is edge-sensitive only, a falling edge on a keyboard pin does not latch an interrupt request if another keyboard pin is already low. To prevent losing an interrupt request on one pin because another pin is still low, software can disable the latter pin while it is low. * If the keyboard interrupt is falling edge- and low level-sensitive, an interrupt request is present as long as any keyboard pin is low. If the MODEK bit is set, the keyboard interrupt pins are both falling edge- and low level-sensitive, and both of the following actions must occur to clear a keyboard interrupt request: * Vector fetch or software clear -- A vector fetch generates an interrupt acknowledge signal to clear the interrupt request. Software may generate the interrupt acknowledge signal by writing a logic 1 to the ACKK bit in the keyboard status and control register KBSCR. The ACKK bit is useful in applications that poll the keyboard interrupt pins and require software to clear the keyboard interrupt request. Writing to the ACKK bit prior to leaving an interrupt service routine can also prevent spurious interrupts due to noise. Setting ACKK does not affect subsequent transitions on the keyboard interrupt pins. A falling edge that occurs after writing to the ACKK bit latches another interrupt request. If the keyboard interrupt mask bit, IMASKK, is clear, the CPU loads the program counter with the vector address at locations $FFE0 and $FFE1. * Return of all enabled keyboard interrupt pins to logic 1 -- As long as any enabled keyboard interrupt pin is at logic 0, the keyboard interrupt remains set. The vector fetch or software clear and the return of all enabled keyboard interrupt pins to logic 1 may occur in any order.
MC68HC908AP A-Family Data Sheet, Rev. 2 274 Freescale Semiconductor
Keyboard Interrupt Registers
If the MODEK bit is clear, the keyboard interrupt pin is falling-edge-sensitive only. With MODEK clear, a vector fetch or software clear immediately clears the keyboard interrupt request. Reset clears the keyboard interrupt request and the MODEK bit, clearing the interrupt request even if a keyboard interrupt pin stays at logic 0. The keyboard flag bit (KEYF) in the keyboard status and control register can be used to see if a pending interrupt exists. The KEYF bit is not affected by the keyboard interrupt mask bit (IMASKK) which makes it useful in applications where polling is preferred. To determine the logic level on a keyboard interrupt pin, use the data direction register to configure the pin as an input and read the data register. NOTE Setting a keyboard interrupt enable bit (KBIEx) forces the corresponding keyboard interrupt pin to be an input, overriding the data direction register. However, the data direction register bit must be a logic 0 for software to read the pin.
18.4.1 Keyboard Initialization
When a keyboard interrupt pin is enabled, it takes time for the internal pull-up to reach a logic 1. Therefore a false interrupt can occur as soon as the pin is enabled. To prevent a false interrupt on keyboard initialization: 1. Mask keyboard interrupts by setting the IMASKK bit in the keyboard status and control register. 2. Enable the KBI pins by setting the appropriate KBIEx bits in the keyboard interrupt enable register. 3. Write to the ACKK bit in the keyboard status and control register to clear any false interrupts. 4. Clear the IMASKK bit. An interrupt signal on an edge-triggered pin can be acknowledged immediately after enabling the pin. An interrupt signal on an edge- and level-triggered interrupt pin must be acknowledged after a delay that depends on the external load. Another way to avoid a false interrupt: 1. Configure the keyboard pins as outputs by setting the appropriate DDR bits in data direction register. 2. Write logic 1s to the appropriate data register bits. 3. Enable the KBI pins by setting the appropriate KBIEx bits in the keyboard interrupt enable register.
18.5 Keyboard Interrupt Registers
Two registers control the operation of the keyboard interrupt module: * Keyboard Status and Control Register -- $001A * Keyboard Interrupt Enable Register -- $001B
18.5.1 Keyboard Status and Control Register
* * * * Flags keyboard interrupt requests Acknowledges keyboard interrupt requests Masks keyboard interrupt requests Controls keyboard interrupt triggering sensitivity
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 275
Keyboard Interrupt Module (KBI)
Address: Read: Write: Reset:
$001A Bit 7 0 0 6 0 0 5 0 0 4 0 0 3 KEYF 0 2 0 ACKK 0 = Unimplemented 1 IMASKK 0 Bit 0 MODEK 0
Figure 18-3. Keyboard Status and Control Register (KBSCR) KEYF -- Keyboard Flag Bit This read-only bit is set when a keyboard interrupt is pending. Reset clears the KEYF bit. 1 = Keyboard interrupt pending 0 = No keyboard interrupt pending ACKK -- Keyboard Acknowledge Bit Writing a logic 1 to this write-only bit clears the keyboard interrupt request. ACKK always reads as logic 0. Reset clears ACKK. IMASKK -- Keyboard Interrupt Mask Bit Writing a logic 1 to this read/write bit prevents the output of the keyboard interrupt mask from generating interrupt requests. Reset clears the IMASKK bit. 1 = Keyboard interrupt requests masked 0 = Keyboard interrupt requests not masked MODEK -- Keyboard Triggering Sensitivity Bit This read/write bit controls the triggering sensitivity of the keyboard interrupt pins. Reset clears MODEK. 1 = Keyboard interrupt requests on falling edges and low levels 0 = Keyboard interrupt requests on falling edges only
18.5.2 Keyboard Interrupt Enable Register
The port-D keyboard interrupt enable register enables or disables each port-D pin to operate as a keyboard interrupt pin.
Address: Read: Write: Reset: $001B Bit 7 KBIE7 0 6 KBIE6 0 5 KBIE5 0 4 KBIE4 0 3 KBIE3 0 2 KBIE2 0 1 KBIE1 0 Bit 0 KBIE0 0
Figure 18-4. Keyboard Interrupt Enable Register (KBIER) KBIE7-KBIE0 -- Keyboard Interrupt Enable Bits Each of these read/write bits enables the corresponding keyboard interrupt pin to latch interrupt requests. Reset clears the keyboard interrupt enable register. 1 = KBIx pin enabled as keyboard interrupt pin 0 = KBIx pin not enabled as keyboard interrupt pin
MC68HC908AP A-Family Data Sheet, Rev. 2 276 Freescale Semiconductor
Low-Power Modes
18.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
18.6.1 Wait Mode
The keyboard interrupt module remains active in wait mode. Clearing the IMASKK bit in the keyboard status and control register enables keyboard interrupt requests to bring the MCU out of wait mode.
18.6.2 Stop Mode
The keyboard interrupt module remains active in stop mode. Clearing the IMASKK bit in the keyboard status and control register enables keyboard interrupt requests to bring the MCU out of stop mode.
