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Features
* High Performance, Low Power AVR(R) 8-Bit Microcontroller * Advanced RISC Architecture
- 125 Powerful Instructions - Most Single Clock Cycle Execution - 32 x 8 General Purpose Working Registers - Fully Static Operation - Up to 16 MIPS Throughput at 16 MHz Non-volatile Program and Data Memories - 8K / 16K Bytes of In-System Self-Programmable Flash * Endurance: 10,000 Write/Erase Cycles - Optional Boot Code Section with Independent Lock Bits * USB boot-loader programmed by default in the factory * In-System Programming by on-chip Boot Program hardware-activated after reset * True Read-While-Write Operation - 512 Bytes EEPROM * Endurance: 100,000 Write/Erase Cycles - 512 Bytes Internal SRAM - Programming Lock for Software Security USB 2.0 Full-speed Device Module with Interrupt on Transfer Completion - Complies fully with Universal Serial Bus Specification REV 2.0 - 48 MHz PLL for Full-speed Bus Operation : data transfer rates at 12 Mbit/s - Fully independant 176 bytes USB DPRAM for endpoint memory allocation - Endpoint 0 for Control Transfers: from 8 up to 64-bytes - 4 Programmable Endpoints: * IN or Out Directions * Bulk, Interrupt and IsochronousTransfers * Programmable maximum packet size from 8 to 64 bytes * Programmable single or double buffer - Suspend/Resume Interrupts - Microcontroller reset on USB Bus Reset without detach - USB Bus Disconnection on Microcontroller Request - USB pad multiplexed with PS/2 peripheral for single cable capability Peripheral Features - PS/2 compliant pad - One 8-bit Timer/Counters with Separate Prescaler and Compare Mode (two 8-bit PWM channels) - One 16-bit Timer/Counter with Separate Prescaler, Compare and Capture Mode (three 8-bit PWM channels) - USART with SPI master only mode and hardware flow control (RTS/CTS) - Master/Slave SPI Serial Interface - Programmable Watchdog Timer with Separate On-chip Oscillator - On-chip Analog Comparator - Interrupt and Wake-up on Pin Change On Chip Debug Interface (debugWIRE) Special Microcontroller Features - Power-On Reset and Programmable Brown-out Detection - Internal Calibrated Oscillator - External and Internal Interrupt Sources
*
*
8-bit Microcontroller with 8/16K Bytes of ISP Flash and USB Controller AT90USB82 AT90USB162
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* I/O and Packages
- Five Sleep Modes: Idle, Power-save, Power-down, Standby, and Extended Standby
- 22 Programable I/O Lines - QFN32 (5x5mm) / TQFP32 packages * Operating Voltages - 2.7 - 5.5V * Operating temperature - Industrial (-40C to +85C) * Maximum Frequency - 8 MHz at 2.7V - Industrial range - 16 MHz at 4.5V - Industrial range
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1. Pin Configurations
Figure 1-1. Pinout AT90USB82/162
32 31 30 29 28 27 26 25
XTAL1 (PC0) XTAL2 GND VCC (PCINT11) PC2 (OC.0B / INT0) PD0 (AIN0 / INT1) PD1 (RXD1 / AIN1 / INT2) PD2
PB5 (PCINT5) PB3 (PDO / MISO / PCINT3) AVCC UVCC D- / SDATA D+ / SCK UGND UCAP PC4 (PCINT10) PB4 (T1 / PCINT4)
9 10 11 12 13 14 15 16
(INT5) PD4 (XCK / PCINT12) PD5 (RTS / INT6) PD6 (CTS / HWB / T0 / INT7) PD7 (SCLK / PCINT1) PB1 (PDI / MOSI / PCINT2) PB2 (SS / PCINT0) PB0 (TXD1 / INT3) PD3
32 31 30 29 28 27 26 25
XTAL1 (PC0) XTAL2 GND VCC (PCINT11) PC2 (OC.0B / INT0) PD0 (AIN0 / INT1) PD1 (RXD1 / AIN1 / INT2) PD2
PC5 ( PCINT9/ OC.1B)
1 2 3 4 5 6 7 8
PC5 ( PCINT9/ OC.1B)
UCAP PC4 (PCINT10)
AVCC UVCC D- / SDATA
D+ / SCK
UGND
QFN32
24 23 22 21 20 19 18 17
Reset (PC1 / dW) PC6 (OC.1A / PCINT8) PC7 (INT4 / ICP1 / CLKO) PB7 (PCINT7 / OC.0A / OC.1C) PB6 (PCINT6)
1 2 3 4 5 6 7 8
(TXD1 / INT3) PD3
TQFP32
24 23 22 21 20 19 18 17
Reset (PC1 / dW) PC6 (OC.1A / PCINT8) PC7 (INT4 / ICP1 / CLKO) PB7 (PCINT7 / OC.0A / OC.1C) PB6 (PCINT6) PB5 (PCINT5) PB4 (T1 / PCINT4) PB3 (PDO / MISO / PCINT3)
9 10 11 12 13 14 15 16
(RTS / INT6) PD6 (CTS / HWB / T0 / INT7) PD7 (SCLK / PCINT1) PB1 (PDI / MOSI / PCINT2) PB2 (INT5) PD4 (XCK / PCINT12) PD5 (SS / PCINT0) PB0
Note:
The large center pad underneath the QFN packages is made of metal and must be connected to GND. It should be soldered or glued to the board to ensure good mechanical stability. If the center pad is left unconnected, the package might loosen from the board.
1.1
Disclaimer
Typical values contained in this datasheet are based on simulations and characterization of other AVR microcontrollers manufactured on the same process technology. Min and Max values will be available after the device is characterized.
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2. Overview
The AT90USB82/162 is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. By executing powerful instructions in a single clock cycle, the AT90USB82/162 achieves throughputs approaching 1 MIPS per MHz allowing the system designer to optimize power consumption versus processing speed.
2.1
Block Diagram
Block Diagram
Figure 2-1.
PD7 - PD0
PC7 - PC0
PB7 - PB0
PORTD DRIVERS
PORTC DRIVERS
PORTB DRIVERS
ANALOG COMPARATOR
DATA REGISTER PORTD
DATA DIR. REG. PORTD
DATA REGISTER PORTC
DATA DIR. REG. PORTC
DATA REGISTER PORTB
DATA DIR. REG. PORTB
8-BIT DA TA BUS
VCC GND
POR - BOD RESET
INTERNAL OSCILLATOR
CALIB. OSC
Debug-Wire
PROGRAM COUNTER
STACK POINTER
WATCHDOG TIMER
OSCILLATOR
ON-CHIP DEBUG
PROGRAM FLASH
SRAM
MCU CONTROL REGISTER
TIMING AND CONTROL
PROGRAMMING LOGIC
INSTRUCTION REGISTER
GENERAL PURPOSE REGISTERS
X Y Z
TIMER/ COUNTERS UVcc INTERRUPT UNIT ON-CHIP 3.3V REGULATOR
1uF
INSTRUCTION DECODER
RESET
XTAL1
XTAL2
+ -
UCap
CONTROL LINES
ALU
EEPROM PLL
STATUS REGISTER USB
D+/SCK D-/SDATA
USART1
SPI
PS/2
The AVR core combines a rich instruction set with 32 general purpose working registers. All the 32 registers are directly connected to the Arithmetic Logic Unit (ALU), allowing two independent registers to be accessed in one single instruction executed in one clock cycle. The resulting
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architecture is more code efficient while achieving throughputs up to ten times faster than conventional CISC microcontrollers. The AT90USB82/162 provides the following features: 8K / 16K bytes of In-System Programmable Flash with Read-While-Write capabilities, 512 bytes EEPROM, 512 bytes SRAM, 22 general purpose I/O lines, 32 general purpose working registers, two flexible Timer/Counters with compare modes and PWM, one USART, a programmable Watchdog Timer with Internal Oscillator, an SPI serial port, debugWIRE interface, also used for accessing the On-chip Debug system and programming and five software selectable power saving modes. The Idle mode stops the CPU while allowing the SRAM, Timer/Counters, SPI port, and interrupt system to continue functioning. The Power-down mode saves the register contents but freezes the Oscillator, disabling all other chip functions until the next interrupt or Hardware Reset. In Standby mode, the Crystal/Resonator Oscillator is running while the rest of the device is sleeping. This allows very fast start-up combined with low power consumption. In Extended Standby mode, the main Oscillator continues to run. The device is manufactured using Atmel's high-density nonvolatile memory technology. The onchip ISP Flash allows the program memory to be reprogrammed in-system through an SPI serial interface, by a conventional nonvolatile memory programmer, or by an on-chip Boot program running on the AVR core. The boot program can use any interface to download the application program in the application Flash memory. Software in the Boot Flash section will continue to run while the Application Flash section is updated, providing true Read-While-Write operation. By combining an 8-bit RISC CPU with In-System Self-Programmable Flash on a monolithic chip, the Atmel AT90USB82/162 is a powerful microcontroller that provides a highly flexible and cost effective solution to many embedded control applications. The AT90USB82/162 AVR is supported with a full suite of program and system development tools including: C compilers, macro assemblers, program debugger/simulators, in-circuit emulators, and evaluation kits.
2.2
2.2.1
Pin Descriptions
VCC Digital supply voltage.
2.2.2
GND Ground.
2.2.3
Port B (PB7..PB0) Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port B output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port B also serves the functions of various special features of the AT90USB82/162 as listed on page 74.
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2.2.4
Port C (PC7..PC0) Port C is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port C output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port C pins that are externally pulled low will source current if the pull-up resistors are activated. The Port C pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port C also serves the functions of various special features of the AT90USB82/162 as listed on page 76.
2.2.5
Port D (PD7..PD0) Port D serves as analog inputs to the analog comparator. Port D also serves as an 8-bit bi-directional I/O port, if the analog comparator is not used (concerns PD2/PD1 pins). Port pins can provide internal pull-up resistors (selected for each bit). The Port D output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port D pins that are externally pulled low will source current if the pull-up resistors are activated. The Port D pins are tri-stated when a reset condition becomes active, even if the clock is not running.
2.2.6
D-/SDATA USB Full Speed Negative Data Upstream Port / Data port for PS/2
2.2.7
D+/SCK USB Full Speed Positive Data Upstream Port / Clock port for PS/2
2.2.8
UGND USB Ground.
2.2.9
UVCC USB Pads Internal Regulator Input supply voltage.
2.2.10
UCAP USB Pads Internal Regulator Output supply voltage. Should be connected to an external capacitor (1F).
2.2.11
RESET/PC1/dW Reset input. A low level on this pin for longer than the minimum pulse length will generate a reset, even if the clock is not running. The minimum pulse length is given in Section 9.. Shorter pulses are not guaranteed to generate a reset. This pin alternatively serves as debugWire channel or as generic I/O. The configuration depends on the fuses RSTDISBL and DWEN. XTAL1 Input to the inverting Oscillator amplifier and input to the internal clock operating circuit.
2.2.12
2.2.13
XTAL2/PC0 Output from the inverting Oscillator amplifier if enabled by Fuse. Also serves as a generic I/O.
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3. About Code Examples
This documentation contains simple code examples that briefly show how to use various parts of the device. Be aware that not all C compiler vendors include bit definitions in the header files and interrupt handling in C is compiler dependent. Please confirm with the C compiler documentation for more details. These code examples assume that the part specific header file is included before compilation. For I/O registers located in extended I/O map, "IN", "OUT", "SBIS", "SBIC", "CBI", and "SBI" instructions must be replaced with instructions that allow access to extended I/O. Typically "LDS" and "STS" combined with "SBRS", "SBRC", "SBR", and "CBR".
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4. AVR CPU Core
4.1 Introduction
This section discusses the AVR core architecture in general. The main function of the CPU core is to ensure correct program execution. The CPU must therefore be able to access memories, perform calculations, control peripherals, and handle interrupts.
4.2
Architectural Overview
Figure 4-1. Block Diagram of the AVR Architecture
Data Bus 8-bit
Flash Program Memory
Program Counter
Status and Control Interrupt Unit SPI Unit Watchdog Timer ALU Analog Comparator
Instruction Register
32 x 8 General Purpose Registrers
Control Lines
Indirect Addressing
Instruction Decoder
Direct Addressing
I/O Module1 Data SRAM
I/O Module 2
I/O Module n EEPROM
I/O Lines
In order to maximize performance and parallelism, the AVR uses a Harvard architecture - with separate memories and buses for program and data. Instructions in the program memory are executed with a single level pipelining. While one instruction is being executed, the next instruction is pre-fetched from the program memory. This concept enables instructions to be executed in every clock cycle. The program memory is In-System Reprogrammable Flash memory.
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The fast-access Register File contains 32 x 8-bit general purpose working registers with a single clock cycle access time. This allows single-cycle Arithmetic Logic Unit (ALU) operation. In a typical ALU operation, two operands are output from the Register File, the operation is executed, and the result is stored back in the Register File - in one clock cycle. Six of the 32 registers can be used as three 16-bit indirect address register pointers for Data Space addressing - enabling efficient address calculations. One of these address pointers can also be used as an address pointer for look up tables in Flash program memory. These added function registers are the 16-bit X-, Y-, and Z-register, described later in this section. The ALU supports arithmetic and logic operations between registers or between a constant and a register. Single register operations can also be executed in the ALU. After an arithmetic operation, the Status Register is updated to reflect information about the result of the operation. Program flow is provided by conditional and unconditional jump and call instructions, able to directly address the whole address space. Most AVR instructions have a single 16-bit word format. Every program memory address contains a 16- or 32-bit instruction. Program Flash memory space is divided in two sections, the Boot Program section and the Application Program section. Both sections have dedicated Lock bits for write and read/write protection. The SPM instruction that writes into the Application Flash memory section must reside in the Boot Program section. During interrupts and subroutine calls, the return address Program Counter (PC) is stored on the Stack. The Stack is effectively allocated in the general data SRAM, and consequently the Stack size is only limited by the total SRAM size and the usage of the SRAM. All user programs must initialize the SP in the Reset routine (before subroutines or interrupts are executed). The Stack Pointer (SP) is read/write accessible in the I/O space. The data SRAM can easily be accessed through the five different addressing modes supported in the AVR architecture. The memory spaces in the AVR architecture are all linear and regular memory maps. A flexible interrupt module has its control registers in the I/O space with an additional Global Interrupt Enable bit in the Status Register. All interrupts have a separate Interrupt Vector in the Interrupt Vector table. The interrupts have priority in accordance with their Interrupt Vector position. The lower the Interrupt Vector address, the higher the priority. The I/O memory space contains 64 addresses for CPU peripheral functions as Control Registers, SPI, and other I/O functions. The I/O Memory can be accessed directly, or as the Data Space locations following those of the Register File, 0x20 - 0x5F. In addition, the AT90USB82/162 has Extended I/O space from 0x60 - 0xFF in SRAM where only the ST/STS/STD and LD/LDS/LDD instructions can be used.
4.3
ALU - Arithmetic Logic Unit
The high-performance AVR ALU operates in direct connection with all the 32 general purpose working registers. Within a single clock cycle, arithmetic operations between general purpose registers or between a register and an immediate are executed. The ALU operations are divided into three main categories - arithmetic, logical, and bit-functions. See the "Instruction Set" section for a detailed description.
4.4
Status Register
The Status Register contains information about the result of the most recently executed arithmetic instruction. This information can be used for altering program flow in order to perform
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conditional operations. Note that the Status Register is updated after all ALU operations, as specified in the Instruction Set Reference. This will in many cases remove the need for using the dedicated compare instructions, resulting in faster and more compact code. The Status Register is not automatically stored when entering an interrupt routine and restored when returning from an interrupt. This must be handled by software. The AVR Status Register - SREG - is defined as:
Bit Read/Write Initial Value 7 I R/W 0 6 T R/W 0 5 H R/W 0 4 S R/W 0 3 V R/W 0 2 N R/W 0 1 Z R/W 0 0 C R/W 0 SREG
* Bit 7 - I: Global Interrupt Enable The Global Interrupt Enable bit must be set for the interrupts to be enabled. The individual interrupt enable control is then performed in separate control registers. If the Global Interrupt Enable Register is cleared, none of the interrupts are enabled independent of the individual interrupt enable settings. The I-bit is cleared by hardware after an interrupt has occurred, and is set by the RETI instruction to enable subsequent interrupts. The I-bit can also be set and cleared by the application with the SEI and CLI instructions, as described in the instruction set reference. * Bit 6 - T: Bit Copy Storage The Bit Copy instructions BLD (Bit LoaD) and BST (Bit STore) use the T-bit as source or destination for the operated bit. A bit from a register in the Register File can be copied into T by the BST instruction, and a bit in T can be copied into a bit in a register in the Register File by the BLD instruction. * Bit 5 - H: Half Carry Flag The Half Carry Flag H indicates a Half Carry in some arithmetic operations. Half Carry Is useful in BCD arithmetic. See the "Instruction Set Description" for detailed information. * Bit 4 - S: Sign Bit, S = N V The S-bit is always an exclusive or between the Negative Flag N and the Two's Complement Overflow Flag V. See the "Instruction Set Description" for detailed information. * Bit 3 - V: Two's Complement Overflow Flag The Two's Complement Overflow Flag V supports two's complement arithmetics. See the "Instruction Set Description" for detailed information. * Bit 2 - N: Negative Flag The Negative Flag N indicates a negative result in an arithmetic or logic operation. See the "Instruction Set Description" for detailed information. * Bit 1 - Z: Zero Flag The Zero Flag Z indicates a zero result in an arithmetic or logic operation. See the "Instruction Set Description" for detailed information. * Bit 0 - C: Carry Flag The Carry Flag C indicates a carry in an arithmetic or logic operation. See the "Instruction Set Description" for detailed information.
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4.5 General Purpose Register File
The Register File is optimized for the AVR Enhanced RISC instruction set. In order to achieve the required performance and flexibility, the following input/output schemes are supported by the Register File: * One 8-bit output operand and one 8-bit result input * Two 8-bit output operands and one 8-bit result input * Two 8-bit output operands and one 16-bit result input * One 16-bit output operand and one 16-bit result input Figure 4-2 shows the structure of the 32 general purpose working registers in the CPU. Figure 4-2. AVR CPU General Purpose Working Registers
7 R0 R1 R2 ... R13 General Purpose Working Registers R14 R15 R16 R17 ... R26 R27 R28 R29 R30 R31 0x1A 0x1B 0x1C 0x1D 0x1E 0x1F X-register Low Byte X-register High Byte Y-register Low Byte Y-register High Byte Z-register Low Byte Z-register High Byte 0x0D 0x0E 0x0F 0x10 0x11 0 Addr. 0x00 0x01 0x02
Most of the instructions operating on the Register File have direct access to all registers, and most of them are single cycle instructions. As shown in Figure 4-2, each register is also assigned a data memory address, mapping them directly into the first 32 locations of the user Data Space. Although not being physically implemented as SRAM locations, this memory organization provides great flexibility in access of the registers, as the X-, Y- and Z-pointer registers can be set to index any register in the file. 4.5.1 The X-register, Y-register, and Z-register The registers R26..R31 have some added functions to their general purpose usage. These registers are 16-bit address pointers for indirect addressing of the data space. The three indirect address registers X, Y, and Z are defined as described in Figure 4-3. Figure 4-3.
X-register
The X-, Y-, and Z-registers
15 7 R27 (0x1B) XH 0 7 R26 (0x1A) XL 0 0
15
YH
YL
0
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Y-register
7 R29 (0x1D) 15 ZH 0
0
7 R28 (0x1C) ZL 7 R30 (0x1E) 0
0
0
Z-register
7 R31 (0x1F)
In the different addressing modes these address registers have functions as fixed displacement, automatic increment, and automatic decrement (see the instruction set reference for details).
4.6
Stack Pointer
The Stack is mainly used for storing temporary data, for storing local variables and for storing return addresses after interrupts and subroutine calls. The Stack Pointer Register always points to the top of the Stack. Note that the Stack is implemented as growing from higher memory locations to lower memory locations. This implies that a Stack PUSH command decreases the Stack Pointer. The Stack Pointer points to the data SRAM Stack area where the Subroutine and Interrupt Stacks are located. This Stack space in the data SRAM must be defined by the program before any subroutine calls are executed or interrupts are enabled. The Stack Pointer must be set to point above 0x0100. The initial value of the stack pointer is the last address of the internal SRAM. The Stack Pointer is decremented by one when data is pushed onto the Stack with the PUSH instruction, and it is decremented by three when the return address is pushed onto the Stack with subroutine call or interrupt. The Stack Pointer is incremented by one when data is popped from the Stack with the POP instruction, and it is incremented by three when data is popped from the Stack with return from subroutine RET or return from interrupt RETI. The AVR Stack Pointer is implemented as two 8-bit registers in the I/O space. The number of bits actually used is implementation dependent. Note that the data space in some implementations of the AVR architecture is so small that only SPL is needed. In this case, the SPH Register will not be present.
Bit 15 SP15 SP7 7 Read/Write Initial Value R/W R/W 0 1 14 SP14 SP6 6 R/W R/W 0 1 13 SP13 SP5 5 R/W R/W 1 1 12 SP12 SP4 4 R/W R/W 0 1 11 SP11 SP3 3 R/W R/W 0 1 10 SP10 SP2 2 R/W R/W 0 1 9 SP9 SP1 1 R/W R/W 0 1 8 SP8 SP0 0 R/W R/W 0 1 SPH SPL
4.7
Instruction Execution Timing
This section describes the general access timing concepts for instruction execution. The AVR CPU is driven by the CPU clock clkCPU, directly generated from the selected clock source for the chip. No internal clock division is used. Figure 4-4 shows the parallel instruction fetches and instruction executions enabled by the Harvard architecture and the fast-access Register File concept. This is the basic pipelining concept to obtain up to 1 MIPS per MHz with the corresponding unique results for functions per cost, functions per clocks, and functions per power-unit.
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Figure 4-4. The Parallel Instruction Fetches and Instruction Executions
T1 T2 T3 T4
clkCPU 1st Instruction Fetch 1st Instruction Execute 2nd Instruction Fetch 2nd Instruction Execute 3rd Instruction Fetch 3rd Instruction Execute 4th Instruction Fetch
Figure 4-5 shows the internal timing concept for the Register File. In a single clock cycle an ALU operation using two register operands is executed, and the result is stored back to the destination register. Figure 4-5. Single Cycle ALU Operation
T1 T2 T3 T4
clkCPU Total Execution Time Register Operands Fetch ALU Operation Execute Result Write Back
4.8
Reset and Interrupt Handling
The AVR provides several different interrupt sources. These interrupts and the separate Reset Vector each have a separate program vector in the program memory space. All interrupts are assigned individual enable bits which must be written logic one together with the Global Interrupt Enable bit in the Status Register in order to enable the interrupt. Depending on the Program Counter value, interrupts may be automatically disabled when Boot Lock bits BLB02 or BLB12 are programmed. This feature improves software security. See the section "Memory Programming" on page 243 for details. The lowest addresses in the program memory space are by default defined as the Reset and Interrupt Vectors. The complete list of vectors is shown in "Interrupts" on page 63. The list also determines the priority levels of the different interrupts. The lower the address the higher is the priority level. RESET has the highest priority, and next is INT0 - the External Interrupt Request 0. The Interrupt Vectors can be moved to the start of the Boot Flash section by setting the IVSEL bit in the MCU Control Register (MCUCR). Refer to "Interrupts" on page 63 for more information. The Reset Vector can also be moved to the start of the Boot Flash section by programming the BOOTRST Fuse, see "Memory Programming" on page 243. When an interrupt occurs, the Global Interrupt Enable I-bit is cleared and all interrupts are disabled. The user software can write logic one to the I-bit to enable nested interrupts. All enabled interrupts can then interrupt the current interrupt routine. The I-bit is automatically set when a Return from Interrupt instruction - RETI - is executed. 13
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There are basically two types of interrupts. The first type is triggered by an event that sets the Interrupt Flag. For these interrupts, the Program Counter is vectored to the actual Interrupt Vector in order to execute the interrupt handling routine, and hardware clears the corresponding Interrupt Flag. Interrupt Flags can also be cleared by writing a logic one to the flag bit position(s) to be cleared. If an interrupt condition occurs while the corresponding interrupt enable bit is cleared, the Interrupt Flag will be set and remembered until the interrupt is enabled, or the flag is cleared by software. Similarly, if one or more interrupt conditions occur while the Global Interrupt Enable bit is cleared, the corresponding Interrupt Flag(s) will be set and remembered until the Global Interrupt Enable bit is set, and will then be executed by order of priority. The second type of interrupts will trigger as long as the interrupt condition is present. These interrupts do not necessarily have Interrupt Flags. If the interrupt condition disappears before the interrupt is enabled, the interrupt will not be triggered. When the AVR exits from an interrupt, it will always return to the main program and execute one more instruction before any pending interrupt is served. Note that the Status Register is not automatically stored when entering an interrupt routine, nor restored when returning from an interrupt routine. This must be handled by software. When using the CLI instruction to disable interrupts, the interrupts will be immediately disabled. No interrupt will be executed after the CLI instruction, even if it occurs simultaneously with the CLI instruction. The following example shows how this can be used to avoid interrupts during the timed EEPROM write sequence.. Assembly Code Example
in r16, SREG cli sbi EECR, EEMPE sbi EECR, EEPE out SREG, r16 ; restore SREG value (I-bit) ; store SREG value ; start EEPROM write ; disable interrupts during timed sequence
C Code Example
char cSREG; cSREG = SREG; /* store SREG value */ /* disable interrupts during timed sequence */ __disable_interrupt(); EECR |= (1<When using the SEI instruction to enable interrupts, the instruction following SEI will be executed before any pending interrupts, as shown in this example.