18.7 Keyboard Module During Break Interrupts
The system integration module (SIM) controls whether the keyboard interrupt latch can be cleared during the break state. The BCFE bit in the SIM break flag control register (BFCR) enables software to clear status bits during the break state. To allow software to clear the keyboard interrupt latch during a break interrupt, write a logic 1 to the BCFE bit. If a latch is cleared during the break state, it remains cleared when the MCU exits the break state. To protect the latch during the break state, write a logic 0 to the BCFE bit. With BCFE at logic 0 (its default state), writing to the keyboard acknowledge bit (ACKK) in the keyboard status and control register during the break state has no effect.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 277
Keyboard Interrupt Module (KBI)
MC68HC908AP A-Family Data Sheet, Rev. 2 278 Freescale Semiconductor
Chapter 19 Computer Operating Properly (COP)
19.1 Introduction
The computer operating properly (COP) module contains a free-running counter that generates a reset if allowed to overflow. The COP module helps software recover from runaway code. Prevent a COP reset by clearing the COP counter periodically. The COP module can be disabled through the COPD bit in the configuration register 1 (CONFIG1).
19.2 Functional Description
Figure 19-1 shows the structure of the COP module.
ICLK 12-BIT COP PRESCALER CLEAR ALL STAGES CLEAR STAGES 5-12 RESET CIRCUIT RESET STATUS REGISTER
STOP INSTRUCTION INTERNAL RESET SOURCES RESET VECTOR FETCH COPCTL WRITE
COP CLOCK
6-BIT COP COUNTER COPEN (FROM SIM) COP DISABLE (COPD FROM CONFIG1) RESET COPCTL WRITE COP RATE SEL (COPRS FROM CONFIG1)
CLEAR COP COUNTER
Figure 19-1. COP Block Diagram The COP counter is a free-running 6-bit counter preceded by a 12-bit prescaler counter. If not cleared by software, the COP counter overflows and generates an asynchronous reset after 218 - 24 or 213 - 24 ICLK cycles, depending on the state of the COP rate select bit, COPRS, in the CONFIG1 register. With a 213 - 24 ICLK cycle overflow option, a 88-kHz ICLK gives a COP timeout period of ~93ms. Writing any value to location $FFFF before an overflow occurs prevents a COP reset by clearing the COP counter and stages 12 through 5 of the prescaler.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 279
COP TIMEOUT
Computer Operating Properly (COP)
NOTE Service the COP immediately after reset and before entering or after exiting STOP Mode to guarantee the maximum time before the first COP counter overflow. A COP reset pulls the RST pin low for 32 ICLK cycles and sets the COP bit in the SIM reset status register (SRSR). In monitor mode, the COP is disabled if the RST pin or the IRQ1 is held at VTST. During the break state, VTST on the RST pin disables the COP. NOTE Place COP clearing instructions in the main program and not in an interrupt subroutine. Such an interrupt subroutine could keep the COP from generating a reset even while the main program is not working properly.
19.3 I/O Signals
The following paragraphs describe the signals shown in Figure 19-1.
19.3.1 ICLK
ICLK is the internal oscillator output signal. See Chapter 22 Electrical Specifications for ICLK frequency specification.
19.3.2 STOP Instruction
The STOP instruction clears the COP prescaler.
19.3.3 COPCTL Write
Writing any value to the COP control register (COPCTL) (see 19.4 COP Control Register) clears the COP counter and clears bits 12 through 5 of the prescaler. Reading the COP control register returns the low byte of the reset vector.
19.3.4 Power-On Reset
The power-on reset (POR) circuit clears the COP prescaler 4096 ICLK cycles after power-up.
19.3.5 Internal Reset
An internal reset clears the COP prescaler and the COP counter.
19.3.6 Reset Vector Fetch
A reset vector fetch occurs when the vector address appears on the data bus. A reset vector fetch clears the COP prescaler.
19.3.7 COPD (COP Disable)
The COPD signal reflects the state of the COP disable bit (COPD) in the CONFIG1 register. (See Figure 19-2 . Configuration Register 1 (CONFIG1).)
MC68HC908AP A-Family Data Sheet, Rev. 2 280 Freescale Semiconductor
COP Control Register
19.3.8 COPRS (COP Rate Select)
The COPRS signal reflects the state of the COP rate select bit (COPRS) in the CONFIG1 register.
Address: Read: Write: Reset: $001F Bit 7 COPRS 0 6 LVISTOP 0 5 LVIRSTD 0 4 LVIPWRD 0 3 LVIREGD 0 2 SSREC 0 1 STOP 0 Bit 0 COPD 0
Figure 19-2. Configuration Register 1 (CONFIG1) COPRS -- COP Rate Select Bit COPRS selects the COP time out period. Reset clears COPRS. 1 = COP time out period = 213 - 24 ICLK cycles 0 = COP time out period = 218 - 24 ICLK cycles COPD -- COP Disable Bit COPD disables the COP module. 1 = COP module disabled 0 = COP module enabled
19.4 COP Control Register
The COP control register is located at address $FFFF and overlaps the reset vector. Writing any value to $FFFF clears the COP counter and starts a new timeout period. Reading location $FFFF returns the low byte of the reset vector.
Address: Read: Write: Reset: $FFFF Bit 7 6 5 4 3 2 1 Bit 0 Low byte of reset vector Clear COP counter Unaffected by reset
Figure 19-3. COP Control Register (COPCTL)
19.5 Interrupts
The COP does not generate CPU interrupt requests.
19.6 Monitor Mode
When monitor mode is entered with VTST on the IRQ1 pin, the COP is disabled as long as VTST remains on the IRQ1 pin or the RST pin. When monitor mode is entered by having blank reset vectors and not having VTST on the IRQ1 pin, the COP is automatically disabled until a POR occurs.
19.7 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 281
Computer Operating Properly (COP)
19.7.1 Wait Mode
The COP remains active during wait mode. To prevent a COP reset during wait mode, periodically clear the COP counter in a CPU interrupt routine.
19.7.2 Stop Mode
Stop mode turns off the ICLK input to the COP and clears the COP prescaler. Service the COP immediately before entering or after exiting stop mode to ensure a full COP timeout period after entering or exiting stop mode. To prevent inadvertently turning off the COP with a STOP instruction, a configuration option is available that disables the STOP instruction. When the STOP bit in the configuration register has the STOP instruction is disabled, execution of a STOP instruction results in an illegal opcode reset.
19.8 COP Module During Break Mode
The COP is disabled during a break interrupt when VTST is present on the RST pin.
MC68HC908AP A-Family Data Sheet, Rev. 2 282 Freescale Semiconductor
Chapter 20 Low-Voltage Inhibit (LVI)
20.1 Introduction
This section describes the low-voltage inhibit (LVI) module. The LVI module monitors the voltage on the VDD pin and VREG pin, and can force a reset when VDD voltage falls below VTRIPF1, or VREG voltage falls below VTRIPF2. NOTE The VREG pin is the output of the internal voltage regulator and is guaranteed to meet operating specification as long as VDD is within the MCU operating voltage. The LVI feature is intended to provide the safe shutdown of the microcontroller and thus protection of related circuitry prior to any application VDD voltage collapsing completely to an unsafe level. It is not intended that users operate the microcontroller at lower than the specified operating voltage, VDD.
20.2 Features
Features of the LVI module include: * Independent voltage monitoring circuits for VDD and VREG * Independent disable for VDD and VREG LVI circuits * Programmable LVI reset * Programmable stop mode operation
Addr. $FE0F Register Name Read: LVI Status Register Write: (LVISR) Reset: Bit 7 LVIOUT 0 6 0 5 0 4 0 0 3 0 0 2 0 0 1 0 0 Bit 0 0 0
0 0 = Unimplemented
Figure 20-1. LVI I/O Register Summary
20.3 Functional Description
Figure 20-2 shows the structure of the LVI module. The LVI is enabled out of reset. The LVI module contains independent bandgap reference circuit and comparator for monitoring the VDD voltage and the VREG voltage. An LVI reset performs a MCU internal reset and drives the RST pin low to provide low-voltage protection to external peripheral devices. LVISTOP, LVIPWRD, LVIRSTD, and LVIREGD are in the CONFIG1 register. See Chapter 3 Configuration & Mask Option Registers (CONFIG & MOR) for details of the LVI configuration bits. Once
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 283
Low-Voltage Inhibit (LVI)
an LVI reset occurs, the MCU remains in reset until VDD rises above VTRIPR1 and VREG rises above VTRIPR2, which causes the MCU to exit reset. The output of the comparator controls the state of the LVIOUT flag in the LVI status register (LVISR). An LVI reset also drives the RST pin low to provide low-voltage protection to external peripheral devices.
VDD STOP INSTRUCTION LVISTOP FROM CONFIG1
LVIPWRD FROM CONFIG1 LOW VDD DETECTOR VDD > VTRIPR1 = 0 VDD VTRIPF1 = 1 VREG > VTRIPR2 = 0 VREG VTRIPF2 = 1
FROM CONFIG1 LVIRSTD
LVI RESET
LOW VREG DETECTOR
LVIOUT FROM CONFIG1 LVIREGD TO LVISR
FROM CONFIG1 LVISTOP VREG STOP INSTRUCTION
Figure 20-2. LVI Module Block Diagram
20.3.1 Low VDD Detector
The low VDD detector circuit monitors the VDD voltage and forces a LVI reset when the VDD voltage falls below the trip voltage, VTRIPF1. The VDD LVI circuit can be disabled by the setting the LVIPWRD bit in CONFIG1 register.
20.3.2 Low VREG Detector
The low VREG detector circuit monitors the VREG voltage and forces a LVI reset when the VREG voltage falls below the trip voltage, VTRIPF2. The VREG LVI circuit can be disabled by the setting the LVIREGD bit in CONFIG1 register.
20.3.3 Polled LVI Operation
In applications that can operate at VDD levels below the VTRIPF1 level, software can monitor VDD by polling the LVIOUT bit. In the CONFIG1 register, the LVIPWRD bit must be at logic 0 to enable the LVI module, and the LVIRSTD bit must be at logic 1 to disable LVI resets.
MC68HC908AP A-Family Data Sheet, Rev. 2 284 Freescale Semiconductor
LVI Status Register
20.3.4 Forced Reset Operation
In applications that require VDD to remain above the VTRIPF1 level, enabling LVI resets allows the LVI module to reset the MCU when VDD falls below the VTRIPF1 level. In the CONFIG1 register, the LVIPWRD and LVIRSTD bits must be at logic 0 to enable the LVI module and to enable LVI resets.
20.3.5 Voltage Hysteresis Protection
Once the LVI has triggered (by having VDD fall below VTRIPF1), the LVI will maintain a reset condition until VDD rises above the rising trip point voltage, VTRIPR1. This prevents a condition in which the MCU is continually entering and exiting reset if VDD is approximately equal to VTRIPF1. VTRIPR1 is greater than VTRIPF1 by the hysteresis voltage, VHYS.
20.4 LVI Status Register
The LVI status register (LVISR) indicates if the VDD voltage was detected below VTRIPF1 or VREG voltage was detected below VTRIPF2.
Address: Read: Write: Reset: 0 0 = Unimplemented 0 0 0 0 0 0 $FE0F Bit 7 LVIOUT 6 0 5 0 4 0 3 0 2 0 1 0 Bit 0 0
Figure 20-3. LVI Status Register LVIOUT -- LVI Output Bit This read-only flag becomes set when the VDD or VREG falls below their respective trip voltages. Reset clears the LVIOUT bit. Table 20-1. LVIOUT Bit Indication
VDD, VREG VDD > VTRIPR1 and VREG > VTRIPR2 VDD < VTRIPF1 or VDD < VTRIPF2 VTRIPF1 < VDD < VTRIPR1 or VTRIPF2 < VREG< VTRIPR2 LVIOUT
0
1
Previous value
20.5 LVI Interrupts
The LVI module does not generate interrupt requests.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 285
Low-Voltage Inhibit (LVI)
20.6 Low-Power Modes
The STOP and WAIT instructions put the MCU in low power-consumption standby modes.
20.6.1 Wait Mode
If enabled, the LVI module remains active in wait mode. If enabled to generate resets, the LVI module can generate a reset and bring the MCU out of wait mode.
20.6.2 Stop Mode
If enabled in stop mode (LVISTOP = 1), the LVI module remains active in stop mode. If enabled to generate resets (LVIRSTD = 0), the LVI module can generate a reset and bring the MCU out of stop mode.
MC68HC908AP A-Family Data Sheet, Rev. 2 286 Freescale Semiconductor
Chapter 21 Break Module (BRK)
21.1 Introduction
This section describes the break module. The break module can generate a break interrupt that stops normal program flow at a defined address to enter a background program.
21.2 Features
Features of the break module include: * Accessible input/output (I/O) registers during the break interrupt * CPU-generated break interrupts * Software-generated break interrupts * COP disabling during break interrupts
Addr. $FE00 Register Name SIM Break Status Register (SBSR) SIM Break Flag Control Register (SBFCR) Break Address Register High (BRKH) Break Address Register Low (BRKL) Break Status and Control Register (BRKSCR) Bit 7 6 R 5 R 4 R 3 R 2 R
$FE03
$FE0C
$FE0D
$FE0E
Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset:
R
1 SBSW Note 0 R
Bit 0 R
BCFE 0 Bit 15 0 Bit 7 0 BRKE 0
R
R
R
R
R
R
14 0 6 0 BRKA 0
13 0 5 0 0 0
12 0 4 0 0 0
11 0 3 0 0 0
10 0 2 0 0 0
9 0 1 0 0 0
Bit 8 0 Bit 0 0 0 0
Note: Writing a logic 0 clears BW.
= Unimplemented
R
= Reserved
Figure 21-1. Break Module I/O Register Summary
21.3 Functional Description
When the internal address bus matches the value written in the break address registers, the break module issues a breakpoint signal to the CPU. The CPU then loads the instruction register with a software interrupt instruction (SWI) after completion of the current CPU instruction. The program counter vectors to $FFFC and $FFFD ($FEFC and $FEFD in monitor mode).
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 287
Break Module (BRK)
The following events can cause a break interrupt to occur: * A CPU-generated address (the address in the program counter) matches the contents of the break address registers. * Software writes a logic 1 to the BRKA bit in the break status and control register. When a CPU-generated address matches the contents of the break address registers, the break interrupt begins after the CPU completes its current instruction. A return-from-interrupt instruction (RTI) in the break routine ends the break interrupt and returns the MCU to normal operation. Figure 21-2 shows the structure of the break module.