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Assembly Code Example
sei ; set Global Interrupt Enable sleep; enter sleep, waiting for interrupt ; note: will enter sleep before any pending ; interrupt(s)
C Code Example
__enable_interrupt(); /* set Global Interrupt Enable */ __sleep(); /* enter sleep, waiting for interrupt */ /* note: will enter sleep before any pending interrupt(s) */
4.8.1
Interrupt Response Time The interrupt execution response for all the enabled AVR interrupts is five clock cycles minimum. After five clock cycles the program vector address for the actual interrupt handling routine is executed. During these five clock cycle period, the Program Counter is pushed onto the Stack. The vector is normally a jump to the interrupt routine, and this jump takes three clock cycles. If an interrupt occurs during execution of a multi-cycle instruction, this instruction is completed before the interrupt is served. If an interrupt occurs when the MCU is in sleep mode, the interrupt execution response time is increased by five clock cycles. This increase comes in addition to the start-up time from the selected sleep mode. A return from an interrupt handling routine takes three clock cycles. During these three clock cycles, the Program Counter (three bytes) is popped back from the Stack, the Stack Pointer is incremented by three, and the I-bit in SREG is set.
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5. AVR AT90USB82/162 Memories
This section describes the different memories in the AT90USB82/162. The AVR architecture has two main memory spaces, the Data Memory and the Program Memory space. In addition, the AT90USB82/162 features an EEPROM Memory for data storage. All three memory spaces are linear and regular.
5.1
In-System Reprogrammable Flash Program Memory
The AT90USB82/162 contains 8K / 16K bytes On-chip In-System Reprogrammable Flash memory for program storage. Since all AVR instructions are 16 or 32 bits wide, the Flash is organized as 4K x 16, 8K x 16. For software security, the Flash Program memory space is divided into two sections, Boot Program section and Application Program section. The Flash memory has an endurance of at least 100,000 write/erase cycles. The AT90USB82/162 Program Counter (PC) is 16 bits wide, thus addressing the 8K / 16K program memory locations. The operation of Boot Program section and associated Boot Lock bits for software protection are described in detail in "Memory Programming" on page 243. "Memory Programming" on page 243 contains a detailed description on Flash data serial downloading using the SPI pins or the debugWIRE interface. Constant tables can be allocated within the entire program memory address space (see the LPM - Load Program Memory instruction description and ELPM - Extended Load Program Memory instruction description). Timing diagrams for instruction fetch and execution are presented in "Instruction Execution Timing" on page 12.
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Figure 5-1. Program Memory Map
Program Memory 0x00000
Application Flash Section
Boot Flash Section 0x3FFF (16KBytes) 0x1FFF (8KBytes)
5.2
SRAM Data Memory
Figure 5-2 shows how the AT90USB82/162 SRAM Memory is organized. The AT90USB82/162 is a complex microcontroller with more peripheral units than can be supported within the 64 location reserved in the Opcode for the IN and OUT instructions. For the Extended I/O space from $060 - $0FF in SRAM, only the ST/STS/STD and LD/LDS/LDD instructions can be used. The first 768 Data Memory locations address the Register File, the I/O Memory, Extended I/O Memory, and the internal data SRAM. The first 32 locations address the Register file, the next 64 location the standard I/O Memory, then 160 locations of Extended I/O memory, and the 512 locations of internal data SRAM.The five different addressing modes for the data memory cover: Direct, Indirect with Displacement, Indirect, Indirect with Pre-decrement, and Indirect with Postincrement. In the Register file, registers R26 to R31 feature the indirect addressing pointer registers. The direct addressing reaches the entire data space. The Indirect with Displacement mode reaches 63 address locations from the base address given by the Y- or Z-register. When using register indirect addressing modes with automatic pre-decrement and post-increment, the address registers X, Y, and Z are decremented or incremented.
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The 32 general purpose working registers, 64 I/O registers, and the 512 bytes of internal data SRAM in the AT90USB82/162 are all accessible through all these addressing modes. The Register File is described in "General Purpose Register File" on page 11. Figure 5-2. Data Memory Map
Data Memory
32 Registers 64 I/O Registers 160 E xt I/O Reg. Internal S RAM (512 x 8) $2FF $0000 - $001F $0020 - $005F $0060 - $00FF $0100
5.2.1
Data Memory Access Times This section describes the general access timing concepts for internal memory access. The internal data SRAM access is performed in two clkCPU cycles as described in Figure 5-3. Figure 5-3. On-chip Data SRAM Access Cycles
T1 T2 T3
clkCPU Address Data WR Data RD
Compute Address Address valid
Memory Access Instruction
Next Instruction
5.3
EEPROM Data Memory
The AT90USB82/162 contains 512 bytes of data EEPROM memory. It is organized as a separate data space, in which single bytes can be read and written. The EEPROM has an endurance of at least 100,000 write/erase cycles. The access between the EEPROM and the CPU is described in the following, specifying the EEPROM Address Registers, the EEPROM Data Register, and the EEPROM Control Register.
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Read
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Write
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For a detailed description of SPI, debugWIRE and Parallel data downloading to the EEPROM, see page 257, page 241, and page 246 respectively. 5.3.1 EEPROM Read/Write Access The EEPROM Access Registers are accessible in the I/O space. The write access time for the EEPROM is given in Table 5-2. A self-timing function, however, lets the user software detect when the next byte can be written. If the user code contains instructions that write the EEPROM, some precautions must be taken. In heavily filtered power supplies, VCC is likely to rise or fall slowly on power-up/down. This causes the device for some period of time to run at a voltage lower than specified as minimum for the clock frequency used. See "Preventing EEPROM Corruption" on page 23. for details on how to avoid problems in these situations. In order to prevent unintentional EEPROM writes, a specific write procedure must be followed. Refer to the description of the EEPROM Control Register for details on this. When the EEPROM is read, the CPU is halted for four clock cycles before the next instruction is executed. When the EEPROM is written, the CPU is halted for two clock cycles before the next instruction is executed. 5.3.2 The EEPROM Address Register - EEARH and EEARL
Bit 15 - EEAR7 7 Read/Write Initial Value R R/W 0 X 14 - EEAR6 6 R R/W 0 X 13 - EEAR5 5 R R/W 0 X 12 - EEAR4 4 R R/W 0 X 11 EEAR11 EEAR3 3 R/W R/W X X 10 EEAR10 EEAR2 2 R/W R/W X X 9 EEAR9 EEAR1 1 R/W R/W X X 8 EEAR8 EEAR0 0 R/W R/W X X EEARH EEARL
* Bits 15..12 - Res: Reserved Bits These bits are reserved bits in the AT90USB82/162 and will always read as zero. * Bits 11..0 - EEAR8..0: EEPROM Address The EEPROM Address Registers - EEARH and EEARL specify the EEPROM address in the 512 bytes EEPROM space. The EEPROM data bytes are addressed linearly between 0 and 512. The initial value of EEAR is undefined. A proper value must be written before the EEPROM may be accessed. 5.3.3 The EEPROM Data Register - EEDR
Bit Read/Write Initial Value 7 MSB R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 LSB R/W 0 EEDR
* Bits 7..0 - EEDR7.0: EEPROM Data For the EEPROM write operation, the EEDR Register contains the data to be written to the EEPROM in the address given by the EEAR Register. For the EEPROM read operation, the EEDR contains the data read out from the EEPROM at the address given by EEAR.
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5.3.4
The EEPROM Control Register - EECR
Bit Read/Write Initial Value 7 - R 0 6 - R 0 5 EEPM1 R/W X 4 EEPM0 R/W X 3 EERIE R/W 0 2 EEMPE R/W 0 1 EEPE R/W X 0 EERE R/W 0 EECR
* Bits 7..6 - Res: Reserved Bits These bits are reserved bits in the AT90USB82/162 and will always read as zero. * Bits 5, 4 - EEPM1 and EEPM0: EEPROM Programming Mode Bits The EEPROM Programming mode bit setting defines which programming action that will be triggered when writing EEPE. It is possible to program data in one atomic operation (erase the old value and program the new value) or to split the Erase and Write operations in two different operations. The Programming times for the different modes are shown in Table 5-1. While EEPE is set, any write to EEPMn will be ignored. During reset, the EEPMn bits will be reset to 0b00 unless the EEPROM is busy programming.
Table 5-1.
EEPM1 0 0 1 1
EEPROM Mode Bits
EEPM0 0 1 0 1 Programming Time 3.4 ms 1.8 ms 1.8 ms - Operation Erase and Write in one operation (Atomic Operation) Erase Only Write Only Reserved for future use
* Bit 3 - EERIE: EEPROM Ready Interrupt Enable Writing EERIE to one enables the EEPROM Ready Interrupt if the I bit in SREG is set. Writing EERIE to zero disables the interrupt. The EEPROM Ready interrupt generates a constant interrupt when EEPE is cleared. * Bit 2 - EEMPE: EEPROM Master Programming Enable The EEMPE bit determines whether setting EEPE to one causes the EEPROM to be written. When EEMPE is set, setting EEPE within four clock cycles will write data to the EEPROM at the selected address If EEMPE is zero, setting EEPE will have no effect. When EEMPE has been written to one by software, hardware clears the bit to zero after four clock cycles. See the description of the EEPE bit for an EEPROM write procedure. * Bit 1 - EEPE: EEPROM Programming Enable The EEPROM Write Enable Signal EEPE is the write strobe to the EEPROM. When address and data are correctly set up, the EEPE bit must be written to one to write the value into the EEPROM. The EEMPE bit must be written to one before a logical one is written to EEPE, otherwise no EEPROM write takes place. The following procedure should be followed when writing the EEPROM (the order of steps 3 and 4 is not essential): 1. Wait until EEPE becomes zero. 2. Wait until SELFPRGEN in SPMCSR becomes zero. 3. Write new EEPROM address to EEAR (optional).
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4. Write new EEPROM data to EEDR (optional). 5. Write a logical one to the EEMPE bit while writing a zero to EEPE in EECR. 6. Within four clock cycles after setting EEMPE, write a logical one to EEPE. The EEPROM can not be programmed during a CPU write to the Flash memory. The software must check that the Flash programming is completed before initiating a new EEPROM write. Step 2 is only relevant if the software contains a Boot Loader allowing the CPU to program the Flash. If the Flash is never being updated by the CPU, step 2 can be omitted. See "Memory Programming" on page 243 for details about Boot programming. Caution: An interrupt between step 5 and step 6 will make the write cycle fail, since the EEPROM Master Write Enable will time-out. If an interrupt routine accessing the EEPROM is interrupting another EEPROM access, the EEAR or EEDR Register will be modified, causing the interrupted EEPROM access to fail. It is recommended to have the Global Interrupt Flag cleared during all the steps to avoid these problems. When the write access time has elapsed, the EEPE bit is cleared by hardware. The user software can poll this bit and wait for a zero before writing the next byte. When EEPE has been set, the CPU is halted for two cycles before the next instruction is executed. * Bit 0 - EERE: EEPROM Read Enable The EEPROM Read Enable Signal EERE is the read strobe to the EEPROM. When the correct address is set up in the EEAR Register, the EERE bit must be written to a logic one to trigger the EEPROM read. The EEPROM read access takes one instruction, and the requested data is available immediately. When the EEPROM is read, the CPU is halted for four cycles before the next instruction is executed. The user should poll the EEPE bit before starting the read operation. If a write operation is in progress, it is neither possible to read the EEPROM, nor to change the EEAR Register. The calibrated Oscillator is used to time the EEPROM accesses. Table 5-2 lists the typical programming time for EEPROM access from the CPU. Table 5-2.
Symbol EEPROM write (from CPU)
EEPROM Programming Time
Number of Calibrated RC Oscillator Cycles 26,368 Typ Programming Time 3.3 ms
The following code examples show one assembly and one C function for writing to the EEPROM. The examples assume that interrupts are controlled (e.g. by disabling interrupts globally) so that no interrupts will occur during execution of these functions. The examples also
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assume that no Flash Boot Loader is present in the software. If such code is present, the EEPROM write function must also wait for any ongoing SPM command to finish. Assembly Code Example(1)
EEPROM_write: ; Wait for completion of previous write sbic EECR,EEPE rjmp EEPROM_write ; Set up address (r18:r17) in address register out EEARH, r18 out EEARL, r17 ; Write data (r16) to Data Register out EEDR,r16 ; Write logical one to EEMPE sbi EECR,EEMPE ; Start eeprom write by setting EEPE sbi EECR,EEPE ret
C Code Example(1)
void EEPROM_write(unsigned int uiAddress, unsigned char ucData) { /* Wait for completion of previous write */ while(EECR & (1<22
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The next code examples show assembly and C functions for reading the EEPROM. The examples assume that interrupts are controlled so that no interrupts will occur during execution of these functions. Assembly Code Example(1)
EEPROM_read: ; Wait for completion of previous write sbic EECR,EEPE rjmp EEPROM_read ; Set up address (r18:r17) in address register out EEARH, r18 out EEARL, r17 ; Start eeprom read by writing EERE sbi EECR,EERE ; Read data from Data Register in ret r16,EEDR
C Code Example(1)
unsigned char EEPROM_read(unsigned int uiAddress) { /* Wait for completion of previous write */ while(EECR & (1<5.3.5
Preventing EEPROM Corruption During periods of low VCC, the EEPROM data can be corrupted because the supply voltage is too low for the CPU and the EEPROM to operate properly. These issues are the same as for board level systems using EEPROM, and the same design solutions should be applied. An EEPROM data corruption can be caused by two situations when the voltage is too low. First, a regular write sequence to the EEPROM requires a minimum voltage to operate correctly. Secondly, the CPU itself can execute instructions incorrectly, if the supply voltage is too low. EEPROM data corruption can easily be avoided by following this design recommendation: Keep the AVR RESET active (low) during periods of insufficient power supply voltage. This can be done by enabling the internal Brown-out Detector (BOD). If the detection level of the internal BOD does not match the needed detection level, an external low VCC reset Protection circuit can
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be used. If a reset occurs while a write operation is in progress, the write operation will be completed provided that the power supply voltage is sufficient.
5.4
I/O Memory
The I/O space definition of the AT90USB82/162 is shown in "Register Summary" on page 288. All AT90USB82/162 I/Os and peripherals are placed in the I/O space. All I/O locations may be accessed by the LD/LDS/LDD and ST/STS/STD instructions, transferring data between the 32 general purpose working registers and the I/O space. I/O Registers within the address range 0x00 - 0x1F are directly bit-accessible using the SBI and CBI instructions. In these registers, the value of single bits can be checked by using the SBIS and SBIC instructions. Refer to the instruction set section for more details. When using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be used. When addressing I/O Registers as data space using LD and ST instructions, 0x20 must be added to these addresses. The AT90USB82/162 is a complex microcontroller with more peripheral units than can be supported within the 64 location reserved in Opcode for the IN and OUT instructions. For the Extended I/O space from 0x60 0x1FF in SRAM, only the ST/STS/STD and LD/LDS/LDD instructions can be used. For compatibility with future devices, reserved bits should be written to zero if accessed. Reserved I/O memory addresses should never be written. Some of the Status Flags are cleared by writing a logical one to them. Note that, unlike most other AVRs, the CBI and SBI instructions will only operate on the specified bit, and can therefore be used on registers containing such Status Flags. The CBI and SBI instructions work with registers 0x00 to 0x1F only. The I/O and peripherals control registers are explained in later sections.
5.4.1
General Purpose I/O Registers The AT90USB82/162 contains three General Purpose I/O Registers. These registers can be used for storing any information, and they are particularly useful for storing global variables and Status Flags. General Purpose I/O Registers within the address range 0x00 - 0x1F are directly bit-accessible using the SBI, CBI, SBIS, and SBIC instructions. General Purpose I/O Register 2 - GPIOR2
Bit Read/Write Initial Value 7 MSB R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 LSB R/W 0 GPIOR2
5.4.2
5.4.3
General Purpose I/O Register 1 - GPIOR1
Bit Read/Write Initial Value 7 MSB R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 LSB R/W 0 GPIOR1
5.4.4
General Purpose I/O Register 0 - GPIOR0
Bit Read/Write Initial Value 7 MSB R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 LSB R/W 0 GPIOR0
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6. System Clock and Clock Options
6.1 Clock Systems and their Distribution
Figure 6-1 presents the principal clock systems in the AVR and their distribution. All of the clocks need not be active at a given time. In order to reduce power consumption, the clocks to modules not being used can be halted by using different sleep modes, as described in "Power Management and Sleep Modes" on page 41. The clock systems are detailed below. Figure 6-1. Clock Distribution
General I/O Modules Flash and EEPROM
USB
CPU Core
RAM
clkUSB (48MHz) USB PLL X6
clkI/O
AVR Clock Control Unit
clkCPU clkFLASH
clkPllin (8MHz) PLL Clock Prescaler
Reset Logic
Watchdog Timer
Source clock System Clock Prescaler
Watchdog clock
clkXTAL (2-16 MHz)
Clock Multiplexer Clock Switch
Crystal Oscillator
External Clock
Watchdog Oscillator
Calibrated RC Oscillator
6.1.1
CPU Clock - clkCPU The CPU clock is routed to parts of the system concerned with operation of the AVR core. Examples of such modules are the General Purpose Register File, the Status Register and the data memory holding the Stack Pointer. Halting the CPU clock inhibits the core from performing general operations and calculations. I/O Clock - clkI/O The I/O clock is used by the majority of the I/O modules, like Timer/Counters, SPI, and USART. The I/O clock is also used by the External Interrupt module, but note that some external interrupts are detected by asynchronous logic, allowing such interrupts to be detected even if the I/O clock is halted. Flash Clock - clkFLASH The Flash clock controls operation of the Flash interface. The Flash clock is usually active simultaneously with the CPU clock.
6.1.2
6.1.3
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6.1.4
USB Clock - clkUSB The USB is provided with a dedicated clock domain. This clock is generated with an on-chip PLL running at 48MHz. The PLL always multiply its input frequency by 6. Thus the PLL clock register should be programmed by software to generate a 8MHz clock on the PLL input.
6.2
Clock Switch
In the AT90USB82/162 product, the Clock Multiplexer and the System Clock Prescaler can be modified by software.
6.2.1
Exemple of use The modification can occur when the device enters in USB Suspend mode. It then switches from External Clock to Calibrated RC Oscillator in order to reduce consumption. In such a configuration, the External Clock is disabled. The firmware can use the watchdog timer to be woken-up from power-down in order to check if there is an event on the application. If an event occurs on the application or if the USB controller signals a non-idle state on the USB line (Resume for example), the firmware switches the Clock Multiplexer from the Calibrated RC Oscillator to the External Clock. Figure 6-2. Example of clock switching with wake-up from USB Host resume
1 Resume from Host
USB CPU Clock External Oscillator RC oscillator
non-Idle
Idle Ext
(Suspend)
non-Idle
1
RC
Ext
3ms
watchdog wake-up from power-down
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Figure 6-3. Example of clock switching with wake-up from Device upstream-resume
2 Upstream Resume from device
USB CPU Clock External Oscillator RC oscillator
non-Idle
Idle Ext
(Suspend)
non-Idle
2
RC
Ext
3ms 6.2.2 6.2.2.1 Clock switch Algorythm Swith from external clock to RC clock
watchdog wake-up from power-down
if (Usb_suspend_detected()) { Usb_ack_suspend(); Usb_freeze_clock(); Disable_pll(); Enable_RC_clock(); while (!RC_clock_ready()); Select_RC_clock(); Disable_external_clock(); }
// if (UDINT.SUSPI == 1) // UDINT.SUSPI = 0; // USBCON.FRZCLK = 1; // PLLCSR.PLLE = 0; // CLKSEL0.RCE = 1; // while (CLKSTA.RCON != 1); // CLKSEL0.CLKS = 0; // CLKSEL0.EXTE = 0;
6.2.2.2
Switch from RC clock to external clock
if (Usb_wake_up_detected()) { Usb_ack_wake_up(); Enable_external_clock(); Select_external_clock(); Enable_pll(); Disable_RC_clock(); while (!Pll_ready()); Usb_unfreeze_clock(); } // UDINT.WAKEUPI = 0; // CLKSEL0.EXTE = 1; // CLKSEL0.CLKS = 1; // PLLCSR.PLLE = 1; // CLKSEL0.RCE = 0; // while (PLLCSR.PLOCK != 1); // USBCON.FRZCLK = 0; // if (UDINT.WAKEUPI == 1)
while (!External_clock_ready()); // while (CLKSTA.EXTON != 1);
6.2.3
Clock Selection Register 0 - CLKSEL0
Bit Read/Write Initial Value 7 RCSUT1 R/W 0 6 RCSUT0 R/W 0 5 EXSUT1 R/W 0 4 EXSUT0 R/W 0 3 RCE R/W 2 EXTE R/W 1 R 0 CLKS R/W CLKSEL0
See Bit Description
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* Bit 7-6 - RCSUT[1:0]: SUT for RC oscillator These 2 bits are the SUT value for the RC Oscillator. If the RC oscillator is selected by fuse bits, the SUT fuse are copied into these bits. A firmware change will not have any effect because this additionnal start-up time is only used after a reset and not after a clock switch. * Bit 5-4 - EXSUT[1:0]: SUT for External Oscillator / Low Power Oscillator These 2 bits are the SUT value for the External Oscillator / Low Power Oscillator. If the External oscillator / Low Power Oscillator is selected by fuse bits, the SUT fuse are copyed into these bits. The firmware can modify these bits by writing a new value. This value will be used at the next start of the External Oscillator / Low Power Oscillator. * Bit 3 - RCE: Enable RC Oscillator The RCE bit must be written to logic one to enable the RC Oscillator. The RCE bit must be written to logic zero to disable the RC Oscillator. * Bit 2 - EXTE: Enable External Oscillator / Low Power Oscillator The OSCE bit must be written to logic one to enable External Oscillator / Low Power Oscillator. The OSCE bit must be written to logic zero to disable the External Oscillator / Low Power Oscillator. * Bit 0 - CLKS: Clock Selector The CLKS bit must be written to logic one to select the External Oscillator / Low Power Oscillator as CPU clock. The CLKS bit must be written to logic zero to select the RC Oscillator as CPU clock. After a reset, the CLKS bit is set by hardware if the External Oscillator / Low Power Oscillator is selected by the fuse bits configuration. The firmware has to check if the clock is correctly started before selected it. 6.2.4 Clock Selection Register 1 - CLKSEL1
Bit 7 RCCKSE L3 Read/Write Initial Value R/W 0 6 RCCKS EL2 R/W 0 5 RCCLK SEL1 R/W 1 4 RCCLK SEL0 R/W 0 3 EXCKSE L3 R/W 0 2 EXCKSE L2 R/W 0 1 EXCLKS EL1 R/W 0 0 EXCLKS EL0 R/W 0 CLKSEL1
* Bit 7-4 - RCCKSEL[3:0]: CKSEL for RC oscillator Clock configuration for the RC Oscillator. After a reset, this part of the register is loaded with the 0010b value that corresponds to the RC oscillator. Modifying this value by firmware before switching to RC oscillator is prohibited because the RC clock will not start. * Bit 3-0 - EXCKSEL[3:0]: CKSEL for External oscillator / Low Power Oscillator Clock configuration for the External Oscillator / Low Power Oscillator. After a reset, if the External oscillator / Low Power Oscillator is selected by fuse bits, this part of the register is loaded with the fuse configuration. Firmware can modify it to change the start-up time after the clock switch.
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6.2.5 Clock Status Register - CLKSTA
Bit Read/Write Initial Value 7 R 0 6 R 0 5 R 0 4 R 0 3 R 2 R 1 RCON R 0 EXTON R CLKSTA
See Bit Description
* Bit 7-2 - Reserved bits These bits are reserved and will always read as zero. * Bit 1 - RCON: RC Oscillator On This bit is set by hardware to one if the RC Oscillator is running. This bit is set by hardware to zero if the RC Oscillator is stoped. * Bit 0 - EXTON: External Oscillator / Low Power Oscillator On This bit is set by hardware to one if the External Oscillator / Low Power Oscillator is running. This bit is set by hardware to zero if the External Oscillator / Low Power Oscillator is stoped.
6.3
Clock Sources
The device has the following clock source options, selectable by Flash Fuse bits as shown below. The clock from the selected source is input to the AVR clock generator, and routed to the appropriate modules. Table 6-1. Device Clocking Options Select(1)
CKSEL3..0 1111 - 1000 0111 - 0110 0101 - 0100 0011 0010 0000 0001
Device Clocking Option Low Power Crystal Oscillator Reserved Reserved Reserved Calibrated Internal RC Oscillator External Clock Reserved Note: 1. For all fuses "1" means unprogrammed while "0" means programmed.
6.3.1
Default Clock Source The device is shipped with low power crystal oscillator and with the fuse CKDIV8 programmed. The startup time is set to maximum and time-out period enabled. (CKSEL = "1110", SUT = "01", CKDIV8 = "0"). Clock Startup Sequence Any clock source needs a sufficient VCC to start oscillating and a minimum number of oscillating cycles before it can be considered stable. To ensure sufficient VCC, the device issues an internal reset with a time-out delay (tTOUT) after the device reset is released by all other reset sources. "On-chip Debug System" on page 45 describes the start conditions for the internal reset. The delay (tTOUT) is timed from the Watchdog Oscillator and the number of cycles in the delay is set by the SUTx and CKSELx fuse bits. The selectable delays are shown in Table 6-2. The frequency of the Watchdog Oscillator is voltage
6.3.2
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dependent as shown in "AT90USB82/162 Typical Characteristics - Preliminary Data" on page 268. Table 6-2. Number of Watchdog Oscillator Cycles
Typ Time-out (VCC = 3.0V) 0 ms 4.3 ms 69 ms Number of Cycles 0 512 8K (8,192) 0 ms 4.1 ms 65 ms
Typ Time-out (VCC = 5.0V)
Main purpose of the delay is to keep the AVR in reset until it is supplied with minimum Vcc. The delay will not monitor the actual voltage and it will be required to select a delay longer than the Vcc rise time. If this is not possible, an internal or external Brown-Out Detection circuit should be used. A BOD circuit will ensure sufficient Vcc before it releases the reset, and the time-out delay can be disabled. Disabling the time-out delay without utilizing a Brown-Out Detection circuit is not recommended. The oscillator is required to oscillate for a minimum number of cycles before the clock is considered stable. An internal ripple counter monitors the oscillator output clock, and keeps the internal reset active for a given number of clock cycles. The reset is then released and the device will start to execute. The recommended oscillator start-up time is dependent on the clock type, and varies from 6 cycles for an externally applied clock to 32K cycles for a low frequency crystal. The start-up sequence for the clock includes both the time-out delay and the start-up time when the device starts up from reset. When starting up from Power-save or Power-down mode, Vcc is assumed to be at a sufficient level and only the start-up time is included.
6.4
Low Power Crystal Oscillator
Pins XTAL1 and XTAL2 are input and output, respectively, of an inverting amplifier which can be configured for use as an On-chip Oscillator, as shown in Figure 6-4. Either a quartz crystal or a ceramic resonator may be used. This Crystal Oscillator is a low power oscillator, with reduced voltage swing on the XTAL2 output. It gives the lowest power consumption, but is not capable of driving other clock inputs, and may be more susceptible to noise in noisy environments. C1 and C2 should always be equal for both crystals and resonators. The optimal value of the capacitors depends on the crystal or resonator in use, the amount of stray capacitance, and the electromagnetic noise of the environment. Some initial guidelines for choosing capacitors for use with crystals are given in Table 6-3. For ceramic resonators, the capacitor values given by the manufacturer should be used.
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Figure 6-4. Crystal Oscillator Connections
C2 C1
XTAL2 XTAL1 GND
The Low Power Oscillator can operate in three different modes, each optimized for a specific frequency range. The operating mode is selected by the fuses CKSEL3..1 as shown in Table 6-3. Table 6-3. Low Power Crystal Oscillator Operating Modes(3)
CKSEL3..1 100(2) 101 110 111 Recommended Range for Capacitors C1 and C2 (pF) - 12 - 22 12 - 22 12 - 22
Frequency Range(1) (MHz) 0.4 - 0.9 0.9 - 3.0 3.0 - 8.0 8.0 - 16.0 Notes:
1. The frequency ranges are preliminary values. Actual values are TBD. 2. This option should not be used with crystals, only with ceramic resonators. 3. If 8 MHz frequency exceeds the specification of the device (depends on VCC), the CKDIV8 Fuse can be programmed in order to divide the internal frequency by 8. It must be ensured that the resulting divided clock meets the frequency specification of the device.
The CLKSEL0 Fuse together with the SUT1..0 Fuses select the start-up times as shown in Table 6-4.
Table 6-4.
Start-up Times for the Low Power Crystal Oscillator Clock Selection
Start-up Time from Power-down and Power-save 258 CK 258 CK 1K CK 1K CK 1K CK Additional Delay from Reset (VCC = 5.0V) 14CK + 4.1 ms(1) 14CK + 65 ms(1) 14CK(2) 14CK + 4.1 ms(2) 14CK + 65 ms(2) CLKSEL 0 0 0 0 0 1
Oscillator Source / Power Conditions Ceramic resonator, fast rising power Ceramic resonator, slowly rising power Ceramic resonator, BOD enabled Ceramic resonator, fast rising power Ceramic resonator, slowly rising power
SUT1..0 00 01 10 11 00
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Table 6-4.
Start-up Times for the Low Power Crystal Oscillator Clock Selection (Continued)
Start-up Time from Power-down and Power-save 16K CK 16K CK 16K CK Additional Delay from Reset (VCC = 5.0V) 14CK 14CK + 4.1 ms 14CK + 65 ms CLKSEL 0 1 1 1
Oscillator Source / Power Conditions Crystal Oscillator, BOD enabled Crystal Oscillator, fast rising power Crystal Oscillator, slowly rising power Notes:
SUT1..0 01 10 11
1. These options should only be used when not operating close to the maximum frequency of the device, and only if frequency stability at start-up is not important for the application. These options are not suitable for crystals. 2. These options are intended for use with ceramic resonators and will ensure frequency stability at start-up. They can also be used with crystals when not operating close to the maximum frequency of the device, and if frequency stability at start-up is not important for the application.
Table 6-5.
Start-up times for the internal calibrated RC Oscillator clock selection
Start-up Time from Powerdown and Power-save 6 CK 6 CK 6 CK Reserved Additional Delay from Reset (VCC = 5.0V) 14CK 14CK + 4.1 ms 14CK + 65 ms
(1)
Power Conditions BOD enabled Fast rising power Slowly rising power Note:
SUT1..0 00 01 10 11
1. The device is shipped with this option selected.
6.5
Calibrated Internal RC Oscillator
The calibrated internal RC Oscillator by default provides a 8.0 MHz clock. The frequency is nominal value at 3.0V and 25C. At 3.0V and 25C, this calibration gives a frequency of 8 MHz 10%. The device is shipped with the CKDIV8 Fuse programmed. See "System Clock Prescaler" on page 34 for more details. This clock may be selected as the system clock by programming the CKSEL Fuses as shown in Table 6-6. If selected, it will operate with no external components. During reset, hardware loads the calibration byte into the OSCCAL Register and thereby automatically calibrates the RC Oscillator. At 3.3V and 25C, this calibration gives a frequency of 8 MHz 1%. The oscillator can be calibrated to any frequency in the range 7.3 - 8.1 MHz within 1% accuracy, by changing the OSCCAL register. When this Oscillator is used as the chip clock, the Watchdog Oscillator will still be used for the Watchdog Timer and for the Reset Time-out. For more information on the pre-programmed calibration value, see the section "Calibration Byte" on page 246
Table 6-6. Internal Calibrated RC Oscillator Operating Modes(1)(3)
Frequency Range(2) (MHz) 7.3 - 8.1 Notes: 1. The device is shipped with this option selected. 2. The frequency ranges are preliminary values. Actual values are TBD. CKSEL3..0 0010
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3. If 8 MHz frequency exceeds the specification of the device (depends on VCC), the CKDIV8 Fuse can be programmed in order to divide the internal frequency by 8.
When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in Table 6-5 on page 32. Table 6-7. Start-up times for the internal calibrated RC Oscillator clock selection
Start-up Time from Powerdown and Power-save 6 CK 6 CK 6 CK Reserved Note: 1. The device is shipped with this option selected. Additional Delay from Reset (VCC = 5.0V) 14 CK 14 CK + 4.1 ms 14 CK + 65 ms
(1)
Power Conditions BOD enabled Fast rising power Slowly rising power
SUT1..0 00 01 10 11
6.5.1
Oscillator Calibration Register - OSCCAL
Bit Read/Write Initial Value 7 CAL7 R/W 6 CAL6 R/W 5 CAL5 R/W 4 CAL4 R/W 3 CAL3 R/W 2 CAL2 R/W 1 CAL1 R/W 0 CAL0 R/W OSCCAL
Device Specific Calibration Value
* Bits 7..0 - CAL7..0: Oscillator Calibration Value The Oscillator Calibration Register is used to trim the Calibrated Internal RC Oscillator to remove process variations from the oscillator frequency. The factory-calibrated value is automatically written to this register during chip reset, giving an oscillator frequency of 8.0 MHz at 25C. The application software can write this register to change the oscillator frequency. The oscillator can be calibrated to any frequency in the range 7.3 - 8.1 MHz within 1% accuracy. Calibration outside that range is not guaranteed. Note that this oscillator is used to time EEPROM and Flash write accesses, and these write times will be affected accordingly. If the EEPROM or Flash are written, do not calibrate to more than 8.8 MHz. Otherwise, the EEPROM or Flash write may fail. The CAL7 bit determines the range of operation for the oscillator. Setting this bit to 0 gives the lowest frequency range, setting this bit to 1 gives the highest frequency range. The two frequency ranges are overlapping, in other words a setting of OSCCAL = 0x7F gives a higher frequency than OSCCAL = 0x80. The CAL6..0 bits are used to tune the frequency within the selected range. A setting of 0x00 gives the lowest frequency in that range, and a setting of 0x7F gives the highest frequency in the range. Incrementing CAL6..0 by 1 will give a frequency increment of less than 2% in the frequency range 7.3 - 8.1 MHz.
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6.6
External Clock
The device can utilize a external clock source as shown in Figure 6-5. To run the device on an external clock, the CKSEL Fuses must be programmed as shown in Table 6-1. Figure 6-5. External Clock Drive Configuration
NC
XTAL2
EXTERNAL CLOCK SIGNAL
XTAL1
GND
When this clock source is selected, start-up times are determined by the SUT Fuses as shown in Table 6-8. Table 6-8. Start-up Times for the External Clock Selection
Start-up Time from Powerdown and Power-save 6 CK 6 CK 6 CK Reserved Additional Delay from Reset (VCC = 5.0V) 14CK 14CK + 4.1 ms 14CK + 65 ms SUT1..0 00 01 10 11
Power Conditions BOD enabled Fast rising power Slowly rising power
When applying an external clock, it is required to avoid sudden changes in the applied clock frequency to ensure stable operation of the MCU. A variation in frequency of more than 2% from one clock cycle to the next can lead to unpredictable behavior. If changes of more than 2% is required, ensure that the MCU is kept in Reset during the changes. Note that the System Clock Prescaler can be used to implement run-time changes of the internal clock frequency while still ensuring stable operation. Refer to "System Clock Prescaler" on page 34 for details.
6.7
Clock Output Buffer
The device can output the system clock on the CLKO pin. To enable the output, the CKOUT Fuse has to be programmed. This mode is suitable when the chip clock is used to drive other circuits on the system. The clock also will be output during reset, and the normal operation of I/O pin will be overridden when the fuse is programmed. Any clock source, including the internal RC Oscillator, can be selected when the clock is output on CLKO. If the System Clock Prescaler is used, it is the divided system clock that is output.
6.8
System Clock Prescaler
The AT90USB82/162 has a system clock prescaler, and the system clock can be divided by setting the "Clock Prescale Register - CLKPR" on page 35. This feature can be used to decrease
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the system clock frequency and the power consumption when the requirement for processing power is low. This can be used with all clock source options, and it will affect the clock frequency of the CPU and all synchronous peripherals. clkI/O, clkCPU, and clkFLASH are divided by a factor as shown in Table 6-9. When switching between prescaler settings, the System Clock Prescaler ensures that no glitches occurs in the clock system. It also ensures that no intermediate frequency is higher than neither the clock frequency corresponding to the previous setting, nor the clock frequency corresponding to the new setting. The ripple counter that implements the prescaler runs at the frequency of the undivided clock, which may be faster than the CPU's clock frequency. Hence, it is not possible to determine the state of the prescaler - even if it were readable, and the exact time it takes to switch from one clock division to the other cannot be exactly predicted. From the time the CLKPS values are written, it takes between T1 + T2 and T1 + 2 * T2 before the new clock frequency is active. In this interval, 2 active clock edges are produced. Here, T1 is the previous clock period, and T2 is the period corresponding to the new prescaler setting. To avoid unintentional changes of clock frequency, a special write procedure must be followed to change the CLKPS bits: 1. Write the Clock Prescaler Change Enable (CLKPCE) bit to one and all other bits in CLKPR to zero. 2. Within four cycles, write the desired value to CLKPS while writing a zero to CLKPCE. Interrupts must be disabled when changing prescaler setting to make sure the write procedure is not interrupted. 6.8.1 Clock Prescale Register - CLKPR
Bit Read/Write Initial Value 7 CLKPCE R/W 0 6 - R 0 5 - R 0 4 - R 0 3 CLKPS3 R/W 2 CLKPS2 R/W 1 CLKPS1 R/W 0 CLKPS0 R/W CLKPR
See Bit Description
* Bit 7 - CLKPCE: Clock Prescaler Change Enable The CLKPCE bit must be written to logic one to enable change of the CLKPS bits. The CLKPCE bit is only updated when the other bits in CLKPR are simultaneously written to zero. CLKPCE is cleared by hardware four cycles after it is written or when CLKPS bits are written. Rewriting the CLKPCE bit within this time-out period does neither extend the time-out period, nor clear the CLKPCE bit. * Bit 6-4 - Reserved bits These bits are reserved and will always read as zero. * Bits 3..0 - CLKPS3..0: Clock Prescaler Select Bits 3 - 0 These bits define the division factor between the selected clock source and the internal system clock. These bits can be written run-time to vary the clock frequency to suit the application requirements. As the divider divides the master clock input to the MCU, the speed of all synchronous peripherals is reduced when a division factor is used. The division factors are given in Table 6-9. The CKDIV8 Fuse determines the initial value of the CLKPS bits. If CKDIV8 is unprogrammed, the CLKPS bits will be reset to "0000". If CKDIV8 is programmed, CLKPS bits are reset to
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"0011", giving a division factor of 8 at start up. This feature should be used if the selected clock source has a higher frequency than the maximum frequency of the device at the present operating conditions. Note that any value can be written to the CLKPS bits regardless of the CKDIV8 Fuse setting. The Application software must ensure that a sufficient division factor is chosen if the selected clock source has a higher frequency than the maximum frequency of the device at the present operating conditions. The device is shipped with the CKDIV8 Fuse programmed.
Table 6-9.
CLKPS3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
Clock Prescaler Select
CLKPS2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 CLKPS1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 CLKPS0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 Clock Division Factor 1 2 4 8 16 32 64 128 256 Reserved Reserved Reserved Reserved Reserved Reserved Reserved
6.9
PLL
The PLL is used to generate internal high frequency (48 MHz) clock for USB interface, the PLL input is generated from an external low-frequency (the crystal oscillator or external clock input pin from XTAL1).
6.9.1
Internal PLL for USB interface The internal PLL in AT90USB82/162 generates a clock frequency that is 6x multiplied from nominally 8 MHz input. The source of the 8 MHz PLL input clock is the output of the internal PLL clock prescaler that generates the 8 MHz.
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Figure 6-6. PLL Clocking System
PLLE PLOCK
Lock Detector
PLL clock Prescaler
clk 8MHz
PLL 6x
clk USB (48MHz)
System Clock
Clock Mux (fuse) Clock Switch XTAL2 XTAL1 Int RC 8MHz.
XTAL
Ext.
6.9.2
PLL Control and Status Register - PLLCSR
Bit $29 ($29) Read/Write Initial Value R 0 R 0 R 0 7 6 5 4 PLLP2 R 0 3 PLLP1 R 0 2 PLLP0 R 0 1 PLLE R/W 0/1 0 PLOCK R 0 PLLCSR
* Bit 7..5 - Res: Reserved Bits These bits are reserved bits in the AT90USB82/162 and always read as zero. * Bit 4..2 - PLLP2:0 PLL prescaler These bits allow to configure the PLL input prescaler to generate the 8MHz input clock for the PLL. Table 6-10.
PLLP2 0 0 0 0 1 1 1 1
PLL input prescaler configurations
PLLP1 0 0 1 1 0 0 1 1 PLLP0 0 1 0 1 0 1 0 1 Clock Division Factor 1 2 Reserved Reserved Reserved Reserved Reserved Reserved
* Bit 1 - PLLE: PLL Enable When the PLLE is set, the PLL is started and if needed internal RC Oscillator is started as a PLL reference clock. If PLL is selected as a system clock source the value for this bit is always 1.
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* Bit 0 - PLOCK: PLL Lock Detector When the PLOCK bit is set, the PLL is locked to the reference clock, and it is safe to enable PCK for Timer/Counter1. After the PLL is enabled, it takes about 1ms up to 100 ms for the PLL to lock.
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7. Power Distribution
The AT90USB82/162 product includes an internal 5V to 3.3V regulator that allows to supply the USB pad (see Figure 7-1.) and, depending on the application, external components or even the microcontroller itself (see Figure 7-2.).
Figure 7-1. 5V configuration
USB or PS/2 connector
VBus or PS/2 Vcc (5V)
UVCC
UCAP
VCC
AVCC
PS/2 Pad
3.3V Reg
Band Gap
AVR Core
I/O
POR BOD
PLL
Comparator
USB Pad
UVSS VSS
Figure 7-2.
5V / 3.3V configuration
USB or PS/2 connector
VBus or PS/2 Vcc (5V) (3.3V)
VCC AVCC
at least 50 mA for external chips
UVCC
UCAP
PS/2 Pad
3.3V Reg
Band Gap
AVR Core
I/O
POR BOD
PLL
Comparator
USB Pad
UVSS VSS
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Figure 7-3.
3.3V configuration
(3.3V)
UVCC UCAP VCC AVCC
PS/2 Pad
3.3V Reg
Band Gap
AVR Core
I/O
POR BOD
PLL
Comparator
USB Pad
UVSS VSS
Important note: In the 3.3V configuration, the internal regulator is bypassed. The regulator has to be disabled to avoid extra power consumption.
7.0.1
Regulator Control Register - REGCR
Bit Read/Write Initial Value 7 R 0 6 R 0 5 R 0 4 R 0 3 R 0 2 R 0 1 R 0 0 REGDIS R/W 0 REGCR
* Bit 0 - REGDIS: Regulator Disable Set this bit to disable the internal 3.3V regulator. This bit should be used only in a full 3.3V application. This bit is reset to 0 in every case. The firmware has the responsability to set it after each reset if required.
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8. Power Management and Sleep Modes
Sleep modes enable the application to shut down unused modules in the MCU, thereby saving power. The AVR provides various sleep modes allowing the user to tailor the power consumption to the application's requirements. To enter any of the five sleep modes, the SE bit in SMCR must be written to logic one and a SLEEP instruction must be executed. The SM2, SM1, and SM0 bits in the SMCR Register select which sleep mode (Idle, Power-down, Power-save, Standby or Extended standby) will be activated by the SLEEP instruction. See Table 8-1 for a summary. If an enabled interrupt occurs while the MCU is in a sleep mode, the MCU wakes up. The MCU is then halted for four cycles in addition to the start-up time, executes the interrupt routine, and resumes execution from the instruction following SLEEP. The contents of the Register File and SRAM are unaltered when the device wakes up from sleep. If a reset occurs during sleep mode, the MCU wakes up and executes from the Reset Vector. Figure 6-1 on page 25 presents the different clock systems in the AT90USB82/162, and their distribution. The figure is helpful in selecting an appropriate sleep mode. 8.0.1 Sleep Mode Control Register - SMCR The Sleep Mode Control Register contains control bits for power management.
Bit Read/Write Initial Value 7 - R 0 6 - R 0 5 - R 0 4 - R 0 3 SM2 R/W 0 2 SM1 R/W 0 1 SM0 R/W 0 0 SE R/W 0 SMCR
* Bit 7-4 - Reserved bits These bits are reserved and will always read as zero. * Bits 3-1 - SM2..0: Sleep Mode Select Bits 2, 1, and 0 These bits select between the five available sleep modes as shown in Table 8-1. Table 8-1.
SM2 0 0 0 0 1 1 1 1 Note:
Sleep Mode Select
SM1 0 0 1 1 0 0 1 1 SM0 0 1 0 1 0 1 0 1 Sleep Mode Idle Reserved Power-down Power-save Reserved Reserved Standby(1) Extended Standby(1)
1. Standby modes are only recommended for use with external crystals or resonators.
* Bit 0- SE: Sleep Enable The SE bit must be written to logic one to make the MCU enter the sleep mode when the SLEEP instruction is executed. To avoid the MCU entering the sleep mode unless it is the programmer's
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purpose, it is recommended to write the Sleep Enable (SE) bit to one just before the execution of the SLEEP instruction and to clear it immediately after waking up.