IAB15-IAB8
BREAK ADDRESS REGISTER HIGH 8-BIT COMPARATOR IAB15-IAB0 CONTROL 8-BIT COMPARATOR BREAK ADDRESS REGISTER LOW BREAK
IAB7-IAB0
Figure 21-2. Break Module Block Diagram
21.3.1 Flag Protection During Break Interrupts
The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state.
21.3.2 CPU During Break Interrupts
The CPU starts a break interrupt by: * Loading the instruction register with the SWI instruction * Loading the program counter with $FFFC and $FFFD ($FEFC and $FEFD in monitor mode) The break interrupt begins after completion of the CPU instruction in progress. If the break address register match occurs on the last cycle of a CPU instruction, the break interrupt begins immediately.
21.3.3 TIMI and TIM2 During Break Interrupts
A break interrupt stops the timer counters.
21.3.4 COP During Break Interrupts
The COP is disabled during a break interrupt when VTST is present on the RST pin.
21.4 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
MC68HC908AP A-Family Data Sheet, Rev. 2 288 Freescale Semiconductor
Break Module Registers
21.4.1 Wait Mode
If enabled, the break module is active in wait mode. In the break routine, the user can subtract one from the return address on the stack if SBSW is set. (see Chapter 7 System Integration Module (SIM)) Clear the BW bit by writing logic 0 to it.
21.4.2 Stop Mode
A break interrupt causes exit from stop mode and sets the SBSW bit in the break status register.
21.5 Break Module Registers
These registers control and monitor operation of the break module: * Break status and control register (BRKSCR) * Break address register high (BRKH) * Break address register low (BRKL) * SIM break status register (SBSR) * SIM break flag control register (SBFCR)
21.5.1 Break Status and Control Register
The break status and control register (BRKSCR) contains break module enable and status bits.
Address: Read: Write: Reset: $FE0E Bit 7 BRKE 0 6 BRKA 0 5 0 0 4 0 0 3 0 0 2 0 0 1 0 0 Bit 0 0 0
= Unimplemented
Figure 21-3. Break Status and Control Register (BRKSCR) BRKE -- Break Enable Bit This read/write bit enables breaks on break address register matches. Clear BRKE by writing a logic 0 to bit 7. Reset clears the BRKE bit. 1 = Breaks enabled on 16-bit address match 0 = Breaks disabled on 16-bit address match BRKA -- Break Active Bit This read/write status and control bit is set when a break address match occurs. Writing a logic 1 to BRKA generates a break interrupt. Clear BRKA by writing a logic 0 to it before exiting the break routine. Reset clears the BRKA bit. 1 = (When read) Break address match 0 = (When read) No break address match
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 289
Break Module (BRK)
21.5.2 Break Address Registers
The break address registers (BRKH and BRKL) contain the high and low bytes of the desired breakpoint address. Reset clears the break address registers.
Address: Read: Write: Reset: $FE0C Bit 7 Bit 15 0 6 14 0 5 13 0 4 12 0 3 11 0 2 10 0 1 9 0 Bit 0 Bit 8 0
Figure 21-4. Break Address Register High (BRKH)
Address: Read: Write: Reset: $FE0D Bit 7 Bit 7 0 6 6 0 5 5 0 4 4 0 3 3 0 2 2 0 1 1 0 Bit 0 Bit 0 0
Figure 21-5. Break Address Register Low (BRKL)
21.5.3 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a break caused an exit from wait mode. The flag is useful in applications requiring a return to wait mode after exiting from a break interrupt.
Address: Read: Write: Reset: Note: Writing a logic 0 clears SBSW. R = Reserved $FE00 Bit 7 R 6 R 5 R 4 R 3 R 2 R 1 SBSW Note 0 Bit 0 R
Figure 21-6. SIM Break Status Register (SBSR)
SBSW -- Break Wait Bit This status bit is set when a break interrupt causes an exit from wait mode or stop mode. Clear SBSW by writing a logic 0 to it. Reset clears SBSW. 1 = Stop mode or wait mode was exited by break interrupt 0 = Stop mode or wait mode was not exited by break interrupt SBSW can be read within the break interrupt routine. The user can modify the return address on the stack by subtracting 1 from it. The following code is an example.
MC68HC908AP A-Family Data Sheet, Rev. 2 290 Freescale Semiconductor
Break Module Registers
; This code works if the H register has been pushed onto the stack in the break ; service routine software. This code should be executed at the end of the break ; service routine software. HIBYTE LOBYTE ; EQU EQU 5 6
If not SBSW, do RTI BRCLR TST BNE DEC DOLO RETURN DEC PULH RTI SBSW,SBSR, RETURN LOBYTE,SP DOLO HIBYTE,SP LOBYTE,SP ; See if wait mode or stop mode was exited by ; break. ;If RETURNLO is not zero, ;then just decrement low byte. ;Else deal with high byte, too. ;Point to WAIT/STOP opcode. ;Restore H register.
21.5.4 SIM Break Flag Control Register
The SIM break flag control register (SBFCR) contains a bit that enables software to clear status bits while the MCU is in a break state.
Address: Read: Write: Reset: $FE03 Bit 7 BCFE 0 R = Reserved 6 R 5 R 4 R 3 R 2 R 1 R Bit 0 R
Figure 21-7. SIM Break Flag Control Register (SBFCR) BCFE -- Break Clear Flag Enable Bit This read/write bit enables software to clear status bits by accessing status registers while the MCU is in a break state. To clear status bits during the break state, the BCFE bit must be set. 1 = Status bits clearable during break 0 = Status bits not clearable during break
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 291
Break Module (BRK)
MC68HC908AP A-Family Data Sheet, Rev. 2 292 Freescale Semiconductor
Chapter 22 Electrical Specifications
22.1 Introduction
This section contains electrical and timing specifications.
22.2 Absolute Maximum Ratings
Maximum ratings are the extreme limits to which the MCU can be exposed without permanently damaging it. NOTE This device is not guaranteed to operate properly at the maximum ratings. Refer to 5V DC Electrical Characteristics for guaranteed operating conditions. Table 22-1. Absolute Maximum Ratings
Characteristic(1) Supply voltage Input voltage All pins (except IRQ1) IRQ1 pin Maximum current per pin excluding VDD and VSS Maximum current out of VSS Maximum current into VDD Storage temperature 1. Voltages referenced to VSS. Symbol VDD VIN Value -0.3 to +6.0 VSS -0.3 to VDD +0.3 VSS -0.3 to 8.5 25 100 100 -55 to +150 Unit V
V V mA mA mA C
I IMVSS IMVDD TSTG
NOTE This device contains circuitry to protect the inputs against damage due to high static voltages or electric fields; however, it is advised that normal precautions be taken to avoid application of any voltage higher than maximum-rated voltages to this high-impedance circuit. For proper operation, it is recommended that VIN and VOUT be constrained to the range VSS (VIN or VOUT) VDD. Reliability of operation is enhanced if unused inputs are connected to an appropriate logic voltage level (for example, either VSS or VDD.)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 293
Electrical Specifications
22.3 Functional Operating Range
Table 22-2. Operating Range
Characteristic Operating temperature range Operating voltage range Symbol TA VDD Value - 40 to +85 4.5 to 5.5 (1) Unit C V
1. Functionality of the device has been characterized down to the LVI trip voltage, but user should ensure that the device supply voltage is within the specified range of 4.5 to 5.5V after power-up in order for the LVI circuit to configure properly.