8.1
Idle Mode
When the SM2..0 bits are written to 000, the SLEEP instruction makes the MCU enter Idle mode, stopping the CPU but allowing the USB, SPI, USART, Analog Comparator, Timer/Counters, Watchdog, and the interrupt system to continue operating. This sleep mode basically halts clkCPU and clkFLASH, while allowing the other clocks to run. Idle mode enables the MCU to wake up from external triggered interrupts as well as internal ones like the Timer Overflow, USART Transmit Complete or some USB interrupts (like SOFI, WAKEUPI...). If wake-up from the Analog Comparator interrupt is not required, the Analog Comparator can be powered down by setting the ACD bit in the Analog Comparator Control and Status Register - ACSR. This will reduce power consumption in Idle mode.
8.2
Power-down Mode
When the SM2..0 bits are written to 010, the SLEEP instruction makes the MCU enter Powerdown mode. In this mode, the external Oscillator is stopped, while the external interrupts, the 2wire Serial Interface, and the Watchdog continue operating (if enabled). Only an External Reset, a Watchdog Reset, a Brown-out Reset, 2-wire Serial Interface address match, an external level interrupt on INT7:4, an external interrupt on INT3:0, a pin change interrupt or an asynchronous USB interrupt source (WAKEUPI only), can wake up the MCU. This sleep mode basically halts all generated clocks, allowing operation of asynchronous modules only. Note that if a level triggered interrupt is used for wake-up from Power-down mode, the changed level must be held for some time to wake up the MCU. Refer to "External Interrupts" on page 84 for details. When waking up from Power-down mode, there is a delay from the wake-up condition occurs until the wake-up becomes effective. This allows the clock to restart and become stable after having been stopped. The wake-up period is defined by the same CKSEL Fuses that define the Reset Time-out period, as described in "Clock Sources" on page 29.
8.3
Power-save Mode
When the SM2..0 bits are written to 011, the SLEEP instruction makes the MCU enter Powersave mode. This mode is identical to Power-down. This mode has been conserved for compatibility purpose with higher-end products.
8.4
Standby Mode
When the SM2..0 bits are 110 and an external crystal/resonator clock option is selected, the SLEEP instruction makes the MCU enter Standby mode. This mode is identical to Power-down with the exception that the Oscillator is kept running. From Standby mode, the device wakes up in six clock cycles.
8.5
Extended Standby Mode
When the SM2..0 bits are 111 and an external crystal/resonator clock option is selected, the SLEEP instruction makes the MCU enter Extended Standby mode. This mode is identical to Power-save mode with the exception that the Oscillator is kept running. So Extended Standby
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Mode is equivalent to Standy Mode, but is also conserved for compatibility purpose. From Extended Standby mode, the device wakes up in six clock cycle.
Table 8-2.
Active Clock Domains and Wake-up Sources in the Different Sleep Modes.
Active Clock Domains Oscillators Wake-up Sources
USB Asynchonous USB Synchronous SPM/ EEPROM Ready
WDT Interrupt
Sleep Mode Idle Power-down Power-save Standby
(1)
X
X
X X
(1)
X
X X X X X
X
X
X X X X X
X(1) X X X
(1)
Extended Standby Notes: Notes: Notes: 1. For INT7:4, only level interrupt.
X(1)
1. Only recommended with external crystal or resonator selected as clock source. 1. Asynchronous USB interrupt is WAKEUPI only.
8.6
Power Reduction Register
The Power Reduction Register, PRR, provides a method to stop the clock to individual peripherals to reduce power consumption. The current state of the peripheral is frozen and the I/O registers can not be read or written. Resources used by the peripheral when stopping the clock will remain occupied, hence the peripheral should in most cases be disabled before stopping the clock. Waking up a module, which is done by clearing the bit in PRR, puts the module in the same state as before shutdown. Module shutdown can be used in Idle mode and Active mode to significantly reduce the overall power consumption.
8.6.1
Power Reduction Register 0 - PRR0
Bit Read/Write Initial Value 7 R/W 0 6 R/W 0 5 PRTIM0 R/W 0 4 - R 0 3 PRTIM1 R/W 0 2 PRSPI R/W 0 1 R 0 0 R/W 0 PRR0
* Bit 7-6 - Reserved bits These bits are reserved and will always read as zero. * Bit 5 - PRTIM0: Power Reduction Timer/Counter0 Writing a logic one to this bit shuts down the Timer/Counter0 module. When the Timer/Counter0 is enabled, operation will continue like before the shutdown.
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Interrupts(1)
Main Clock Source Enabled
INT7:0 and PCINT12-0
Interrupts
Other I/O
clkFLASH
clkCPU
clkIO
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* Bit 4 - Res: Reserved bit This bit is reserved and will always read as zero. * Bit 3 - PRTIM1: Power Reduction Timer/Counter1 Writing a logic one to this bit shuts down the Timer/Counter1 module. When the Timer/Counter1 is enabled, operation will continue like before the shutdown. * Bit 2 - PRSPI: Power Reduction Serial Peripheral Interface Writing a logic one to this bit shuts down the Serial Peripheral Interface by stopping the clock to the module. When waking up the SPI again, the SPI should be re initialized to ensure proper operation. * Bit 1 - Res: Reserved bit These bits are reserved and will always read as zero. * Bit 0 - Res: Reserved bit These bits are reserved and will always read as zero. 8.6.2 Power Reduction Register 1 - PRR1
Bit Read/Write Initial Value 7 PRUSB R/W 0 6 - R 0 5 - R 0 4 - R 0 3 R/W 0 2 - R 0 1 - R 0 0 PRUSART1 R/W 0 PRR1
* Bit 7 - PRUSB: Power Reduction USB Writing a logic one to this bit shuts down the USB by stopping the clock to the module. When waking up the USB again, the USB should be re initialized to ensure proper operation. * Bit 6..1 - Res: Reserved bits These bits are reserved and will always read as zero. * Bit 0 - PRUSART1: Power Reduction USART1 Writing a logic one to this bit shuts down the USART1 by stopping the clock to the module. When waking up the USART1 again, the USART1 should be re initialized to ensure proper operation.
8.7
Minimizing Power Consumption
There are several issues to consider when trying to minimize the power consumption in an AVR controlled system. In general, sleep modes should be used as much as possible, and the sleep mode should be selected so that as few as possible of the device's functions are operating. All functions not needed should be disabled. In particular, the following modules may need special consideration when trying to achieve the lowest possible power consumption.
8.7.1
Analog Comparator When entering Idle mode, the Analog Comparator should be disabled if not used. In other sleep modes, the Analog Comparator is automatically disabled. However, if the Analog Comparator is set up to use the Internal Voltage Reference as input, the Analog Comparator should be disabled in all sleep modes. Otherwise, the Internal Voltage Reference will be enabled,
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independent of sleep mode. Refer to "Analog Comparator" on page 223 for details on how to configure the Analog Comparator. 8.7.2 Brown-out Detector If the Brown-out Detector is not needed by the application, this module should be turned off. If the Brown-out Detector is enabled by the BODLEVEL Fuses, it will be enabled in all sleep modes, and hence, always consume power. In the deeper sleep modes, this will contribute significantly to the total current consumption. Refer to "Brown-out Detection" on page 49 for details on how to configure the Brown-out Detector. Internal Voltage Reference The Internal Voltage Reference will be enabled when needed by the Brown-out Detection, or the Analog Comparator. If these modules are disabled as described in the sections above, the internal voltage reference will be disabled and it will not be consuming power. When turned on again, the user must allow the reference to start up before the output is used. If the reference is kept on in sleep mode, the output can be used immediately. Refer to "Internal Voltage Reference" on page 52 for details on the start-up time. Watchdog Timer If the Watchdog Timer is not needed in the application, the module should be turned off. If the Watchdog Timer is enabled, it will be enabled in all sleep modes, and hence, always consume power. In the deeper sleep modes, this will contribute significantly to the total current consumption. Refer to "Interrupts" on page 63 for details on how to configure the Watchdog Timer. Port Pins When entering a sleep mode, all port pins should be configured to use minimum power. The most important is then to ensure that no pins drive resistive loads. In sleep modes where the I/O clock (clkI/O) is stopped, the input buffers of the device will be disabled. This ensures that no power is consumed by the input logic when not needed. In some cases, the input logic is needed for detecting wake-up conditions, and it will then be enabled. Refer to the section "Digital Input Enable and Sleep Modes" on page 71 for details on which pins are enabled. If the input buffer is enabled and the input signal is left floating or have an analog signal level close to VCC/2, the input buffer will use excessive power. For analog input pins, the digital input buffer should be disabled at all times. An analog signal level close to VCC/2 on an input pin can cause significant current even in active mode. Digital input buffers can be disabled by writing to the Digital Input Disable Registers (DIDR1). Refer to "Digital Input Disable Register 1 - DIDR1" on page 224 for details. 8.7.6 On-chip Debug System If the On-chip debug system is enabled by the OCDEN Fuse and the chip enters sleep mode, the main clock source is enabled, and hence, always consumes power. In the deeper sleep modes, this will contribute significantly to the total current consumption.
8.7.3
8.7.4
8.7.5
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9. System Control and Reset
9.1 Resetting the AVR
During reset, all I/O Registers are set to their initial values, and the program starts execution from the Reset Vector. The instruction placed at the Reset Vector must be a JMP - Absolute Jump - instruction to the reset handling routine. If the program never enables an interrupt source, the Interrupt Vectors are not used, and regular program code can be placed at these locations. This is also the case if the Reset Vector is in the Application section while the Interrupt Vectors are in the Boot section or vice versa. The circuit diagram in Figure 9-1 shows the reset logic. Table 9-1 defines the electrical parameters of the reset circuitry. The I/O ports of the AVR are immediately reset to their initial state when a reset source goes active. This does not require any clock source to be running. After all reset sources have gone inactive, a delay counter is invoked, stretching the internal reset. This allows the power to reach a stable level before normal operation starts. The time-out period of the delay counter is defined by the user through the SUT and CKSEL Fuses. The different selections for the delay period are presented in "Clock Sources" on page 29.
9.2
Reset Sources
The AT90USB82/162 has five sources of reset: * Power-on Reset. The MCU is reset when the supply voltage is below the Power-on Reset threshold (VPOT). * External Reset. The MCU is reset when a low level is present on the RESET pin for longer than the minimum pulse length. * Watchdog Reset. The MCU is reset when the Watchdog Timer period expires and the Watchdog is enabled. 9.9See "Watchdog Timer" on page 52.9.9 * Brown-out Reset. The MCU is reset when the supply voltage VCC is below the Brown-out Reset threshold (VBOT) and the Brown-out Detector is enabled. * USB Reset. The MCU is reset when the USB macro is enabled and detects a USB Reset. Note that with this reset the USB macro remains enabled so that the device stays attached to the bus.
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Figure 9-1. Reset Logic
DATA BUS
MCU Status Register (MCUSR)
PORF BORF EXTRF WDRF USBRF
Power-on Reset Circuit
BODLEVEL [2..0] Pull-up Resistor
SPIKE FILTER
Brown-out Reset Circuit
USB Device Reset Detection
Watchdog Oscillator Delay Counters TIMEOUT
Clock Generator
CK
CKSEL[3:0] SUT[1:0]
Table 9-1.
Symbol VPOT VPOR VCCRR VRST tRST Notes:
Reset Characteristics
Parameter Power-on Reset Threshold Voltage (rising) Power-on Reset Threshold Voltage (falling)
(1)
Condition
Min
Typ 1.4 1.3
Max 2.3 2.3 0.1
Units V V V V/ms
VCC Start Voltage to ensure internal Power-on Reset signal VCC Rise Rate to ensure internal Power_on Reset signal RESET Pin Threshold Voltage Minimum pulse width on RESET Pin 5V, 25C
-0.1 0.8 0.2 Vcc 400
0.85 Vcc
V ns
1. The POR will not work unless the supply voltage has been below VPOT (falling)
9.3
Power-on Reset
A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The detection level is defined in Table 9-1. The POR is activated whenever VCC is below the detection level. The POR circuit can be used to trigger the start-up Reset, as well as to detect a failure in supply voltage. A Power-on Reset (POR) circuit ensures that the device is reset from Power-on. Reaching the Power-on Reset threshold voltage invokes the delay counter, which determines how long the
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device is kept in RESET after VCC rise. The RESET signal is activated again, without any delay, when VCC decreases below the detection level. Figure 9-2.
VCC
MCU Start-up, RESET Tied to VCC
VPOT
RESET
VRST
TIME-OUT
tTOUT
INTERNAL RESET
Figure 9-3.
VCC
MCU Start-up, RESET Extended Externally
VPOT
RESET
VRST
TIME-OUT
tTOUT
INTERNAL RESET
9.4
External Reset
An External Reset is generated by a low level on the RESET pin. Reset pulses longer than the minimum pulse width (see Table 9-1) will generate a reset, even if the clock is not running. Shorter pulses are not guaranteed to generate a reset. When the applied signal reaches the Reset Threshold Voltage - VRST - on its positive edge, the delay counter starts the MCU after the Time-out period - tTOUT - has expired. Figure 9-4.
CC
External Reset During Operation
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9.5 Brown-out Detection
AT90USB82/162 has an On-chip Brown-out Detection (BOD) circuit for monitoring the VCC level during operation by comparing it to a fixed trigger level. The trigger level for the BOD can be selected by the BODLEVEL Fuses. The trigger level has a hysteresis to ensure spike free Brown-out Detection. The hysteresis on the detection level should be interpreted as V BOT+ = VBOT + VHYST/2 and VBOT- = VBOT - VHYST/2. Table 9-2. BODLEVEL Fuse Coding(1)
Min VBOT 2.5 2.7 2.8 3.3 3.4 3.8 4.1 Typ VBOT 2.7 2.9 3.0 3.5 3.6 4.0 4.3 Max VBOT 2.9 3.1 3.2 3.7 3.8 4.2 4.5 V Units 111 110 101 100 011 010 001 000 Note: BOD Disabled
BODLEVEL 2..0 Fuses
1. VBOT may be below nominal minimum operating voltage for some devices. For devices where this is the case, the device is tested down to VCC = VBOT during the production test. This guarantees that a Brown-Out Reset will occur before VCC drops to a voltage where correct operation of the microcontroller is no longer guaranteed. The test is performed using BODLEVEL = 110 for AT90USB82/162 and BODLEVEL = 101 for AT90USB82/162L.
Table 9-3.
Symbol VHYST tBOD
Brown-out Characteristics
Parameter Brown-out Detector Hysteresis Min Pulse Width on Brown-out Reset Min Typ 50 2 Max Units mV ns
When the BOD is enabled, and VCC decreases to a value below the trigger level (VBOT- in Figure 9-5), the Brown-out Reset is immediately activated. When VCC increases above the trigger level (V BOT+ in Figure 9-5), the delay counter starts the MCU after the Time-out period tTOUT has expired. The BOD circuit will only detect a drop in VCC if the voltage stays below the trigger level for longer than tBOD given in Table 9-1.
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Figure 9-5.
Brown-out Reset During Operation
VCC VBOTVBOT+
RESET
TIME-OUT
tTOUT
INTERNAL RESET
9.6
Watchdog Reset
When the Watchdog times out, it will generate a short reset pulse of one CK cycle duration. On the falling edge of this pulse, the delay timer starts counting the Time-out period tTOUT. Refer to page 52 for details on operation of the Watchdog Timer. Figure 9-6.
CC
Watchdog Reset During Operation
CK
9.7
USB Reset
When the USB macro is enabled and configured with the USB reset MCU feature enabled, and if a valid USB Reset signalling is detected, the microcontroller is reset unless the USB macro that remains enabled. This allows the device to stay attached to the bus during and after the reset, while enhancing firmware reliability.
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Figure 9-7.
CC
USB Reset During Operation
(USB Lines)
DP DM
t USBRSTMIN
USB Traffic
End of Reset
USB Traffic
9.7.1
MCU Status Register -MCUSR The MCU Status Register provides information on which reset source caused an MCU reset.
Bit Read/Write Initial Value 7 - R 0 6 - R 0 5 USBRF R 0 4 - R/W 3 WDRF R/W 2 BORF R/W 1 EXTRF R/W 0 PORF R/W MCUSR
See Bit Description
* Bit 7-6 - Res: Reserved Bit These bits are reserved and will always read as zero. * Bit 5 - USBRF: USB Reset Flag This bit is set if a USB Reset occurs. The bit is reset by a Power-on Reset, or by writing a logic zero to the flag. * Bit 4- Res: Reserved Bit This bit is reserved. * Bit 3 - WDRF: Watchdog Reset Flag This bit is set if a Watchdog Reset occurs. The bit is reset by a Power-on Reset, or by writing a logic zero to the flag. * Bit 2 - BORF: Brown-out Reset Flag This bit is set if a Brown-out Reset occurs. The bit is reset by a Power-on Reset, or by writing a logic zero to the flag. * Bit 1 - EXTRF: External Reset Flag This bit is set if an External Reset occurs. The bit is reset by a Power-on Reset, or by writing a logic zero to the flag. * Bit 0 - PORF: Power-on Reset Flag This bit is set if a Power-on Reset occurs. The bit is reset only by writing a logic zero to the flag. To make use of the Reset Flags to identify a reset condition, the user should read and then Reset the MCUSR as early as possible in the program. If the register is cleared before another reset occurs, the source of the reset can be found by examining the Reset Flags. 51
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9.8
Internal Voltage Reference
AT90USB82/162 features an internal bandgap reference. This reference is used for Brown-out Detection, and it can be used as an input to the Analog Comparator.
9.8.1
Voltage Reference Enable Signals and Start-up Time The voltage reference has a start-up time that may influence the way it should be used. The start-up time is given in Table 9-4. To save power, the reference is not always turned on. The reference is on during the following situations: 1. When the BOD is enabled (by programming the BODLEVEL [2..0] Fuse). 2. When the bandgap reference is connected to the Analog Comparator (by setting the ACBG bit in ACSR). Thus, when the BOD is not enabled, after setting the ACBG bit, the user must always allow the reference to start up before the output from the Analog Comparator is used. To reduce power consumption in Power-down mode, the user can avoid the three conditions above to ensure that the reference is turned off before entering Power-down mode . Table 9-4.
Symbol VBG tBG IBG
Internal Voltage Reference Characteristics
Parameter Bandgap reference voltage Bandgap reference start-up time Bandgap reference current consumption Condition VCC = 2.7V - 5.5V Min 1.0 Typ 1.1 40 10 Max 1.2 70 Units V s A
9.9
Watchdog Timer
AT90USB82/162 has an Enhanced Watchdog Timer (WDT). The main features are: * Clocked from separate On-chip Oscillator * 3 Operating modes
- Interrupt - System Reset - Interrupt and System Reset
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* Selectable Time-out period from 16ms to 8s * Possible Hardware fuse Watchdog always on (WDTON) for fail-safe mode * Early warning after one Time-Out period reached, programmable Reset (see operating modes)
after 2 Time-Out periods reached.
Figure 9-8.
Watchdog Timer
128kHz OSCILLATOR
CLOCK DIVIDER
OSC/1 OSC/3 OSC/5
OSC/2K OSC/4K OSC/8K OSC/16K OSC/32K OSC/64K OSC/128K OSC/256K OSC/512K OSC/1024K
OSC/7
WCLKD0 WCLKD1
WATCHDOG RESET WDE
WDP0 WDP1 WDP2 WDP3
MCU RESET
WDIF INTERRUPT EARLY WARNING INTERRUPT
WDIE
WDEWIE
The Watchdog Timer (WDT) is a timer counting cycles of a separate on-chip 128 kHz oscillator. The WDT gives a early warning interrupt when the counter reaches a given time-out value. The WDT gives an interrupt or a system reset when the counter reaches two times the given time-out value. In normal operation mode, it is required that the system uses the WDR - Watchdog Timer Reset - instruction to restart the counter before the time-out value is reached. If the system doesn't restart the counter, an interrupt or system reset will be issued. In Interrupt mode, the WDT gives an interrupt when the timer expires two times. This interrupt can be used to wake the device from sleep-modes, and also as a general system timer. One example is to limit the maximum time allowed for certain operations, giving an interrupt when the operation has run longer than expected. In System Reset mode, the WDT gives a reset when the timer expires two times. This is typically used to prevent system hang-up in case of runaway code. The third mode, Interrupt and System Reset mode, combines the other two modes by first giving an interrupt and then switch to System Reset mode. This mode will for instance allow a safe shutdown by saving critical parameters before a system reset. In addition to these modes, the early warning interrupt can be enabled in order to generate an interrupt when the WDT counter expires the first time. The Watchdog always on (WDTON) fuse, if programmed, will force the Watchdog Timer to System Reset mode. With the fuse programmed the System Reset mode bit (WDE) and Interrupt mode bit (WDIE) are locked to 1 and 0 respectively. To further ensure program security, alterations to the Watchdog set-up must follow timed sequences. The sequence for clearing WDE or changing time-out configuration is as follows:
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1. In the same operation, write a logic one to the Watchdog change enable bits WDCE and WDE. A logic one must be written to WDE regardless of the previous value of the WDE bit and even if it will be cleared after the operation. 2. Within the next four clock cycles, write the WDE and Watchdog prescaler bits (WDP) as desired, but with the WDCE bit cleared. This must be done in one operation. While the WDT prescaler allows only even division factors (2, 4, 8...), the WDT peripheral also includes a clock divider that directly acts on the clock source. This divider handles odd division factors (3, 5, 7). In combination with the prescaler, a large number of time-out values can be obtained. The divider factor change is also ruled by the secure timed sequence : first the WDE and WDCE bits must be set, and then four cycles are available to load the new divider value into the WDTCKD register. Be aware that after this operation WDE will still be set. So keep in mind the importance of order of operations. When setting up the WDT in Interrupt mode with specific values of prescaler and divider, the divider register must be loaded before the prescaler register : 1. Set WDCE and WDE 2. Load the divider factor into WDTCKD 3. Wait WDCE being automatically cleared (just wait 2 more cycles) 4. Set again WDCE and WDE 5. Clear WDE, set WDIE and load the prescaler factor into WDTCSR in a same operation 6. Now the system is properly configured for Interrupt only mode. Inverting the two operations would have been resulted into "Reset and Interrupt mode" and needed a third operation to clear WDE.
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The following code example shows one assembly and one C function for turning off the Watchdog Timer. The example assumes that interrupts are controlled (e.g. by disabling interrupts globally) so that no interrupts will occur during the execution of these functions. Assembly Code Example(1)
WDT_off: ; Turn off global interrupt cli ; Reset Watchdog Timer wdr ; Clear WDRF in MCUSR in andi out r16, MCUSR r16, (0xff & (0<; Write logical one to WDCE and WDE ; Keep old prescaler setting to prevent unintentional time-out in ori out ldi out sei ret r16, WDTCSR r16, (1<; Turn off WDT
; Turn on global interrupt
C Code Example(1)
void WDT_off(void) { __disable_interrupt(); __watchdog_reset(); /* Clear WDRF in MCUSR */ MCUSR &= ~(1<Note: If the Watchdog is accidentally enabled, for example by a runaway pointer or brown-out condition, the device will be reset and the Watchdog Timer will stay enabled. If the code is not set up to handle the Watchdog, this might lead to an eternal loop of time-out resets. To avoid this situation, the application software should always clear the Watchdog System Reset Flag (WDRF) and the WDE control bit in the initialisation routine, even if the Watchdog is not in use.
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The following code example shows one assembly and one C function for changing the time-out value of the Watchdog Timer. Assembly Code Example(1)
WDT_Prescaler_Change: ; Turn off global interrupt cli ; Reset Watchdog Timer wdr ; Start timed sequence in ori out ; -ldi out ; -sei ret r16, WDTCSR r16, (1<; Set new prescaler(time-out) value = 64K cycles (~0.5 s)
; Turn on global interrupt
C Code Example(1)
void WDT_Prescaler_Change(void) { __disable_interrupt(); __watchdog_reset(); /* Start timed equence */ WDTCSR |= (1<Note: The Watchdog Timer should be reset before any change of the WDP bits, since a change in the WDP bits can result in a time-out when switching to a shorter time-out period. 9.9.1 Watchdog Timer Control Register - WDTCSR
Bit Read/Write Initial Value 7 WDIF R/W 0 6 WDIE R/W 0 5 WDP3 R/W 0 4 WDCE R/W 0 3 WDE R/W X 2 WDP2 R/W 0 1 WDP1 R/W 0 0 WDP0 R/W 0 WDTCSR
* Bit 7 - WDIF: Watchdog Interrupt Flag This bit is set when a time-out occurs twice in the Watchdog Timer and if the Watchdog Timer is configured for interrupt. WDIF is automatically cleared by hardware when executing the corre-
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sponding interrupt handling vector. Alternatively, WDIF is cleared by writing a logic one to the flag. When the I-bit in SREG and WDIE are set, the Watchdog Time-out Interrupt is executed. * Bit 6 - WDIE: Watchdog Interrupt Enable When this bit is written to one and the I-bit in the Status Register is set, the Watchdog Interrupt is enabled. If WDE is cleared in combination with this setting, the Watchdog Timer is in Interrupt Mode, and the corresponding interrupt is executed if time-out in the Watchdog Timer occurs. If WDE is set, the Watchdog Timer is in Interrupt and System Reset Mode. Two consecutives times-out in the Watchdog Timer will set WDIF. Executing the corresponding interrupt vector will clear WDIE and WDIF automatically by hardware : the Watchdog goes to System Reset Mode. This is useful for keeping the Watchdog Timer security while using the interrupt. To reinitialize the Interrupt and System Reset Mode, WDIE must be set after each interrupt. This should however not be done within the interrupt service routine itself, as this might compromise the safetyfunction of the Watchdog System Reset mode. If the interrupt is not executed before the next time-out, a System Reset will be applied. Table 9-5. Watchdog Timer Configuration
WDE 0 0 1 1 x WDIE 0 1 0 1 x Mode Stopped Interrupt Mode System Reset Mode Interrupt and System Reset Mode System Reset Mode Action on 2x Time-out None Interrupt Reset Interrupt, then go to System Reset Mode Reset
WDTON (Fuse) 1 (unprogrammed) 1 (unprogrammed) 1 (unprogrammed) 1 (unprogrammed) 0 (programmed)
* Bit 4 - WDCE: Watchdog Change Enable This bit is used in timed sequences for changing WDE and prescaler bits. To clear the WDE bit, and/or change the prescaler bits, WDCE must be set. Once written to one, hardware will clear WDCE after four clock cycles. * Bit 3 - WDE: Watchdog System Reset Enable WDE is overridden by WDRF in MCUSR. This means that WDE is always set when WDRF is set. To clear WDE, WDRF must be cleared first. This feature ensures multiple resets during conditions causing failure, and a safe start-up after the failure. * Bit 5, 2..0 - WDP3..0: Watchdog Timer Prescaler 3, 2, 1 and 0 The WDP3..0 bits determine the Watchdog Timer prescaling when the Watchdog Timer is running. The different prescaling values and their corresponding time-out periods are shown in Table 9-6 on page 59. 9.9.2 Watchdog Timer Clock Divider Register - WDTCKD
Bit 7 6 5 4 3 WDEWIF R/W 0 2 WDEWIE R/W 0 1 WCLKD 1 R/W 0 0 WCLKD 0 R/W 0 WDTCKD
Read/Write Initial Value
R/W 0
R/W 0
R/W 0
R/W 0
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* Bit 7-4 - Reserved bits These bits are reserved and will always read as zero. * Bit 3 - WDEWIF: Watchdog Early Warning Interrupt Flag This bit is set when a first time-out occurs in the Watchdog Timer and if the WDEWIE bit is enabled. WDEWIF is automatically cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, WDIF can be cleared by writing a logic one to the flag. When the I-bit in SREG and WDEWIE are set, the Watchdog Time-out Interrupt is executed. * Bit 2 - WDEWIE: Watchdog Early Warning Interrupt Enable When this bit has been set by software, an interrupt will be generated on the watchdog interrupt vector when the Early warning flag is set to one by hardware. * Bit 1:0 - WCLKD[1:0]: Watchdog Timer Clock Divider - WCLKD = 0 : ClkWDT = Clk128k - WCLKD = 1 : ClkWDT = Clk128k / 3 - WCLKD = 2 : ClkWDT = Clk128k / 5 - WCLKD = 3 : ClkWDT = Clk128k / 7
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.
Table 9-6.
Watchdog Timer Prescale Select, DIV = 0 (CLKwdt = CLK128 / 1)
Watchdog Reset/Interrupt Typical Time-out at VCC = 5.0V 32 ms 64 ms 128 ms 0.250 s 0.5 s 1.0 s 2.0 s 4.0 s 8.0 s 16.0 s
WDP3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
WDP2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
WDP1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
WDP0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
Number of WDT Oscillator Cycles before 1st time-out (Early warning) 2K (2048) cycles 4K (4096) cycles 8K (8192) cycles 16K (16384) cycles 32K (32768) cycles 64K (65536) cycles 128K (131072) cycles 256K (262144) cycles 512K (524288) cycles 1024K (1048576) cycles
Early warning Typical Time-out at VCC = 5.0V 16 ms 32 ms 64 ms 0.125 s 0.25 s 0.5 s 1.0 s 2.0 s 4.0 s 8.0 s
Reserved
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Table 9-7.
Watchdog Timer Prescale Select, DIV = 1 (CLKwdt = CLK128 / 3)
Watchdog Reset/Interrupt Typical Time-out at VCC = 5.0V 96 ms 192 ms 384 ms 0.75 s 1.5 s 3s 6s 12 s 24 s 48 s
WDP3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
WDP2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
WDP1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
WDP0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
Number of WDT Oscillator Cycles before 1st time-out (Early warning) 2K (2048) cycles 4K (4096) cycles 8K (8192) cycles 16K (16384) cycles 32K (32768) cycles 64K (65536) cycles 128K (131072) cycles 256K (262144) cycles 512K (524288) cycles 1024K (1048576) cycles
Early warning Typical Time-out at VCC = 5.0V 48 ms 96 ms 192 ms 0.375 s 0.75 s 1.5 s 3s 6s 12 s 24 s
Reserved
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Table 9-8. Watchdog Timer Prescale Select, DIV = 2 (CLKwdt = CLK128 / 5)
Watchdog Reset/Interrupt Typical Time-out at VCC = 5.0V 160 ms 320 ms 640 ms 1.25 s 2.5 s 5s 10 s 20 s 40 s 80 s
WDP3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
WDP2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
WDP1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
WDP0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
Number of WDT Oscillator Cycles before 1st time-out (Early warning) 2K (2048) cycles 4K (4096) cycles 8K (8192) cycles 16K (16384) cycles 32K (32768) cycles 64K (65536) cycles 128K (131072) cycles 256K (262144) cycles 512K (524288) cycles 1024K (1048576) cycles
Early warning Typical Time-out at VCC = 5.0V 80 ms 160 ms 320 ms 0.625 s 1.25 s 2.5 s 5s 10 s 20 s 40 s
Reserved
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Table 9-9.
Watchdog Timer Prescale Select, DIV = 3 (CLKwdt = CLK128 / 7)
Watchdog Reset/Interrupt Typical Time-out at VCC = 5.0V 224 ms 448 ms 896 ms 1.75 s 3.5 s 7s 14 s 28 s 56 s 112 s
WDP3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
WDP2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
WDP1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1
WDP0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
Number of WDT Oscillator Cycles before 1st time-out (Early warning) 2K (2048) cycles 4K (4096) cycles 8K (8192) cycles 16K (16384) cycles 32K (32768) cycles 64K (65536) cycles 128K (131072) cycles 256K (262144) cycles 512K (524288) cycles 1024K (1048576) cycles
Early warning Typical Time-out at VCC = 5.0V 112 ms 224 ms 448 ms 0.875 s 1.75 s 3.5 s 7s 14 s 28 s 56 s
Reserved
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10. Interrupts
This section describes the specifics of the interrupt handling as performed in AT90USB82/162. For a general explanation of the AVR interrupt handling, refer to "Reset and Interrupt Handling" on page 13.
10.1
Interrupt Vectors in AT90USB82/162
Table 10-1.
Vector No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Reset and Interrupt Vectors
Program Address(2) $0000(1) $0002 $0004 $0006 $0008 $000A $000C $000E $0010 $0012 $0014 $0016 $0018 $001A $001C $001E $0020 $0022 $0024 $0026 $0028 $002A $002C $002E $0030 $0032 Source RESET INT0 INT1 INT2 INT3 INT4 INT5 INT6 INT7 PCINT0 PCINT1 USB General USB Endpoint WDT TIMER1 CAPT TIMER1 COMPA TIMER1 COMPB TIMER1 COMPC TIMER1 OVF TIMER0 COMPA TIMER0 COMPB TIMER0 OVF SPI, STC USART1 RX USART1 UDRE USART1TX Interrupt Definition External Pin, Power-on Reset, Brown-out Reset, Watchdog Reset, USB Reset and debugWIRE AVR Reset External Interrupt Request 0 External Interrupt Request 1 External Interrupt Request 2 External Interrupt Request 3 External Interrupt Request 4 External Interrupt Request 5 External Interrupt Request 6 External Interrupt Request 7 Pin Change Interrupt Request 0 Pin Change Interrupt Request 1 USB General Interrupt request USB Endpoint Interrupt request Watchdog Time-out Interrupt Timer/Counter1 Capture Event Timer/Counter1 Compare Match A Timer/Counter1 Compare Match B Timer/Counter1 Compare Match C Timer/Counter1 Overflow Timer/Counter0 Compare Match A Timer/Counter0 Compare match B Timer/Counter0 Overflow SPI Serial Transfer Complete USART1 Rx Complete USART1 Data Register Empty USART1 Tx Complete
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Table 10-1.
Vector No. 27 28 29 Notes:
Reset and Interrupt Vectors (Continued)
Program Address(2) $0034 $0036 $0038 Source ANALOG COMP EE READY SPM READY Interrupt Definition Analog Comparator EEPROM Ready Store Program Memory Ready
1. When the BOOTRST Fuse is programmed, the device will jump to the Boot Loader address at reset, see "Memory Programming" on page 243. 2. When the IVSEL bit in MCUCR is set, Interrupt Vectors will be moved to the start of the Boot Flash Section. The address of each Interrupt Vector will then be the address in this table added to the start address of the Boot Flash Section. Moreover, contrary to other 8K/16K devices, the interrupt vectors spacing remains identical (2 words) for both 8KB and 16KB versions.
Table 10-2 shows reset and Interrupt Vectors placement for the various combinations of BOOTRST and IVSEL settings. If the program never enables an interrupt source, the Interrupt Vectors are not used, and regular program code can be placed at these locations. This is also the case if the Reset Vector is in the Application section while the Interrupt Vectors are in the Boot section or vice versa.
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Table 10-2.
BOOTRST 1 1 0 0 Note:
Reset and Interrupt Vectors Placement(1)
IVSEL 0 1 0 1 Reset Address 0x0000 0x0000 Boot Reset Address Boot Reset Address Interrupt Vectors Start Address 0x0002 Boot Reset Address + 0x0002 0x0002 Boot Reset Address + 0x0002
1. The Boot Reset Address is shown in Table 23-8 on page 239. For the BOOTRST Fuse "1" means unprogrammed while "0" means programmed.
10.1.1
Moving Interrupts Between Application and Boot Space The General Interrupt Control Register controls the placement of the Interrupt Vector table. MCU Control Register - MCUCR
Bit Read/Write Initial Value 7 JTD R/W 0 6 - R 0 5 - R 0 4 PUD R/W 0 3 - R 0 2 - R 0 1 IVSEL R/W 0 0 IVCE R/W 0 MCUCR
10.1.2
* Bit 1 - IVSEL: Interrupt Vector Select When the IVSEL bit is cleared (zero), the Interrupt Vectors are placed at the start of the Flash memory. When this bit is set (one), the Interrupt Vectors are moved to the beginning of the Boot Loader section of the Flash. The actual address of the start of the Boot Flash Section is determined by the BOOTSZ Fuses. Refer to the section "Memory Programming" on page 243 for details. To avoid unintentional changes of Interrupt Vector tables, a special write procedure must be followed to change the IVSEL bit: a. Write the Interrupt Vector Change Enable (IVCE) bit to one. b. Within four cycles, write the desired value to IVSEL while writing a zero to IVCE. Interrupts will automatically be disabled while this sequence is executed. Interrupts are disabled in the cycle IVCE is set, and they remain disabled until after the instruction following the write to IVSEL. If IVSEL is not written, interrupts remain disabled for four cycles. The I-bit in the Status Register is unaffected by the automatic disabling.
Note: If Interrupt Vectors are placed in the Boot Loader section and Boot Lock bit BLB02 is programmed, interrupts are disabled while executing from the Application section. If Interrupt Vectors are placed in the Application section and Boot Lock bit BLB12 is programed, interrupts are disabled while executing from the Boot Loader section. Refer to the section "Memory Programming" on page 243 for details on Boot Lock bits.
* Bit 0 - IVCE: Interrupt Vector Change Enable
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The IVCE bit must be written to logic one to enable change of the IVSEL bit. IVCE is cleared by hardware four cycles after it is written or when IVSEL is written. Setting the IVCE bit will disable interrupts, as explained in the IVSEL description above. See Code Example below. Assembly Code Example
Move_interrupts: ; Enable change of Interrupt Vectors ldi r16, (1<C Code Example
void Move_interrupts(void) { /* Enable change of Interrupt Vectors */ MCUCR = (1<66
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11. I/O-Ports
11.1 Introduction
All AVR ports have true Read-Modify-Write functionality when used as general digital I/O ports. This means that the direction of one port pin can be changed without unintentionally changing the direction of any other pin with the SBI and CBI instructions. The same applies when changing drive value (if configured as output) or enabling/disabling of pull-up resistors (if configured as input). Each output buffer has symmetrical drive characteristics with both high sink and source capability. The pin driver is strong enough to drive LED displays directly. All port pins have individually selectable pull-up resistors with a supply-voltage invariant resistance. All I/O pins have protection diodes to both VCC and Ground as indicated in Figure 11-1. Refer to "Electrical Characteristics" on page 262 for a complete list of parameters. Figure 11-1. I/O Pin Equivalent Schematic
Rpu
Pxn
Logic Cpin
See Figure "General Digital I/O" for Details
All registers and bit references in this section are written in general form. A lower case "x" represents the numbering letter for the port, and a lower case "n" represents the bit number. However, when using the register or bit defines in a program, the precise form must be used. For example, PORTB3 for bit no. 3 in Port B, here documented generally as PORTxn. The physical I/O Registers and bit locations are listed in "Register Description for I/O-Ports" on page 82. Three I/O memory address locations are allocated for each port, one each for the Data Register - PORTx, Data Direction Register - DDRx, and the Port Input Pins - PINx. The Port Input Pins I/O location is read only, while the Data Register and the Data Direction Register are read/write. However, writing a logic one to a bit in the PINx Register, will result in a toggle in the corresponding bit in the Data Register. In addition, the Pull-up Disable - PUD bit in MCUCR disables the pull-up function for all pins in all ports when set. Using the I/O port as General Digital I/O is described in "Ports as General Digital I/O" on page 68. Most port pins are multiplexed with alternate functions for the peripheral features on the device. How each alternate function interferes with the port pin is described in "Alternate Port Functions" on page 72. Refer to the individual module sections for a full description of the alternate functions.
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Note that enabling the alternate function of some of the port pins does not affect the use of the other pins in the port as general digital I/O.
11.2
Ports as General Digital I/O
The ports are bi-directional I/O ports with optional internal pull-ups. Figure 11-2 shows a functional description of one I/O-port pin, here generically called Pxn. Figure 11-2. General Digital I/O(1)
PUD
Q
D
DDxn Q CLR
RESET
WDx RDx
1 Pxn
Q D PORTxn Q CLR
0
RESET WRx SLEEP RRx
WPx
SYNCHRONIZER
D Q D Q
RPx
PINxn L Q Q
clk I/O
PUD: SLEEP: clkI/O:
PULLUP DISABLE SLEEP CONTROL I/O CLOCK
WDx: RDx: WRx: RRx: RPx: WPx:
WRITE DDRx READ DDRx WRITE PORTx READ PORTx REGISTER READ PORTx PIN WRITE PINx REGISTER
Note:
1. WRx, WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port. clkI/O, SLEEP, and PUD are common to all ports.
11.2.1
Configuring the Pin Each port pin consists of three register bits: DDxn, PORTxn, and PINxn. As shown in "Register Description for I/O-Ports" on page 82, the DDxn bits are accessed at the DDRx I/O address, the PORTxn bits at the PORTx I/O address, and the PINxn bits at the PINx I/O address. The DDxn bit in the DDRx Register selects the direction of this pin. If DDxn is written logic one, Pxn is configured as an output pin. If DDxn is written logic zero, Pxn is configured as an input pin. If PORTxn is written logic one when the pin is configured as an input pin, the pull-up resistor is activated. To switch the pull-up resistor off, PORTxn has to be written logic zero or the pin has to be configured as an output pin. The port pins are tri-stated when reset condition becomes active, even if no clocks are running.
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If PORTxn is written logic one when the pin is configured as an output pin, the port pin is driven high (one). If PORTxn is written logic zero when the pin is configured as an output pin, the port pin is driven low (zero). 11.2.2 Toggling the Pin Writing a logic one to PINxn toggles the value of PORTxn, independent on the value of DDRxn. Note that the SBI instruction can be used to toggle one single bit in a port. Switching Between Input and Output When switching between tri-state ({DDxn, PORTxn} = 0b00) and output high ({DDxn, PORTxn} = 0b11), an intermediate state with either pull-up enabled {DDxn, PORTxn} = 0b01) or output low ({DDxn, PORTxn} = 0b10) occurs. Normally, the pull-up enabled state is fully acceptable, as a high-impedant environment will not notice the difference between a strong high driver and a pull-up. If this is not the case, the PUD bit in the MCUCR Register can be set to disable all pullups in all ports. Switching between input with pull-up and output low generates the same problem. The user must use either the tri-state ({DDxn, PORTxn} = 0b00) or the output high state ({DDxn, PORTxn} = 0b11) as an intermediate step. Table 11-1 summarizes the control signals for the pin value. Table 11-1.
DDxn 0 0 0 1 1
11.2.3
Port Pin Configurations
PUD (in MCUCR) X 0 1 X X I/O Input Input Input Output Output Pull-up No Yes No No No Comment Tri-state (Hi-Z) Pxn will source current if ext. pulled low. Tri-state (Hi-Z) Output Low (Sink) Output High (Source)
PORTxn 0 1 1 0 1
11.2.4
Reading the Pin Value Independent of the setting of Data Direction bit DDxn, the port pin can be read through the PINxn Register bit. As shown in Figure 11-2, the PINxn Register bit and the preceding latch constitute a synchronizer. This is needed to avoid metastability if the physical pin changes value near the edge of the internal clock, but it also introduces a delay. Figure 11-3 shows a timing diagram of the synchronization when reading an externally applied pin value. The maximum and minimum propagation delays are denoted tpd,max and tpd,min respectively.
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Figure 11-3. Synchronization when Reading an Externally Applied Pin value
SYSTEM CLK INSTRUCTIONS SYNC LATCH PINxn r17
0x00 t pd, max t pd, min 0xFF XXX XXX in r17, PINx
Consider the clock period starting shortly after the first falling edge of the system clock. The latch is closed when the clock is low, and goes transparent when the clock is high, as indicated by the shaded region of the "SYNC LATCH" signal. The signal value is latched when the system clock goes low. It is clocked into the PINxn Register at the succeeding positive clock edge. As indicated by the two arrows tpd,max and tpd,min, a single signal transition on the pin will be delayed between 1/2 and 11/2 system clock period depending upon the time of assertion. When reading back a software assigned pin value, a nop instruction must be inserted as indicated in Figure 11-4. The out instruction sets the "SYNC LATCH" signal at the positive edge of the clock. In this case, the delay tpd through the synchronizer is 1 system clock period. Figure 11-4. Synchronization when Reading a Software Assigned Pin Value
SYSTEM CLK r16 INSTRUCTIONS SYNC LATCH PINxn r17
0x00 t pd 0xFF out PORTx, r16 nop 0xFF
in r17, PINx
The following code example shows how to set port B pins 0 and 1 high, 2 and 3 low, and define the port pins from 4 to 7 as input with pull-ups assigned to port pins 6 and 7. The resulting pin values are read back again, but as previously discussed, a nop instruction is included to be able to read back the value recently assigned to some of the pins. 70
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Assembly Code Example(1)
... ; Define pull-ups and set outputs high ; Define directions for port pins ldi ldi out out nop ; Read port pins in ... r16,PINB r16,(1<; Insert nop for synchronization
C Code Example
unsigned char i; ... /* Define pull-ups and set outputs high */ /* Define directions for port pins */ PORTB = (1<11.2.5
Digital Input Enable and Sleep Modes As shown in Figure 11-2, the digital input signal can be clamped to ground at the input of the schmitt-trigger. The signal denoted SLEEP in the figure, is set by the MCU Sleep Controller in Power-down mode, Power-save mode, and Standby mode to avoid high power consumption if some input signals are left floating, or have an analog signal level close to VCC/2. SLEEP is overridden for port pins enabled as external interrupt pins. If the external interrupt request is not enabled, SLEEP is active also for these pins. SLEEP is also overridden by various other alternate functions as described in "Alternate Port Functions" on page 72. If a logic high level ("one") is present on an asynchronous external interrupt pin configured as "Interrupt on Rising Edge, Falling Edge, or Any Logic Change on Pin" while the external interrupt is not enabled, the corresponding External Interrupt Flag will be set when resuming from the above mentioned Sleep mode, as the clamping in these sleep mode produces the requested logic change.
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11.2.6
Unconnected Pins If some pins are unused, it is recommended to ensure that these pins have a defined level. Even though most of the digital inputs are disabled in the deep sleep modes as described above, floating inputs should be avoided to reduce current consumption in all other modes where the digital inputs are enabled (Reset, Active mode and Idle mode). The simplest method to ensure a defined level of an unused pin, is to enable the internal pull-up. In this case, the pull-up will be disabled during reset. If low power consumption during reset is important, it is recommended to use an external pull-up or pull-down. Connecting unused pins directly to VCC or GND is not recommended, since this may cause excessive currents if the pin is accidentally configured as an output.
11.3
Alternate Port Functions
Most port pins have alternate functions in addition to being general digital I/Os. Figure 11-5 shows how the port pin control signals from the simplified Figure 11-2 can be overridden by alternate functions. The overriding signals may not be present in all port pins, but the figure serves as a generic description applicable to all port pins in the AVR microcontroller family. Figure 11-5. Alternate Port Functions(1)
PUOExn PUOVxn
1 0
PUD
DDOExn DDOVxn
1 0
Q D DDxn Q CLR
PVOExn PVOVxn
WDx RESET RDx
1 Pxn 0
Q D
1 0
PORTxn
PTOExn WPx
DIEOExn DIEOVxn
1 0
Q CLR
RESET RRx
WRx
SLEEP SYNCHRONIZER
D
SET
RPx
Q
D
Q
PINxn L
CLR
Q
CLR
Q
clk I/O
DIxn
AIOxn
PUOExn: PUOVxn: DDOExn: DDOVxn: PVOExn: PVOVxn: DIEOExn: DIEOVxn: SLEEP: PTOExn:
Pxn PULL-UP OVERRIDE ENABLE Pxn PULL-UP OVERRIDE VALUE Pxn DATA DIRECTION OVERRIDE ENABLE Pxn DATA DIRECTION OVERRIDE VALUE Pxn PORT VALUE OVERRIDE ENABLE Pxn PORT VALUE OVERRIDE VALUE Pxn DIGITAL INPUT-ENABLE OVERRIDE ENABLE Pxn DIGITAL INPUT-ENABLE OVERRIDE VALUE SLEEP CONTROL Pxn, PORT TOGGLE OVERRIDE ENABLE
PUD: WDx: RDx: RRx: WRx: RPx: WPx: clkI/O: DIxn: AIOxn:
PULLUP DISABLE WRITE DDRx READ DDRx READ PORTx REGISTER WRITE PORTx READ PORTx PIN WRITE PINx I/O CLOCK DIGITAL INPUT PIN n ON PORTx ANALOG INPUT/OUTPUT PIN n ON PORTx
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Note: 1. WRx, WPx, WDx, RRx, RPx, and RDx are common to all pins within the same port. clkI/O, SLEEP, and PUD are common to all ports. All other signals are unique for each pin.