22.4 Thermal Characteristics
Table 22-3. Thermal Characteristics
Characteristic Thermal resistance 42-Pin SDIP 44-Pin QFP 48-Pin LQFP I/O pin power dissipation Power dissipation(1) Symbol Value 60 95 80 User determined PD = (IDD x VDD) + PI/O = K/(TJ + 273 C) PD x (TA + 273 C) + PD2 x JA TA + (PD x JA) 100 Unit C/W C/W C/W W W
JA
PI/O PD
Constant(2) Average junction temperature Maximum junction temperature
K TJ TJM
W/C C C
1. Power dissipation is a function of temperature. 2. K constant unique to the device. K can be determined for a known TA and measured PD. With this value of K, PD and TJ can be determined for any value of TA.
MC68HC908AP A-Family Data Sheet, Rev. 2 294 Freescale Semiconductor
5V DC Electrical Characteristics
22.5 5V DC Electrical Characteristics
Table 22-4. DC Electrical Characteristics (5V)
Characteristic(1) Output high voltage (ILOAD = -12mA) PTA[0:7], PTB[4:7], PTC[0:5], PTD[0:7] (ILOAD = -15mA) PTA[0:7], PTB[4:7], PTC[0:5], PTD[0:7] Output low voltage (ILOAD = 6mA) PTA[0:7], PTB[4:7], PTC[0:5], PTD[0:7] (ILOAD = 12mA) PTB[0:3], PTC[6:7] (ILOAD = 15mA) PTA[0:7], PTB[4:7], PTC[0:5], PTD[0:7] (ILOAD = 15mA) PTB[0:3], PTC[6:7] (ILOAD = 15mA) as TxD, RxD, SCTxD, SCRxD (ILOAD = see Table 22-8) as SDA, SCL LED sink current (VOL = 3V) PTA[0:7] Input high voltage PTA[0:7], PTB[0:7], PTC[0:7], PTD[0:7], RST, IRQ1 OSC1 Input low voltage PTA[0:7], PTB[0:7], PTC[0:7], PTD[0:7], RST, IRQ1 OSC1 VDD supply current, fOP = 8 MHz Run(3) Wait(4) Stop (25C) with OSC, TBM, and LVI modules on(5) with OSC and TBM modules on(5) all modules off(6) Stop (-40 to 85C) with OSC, TBM, and LVI modules on(5) with OSC and TBM modules on(5) all modules off(6) Digital I/O ports Hi-Z leakage current Input current Capacitance Ports (as input or output) POR rearm voltage(7) POR rise time ramp rate(8) Monitor mode entry voltage IIL IIN COUT CIN VPOR RPOR VTST -- -- 10 2.5 20 10 mA mA Symbol VOH VOH VOL VOL VOL VOL VOLSCI VOLIIC IOL Min VDD -0.8 VDD -1.0 Typ(2) -- -- Max Unit
-- --
V V
-- -- -- -- -- -- 9
-- -- -- -- -- -- 15
0.4 0.4 0.8 0.6 0.4 0.4 25
V V V V V V mA
VIH
0.7 x VDD 0.7 x VREG VSS VSS
-- --
VDD VREG 0.3 x VDD 0.3 x VREG
V V
VIL
-- --
V V
IDD
-- -- --
1 160 20
2.1 250 125
mA A A
-- -- -- -- -- -- -- 0 0.035 1.4 x VDD
1.2 180 42 -- -- -- -- -- --
2.5 300 250 10 1 12 8 100 -- 8.5
mA A A A A pF pF mV V/ms V
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 295
Electrical Specifications
Table 22-4. DC Electrical Characteristics (5V)
Characteristic(1) Pullup resistors(9) PTD[0:7] RST, IRQ1, IRQ2 Low-voltage inhibit, trip falling voltage1 Low-voltage inhibit, trip rising voltage1 Low-voltage inhibit, trip voltage2 VREG(10) Symbol RPU1 RPU2 VTRIPF1 VTRIPR1 VTRIPF2 VREG Min Typ(2) 27 27 3.10 3.45 2.45 2.50 Max Unit
21 21 2.90 3.25 2.25 2.25
39 39 3.30 3.65 2.65 2.75
k k V V V V
1. VDD = 4.5 to 5.5 Vdc, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted. 2. Typical values reflect average measurements at midpoint of voltage range, 25 C only. 3. Run (operating) IDD measured using external 32MHz clock to OSC1; all inputs 0.2 V from rail; no dc loads; less than 100pF on all outputs; CL = 20 pF on OSC2; all ports configured as inputs; OSC2 capacitance linearly affects run IDD; measured with all modules enabled. 4. Wait IDD measured using external 32MHz to OSC1; all inputs 0.2 V from rail; no dc loads; less than 100 pF on all outputs. CL = 20 pF on OSC2; all ports configured as inputs; OSC2 capacitance linearly affects wait IDD. 5. STOP IDD measured using external 8MHz clock to OSC1; no port pins sourcing current. 6. STOP IDD measured with OSC1 grounded; no port pins sourcing current. 7. Maximum is highest voltage that POR is guaranteed. The rearm voltage is triggered by VREG. 8. If minimum VDD is not reached before the internal POR reset is released, RST must be driven low externally until minimum VDD is reached. 9. RPU1 and RPU2 are measured at VDD = 5.0V 10. Measured from VDD = VTRIPF1 (Min) to 5.5 V.
22.6 5V Control Timing
Table 22-5. Control Timing (5V)
Characteristic(1) Internal operating frequency(2) RST input pulse width low(3) Symbol fOP tIRL Min -- 750 Max 8 -- Unit MHz ns
1. VDD = 4.5 to 5.5 Vdc, VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VDD, unless otherwise noted. 2. Some modules may require a minimum frequency greater than dc for proper operation; see appropriate table for this information. 3. Minimum pulse width reset is guaranteed to be recognized. It is possible for a smaller pulse width to cause a reset.