Table 11-2 summarizes the function of the overriding signals. The pin and port indexes from Figure 11-5 are not shown in the succeeding tables. The overriding signals are generated internally in the modules having the alternate function. Table 11-2.
Signal Name PUOE
Generic Description of Overriding Signals for Alternate Functions
Full Name Pull-up Override Enable Pull-up Override Value Data Direction Override Enable Data Direction Override Value Port Value Override Enable Port Value Override Value Port Toggle Override Enable Digital Input Enable Override Enable Digital Input Enable Override Value Description If this signal is set, the pull-up enable is controlled by the PUOV signal. If this signal is cleared, the pull-up is enabled when {DDxn, PORTxn, PUD} = 0b010. If PUOE is set, the pull-up is enabled/disabled when PUOV is set/cleared, regardless of the setting of the DDxn, PORTxn, and PUD Register bits. If this signal is set, the Output Driver Enable is controlled by the DDOV signal. If this signal is cleared, the Output driver is enabled by the DDxn Register bit. If DDOE is set, the Output Driver is enabled/disabled when DDOV is set/cleared, regardless of the setting of the DDxn Register bit. If this signal is set and the Output Driver is enabled, the port value is controlled by the PVOV signal. If PVOE is cleared, and the Output Driver is enabled, the port Value is controlled by the PORTxn Register bit. If PVOE is set, the port value is set to PVOV, regardless of the setting of the PORTxn Register bit. If PTOE is set, the PORTxn Register bit is inverted. If this bit is set, the Digital Input Enable is controlled by the DIEOV signal. If this signal is cleared, the Digital Input Enable is determined by MCU state (Normal mode, sleep mode). If DIEOE is set, the Digital Input is enabled/disabled when DIEOV is set/cleared, regardless of the MCU state (Normal mode, sleep mode). This is the Digital Input to alternate functions. In the figure, the signal is connected to the output of the schmitt trigger but before the synchronizer. Unless the Digital Input is used as a clock source, the module with the alternate function will use its own synchronizer. This is the Analog Input/output to/from alternate functions. The signal is connected directly to the pad, and can be used bidirectionally.
PUOV
DDOE
DDOV
PVOE
PVOV PTOE DIEOE
DIEOV
DI
Digital Input
AIO
Analog Input/Output
The following subsections shortly describe the alternate functions for each port, and relate the overriding signals to the alternate function. Refer to the alternate function description for further details. 11.3.1 MCU Control Register - MCUCR
Bit 7 JTD 6 - 5 - 4 PUD 3 - 2 - 1 IVSEL 0 IVCE MCUCR
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Read/Write Initial Value
R/W 0
R 0
R 0
R/W 0
R 0
R 0
R/W 0
R/W 0
* Bit 4 - PUD: Pull-up Disable When this bit is written to one, the pull-ups in the I/O ports are disabled even if the DDxn and PORTxn Registers are configured to enable the pull-ups ({DDxn, PORTxn} = 0b01). See "Configuring the Pin" on page 68 for more details about this feature. 11.3.2 Alternate Functions of Port B The Port B pins with alternate functions are shown in Table 11-3. Table 11-3.
Port Pin PB7 PB6 PB5 PB4 PB3 PB2 PB1 PB0
Port B Pins Alternate Functions
Alternate Functions OC0A/OC1C/PCINT7 (Output Compare and PWM Output A for Timer/Counter0, Output Compare and PWM Output C for Timer/Counter1 or Pin Change Interrupt 7) PCINT6 (Pin Change Interrupt 6) PCINT5 (Pin Change Interrupt 5) T1/PCINT4 (Timer/Counter1 Clock Input or Pin Change Interrupt 4) PDO/MISO/PCINT3 (Programming Data Output or SPI Bus Master Input/Slave Output or Pin Change Interrupt 3) PDI/MOSI/PCINT2 (Programming Data Input or SPI Bus Master Output/Slave Input or Pin Change Interrupt 2) SCLK/PCINT1 (SPI Bus Serial Clock or Pin Change Interrupt 1) SS/PCINT0 (SPI Slave Select input or Pin Change Interrupt 0)
The alternate pin configuration is as follows: * OC0A/OC1C/PCINT7, Bit 7 OC0A, Output Compare Match A output: The PB7 pin can serve as an external output for the Timer/Counter0 Output Compare. The pin has to be configured as an output (DDB7 set "one") to serve this function. The OC0A pin is also the output pin for the PWM mode timer function. OC1C, Output Compare Match C output: The PB7 pin can serve as an external output for the Timer/Counter1 Output Compare C. The pin has to be configured as an output (DDB7 set "one") to serve this function. The OC1C pin is also the output pin for the PWM mode timer function. PCINT7, Pin Change Interrupt source 7: The PB7 pin can serve as an external interrupt source. * PCINT6, Bit 6 PCINT6, Pin Change Interrupt source 6: The PB6 pin can serve as an external interrupt source. * PCINT5, Bit 5 PCINT5, Pin Change Interrupt source 5: The PB5 pin can serve as an external interrupt source. * T1/PCINT4, Bit 4 T1, Timer/Counter1 counter source. PCINT4, Pin Change Interrupt source 4: The PB4 pin can serve as an external interrupt source. * PDO/MISO/PCINT3 - Port B, Bit 3 74
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PDO, SPI Serial Programming Data Output. During Serial Program Downloading, this pin is used as data output line for the AT90USB82/162. MISO: Master Data input, Slave Data output pin for SPI channel. When the SPI is enabled as a master, this pin is configured as an input regardless of the setting of DDB3. When the SPI is enabled as a slave, the data direction of this pin is controlled by DDB3. When the pin is forced to be an input, the pull-up can still be controlled by the PORTB3 bit. PCINT3, Pin Change Interrupt source 3: The PB3 pin can serve as an external interrupt source. * PDI/MOSI/PCINT2 - Port B, Bit 2 PDI, SPI Serial Programming Data Input. During Serial Program Downloading, this pin is used as data input line for the AT90USB82/162. MOSI: SPI Master Data output, Slave Data input for SPI channel. When the SPI is enabled as a slave, this pin is configured as an input regardless of the setting of DDB2. When the SPI is enabled as a master, the data direction of this pin is controlled by DDB2. When the pin is forced to be an input, the pull-up can still be controlled by the PORTB2 bit. PCINT2, Pin Change Interrupt source 2: The PB2 pin can serve as an external interrupt source. * SCK/PCINT1 - Port B, Bit 1 SCK: Master Clock output, Slave Clock input pin for SPI channel. When the SPI is enabled as a slave, this pin is configured as an input regardless of the setting of DDB1. When the SPI0 is enabled as a master, the data direction of this pin is controlled by DDB1. When the pin is forced to be an input, the pull-up can still be controlled by the PORTB1 bit. This pin also serves as Clock for the Serial Programming interface. PCINT1, Pin Change Interrupt source 1: The PB1 pin can serve as an external interrupt source. * SS/PCINT0 - Port B, Bit 0 SS: Slave Port Select input. When the SPI is enabled as a slave, this pin is configured as an input regardless of the setting of DDB0. As a slave, the SPI is activated when this pin is driven low. When the SPI is enabled as a master, the data direction of this pin is controlled by DDB0. When the pin is forced to be an input, the pull-up can still be controlled by the PORTB0 bit. PCINT0, Pin Change Interrupt source 0: The PB0 pin can serve as an external interrupt source. Table 11-4 and Table 11-5 relate the alternate functions of Port B to the overriding signals shown in Figure 11-5 on page 72. SPI MSTR INPUT and SPI SLAVE OUTPUT constitute the MISO signal, while MOSI is divided into SPI MSTR OUTPUT and SPI SLAVE INPUT. PCINT0, Pin Change Interrupt source 0: The PB0 pin can serve as an external interrupt source
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.Table 11-4 and Table 11-5 relate the alternate functions of Port B to the overriding signals shown in Figure 11-5 on page 72. SPI MSTR INPUT and SPI SLAVE OUTPUT constitute the MISO signal, while MOSI is divided into SPI MSTR OUTPUT and SPI SLAVE INPUT.. Table 11-4.
Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO
Overriding Signals for Alternate Functions in PB7..PB4
PB7/OC0A/OC1C/PCI NT7 0 0 0 0 OC0A/OC1C ENABLE OC0A/OC1C PCINT7 * PCIE0 1 PCINT7 INPUT - PB6/PCINT6 0 0 0 0 0 0 PCINT6 * PCIE0 1 PCINT6 INPUT - PB5/PCINT5 0 0 0 0 0 0 PCINT5 * PCIE0 1 PCINT5 INPUT - PB4/T1/PCINT4 0 0 0 0 0 0 PCINT4 * PCIE0 1 PCINT4 INPUT T1 INPUT -
Table 11-5.
Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO
Overriding Signals for Alternate Functions in PB3..PB0
PB3/MISO/PCINT3/PD O SPE * MSTR PORTB3 * PUD SPE * MSTR 0 SPE * MSTR SPI SLAVE OUTPUT PCINT3 * PCIE0 1 SPI MSTR INPUT PCINT3 INPUT - PB2/MOSI/PCINT2/P DI SPE * MSTR PORTB2 * PUD SPE * MSTR 0 SPE * MSTR SPI MSTR OUTPUT PCINT2 * PCIE0 1 SPI SLAVE INPUT PCINT2 INPUT - PB1/SCK/PCINT 1 SPE * MSTR PORTB1 * PUD SPE * MSTR 0 SPE * MSTR SCK OUTPUT PCINT1 * PCIE0 1 SCK INPUT PCINT1 INPUT - PB0/SS/PCINT0 SPE * MSTR PORTB0 * PUD SPE * MSTR 0 0 0 PCINT0 * PCIE0 1 SPI SS PCINT0 INPUT -
11.3.3
Alternate Functions of Port C The Port C alternate function is as follows:
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Table 11-6. Port C Pins Alternate Functions
Port Pin PC7 PC6 PC5 PC4 PC2 PC1 PC0 Alternate Function ICP1/INT4/CLKO PCINT8/OC1A PCINT9/OC1B PCINT10 PCINT11 Reset, dW XTAL2
The alternate pin configuration is as follows: * ICP1/INT4/CLK0, Bit 7 ICP1, Input Capture pin 1 :The PC7 pin can act as an input capture for Timer/Counter1. INT4, External Interrupt source 4 : The PC7 pin can serve as an external interrupt source to the MCU. CLK0, Clock Output : The PC7 pin can serve as oscillator clock ouput if the feature is enabled by fuse. * PCINT8/OC1A, Bit 6 PCINT8, Pin Change Interrupt source 8 : The PC6 pin can serve as an external interrupt source. OC1A, Output Compare Match A output: The PC6 pin can serve as an external output for the Timer/Counter1 Output Compare. The pin has to be configured as an output (DDC6 set "one") to serve this function. The OC1A pin is also the output pin for the PWM mode timer function. * PCINT9/OC1B, Bit 5 PCINT9, Pin Change Interrupt source 9: The PC5 pin can serve as an external interrupt source. OC1B, Output Compare Match B output: The PC5 pin can serve as an external output for the Timer/Counter1 Output Compare. The pin has to be configured as an output (DDC5 set "one") to serve this function. The OC1B pin is also the output pin for the PWM mode timer function. * PCINT10, Bit 4 PCINT10, Pin Change Interrupt source 10 : The PC4 pin can serve as an external interrupt source. * PCINT11, Bit 2 PCINT11, Pin Change Interrupt source 11 : The PC2 pin can serve as an external interrupt source. * Reset/dW, Bit 1 Reset, Reset input. External Reset input is active low and enabled by unprogramming ("1") the RSTDISBL Fuse. Pullup is activated and output driver and digital input are deactivated when the pin is used as the RESET pin. 77
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dW, debugWire channel. When the debugWIRE Enable (DWEN) Fuse is programmed and Lock bits are unprogrammed, the debugWIRE system within the target device is activated. The RESET port pin is configured as a wired -AND (open-drain) bi-directional I/O pin with pull-up enabled and becomes the communication gateway between the target and the emulator. * XTAL2, Bit 0 XTAL2, Oscillator. The PC0 pin can serve as Inverting Output for internal Oscillator amplifier. Table 11-7 and Table 11-8 relate the alternate functions of Port C to the overriding signals shown in Figure 11-5 on page 72. Table 11-7.
Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO
Overriding Signals for Alternate Functions in PC7..PC4
PC7/ICP1/INT4/CLK0 0 0 0 0 0 0 INT4 ENABLE 1 INT4 INPUT - PC6/PCINT8/OC1 A 0 0 0 0 OC1A ENABLE OC1A PCINT8 ENABLE 1 PCINT8 INPUT - PC5/PCINT9/OC1 B 0 0 0 0 OC1B ENABLE OC1B PCINT9 ENABLE 1 PCINT9 INPUT - PC4/PCINT10 0 0 0 0 0 0 PCINT10 ENABLE 1 PCINT10 INPUT -
Table 11-8.
Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO
Overriding Signals for Alternate Functions in PC2..PC0
PC2/PCINT11 0 0 0 0 0 0 PCINT11 ENABLE 1 PCINT11 INPUT - PC1/RESET/dW 0 0 0 0 0 0 0 0 - - PC0/XTAL2 0 0 0 0 0 0 0 0 - -
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11.3.4 Alternate Functions of Port D The Port D pins with alternate functions are shown in Table 11-9. Table 11-9.
Port Pin PD7 PD6 PD5 PD4 PD3 PD2 PD1 PD0
Port D Pins Alternate Functions
Alternate Function HWB/TO/INT7/CTS INT6/RTS XCK1/PCINT12 (USART1 External Clock Input/Output) INT5 INT3/TXD1 (External Interrupt3 Input or USART1 Transmit Pin) INT2/AIN1/RXD1(External Interrupt2 Input or USART1 Receive Pin) INT1/AIN0 (External Interrupt1 Input) INT0/OC0B (External Interrupt0 Input)
The alternate pin configuration is as follows: * HWB/TO/INT7/CTS, Bit 7 HWB, Hardware Boot : The PD7 pin can serve as TO, Timer/Counter0 counter source. INT7, External Interrupt source 7: The PD7 pin can serve as an external interrupt source to the MCU. CTS, USART1 Transmitter Flow Control. This pin can control the transmitter in function of its state. * INT6/RTS,Bit 6 INT6, External Interrupt source 6: The PD6 pin can serve as an external interrupt source to the MCU. RTS, USART1 Receiver Flow Control. This pin can control the receiver in function of its state. * XCK1/PCINT12, Bit 5 XCK1, USART1 External Clock : The data direction register DDRD5 controls whether the clock is output (DDRD5 set) or input (DDRD5 cleared). The XCK1 pin is active only when the USART1 operates in Synchronous Mode. PCINT12, Pin Change Interrupt source 12: The PD5 pin can serve as an external interrupt source. * INT5, Bit 4 INT5, External Interrupt source 5: The PD4 pin can serve as an external interrupt source to the MCU. * INT3/TXD1, Bit 3 INT3, External Interrupt source 3: The PD3 pin can serve as an external interrupt source to the MCU.
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TXD1, USART1 Transmit Data : When the USART1 Transmitter is enabled, this pin is configured as an ouput regardless of DDRD3. * INT2/AIN1/RXD1, Bit 2 INT2, External Interrupt source 2: The PD2 pin can serve as an external interrupt source to the MCU. AIN1, Analog Comparator Negative input. This pin is directly connected to the negative input of the Analog Comparator. RXD1, USART1 Receive Data : When the USART1 Receiver is enabled, this pin is configured as an input regardless of DDRD2. When the USART forces this pin to be an input, the pull-up can still be controlled by the PORTD2 bit. * INT1/AIN0, Bit 1 INT1, External Interrupt source 1: The PD1 pin can serve as an external interrupt source to the MCU. AIN0, Analog Comparator Positive input. This pin is directly connected to the positive input of the Analog Comparator. * INT0/OC0B, Bit 0 INT0, External Interrupt source 0: The PD0 pin can serve as an external interrupt source to the MCU. OC0B, Output Compare Match B output: The PD0 pin can serve as an external output for the Timer/Counter0 Output Compare. The pin has to be configured as an output (DDD0 set "one") to serve this function. The OC0B pin is also the output pin for the PWM mode timer function. Table 11-10 and Table 11-11 relates the alternate functions of Port D to the overriding signals shown in Figure 11-5 on page 72.
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Table 11-10. Overriding Signals for Alternate Functions PD7..PD4
Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO PD7/T0/INT7/ HBW/CTS CTS PORTD7 * PUD CTS 0 0 0 INT7/CTS ENABLE 1 T0 INPUT INT7 INPUT CTS INPUT - PD6/INT6/RT S RTS 0 RTS 1 RTS OUTPUT ENABLE RTS OUTPUT INT6 ENABLE 1 INT6 INPUT - PD5/XCK/PCINT12 0 0 0 0 XCK OUTPUT ENABLE XCK1 OUTPUT PCINT12 ENABLE 1 XCK INPUT PCINT12 INPUT - PD4/INT5 0 0 0 0 0 0 INT5 ENABLE 1 INT5 INPUT -
Table 11-11. Overriding Signals for Alternate Functions in PD3..PD0(1)
Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO Note: PD3/INT3/TXD1 TXEN1 0 TXEN1 1 TXEN1 TXD1 INT3 ENABLE 1 INT3 INPUT - PD2/INT2/RXD1/AIN 1 RXEN1 PORTD2 * PUD RXEN1 0 0 0 INT2 ENABLE AIN1 ENABLE AIN1 ENABLE INT2 INPUT/RXD1 AIN1 INPUT PD1/INT1/AIN0 0 0 0 0 0 0 INT1 ENABLE AIN0 ENABLE AIN0 ENABLE INT1 INPUT AIN0 INPUT PD0/INT0/OC0B 0 0 0 0 OC0B ENABLE OC0B INT0 ENABLE 1 INT0 INPUT -
1. When enabled, the 2-wire Serial Interface enables Slew-Rate controls on the output pins PD0 and PD1. This is not shown in this table. In addition, spike filters are connected between the AIO outputs shown in the port figure.
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11.4
11.4.1
Register Description for I/O-Ports
Port B Data Register - PORTB
Bit Read/Write Initial Value 7 PORTB7 R/W 0 6 PORTB6 R/W 0 5 PORTB5 R/W 0 4 PORTB4 R/W 0 3 PORTB3 R/W 0 2 PORTB2 R/W 0 1 PORTB1 R/W 0 0 PORTB0 R/W 0 PORTB
11.4.2
Port B Data Direction Register - DDRB
Bit Read/Write Initial Value 7 DDB7 R/W 0 6 DDB6 R/W 0 5 DDB5 R/W 0 4 DDB4 R/W 0 3 DDB3 R/W 0 2 DDB2 R/W 0 1 DDB1 R/W 0 0 DDB0 R/W 0 DDRB
11.4.3
Port B Input Pins Address - PINB
Bit Read/Write Initial Value 7 PINB7 R/W N/A 6 PINB6 R/W N/A 5 PINB5 R/W N/A 4 PINB4 R/W N/A 3 PINB3 R/W N/A 2 PINB2 R/W N/A 1 PINB1 R/W N/A 0 PINB0 R/W N/A PINB
11.4.4
Port C Data Register - PORTC
Bit Read/Write Initial Value 7 PORTC7 R/W 0 6 PORTC6 R/W 0 5 PORTC5 R/W 0 4 PORTC4 R/W 0 3 R 0 2 PORTC2 R/W 0 1 PORTC1 R/W 0 0 PORTC0 R/W 0 PORTC
11.4.5
Port C Data Direction Register - DDRC
Bit Read/Write Initial Value 7 DDC7 R/W 0 6 DDC6 R/W 0 5 DDC5 R/W 0 4 DDC4 R/W 0 3 R 0 2 DDC2 R/W 0 1 DDC1 R/W 0 0 DDC0 R/W 0 DDRC
11.4.6
Port C Input Pins Address - PINC
Bit Read/Write Initial Value 7 PINC7 R/W N/A 6 PINC6 R/W N/A 5 PINC5 R/W N/A 4 PINC4 R/W N/A 3 R N/A 2 PINC2 R/W N/A 1 PINC1 R/W N/A 0 PINC0 R/W N/A PINC
11.4.7
Port D Data Register - PORTD
Bit Read/Write Initial Value 7 PORTD7 R/W 0 6 PORTD6 R/W 0 5 PORTD5 R/W 0 4 PORTD4 R/W 0 3 PORTD3 R/W 0 2 PORTD2 R/W 0 1 PORTD1 R/W 0 0 PORTD0 R/W 0 PORTD
11.4.8
Port D Data Direction Register - DDRD
Bit Read/Write Initial Value 7 DDD7 R/W 0 6 DDD6 R/W 0 5 DDD5 R/W 0 4 DDD4 R/W 0 3 DDD3 R/W 0 2 DDD2 R/W 0 1 DDD1 R/W 0 0 DDD0 R/W 0 DDRD
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11.4.9 Port D Input Pins Address - PIND
Bit Read/Write Initial Value 7 PIND7 R/W N/A 6 PIND6 R/W N/A 5 PIND5 R/W N/A 4 PIND4 R/W N/A 3 PIND3 R/W N/A 2 PIND2 R/W N/A 1 PIND1 R/W N/A 0 PIND0 R/W N/A PIND
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12. External Interrupts
The External Interrupts are triggered by the INT7:0 pin or any of the PCINT12..0 pins. Observe that, if enabled, the interrupts will trigger even if the INT7:0 or PCINT12..0 pins are configured as outputs. This feature provides a way of generating a software interrupt. The Pin change interrupt PCI0 will trigger if any enabled PCINT7:0 pin toggles. PCMSK0 Register control which pins contribute to the pin change interrupts. The Pin change interrupt PCI1 will trigger if any enabled PCINT12:8 pin toggles. PCMSK1 Register control which pins contribute to the pin change interrupts. Pin change interrupts on PCINT12 ..0 are detected asynchronously. This implies that these interrupts can be used for waking the part also from sleep modes other than Idle mode. The External Interrupts can be triggered by a falling or rising edge or a low level. This is set up as indicated in the specification for the External Interrupt Control Registers - EICRA (INT3:0) and EICRB (INT7:4). When the external interrupt is enabled and is configured as level triggered, the interrupt will trigger as long as the pin is held low. Note that recognition of falling or rising edge interrupts on INT7:4 requires the presence of an I/O clock, described in "System Clock and Clock Options" on page 25. Low level interrupts and the edge interrupt on INT3:0 are detected asynchronously. This implies that these interrupts can be used for waking the part also from sleep modes other than Idle mode. The I/O clock is halted in all sleep modes except Idle mode. Note that if a level triggered interrupt is used for wake-up from Power-down, the required level must be held long enough for the MCU to complete the wake-up to trigger the level interrupt. If the level disappears before the end of the Start-up Time, the MCU will still wake up, but no interrupt will be generated. The start-up time is defined by the SUT and CKSEL Fuses as described in "System Clock and Clock Options" on page 25. 12.0.1 External Interrupt Control Register A - EICRA The External Interrupt Control Register A contains control bits for interrupt sense control.