MC68HC908AP A-Family Data Sheet, Rev. 2 296 Freescale Semiconductor
5V Oscillator Characteristics
22.7 5V Oscillator Characteristics
Table 22-6. Oscillator Specifications (5V)
Characteristic(1) Internal oscillator clock frequency External reference clock to OSC1(3) Crystal reference frequency(4) Crystal load capacitance(5) Crystal fixed capacitance(5) Crystal tuning capacitance(5) Feedback bias resistor Series resistor(5) External RC clock frequency RC oscillator external R RC oscillator external C Symbol fICLK fOSC fXTALCLK CL C1 C2 RB RS fRCCLK REXT CEXT -- See Figure 22-1 10 -- Min 64k dc 1M -- -- -- -- -- -- -- 2 x CL 2 x CL 1M 0 Typ 88k(2) Max 104k 32M 8M -- -- -- -- -- 7.6M Hz pF Unit Hz Hz Hz
1. The oscillator circuit operates at VREG. 2. Typical value reflect average measurements at midpoint of voltage range, 25 C only. 3. No more than 10% duty cycle deviation from 50%. The max. frequency is limited by an EMC filter. 4. Fundamental mode crystals only. 5. Consult crystal vendor data sheet.
RC frequency, fRCCLK (MHz)
8 6 4 2 0 0 10
CEXT = 10 pF VDD = 5V, @ 25C
MCU
OSC1
VREG REXT CEXT
20 30 Resistor, REXT (k)
40
50
Figure 22-1. RC vs. Frequency
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 297
Electrical Specifications
22.8 5V ADC Electrical Characteristics
Table 22-7. ADC Electrical Characteristics (5V)
Characteristic(1) Symbol Min Max Unit Notes VDDA is an dedicated pin and should be tied to VDD on the PCB with proper decoupling. VADIN VDDA
Supply voltage
VDDA VADIN BAD AAD fADIC RAD VREFH VREFL tADC tADS MAD ZADI FADI CADI RADI IVREF
4.5
5.5
V
Input range Resolution Absolute accuracy ADC internal clock Conversion range ADC voltage reference high ADC voltage reference low Conversion time
0 10 -- 500k VREFL -- VSSA - 0.1 16
VDDA 10 1.5 1.048M VREFH VDDA + 0.1 --
V bits LSB Hz V V V tADIC cycles tADIC cycles
Includes quantization. 0.5 LSB = 1 ADC step. tADIC = 1/fADIC
17
Sample time Monotonicity Zero input reading Full-scale reading Input capacitance Input impedance VREFH/VREFL
5
-- Guaranteed
000 3FD -- 20M --
001 3FF 20 -- 1.6
HEX HEX pF mA
VADIN = VREFL VADIN = VREFH Not tested.
Not tested.
1. VDD = 4.5 to 5.5 Vdc, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted.
MC68HC908AP A-Family Data Sheet, Rev. 2 298 Freescale Semiconductor
MMIIC Electrical Characteristics
22.9 MMIIC Electrical Characteristics
Table 22-8. MMIIC DC Electrical Characteristics
Characteristic(1) Input low Input high Output low Input leakage Symbol VIL VIH VOL ILEAK IPULLUP Min -0.5 2.1 -- -- Typ -- -- -- -- Max 0.8 5.5 0.4 5 350 Unit V V V A A Comments Data, clock input low. Data, clock input high. Data, clock output low; @IPULLUP,MAX Input leakage current Current through pull-up resistor or current source. See note.(2)
Pullup current
100
--
1. VDD = 4.5 to 5.5Vdc, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted. 2. The IPULLUP (max) specification is determined primarily by the need to accommodate a maximum of 1.1k equivalent series resistor of removable SMBus devices, such as the smart battery, while maintaining the VOL (max) of the bus.
SDA
SCL
tHD.STA
tLOW
tHIGH
tSU.DAT
tHD.DAT
tSU.STA
tSU.STO
Figure 22-2. MMIIC Signal Timings See Table 22-9 for MMIIC timing parameters.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 299
Electrical Specifications
Table 22-9. MMIIC Interface Input/Output Signal Timing
Characteristic Operating frequency Bus free time Symbol fSMB tBUF Min 10 4.7 Typ -- -- Max 100 -- Unit kHz s Comments MMIIC operating frequency Bus free time between STOP and START condition Hold time after (repeated) START condition. After this period, the first clock is generated. Repeated START condition setup time. Stop condition setup time. Data hold time. Data setup time. Clock low time-out.(1) Clock low period Clock high period.(2) Cumulative clock low extend time (slave device)(3) Cumulative clock low extend time (master device) (4) Clock/Data Fall Time(5) Clock/Data Rise Time(5)
Repeated start hold time.
tHD.STA tSU.STA tSU.STO tHD.DAT tSU.DAT tTIMEOUT tLOW tHIGH tLOW.SEXT tLOW.MEXT tF tR
4.0
--
--
s s s ns ns ms s s ms
Repeated start setup time. Stop setup time Hold time Setup time Clock low time-out Clock low Clock high Slave clock low extend time
4.7 4.0 300 250 25 4.7 4.0 --
-- -- -- -- -- -- -- --
-- -- -- -- 35 -- -- 25
Master clock low extend time Fall time Rise time
-- -- --
-- -- --
10 300 1000
ms ns ns
1. Devices participating in a transfer will timeout when any clock low exceeds the value of TTIMEOUT min. of 25ms. Devices that have detected a timeout condition must reset the communication no later than TTIMEOUT max of 35ms. The maximum value specified must be adhered to by both a master and a slave as it incorporates the cumulative limit for both a master (10 ms) and a slave (25 ms). Software should turn-off the MMIIC module to release the SDA and SCL lines. 2. THIGH MAX provides a simple guaranteed method for devices to detect the idle conditions. 3. TLOW.SEXT is the cumulative time a slave device is allowed to extend the clock cycles in one message from the initial start to the stop. If a slave device exceeds this time, it is expected to release both its clock and data lines and reset itself. 4. TLOW.MEXT is the cumulative time a master device is allowed to extend its clock cycles within each byte of a message as defined from start-to-ack, ack-to-ack, or ack-to-stop. 5. Rise and fall time is defined as follows: TR = (VILMAX - 0.15) to (VIHMIN + 0.15), TF = 0.9xVDD to (VILMAX - 0.15).