Bit Read/Write Initial Value 7 ISC31 R/W 0 6 ISC30 R/W 0 5 ISC21 R/W 0 4 ISC20 R/W 0 3 ISC11 R/W 0 2 ISC10 R/W 0 1 ISC01 R/W 0 0 ISC00 R/W 0 EICRA
* Bits 7..0 - ISC31, ISC30 - ISC00, ISC00: External Interrupt 3 - 0 Sense Control Bits The External Interrupts 3 - 0 are activated by the external pins INT3:0 if the SREG I-flag and the corresponding interrupt mask in the EIMSK is set. The level and edges on the external pins that activate the interrupts are defined in Table 12-1. Edges on INT3..INT0 are registered asynchronously. Pulses on INT3:0 pins wider than the minimum pulse width given in Table 12-2 will generate an interrupt. Shorter pulses are not guaranteed to generate an interrupt. If low level interrupt is selected, the low level must be held until the completion of the currently executing instruction to generate an interrupt. If enabled, a level triggered interrupt will generate an interrupt request as long as the pin is held low. When changing the ISCn bit, an interrupt can occur. Therefore, it is recommended to first disable INTn by clearing its Interrupt Enable bit in the EIMSK Register. Then, the ISCn bit can be changed. Finally, the INTn interrupt flag should be cleared by writing a logical one to its Interrupt Flag bit (INTFn) in the EIFR Register before the interrupt is re-enabled.
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Table 12-1.
ISCn1 0 0 1 1 Note: 0 1 0 1
Interrupt Sense Control(1)
ISCn0 Description The low level of INTn generates an interrupt request. Any edge of INTn generates asynchronously an interrupt request. The falling edge of INTn generates asynchronously an interrupt request. The rising edge of INTn generates asynchronously an interrupt request.
1. n = 3, 2, 1or 0. When changing the ISCn1/ISCn0 bits, the interrupt must be disabled by clearing its Interrupt Enable bit in the EIMSK Register. Otherwise an interrupt can occur when the bits are changed.
Table 12-2.
Symbol tINT
Asynchronous External Interrupt Characteristics
Parameter Minimum pulse width for asynchronous external interrupt Condition Min Typ 50 Max Units ns
12.0.2
External Interrupt Control Register B - EICRB
Bit Read/Write Initial Value 7 ISC71 R/W 0 6 ISC70 R/W 0 5 ISC61 R/W 0 4 ISC60 R/W 0 3 ISC51 R/W 0 2 ISC50 R/W 0 1 ISC41 R/W 0 0 ISC40 R/W 0 EICRB
* Bits 7..0 - ISC71, ISC70 - ISC41, ISC40: External Interrupt 7 - 4 Sense Control Bits The External Interrupts 7 - 4 are activated by the external pins INT7:4 if the SREG I-flag and the corresponding interrupt mask in the EIMSK is set. The level and edges on the external pins that activate the interrupts are defined in Table 12-3. The value on the INT7:4 pins are sampled before detecting edges. If edge or toggle interrupt is selected, pulses that last longer than one clock period will generate an interrupt. Shorter pulses are not guaranteed to generate an interrupt. Observe that CPU clock frequency can be lower than the XTAL frequency if the XTAL divider is enabled. If low level interrupt is selected, the low level must be held until the completion of the currently executing instruction to generate an interrupt. If enabled, a level triggered interrupt will generate an interrupt request as long as the pin is held low. Table 12-3.
ISCn1 0 0 1 1 Note: 0 1 0 1
Interrupt Sense Control(1)
Description The low level of INTn generates an interrupt request. Any logical change on INTn generates an interrupt request The falling edge between two samples of INTn generates an interrupt request. The rising edge between two samples of INTn generates an interrupt request.
ISCn0
1. n = 7, 6, 5 or 4. When changing the ISCn1/ISCn0 bits, the interrupt must be disabled by clearing its Interrupt Enable bit in the EIMSK Register. Otherwise an interrupt can occur when the bits are changed.
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12.0.3
External Interrupt Mask Register - EIMSK
Bit Read/Write Initial Value 7 INT7 R/W 0 6 INT6 R/W 0 5 INT5 R/W 0 4 INT4 R/W 0 3 INT3 R/W 0 2 INT2 R/W 0 1 INT1 R/W 0 0 IINT0 R/W 0 EIMSK
* Bits 7..0 - INT7 - INT0: External Interrupt Request 7 - 0 Enable When an INT7 - INT0 bit is written to one and the I-bit in the Status Register (SREG) is set (one), the corresponding external pin interrupt is enabled. The Interrupt Sense Control bits in the External Interrupt Control Registers - EICRA and EICRB - defines whether the external interrupt is activated on rising or falling edge or level sensed. Activity on any of these pins will trigger an interrupt request even if the pin is enabled as an output. This provides a way of generating a software interrupt. 12.0.4 External Interrupt Flag Register - EIFR
Bit Read/Write Initial Value 7 INTF7 R/W 0 6 INTF6 R/W 0 5 INTF5 R/W 0 4 INTF4 R/W 0 3 INTF3 R/W 0 2 INTF2 R/W 0 1 INTF1 R/W 0 0 INTF0 R/W 0 EIFR
* Bits 7..0 - INTF7 - INTF0: External Interrupt Flags 7 - 0 When an edge or logic change on the INT7:0 pin triggers an interrupt request, INTF7:0 becomes set (one). If the I-bit in SREG and the corresponding interrupt enable bit, INT7:0 in EIMSK, are set (one), the MCU will jump to the interrupt vector. The flag is cleared when the interrupt routine is executed. Alternatively, the flag can be cleared by writing a logical one to it. These flags are always cleared when INT7:0 are configured as level interrupt. Note that when entering sleep mode with the INT3:0 interrupts disabled, the input buffers on these pins will be disabled. This may cause a logic change in internal signals which will set the INTF3:0 flags. See "Digital Input Enable and Sleep Modes" on page 71 for more information. 12.0.5 Pin Change Interrupt Control Register - PCICR
Bit Read/Write Initial Value 7 R 0 6 R 0 5 - R 0 4 - R 0 3 - R 0 2 - R 0 1 PCIE1 R/W 0 0 PCIE0 R/W 0 PCICR
* Bit 1..0 - PCIE1- PCIE0: Pin Change Interrupt Enable 1-0 When the PCIE1/0 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), Pin Change interrupt 1/0 is enabled. Any change on any enabled PCINT12..8/7..0 pin will cause an interrupt. The corresponding interrupt of Pin Change Interrupt Request is executed from the PCI1/0 Interrupt Vector. PCINT12..8/7..0 pins are enabled individually by the PCMSK1/0 Register. 12.0.6 Pin Change Interrupt Flag Register - PCIFR
Bit Read/Write Initial Value 7 R 0 6 R 0 5 - R 0 4 - R 0 3 - R 0 2 - R 0 1 PCIF1 R/W 0 0 PCIF0 R/W 0 PCIFR
* Bit 1..0 - PCIF1- PCIF0: Pin Change Interrupt Flag 1-0
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When a logic change on any PCINT12..8/7..0 pin triggers an interrupt request, PCIF1/0 becomes set (one). If the I-bit in SREG and the PCIE1/0 bit in PCICR are set (one), the MCU will jump to the corresponding Interrupt Vector. The flag is cleared when the interrupt routine is executed. Alternatively, the flag can be cleared by writing a logical one to it. 12.0.7 Pin Change Mask Register 0 - PCMSK0
Bit Read/Write Initial Value 7 PCINT7 R/W 0 6 PCINT6 R/W 0 5 PCINT5 R/W 0 4 PCINT4 R/W 0 3 PCINT3 R/W 0 2 PCINT2 R/W 0 1 PCINT1 R/W 0 0 PCINT0 R/W 0 PCMSK0
* Bit 7..0 - PCINT7..0: Pin Change Enable Mask 7..0 Each PCINT7..0 bit selects whether pin change interrupt is enabled on the corresponding I/O pin. If PCINT7..0 is set and the PCIE0 bit in PCICR is set, pin change interrupt is enabled on the corresponding I/O pin. If PCINT7..0 is cleared, pin change interrupt on the corresponding I/O pin is disabled. 12.0.8 Pin Change Mask Register 1- PCMSK1
Bit Read/Write Initial Value 7 R 0 6 R 0 5 R/W 0 4 PCINT12 R/W 0 3 PCINT11 R/W 0 2 PCINT10 R/W 0 1 PCINT9 R/W 0 0 PCINT8 R/W 0 PCMSK1
* Bit 4..0 - PCINT12..8: Pin Change Enable Mask 12..8 Each PCINT12..8 bit selects whether pin change interrupt is enabled on the corresponding I/O pin. If PCINT12..8 is set and the PCIE1 bit in PCICR is set, pin change interrupt is enabled on the corresponding I/O pin. If PCINT12..8 is cleared, pin change interrupt on the corresponding I/O pin is disabled.
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13. Timer/Counter0 and Timer/Counter1 Prescalers
Timer/Counter0 and 1 share the same prescaler module, but the Timer/Counters can have different prescaler settings. The description below applies to all Timer/Counters. Tn is used as a general name, n = 0 or 1. 13.0.1 Internal Clock Source The Timer/Counter can be clocked directly by the system clock (by setting the CSn2:0 = 1). This provides the fastest operation, with a maximum Timer/Counter clock frequency equal to system clock frequency (fCLK_I/O). Alternatively, one of four taps from the prescaler can be used as a clock source. The prescaled clock has a frequency of either fCLK_I/O/8, fCLK_I/O/64, fCLK_I/O/256, or fCLK_I/O/1024. Prescaler Reset The prescaler is free running, i.e., operates independently of the Clock Select logic of the Timer/Counter, and it is shared by the Timer/Counter Tn. Since the prescaler is not affected by the Timer/Counter's clock select, the state of the prescaler will have implications for situations where a prescaled clock is used. One example of prescaling artifacts occurs when the timer is enabled and clocked by the prescaler (6 > CSn2:0 > 1). The number of system clock cycles from when the timer is enabled to the first count occurs can be from 1 to N+1 system clock cycles, where N equals the prescaler divisor (8, 64, 256, or 1024). It is possible to use the prescaler reset for synchronizing the Timer/Counter to program execution. However, care must be taken if the other Timer/Counter that shares the same prescaler also uses prescaling. A prescaler reset will affect the prescaler period for all Timer/Counters it is connected to. 13.0.3 External Clock Source An external clock source applied to the Tn pin can be used as Timer/Counter clock (clkTn). The Tn pin is sampled once every system clock cycle by the pin synchronization logic. The synchronized (sampled) signal is then passed through the edge detector. Figure 13-1 shows a functional equivalent block diagram of the Tn synchronization and edge detector logic. The registers are clocked at the positive edge of the internal system clock (clkI/O). The latch is transparent in the high period of the internal system clock. The edge detector generates one clkTn pulse for each positive (CSn2:0 = 7) or negative (CSn2:0 = 6) edge it detects. Figure 13-1. Tn/T0 Pin Sampling
Tn
13.0.2
D LE
Q
D
Q
D
Q
Tn_sync (To Clock Select Logic)
clk I/O
Synchronization Edge Detector
The synchronization and edge detector logic introduces a delay of 2.5 to 3.5 system clock cycles from an edge has been applied to the Tn pin to the counter is updated. Enabling and disabling of the clock input must be done when Tn has been stable for at least one system clock cycle, otherwise it is a risk that a false Timer/Counter clock pulse is generated. 88
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Each half period of the external clock applied must be longer than one system clock cycle to ensure correct sampling. The external clock must be guaranteed to have less than half the system clock frequency (fExtClk < fclk_I/O/2) given a 50/50% duty cycle. Since the edge detector uses sampling, the maximum frequency of an external clock it can detect is half the sampling frequency (Nyquist sampling theorem). However, due to variation of the system clock frequency and duty cycle caused by Oscillator source (crystal, resonator, and capacitors) tolerances, it is recommended that maximum frequency of an external clock source is less than fclk_I/O/2.5. An external clock source can not be prescaled. Figure 13-2. Prescaler for synchronous Timer/Counters
clk I/O
Clear
PSR10
Tn
Synchronization
Tn
Synchronization
CSn0 CSn1 CSn2
CSn0 CSn1 CSn2
TIMER/COUNTERn CLOCK SOURCE clkTn
TIMER/COUNTERn CLOCK SOURCE clkTn
13.0.4
General Timer/Counter Control Register - GTCCR
Bit 7 TSM Read/Write Initial Value R/W 0 6 - R 0 5 - R 0 4 - R 0 3 - R 0 2 - R 0 1 R/W 0 0 PSRSY NC R/W 0 GTCCR
* Bit 7 - TSM: Timer/Counter Synchronization Mode Writing the TSM bit to one activates the Timer/Counter Synchronization mode. In this mode, the value that is written to the PSRASY and PSRSYNC bits is kept, hence keeping the corresponding prescaler reset signals asserted. This ensures that the corresponding Timer/Counters are halted and can be configured to the same value without the risk of one of them advancing during configuration. When the TSM bit is written to zero, the PSRASY and PSRSYNC bits are cleared by hardware, and the Timer/Counters start counting simultaneously. * Bit 0 - PSRSYNC: Prescaler Reset for Synchronous Timer/Counters When this bit is one, Timer/Counter0 and Timer/Counter1, Timer/Counter3, Timer/Counter4 and Timer/Counter5 prescaler will be Reset. This bit is normally cleared immediately by hardware, except if the TSM bit is set. Note that Timer/Counter0 and Timer/Counter1 share the same prescaler and a reset of this prescaler will affect all timers.
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14. 8-bit Timer/Counter0 with PWM
Timer/Counter0 is a general purpose 8-bit Timer/Counter module, with two independent Output Compare Units, and with PWM support. It allows accurate program execution timing (event management) and wave generation. The main features are: * * * * * * *
Two Independent Output Compare Units Double Buffered Output Compare Registers Clear Timer on Compare Match (Auto Reload) Glitch Free, Phase Correct Pulse Width Modulator (PWM) Variable PWM Period Frequency Generator Three Independent Interrupt Sources (TOV0, OCF0A, and OCF0B)
14.1
Overview
A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 14-1. For the actual placement of I/O pins, refer to "Pinout AT90USB82/162" on page 3. CPU accessible I/O Registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O Register and bit locations are listed in the "8-bit Timer/Counter Register Description" on page 100. Figure 14-1. 8-bit Timer/Counter Block Diagram
Count Clear Direction Control Logic TOVn (Int.Req.) clkTn Clock Select Edge Detector TOP BOTTOM ( From Prescaler ) Timer/Counter TCNTn Tn
=
=0
OCnA (Int.Req.)
=
OCRnA Fixed TOP Value
Waveform Generation
OCnA
DATA BUS
OCnB (Int.Req.) Waveform Generation OCnB
=
OCRnB
TCCRnA
TCCRnB
14.1.1
Registers The Timer/Counter (TCNT0) and Output Compare Registers (OCR0A and OCR0B) are 8-bit registers. Interrupt request (abbreviated to Int.Req. in the figure) signals are all visible in the Timer Interrupt Flag Register (TIFR0). All interrupts are individually masked with the Timer Interrupt Mask Register (TIMSK0). TIFR0 and TIMSK0 are not shown in the figure. The Timer/Counter can be clocked internally, via the prescaler, or by an external clock source on the T0 pin. The Clock Select logic block controls which clock source and edge the Timer/Counter uses to increment (or decrement) its value. The Timer/Counter is inactive when no clock source is selected. The output from the Clock Select logic is referred to as the timer clock (clkT0).
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The double buffered Output Compare Registers (OCR0A and OCR0B) are compared with the Timer/Counter value at all times. The result of the compare can be used by the Waveform Generator to generate a PWM or variable frequency output on the Output Compare pins (OC0A and OC0B). See "Output Compare Unit" on page 92. for details. The Compare Match event will also set the Compare Flag (OCF0A or OCF0B) which can be used to generate an Output Compare interrupt request. 14.1.2 Definitions Many register and bit references in this section are written in general form. A lower case "n" replaces the Timer/Counter number, in this case 0. A lower case "x" replaces the Output Compare Unit, in this case Compare Unit A or Compare Unit B. However, when using the register or bit defines in a program, the precise form must be used, i.e., TCNT0 for accessing Timer/Counter0 counter value and so on. The definitions in Table 14-1 are also used extensively throughout the document. Table 14-1. BOTTOM MAX TOP Definitions The counter reaches the BOTTOM when it becomes 0x00. The counter reaches its MAXimum when it becomes 0xFF (decimal 255). The counter reaches the TOP when it becomes equal to the highest value in the count sequence. The TOP value can be assigned to be the fixed value 0xFF (MAX) or the value stored in the OCR0A Register. The assignment is dependent on the mode of operation.
14.2
Timer/Counter Clock Sources
The Timer/Counter can be clocked by an internal or an external clock source. The clock source is selected by the Clock Select logic which is controlled by the Clock Select (CS02:0) bits located in the Timer/Counter Control Register (TCCR0B). For details on clock sources and prescaler, see "Timer/Counter0 and Timer/Counter1 Prescalers" on page 88.
14.3
Counter Unit
The main part of the 8-bit Timer/Counter is the programmable bi-directional counter unit. Figure 14-2 shows a block diagram of the counter and its surroundings. Figure 14-2. Counter Unit Block Diagram
DATA BUS
TOVn (Int.Req.) Clock Select count TCNTn clear direction Control Logic clkTn Edge Detector Tn
( From Prescaler ) bottom top
Signal description (internal signals): count direction Increment or decrement TCNT0 by 1. Select between increment and decrement. 91
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clear clkTn top bottom
Clear TCNT0 (set all bits to zero). Timer/Counter clock, referred to as clkT0 in the following. Signalize that TCNT0 has reached maximum value. Signalize that TCNT0 has reached minimum value (zero).
Depending of the mode of operation used, the counter is cleared, incremented, or decremented at each timer clock (clkT0). clkT0 can be generated from an external or internal clock source, selected by the Clock Select bits (CS02:0). When no clock source is selected (CS02:0 = 0) the timer is stopped. However, the TCNT0 value can be accessed by the CPU, regardless of whether clkT0 is present or not. A CPU write overrides (has priority over) all counter clear or count operations. The counting sequence is determined by the setting of the WGM01 and WGM00 bits located in the Timer/Counter Control Register (TCCR0A) and the WGM02 bit located in the Timer/Counter Control Register B (TCCR0B). There are close connections between how the counter behaves (counts) and how waveforms are generated on the Output Compare outputs OC0A and OC0B. For more details about advanced counting sequences and waveform generation, see "Modes of Operation" on page 95. The Timer/Counter Overflow Flag (TOV0) is set according to the mode of operation selected by the WGM02:0 bits. TOV0 can be used for generating a CPU interrupt.
14.4
Output Compare Unit
The 8-bit comparator continuously compares TCNT0 with the Output Compare Registers (OCR0A and OCR0B). Whenever TCNT0 equals OCR0A or OCR0B, the comparator signals a match. A match will set the Output Compare Flag (OCF0A or OCF0B) at the next timer clock cycle. If the corresponding interrupt is enabled, the Output Compare Flag generates an Output Compare interrupt. The Output Compare Flag is automatically cleared when the interrupt is executed. Alternatively, the flag can be cleared by software by writing a logical one to its I/O bit location. The Waveform Generator uses the match signal to generate an output according to operating mode set by the WGM02:0 bits and Compare Output mode (COM0x1:0) bits. The max and bottom signals are used by the Waveform Generator for handling the special cases of the extreme values in some modes of operation ("Modes of Operation" on page 95). Figure 14-3 shows a block diagram of the Output Compare unit.
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Figure 14-3. Output Compare Unit, Block Diagram
DATA BUS
OCRnx
TCNTn
= (8-bit Comparator )
OCFnx (Int.Req.) top bottom FOCn
Waveform Generator
OCnx
WGMn1:0
COMnX1:0
The OCR0x Registers are double buffered when using any of the Pulse Width Modulation (PWM) modes. For the normal and Clear Timer on Compare (CTC) modes of operation, the double buffering is disabled. The double buffering synchronizes the update of the OCR0x Compare Registers to either top or bottom of the counting sequence. The synchronization prevents the occurrence of odd-length, non-symmetrical PWM pulses, thereby making the output glitch-free. The OCR0x Register access may seem complex, but this is not case. When the double buffering is enabled, the CPU has access to the OCR0x Buffer Register, and if double buffering is disabled the CPU will access the OCR0x directly. 14.4.1 Force Output Compare In non-PWM waveform generation modes, the match output of the comparator can be forced by writing a one to the Force Output Compare (FOC0x) bit. Forcing Compare Match will not set the OCF0x Flag or reload/clear the timer, but the OC0x pin will be updated as if a real Compare Match had occurred (the COM0x1:0 bits settings define whether the OC0x pin is set, cleared or toggled). Compare Match Blocking by TCNT0 Write All CPU write operations to the TCNT0 Register will block any Compare Match that occur in the next timer clock cycle, even when the timer is stopped. This feature allows OCR0x to be initialized to the same value as TCNT0 without triggering an interrupt when the Timer/Counter clock is enabled. Using the Output Compare Unit Since writing TCNT0 in any mode of operation will block all Compare Matches for one timer clock cycle, there are risks involved when changing TCNT0 when using the Output Compare Unit, independently of whether the Timer/Counter is running or not. If the value written to TCNT0 equals the OCR0x value, the Compare Match will be missed, resulting in incorrect waveform
14.4.2
14.4.3
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generation. Similarly, do not write the TCNT0 value equal to BOTTOM when the counter is down-counting. The setup of the OC0x should be performed before setting the Data Direction Register for the port pin to output. The easiest way of setting the OC0x value is to use the Force Output Compare (FOC0x) strobe bits in Normal mode. The OC0x Registers keep their values even when changing between Waveform Generation modes. Be aware that the COM0x1:0 bits are not double buffered together with the compare value. Changing the COM0x1:0 bits will take effect immediately.
14.5
Compare Match Output Unit
The Compare Output mode (COM0x1:0) bits have two functions. The Waveform Generator uses the COM0x1:0 bits for defining the Output Compare (OC0x) state at the next Compare Match. Also, the COM0x1:0 bits control the OC0x pin output source. Figure 14-4 shows a simplified schematic of the logic affected by the COM0x1:0 bit setting. The I/O Registers, I/O bits, and I/O pins in the figure are shown in bold. Only the parts of the general I/O Port Control Registers (DDR and PORT) that are affected by the COM0x1:0 bits are shown. When referring to the OC0x state, the reference is for the internal OC0x Register, not the OC0x pin. If a system reset occur, the OC0x Register is reset to "0". Figure 14-4. Compare Match Output Unit, Schematic
COMnx1 COMnx0 FOCn
Waveform Generator
D
Q
1 OCnx Pin
OCnx D
DATA BUS
0
Q
PORT D Q
DDR
clk I/O
The general I/O port function is overridden by the Output Compare (OC0x) from the Waveform Generator if either of the COM0x1:0 bits are set. However, the OC0x pin direction (input or output) is still controlled by the Data Direction Register (DDR) for the port pin. The Data Direction Register bit for the OC0x pin (DDR_OC0x) must be set as output before the OC0x value is visible on the pin. The port override function is independent of the Waveform Generation mode. The design of the Output Compare pin logic allows initialization of the OC0x state before the output is enabled. Note that some COM0x1:0 bit settings are reserved for certain modes of operation. See "8-bit Timer/Counter Register Description" on page 100.
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14.5.1 Compare Output Mode and Waveform Generation The Waveform Generator uses the COM0x1:0 bits differently in Normal, CTC, and PWM modes. For all modes, setting the COM0x1:0 = 0 tells the Waveform Generator that no action on the OC0x Register is to be performed on the next Compare Match. For compare output actions in the non-PWM modes refer to Table 14-2 on page 101. For fast PWM mode, refer to Table 14-3 on page 101, and for phase correct PWM refer to Table 14-4 on page 101. A change of the COM0x1:0 bits state will have effect at the first Compare Match after the bits are written. For non-PWM modes, the action can be forced to have immediate effect by using the FOC0x strobe bits.