MC68HC908AP A-Family Data Sheet, Rev. 2 300 Freescale Semiconductor
CGM Electrical Specification
22.10 CGM Electrical Specification
Table 22-10. CGM Electrical Specifications
Characteristic Reference frequency Range nominal multiplies VCO center-of-range frequency VCO range linear range multiplier VCO power-of-two-range multiplier VCO multiply factor VCO prescale multiplier Reference divider factor VCO operating frequency Manual acquisition time Automatic lock time Symbol fRDV fNOM fVRS L 2E N 2P R fVCLK tLOCK tLOCK Min 1 -- 125k 1 1 1 1 1 125k -- -- Typ -- 125 -- -- -- -- -- 1 -- -- -- Max 8 -- 40M 255 4 4095 8 15 40M 50 50 fRCLK x PLL jitter(1) fJ 0 -- 0.025% x 2P N/4 Hz Hz ms ms Unit MHz kHz Hz
1. Deviation of average bus frequency over 2ms. N = VCO multiplier.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 301
Electrical Specifications
22.11 5V SPI Characteristics
Table 22-11. SPI Characteristics (5V)
Diagram Number(1) Characteristic(2) Symbol Min Max Unit
Operating frequency Master Slave Cycle time Master Slave Enable lead time Enable lag time Clock (SPSCK) high time Master Slave Clock (SPSCK) low time Master Slave Data setup time (inputs) Master Slave Data hold time (inputs) Master Slave Access time, slave(3) CPHA = 0 CPHA = 1 Disable time, slave(4) Data valid time, after enable edge Master Slave(5) Data hold time, outputs, after enable edge Master Slave
fOP(M) fOP(S) tCYC(M) tCYC(S) tLead(S) tLag(S) tSCKH(M) tSCKH(S) tSCKL(M) tSCKL(S) tSU(M) tSU(S) tH(M) tH(S) tA(CP0) tA(CP1) tDIS(S) tV(M) tV(S) tHO(M) tHO(S)
fOP/128 dc
fOP/2 fOP 128 -- -- --
MHz MHz
1
2 1 1 1 tCYC -25 1/2 tCYC -25 tCYC -25 1/2 tCYC -25
tCYC tCYC tCYC tCYC ns ns
2 3
4
64 tCYC
--
5
64 tCYC
--
ns ns
6
30
30
-- --
ns ns
7
30
30
-- --
ns ns
8
0 0 --
40 40 40
ns ns ns
9
10
-- --
50
50
ns ns
11
0 0
-- --
ns ns
1. Numbers refer to dimensions in Figure 22-3 and Figure 22-4. 2. All timing is shown with respect to 20% VDD and 70% VDD, unless noted; 100 pF load on all SPI pins. 3. Time to data active from high-impedance state 4. Hold time to high-impedance state 5. With 100 pF on all SPI pins
MC68HC908AP A-Family Data Sheet, Rev. 2 302 Freescale Semiconductor
5V SPI Characteristics
SS INPUT
SS PIN OF MASTER HELD HIGH 1
SPSCK OUTPUT CPOL = 0
NOTE
5 4
SPSCK OUTPUT CPOL = 1
NOTE
5 4 6 7 LSB IN 10 BITS 6-1 11 MASTER LSB OUT
MISO INPUT
MSB IN 11
BITS 6-1
MOSI OUTPUT
MASTER MSB OUT
Note: This first clock edge is generated internally, but is not seen at the SPSCK pin.
a) SPI Master Timing (CPHA = 0)
SS INPUT
SS PIN OF MASTER HELD HIGH 1
SPSCK OUTPUT CPOL = 0
5 4
NOTE
SPSCK OUTPUT CPOL = 1
5 4 6 7 LSB IN 10 BITS 6-1 MASTER LSB OUT
NOTE
MISO INPUT 10 MOSI OUTPUT
MSB IN 11 MASTER MSB OUT
BITS 6-1
Note: This last clock edge is generated internally, but is not seen at the SPSCK pin.
b) SPI Master Timing (CPHA = 1)
Figure 22-3. SPI Master Timing
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 303
Electrical Specifications
SS INPUT 1 SPSCK INPUT CPOL = 0 2 SPSCK INPUT CPOL = 1 8 MISO INPUT SLAVE 6 MOSI OUTPUT MSB IN MSB OUT 7 10 BITS 6-1 BITS 6-1 11 LSB IN SLAVE LSB OUT 11 5 4 9 NOTE 5 4 3
Note: Not defined but normally MSB of character just received
a) SPI Slave Timing (CPHA = 0)
SS INPUT 1 SPSCK INPUT CPOL = 0 2 SPSCK INPUT CPOL = 1 8 MISO OUTPUT 5 4 10 NOTE SLAVE 6 MOSI INPUT MSB IN MSB OUT 7 10 BITS 6-1 BITS 6-1 11 LSB IN 9 SLAVE LSB OUT 5 4 3
Note: Not defined but normally LSB of character previously transmitted
b) SPI Slave Timing (CPHA = 1)
Figure 22-4. SPI Slave Timing
MC68HC908AP A-Family Data Sheet, Rev. 2 304 Freescale Semiconductor
Memory Characteristics
22.12 Memory Characteristics
Table 22-12. Memory Characteristics
Characteristic Data retention voltage Number of rows per page Number of bytes per page Read bus clock frequency Page erase time Mass erase time PGM/ERASE to HVEN setup time High-voltage hold time High-voltage hold time (mass erase) Program hold time Program time Address/data setup time Address/data hold time Recovery time Cumulative HV period Row erase endurance(6) Row program endurance(7) Data retention time(8) fread(1) terase(2) tme(3) tnvs tnvh tnvh1 tpgs tprog tads tadh trcv(4) thv(5) -- -- -- 32k 20 200 5 5 100 10 20 20 -- 1 -- 10k 10k 10 Symbol VRDR Min. 1.3 8 512 8M -- -- -- -- -- -- 40 -- 30 -- 8 -- -- -- Max. -- Unit V Rows Bytes Hz ms ms s s s s s ns ns s ms Cycles Cycles Years
1. fread is defined as the frequency range for which the FLASH memory can be read. 2. If the page erase time is longer than terase (Min.), there is no erase-disturb, but it reduces the endurance of the FLASH memory. 3. If the mass erase time is longer than tme (Min.), there is no erase-disturb, but it reduces the endurance of the FLASH memory. 4. It is defined as the time it needs before the FLASH can be read after turning off the high voltage charge pump, by clearing HVEN to logic 0. 5. thv is the cumulative high voltage programming time to the same row before next erase, and the same address can not be programmed twice before next erase. 6. The minimum row endurance value specifies each row of the FLASH memory is guaranteed to work for at least this many erase/program cycles. 7. The minimum row endurance value specifies each row of the FLASH memory is guaranteed to work for at least this many erase/program cycle. 8. The FLASH is guaranteed to retain data over the entire operating temperature range for at least the minimum time specified.
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 305
Electrical Specifications
MC68HC908AP A-Family Data Sheet, Rev. 2 306 Freescale Semiconductor
Chapter 23 Mechanical Specifications
23.1 Introduction
This section gives the dimensions for: * 48-pin plastic low-profile quad flat pack (case #932) * 44-pin plastic quad flat pack (case #824A) * 42-pin shrink dual in-line package (case #858)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 307
Mechanical Specifications
23.2 48-Pin Low-Profile Quad Flat Pack (LQFP)
4X
0.200 AB T-U Z 9 A1
48 37
A
DETAIL Y
P
1
36
T B B1
12 25
U V AE V1 AE
NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M, 1994. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DATUM PLANE AB IS LOCATED AT BOTTOM OF LEAD AND IS COINCIDENT WITH THE LEAD WHERE THE LEAD EXITS THE PLASTIC BODY AT THE BOTTOM OF THE PARTING LINE. 4. DATUMS T, U, AND Z TO BE DETERMINED AT DATUM PLANE AB. 5. DIMENSIONS S AND V TO BE DETERMINED AT SEATING PLANE AC. 6. DIMENSIONS A AND B DO NOT INCLUDE MOLD PROTRUSION. ALLOWABLE PROTRUSION IS 0.250 PER SIDE. DIMENSIONS A AND B DO INCLUDE MOLD MISMATCH AND ARE DETERMINED AT DATUM PLANE AB. 7. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. DAMBAR PROTRUSION SHALL NOT CAUSE THE D DIMENSION TO EXCEED 0.350. 8. MINIMUM SOLDER PLATE THICKNESS SHALL BE 0.0076. 9. EXACT SHAPE OF EACH CORNER IS OPTIONAL. MILLIMETERS MAX MIN 7.000 BSC 3.500 BSC 7.000 BSC 3.500 BSC 1.400 1.600 0.170 0.270 1.350 1.450 0.170 0.230 0.500 BSC 0.050 0.150 0.090 0.200 0.500 0.700 1 5 12 REF 0.090 0.160 0.250 BSC 0.150 0.250 9.000 BSC 4.500 BSC 9.000 BSC 4.500 BSC 0.200 REF 1.000 REF
13
24
Z S1 S
4X
T, U, Z DETAIL Y
0.200 AC T-U Z
AB
G
0.080 AC
AD AC
BASE METAL
DIM A A1 B B1 C D E F G H J K L M N P R S S1 V V1 W AA
M
TOP & BOTTOM
R
GAUGE PLANE
C F D 0.080
M
E
AC T-U Z H DETAIL AD AA W K L
SECTION AE-AE
Figure 23-1. 48-Pin LQFP (Case #932)
MC68HC908AP A-Family Data Sheet, Rev. 2 308 Freescale Semiconductor
0.250
N
J
44-Pin Quad Flat Pack (QFP)
23.3 44-Pin Quad Flat Pack (QFP)
B L B
33 34
23 22 S
-A-, -B-, -D- D D
S
DETAIL A F
BASE METAL
S
H A-B
0.05 (0.002) A-B
-A- L
-B- B
M
V
0.20 (0.008)
0.20 (0.008)
M
C A-B
S
J D
N
DETAIL A
44 1 11 12
0.20 (0.008)
M
C A-B
S
D
S
SECTION B-B
VIEW ROTATED 90
NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DATUM PLANE -H- IS LOCATED AT BOTTOM OF LEAD AND IS COINCIDENT WITH THE LEAD WHERE THE LEAD EXITS THE PLASTIC BODY AT THE BOTTOM OF THE PARTING LINE. 4. DATUMS -A-, -B- AND -D- TO BE DETERMINED AT DATUM PLANE -H-. 5. DIMENSIONS S AND V TO BE DETERMINED AT SEATING PLANE -C-. 6. DIMENSIONS A AND B DO NOT INCLUDE MOLD PROTRUSION. ALLOWABLE PROTRUSION IS 0.25 (0.010) PER SIDE. DIMENSIONS A AND B DO INCLUDE MOLD MISMATCH AND ARE DETERMINED AT DATUM PLANE -H-. 7. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.08 (0.003) TOTAL IN EXCESS OF THE D DIMENSION AT MAXIMUM MATERIAL CONDITION. DAMBAR CANNOT BE LOCATED ON THE LOWER RADIUS OR THE FOOT. MILLIMETERS MIN MAX 9.90 10.10 9.90 10.10 2.10 2.45 0.30 0.45 2.00 2.10 0.30 0.40 0.80 BSC -- 0.25 0.13 0.23 0.65 0.95 8.00 REF 5 10 0.13 0.17 0 7 0.13 0.30 12.95 13.45 0.13 -- 0 -- 12.95 13.45 0.40 -- 1.6 REF INCHES MIN MAX 0.390 0.398 0.390 0.398 0.083 0.096 0.012 0.018 0.079 0.083 0.012 0.016 0.031 BSC -- 0.010 0.005 0.009 0.026 0.037 0.315 REF 5 10 0.005 0.007 0 7 0.005 0.012 0.510 0.530 0.005 -- 0 -- 0.510 0.530 0.016 -- 0.063 REF
-D- A 0.20 (0.008)
M
H A-B
S
D
S
0.05 (0.002) A-B S 0.20 (0.008)
M
C A-B
S
D M
S
DETAIL C
CE -C-
SEATING PLANE
-H- H
DATUM PLANE
0.10 (0.004) G M
M T
DATUM PLANE
-H-
R
K W X DETAIL C
Q
DIM A B C D E F G H J K L M N Q R S T U V W X
Figure 23-2. 44-Pin QFP (Case #824A)
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 309
Mechanical Specifications
23.4 42-Pin Shrink Dual In-Line Package (SDIP)
-A-
42 22 NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: INCH. 3. DIMENSION L TO CENTER OF LEAD WHEN FORMED PARALLEL. 4. DIMENSIONS A AND B DO NOT INCLUDE MOLD FLASH. MAXIMUM MOLD FLASH 0.25 (0.010). INCHES MIN MAX 1.435 1.465 0.540 0.560 0.155 0.200 0.014 0.022 0.032 0.046 0.070 BSC 0.300 BSC 0.008 0.015 0.115 0.135 0.600 BSC 0 15 0.020 0.040 MILLIMETERS MIN MAX 36.45 37.21 13.72 14.22 3.94 5.08 0.36 0.56 0.81 1.17 1.778 BSC 7.62 BSC 0.20 0.38 2.92 3.43 15.24 BSC 0 15 0.51 1.02
-B-
1 21
L C H
-T-
SEATING PLANE
F D 42 PL 0.25 (0.010)
M
G TA
S
N K J 42 PL 0.25 (0.010)
M
M TB
S
DIM A B C D F G H J K L M N
Figure 23-3. 42-Pin SDIP (Case #858)
MC68HC908AP A-Family Data Sheet, Rev. 2 310 Freescale Semiconductor
Ordering Information
23.5 Introduction
This section contains device ordering numbers.
23.6 MC Order Numbers
Table 23-1. MC Order Numbers
MC Order Number MC908AP64ACB MC908AP64ACFB MC908AP64ACFA MC908AP32ACB MC908AP32ACFB MC908AP32ACFA MC908AP16ACB MC908AP16ACFB MC908AP16ACFA MC908AP8ACB MC908AP8ACFB MC908AP8ACFA RAM Size (bytes) 2,048 2,048 2,048 2,048 2,048 2,048 1,024 1,024 1,024 1,024 1,024 1,024 FLASH Size (bytes) 62,368 62,368 62,368 32,768 32,768 32,768 16,384 16,384 16,384 8,192 8,192 8,192 Package 42-pin SDIP 44-pin QFP 48-pin LQFP 42-pin SDIP 44-pin QFP 48-pin LQFP 42-pin SDIP 44-pin QFP 48-pin LQFP 42-pin SDIP 44-pin QFP 48-pin LQFP Operating Temperature Range - 40 to +85 C - 40 to +85 C - 40 to +85 C - 40 to +85 C - 40 to +85 C - 40 to +85 C - 40 to +85 C - 40 to +85 C - 40 to +85 C - 40 to +85 C - 40 to +85 C - 40 to +85 C
MC68HC908AP A-Family Data Sheet, Rev. 2 Freescale Semiconductor 311
MC68HC908AP A-Family Data Sheet, Rev. 2 312 Freescale Semiconductor
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MC68HC908AP64A Rev. 2, 01/2007

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