14.6
Modes of Operation
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare pins, is defined by the combination of the Waveform Generation mode (WGM02:0) and Compare Output mode (COM0x1:0) bits. The Compare Output mode bits do not affect the counting sequence, while the Waveform Generation mode bits do. The COM0x1:0 bits control whether the PWM output generated should be inverted or not (inverted or non-inverted PWM). For non-PWM modes the COM0x1:0 bits control whether the output should be set, cleared, or toggled at a Compare Match (See "Compare Match Output Unit" on page 94.). For detailed timing information see "Timer/Counter Timing Diagrams" on page 99.
14.6.1
Normal Mode The simplest mode of operation is the Normal mode (WGM02:0 = 0). In this mode the counting direction is always up (incrementing), and no counter clear is performed. The counter simply overruns when it passes its maximum 8-bit value (TOP = 0xFF) and then restarts from the bottom (0x00). In normal operation the Timer/Counter Overflow Flag (TOV0) will be set in the same timer clock cycle as the TCNT0 becomes zero. The TOV0 Flag in this case behaves like a ninth bit, except that it is only set, not cleared. However, combined with the timer overflow interrupt that automatically clears the TOV0 Flag, the timer resolution can be increased by software. There are no special cases to consider in the Normal mode, a new counter value can be written anytime. The Output Compare Unit can be used to generate interrupts at some given time. Using the Output Compare to generate waveforms in Normal mode is not recommended, since this will occupy too much of the CPU time.
14.6.2
Clear Timer on Compare Match (CTC) Mode In Clear Timer on Compare or CTC mode (WGM02:0 = 2), the OCR0A Register is used to manipulate the counter resolution. In CTC mode the counter is cleared to zero when the counter value (TCNT0) matches the OCR0A. The OCR0A defines the top value for the counter, hence also its resolution. This mode allows greater control of the Compare Match output frequency. It also simplifies the operation of counting external events. The timing diagram for the CTC mode is shown in Figure 14-5. The counter value (TCNT0) increases until a Compare Match occurs between TCNT0 and OCR0A, and then counter (TCNT0) is cleared.
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Figure 14-5. CTC Mode, Timing Diagram
OCnx Interrupt Flag Set
TCNTn OCn (Toggle) Period
1 2 3 4
(COMnx1:0 = 1)
An interrupt can be generated each time the counter value reaches the TOP value by using the OCF0A Flag. If the interrupt is enabled, the interrupt handler routine can be used for updating the TOP value. However, changing TOP to a value close to BOTTOM when the counter is running with none or a low prescaler value must be done with care since the CTC mode does not have the double buffering feature. If the new value written to OCR0A is lower than the current value of TCNT0, the counter will miss the Compare Match. The counter will then have to count to its maximum value (0xFF) and wrap around starting at 0x00 before the Compare Match can occur. For generating a waveform output in CTC mode, the OC0A output can be set to toggle its logical level on each Compare Match by setting the Compare Output mode bits to toggle mode (COM0A1:0 = 1). The OC0A value will not be visible on the port pin unless the data direction for the pin is set to output. The waveform generated will have a maximum frequency of f OC0 = fclk_I/O/2 when OCR0A is set to zero (0x00). The waveform frequency is defined by the following equation: f clk_I/O f OCnx = ------------------------------------------------2 N ( 1 + OCRnx ) The N variable represents the prescale factor (1, 8, 64, 256, or 1024). As for the Normal mode of operation, the TOV0 Flag is set in the same timer clock cycle that the counter counts from MAX to 0x00. 14.6.3 Fast PWM Mode The fast Pulse Width Modulation or fast PWM mode (WGM02:0 = 3 or 7) provides a high frequency PWM waveform generation option. The fast PWM differs from the other PWM option by its single-slope operation. The counter counts from BOTTOM to TOP then restarts from BOTTOM. TOP is defined as 0xFF when WGM2:0 = 3, and OCR0A when WGM2:0 = 7. In noninverting Compare Output mode, the Output Compare (OC0x) is cleared on the Compare Match between TCNT0 and OCR0x, and set at BOTTOM. In inverting Compare Output mode, the output is set on Compare Match and cleared at BOTTOM. Due to the single-slope operation, the operating frequency of the fast PWM mode can be twice as high as the phase correct PWM mode that use dual-slope operation. This high frequency makes the fast PWM mode well suited for power regulation, rectification, and DAC applications. High frequency allows physically small sized external components (coils, capacitors), and therefore reduces total system cost. In fast PWM mode, the counter is incremented until the counter value matches the TOP value. The counter is then cleared at the following timer clock cycle. The timing diagram for the fast
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PWM mode is shown in Figure 14-6. The TCNT0 value is in the timing diagram shown as a histogram for illustrating the single-slope operation. The diagram includes non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNT0 slopes represent Compare Matches between OCR0x and TCNT0. Figure 14-6. Fast PWM Mode, Timing Diagram
OCRnx Interrupt Flag Set
OCRnx Update and TOVn Interrupt Flag Set
TCNTn
OCnx OCnx Period
1 2 3 4 5 6 7
(COMnx1:0 = 2) (COMnx1:0 = 3)
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches TOP. If the interrupt is enabled, the interrupt handler routine can be used for updating the compare value. In fast PWM mode, the compare unit allows generation of PWM waveforms on the OC0x pins. Setting the COM0x1:0 bits to two will produce a non-inverted PWM and an inverted PWM output can be generated by setting the COM0x1:0 to three: Setting the COM0A1:0 bits to one allows the OC0A pin to toggle on Compare Matches if the WGM02 bit is set. This option is not available for the OC0B pin (See Table 14-3 on page 101). The actual OC0x value will only be visible on the port pin if the data direction for the port pin is set as output. The PWM waveform is generated by setting (or clearing) the OC0x Register at the Compare Match between OCR0x and TCNT0, and clearing (or setting) the OC0x Register at the timer clock cycle the counter is cleared (changes from TOP to BOTTOM). The PWM frequency for the output can be calculated by the following equation: f clk_I/O f OCnxPWM = ----------------N 256 The N variable represents the prescale factor (1, 8, 64, 256, or 1024). The extreme values for the OCR0A Register represents special cases when generating a PWM waveform output in the fast PWM mode. If the OCR0A is set equal to BOTTOM, the output will be a narrow spike for each MAX+1 timer clock cycle. Setting the OCR0A equal to MAX will result in a constantly high or low output (depending on the polarity of the output set by the COM0A1:0 bits.) A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved by setting OC0x to toggle its logical level on each Compare Match (COM0x1:0 = 1). The waveform generated will have a maximum frequency of fOC0 = fclk_I/O/2 when OCR0A is set to zero. This
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feature is similar to the OC0A toggle in CTC mode, except the double buffer feature of the Output Compare unit is enabled in the fast PWM mode. 14.6.4 Phase Correct PWM Mode The phase correct PWM mode (WGM02:0 = 1 or 5) provides a high resolution phase correct PWM waveform generation option. The phase correct PWM mode is based on a dual-slope operation. The counter counts repeatedly from BOTTOM to TOP and then from TOP to BOTTOM. TOP is defined as 0xFF when WGM2:0 = 1, and OCR0A when WGM2:0 = 5. In noninverting Compare Output mode, the Output Compare (OC0x) is cleared on the Compare Match between TCNT0 and OCR0x while upcounting, and set on the Compare Match while downcounting. In inverting Output Compare mode, the operation is inverted. The dual-slope operation has lower maximum operation frequency than single slope operation. However, due to the symmetric feature of the dual-slope PWM modes, these modes are preferred for motor control applications. In phase correct PWM mode the counter is incremented until the counter value matches TOP. When the counter reaches TOP, it changes the count direction. The TCNT0 value will be equal to TOP for one timer clock cycle. The timing diagram for the phase correct PWM mode is shown on Figure 14-7. The TCNT0 value is in the timing diagram shown as a histogram for illustrating the dual-slope operation. The diagram includes non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNT0 slopes represent Compare Matches between OCR0x and TCNT0. Figure 14-7. Phase Correct PWM Mode, Timing Diagram
OCnx Interrupt Flag Set
OCRnx Update
TOVn Interrupt Flag Set
TCNTn
OCnx OCnx
(COMnx1:0 = 2)
(COMnx1:0 = 3)
Period
1
2
3
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches BOTTOM. The Interrupt Flag can be used to generate an interrupt each time the counter reaches the BOTTOM value. In phase correct PWM mode, the compare unit allows generation of PWM waveforms on the OC0x pins. Setting the COM0x1:0 bits to two will produce a non-inverted PWM. An inverted PWM output can be generated by setting the COM0x1:0 to three: Setting the COM0A0 bits to 98
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one allows the OC0A pin to toggle on Compare Matches if the WGM02 bit is set. This option is not available for the OC0B pin (See Table 14-4 on page 101). The actual OC0x value will only be visible on the port pin if the data direction for the port pin is set as output. The PWM waveform is generated by clearing (or setting) the OC0x Register at the Compare Match between OCR0x and TCNT0 when the counter increments, and setting (or clearing) the OC0x Register at Compare Match between OCR0x and TCNT0 when the counter decrements. The PWM frequency for the output when using phase correct PWM can be calculated by the following equation: f clk_I/O f OCnxPCPWM = ----------------N 510 The N variable represents the prescale factor (1, 8, 64, 256, or 1024). The extreme values for the OCR0A Register represent special cases when generating a PWM waveform output in the phase correct PWM mode. If the OCR0A is set equal to BOTTOM, the output will be continuously low and if set equal to MAX the output will be continuously high for non-inverted PWM mode. For inverted PWM the output will have the opposite logic values. At the very start of period 2 in Figure 14-7 OCnx has a transition from high to low even though there is no Compare Match. The point of this transition is to guarantee symmetry around BOTTOM. There are two cases that give a transition without Compare Match. * OCR0A changes its value from MAX, like in Figure 14-7. When the OCR0A value is MAX the OCn pin value is the same as the result of a down-counting Compare Match. To ensure symmetry around BOTTOM the OCn value at MAX must correspond to the result of an upcounting Compare Match. * The timer starts counting from a value higher than the one in OCR0A, and for that reason misses the Compare Match and hence the OCn change that would have happened on the way up.
14.7
Timer/Counter Timing Diagrams
The Timer/Counter is a synchronous design and the timer clock (clkT0) is therefore shown as a clock enable signal in the following figures. The figures include information on when Interrupt Flags are set. Figure 14-8 contains timing data for basic Timer/Counter operation. The figure shows the count sequence close to the MAX value in all modes other than phase correct PWM mode. Figure 14-8. Timer/Counter Timing Diagram, no Prescaling
clkI/O clkTn
(clkI/O /1)
TCNTn
MAX - 1
MAX
BOTTOM
BOTTOM + 1
TOVn
Figure 14-9 shows the same timing data, but with the prescaler enabled.
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Figure 14-9. Timer/Counter Timing Diagram, with Prescaler (fclk_I/O/8)
clkI/O clkTn
(clkI/O /8)
TCNTn
MAX - 1
MAX
BOTTOM
BOTTOM + 1
TOVn
Figure 14-10 shows the setting of OCF0B in all modes and OCF0A in all modes except CTC mode and PWM mode, where OCR0A is TOP. Figure 14-10. Timer/Counter Timing Diagram, Setting of OCF0x, with Prescaler (fclk_I/O/8)
clkI/O clkTn
(clkI/O /8)
TCNTn
OCRnx - 1
OCRnx
OCRnx + 1
OCRnx + 2
OCRnx
OCRnx Value
OCFnx
Figure 14-11 shows the setting of OCF0A and the clearing of TCNT0 in CTC mode and fast PWM mode where OCR0A is TOP. Figure 14-11. Timer/Counter Timing Diagram, Clear Timer on Compare Match mode, with Prescaler (fclk_I/O/8)
clkI/O clkTn
(clkI/O /8)
TCNTn (CTC) OCRnx
TOP - 1
TOP
BOTTOM
BOTTOM + 1
TOP
OCFnx
14.8
14.8.1
8-bit Timer/Counter Register Description
Timer/Counter Control Register A - TCCR0A
Bit Read/Write 7 COM0A1 R/W 6 COM0A0 R/W 5 COM0B1 R/W 4 COM0B0 R/W 3 - R 2 - R 1 WGM01 R/W 0 WGM00 R/W TCCR0A
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Initial Value 0 0 0 0 0 0 0 0
* Bits 7:6 - COM01A:0: Compare Match Output A Mode These bits control the Output Compare pin (OC0A) behavior. If one or both of the COM0A1:0 bits are set, the OC0A output overrides the normal port functionality of the I/O pin it is connected to. However, note that the Data Direction Register (DDR) bit corresponding to the OC0A pin must be set in order to enable the output driver. When OC0A is connected to the pin, the function of the COM0A1:0 bits depends on the WGM02:0 bit setting. Table 14-2 shows the COM0A1:0 bit functionality when the WGM02:0 bits are set to a normal or CTC mode (non-PWM). Table 14-2.
COM0A1 0 0 1 1
Compare Output Mode, non-PWM Mode
COM0A0 0 1 0 1 Description Normal port operation, OC0A disconnected. Toggle OC0A on Compare Match Clear OC0A on Compare Match Set OC0A on Compare Match
Table 14-3 shows the COM0A1:0 bit functionality when the WGM01:0 bits are set to fast PWM mode. Table 14-3.
COM0A1 0 0 1 1 Note:
Compare Output Mode, Fast PWM Mode(1)
COM0A0 0 1 0 1 Description Normal port operation, OC0A disconnected. WGM02 = 0: Normal Port Operation, OC0A Disconnected. WGM02 = 1: Toggle OC0A on Compare Match. Clear OC0A on Compare Match, set OC0A at TOP Set OC0A on Compare Match, clear OC0A at TOP
1. A special case occurs when OCR0A equals TOP and COM0A1 is set. In this case, the Compare Match is ignored, but the set or clear is done at TOP. See "Fast PWM Mode" on page 96 for more details.
Table 14-4 shows the COM0A1:0 bit functionality when the WGM02:0 bits are set to phase correct PWM mode. Table 14-4.
COM0A1 0 0 1 1
Compare Output Mode, Phase Correct PWM Mode(1)
COM0A0 0 1 0 1 Description Normal port operation, OC0A disconnected. WGM02 = 0: Normal Port Operation, OC0A Disconnected. WGM02 = 1: Toggle OC0A on Compare Match. Clear OC0A on Compare Match when up-counting. Set OC0A on Compare Match when down-counting. Set OC0A on Compare Match when up-counting. Clear OC0A on Compare Match when down-counting.
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Note:
1. A special case occurs when OCR0A equals TOP and COM0A1 is set. In this case, the Compare Match is ignored, but the set or clear is done at TOP. See "Phase Correct PWM Mode" on page 98 for more details.
* Bits 5:4 - COM0B1:0: Compare Match Output B Mode These bits control the Output Compare pin (OC0B) behavior. If one or both of the COM0B1:0 bits are set, the OC0B output overrides the normal port functionality of the I/O pin it is connected to. However, note that the Data Direction Register (DDR) bit corresponding to the OC0B pin must be set in order to enable the output driver. When OC0B is connected to the pin, the function of the COM0B1:0 bits depends on the WGM02:0 bit setting. Table 14-2 shows the COM0A1:0 bit functionality when the WGM02:0 bits are set to a normal or CTC mode (non-PWM). Table 14-5.
COM01 0 0 1 1
Compare Output Mode, non-PWM Mode
COM00 0 1 0 1 Description Normal port operation, OC0B disconnected. Toggle OC0B on Compare Match Clear OC0B on Compare Match Set OC0B on Compare Match
Table 14-3 shows the COM0B1:0 bit functionality when the WGM02:0 bits are set to fast PWM mode. Table 14-6.
COM01 0 0 1 1 Note:
Compare Output Mode, Fast PWM Mode(1)
COM00 0 1 0 1 Description Normal port operation, OC0B disconnected. Reserved Clear OC0B on Compare Match, set OC0B at TOP Set OC0B on Compare Match, clear OC0B at TOP
1. A special case occurs when OCR0B equals TOP and COM0B1 is set. In this case, the Compare Match is ignored, but the set or clear is done at TOP. See "Fast PWM Mode" on page 96 for more details.
Table 14-4 shows the COM0B1:0 bit functionality when the WGM02:0 bits are set to phase correct PWM mode. Table 14-7.
COM0A1 0 0 1 1
Compare Output Mode, Phase Correct PWM Mode(1)
COM0A0 0 1 0 1 Description Normal port operation, OC0B disconnected. Reserved Clear OC0B on Compare Match when up-counting. Set OC0B on Compare Match when down-counting. Set OC0B on Compare Match when up-counting. Clear OC0B on Compare Match when down-counting.
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Note: 1. A special case occurs when OCR0B equals TOP and COM0B1 is set. In this case, the Compare Match is ignored, but the set or clear is done at TOP. See "Phase Correct PWM Mode" on page 98 for more details.
* Bits 3, 2 - Res: Reserved Bits These bits are reserved bits in the AT90USB82/162 and will always read as zero. * Bits 1:0 - WGM01:0: Waveform Generation Mode Combined with the WGM02 bit found in the TCCR0B Register, these bits control the counting sequence of the counter, the source for maximum (TOP) counter value, and what type of waveform generation to be used, see Table 14-8. Modes of operation supported by the Timer/Counter unit are: Normal mode (counter), Clear Timer on Compare Match (CTC) mode, and two types of Pulse Width Modulation (PWM) modes (see "Modes of Operation" on page 95). Table 14-8. Waveform Generation Mode Bit Description
Timer/Counter Mode of Operation Normal PWM, Phase Correct CTC Fast PWM Reserved PWM, Phase Correct Reserved Fast PWM Update of OCRx at Immediate TOP Immediate TOP - TOP - TOP TOV Flag Set on(1)(2) MAX BOTTOM MAX MAX - BOTTOM - TOP
Mode 0 1 2 3 4 5 6 7 Notes:
WGM2 0 0 0 0 1 1 1 1 1. MAX
WGM1 0 0 1 1 0 0 1 1 = 0xFF
WGM0 0 1 0 1 0 1 0 1
TOP 0xFF 0xFF OCRA 0xFF - OCRA - OCRA
2. BOTTOM = 0x00
14.8.2
Timer/Counter Control Register B - TCCR0B
Bit Read/Write Initial Value 7 FOC0A W 0 6 FOC0B W 0 5 - R 0 4 - R 0 3 WGM02 R/W 0 2 CS02 R/W 0 1 CS01 R/W 0 0 CS00 R/W 0 TCCR0B
* Bit 7 - FOC0A: Force Output Compare A The FOC0A bit is only active when the WGM bits specify a non-PWM mode. However, for ensuring compatibility with future devices, this bit must be set to zero when TCCR0B is written when operating in PWM mode. When writing a logical one to the FOC0A bit, an immediate Compare Match is forced on the Waveform Generation unit. The OC0A output is changed according to its COM0A1:0 bits setting. Note that the FOC0A bit is implemented as a strobe. Therefore it is the value present in the COM0A1:0 bits that determines the effect of the forced compare.
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A FOC0A strobe will not generate any interrupt, nor will it clear the timer in CTC mode using OCR0A as TOP. The FOC0A bit is always read as zero. * Bit 6 - FOC0B: Force Output Compare B The FOC0B bit is only active when the WGM bits specify a non-PWM mode. However, for ensuring compatibility with future devices, this bit must be set to zero when TCCR0B is written when operating in PWM mode. When writing a logical one to the FOC0B bit, an immediate Compare Match is forced on the Waveform Generation unit. The OC0B output is changed according to its COM0B1:0 bits setting. Note that the FOC0B bit is implemented as a strobe. Therefore it is the value present in the COM0B1:0 bits that determines the effect of the forced compare. A FOC0B strobe will not generate any interrupt, nor will it clear the timer in CTC mode using OCR0B as TOP. The FOC0B bit is always read as zero. * Bits 5:4 - Res: Reserved Bits These bits are reserved bits and will always read as zero. * Bit 3 - WGM02: Waveform Generation Mode See the description in the "Timer/Counter Control Register A - TCCR0A" on page 100. * Bits 2:0 - CS02:0: Clock Select The three Clock Select bits select the clock source to be used by the Timer/Counter. Table 14-9.
CS02 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1
Clock Select Bit Description
CS00 0 1 0 1 0 1 0 1 Description No clock source (Timer/Counter stopped) clkI/O/(No prescaling) clkI/O/8 (From prescaler) clkI/O/64 (From prescaler) clkI/O/256 (From prescaler) clkI/O/1024 (From prescaler) External clock source on T0 pin. Clock on falling edge. External clock source on T0 pin. Clock on rising edge.
CS01
If external pin modes are used for the Timer/Counter0, transitions on the T0 pin will clock the counter even if the pin is configured as an output. This feature allows software control of the counting. 14.8.3 Timer/Counter Register - TCNT0
Bit Read/Write Initial Value 7 TCNT0[7:0] R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 TCNT0
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The Timer/Counter Register gives direct access, both for read and write operations, to the Timer/Counter unit 8-bit counter. Writing to the TCNT0 Register blocks (removes) the Compare Match on the following timer clock. Modifying the counter (TCNT0) while the counter is running, introduces a risk of missing a Compare Match between TCNT0 and the OCR0x Registers. 14.8.4 Output Compare Register A - OCR0A
Bit Read/Write Initial Value 7 OCR0A[7:0] R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 OCR0A
The Output Compare Register A contains an 8-bit value that is continuously compared with the counter value (TCNT0). A match can be used to generate an Output Compare interrupt, or to generate a waveform output on the OC0A pin. 14.8.5 Output Compare Register B - OCR0B
Bit Read/Write Initial Value 7 OCR0B[7:0] R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 OCR0B
The Output Compare Register B contains an 8-bit value that is continuously compared with the counter value (TCNT0). A match can be used to generate an Output Compare interrupt, or to generate a waveform output on the OC0B pin. 14.8.6 Timer/Counter Interrupt Mask Register - TIMSK0
Bit Read/Write Initial Value 7 - R 0 6 - R 0 5 - R 0 4 - R 0 3 - R 0 2 OCIE0B R/W 0 1 OCIE0A R/W 0 0 TOIE0 R/W 0 TIMSK0
* Bits 7..3 - Res: Reserved Bits These bits are reserved bits and will always read as zero. * Bit 2 - OCIE0B: Timer/Counter Output Compare Match B Interrupt Enable When the OCIE0B bit is written to one, and the I-bit in the Status Register is set, the Timer/Counter Compare Match B interrupt is enabled. The corresponding interrupt is executed if a Compare Match in Timer/Counter occurs, i.e., when the OCF0B bit is set in the Timer/Counter Interrupt Flag Register - TIFR0. * Bit 1 - OCIE0A: Timer/Counter0 Output Compare Match A Interrupt Enable When the OCIE0A bit is written to one, and the I-bit in the Status Register is set, the Timer/Counter0 Compare Match A interrupt is enabled. The corresponding interrupt is executed if a Compare Match in Timer/Counter0 occurs, i.e., when the OCF0A bit is set in the Timer/Counter 0 Interrupt Flag Register - TIFR0. * Bit 0 - TOIE0: Timer/Counter0 Overflow Interrupt Enable When the TOIE0 bit is written to one, and the I-bit in the Status Register is set, the Timer/Counter0 Overflow interrupt is enabled. The corresponding interrupt is executed if an overflow in Timer/Counter0 occurs, i.e., when the TOV0 bit is set in the Timer/Counter 0 Interrupt Flag Register - TIFR0.
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14.8.7
Timer/Counter 0 Interrupt Flag Register - TIFR0
Bit Read/Write Initial Value 7 - R 0 6 - R 0 5 - R 0 4 - R 0 3 - R 0 2 OCF0B R/W 0 1 OCF0A R/W 0 0 TOV0 R/W 0 TIFR0
* Bits 7..3 - Res: Reserved Bits These bits are reserved bits in the AT90USB82/162 and will always read as zero. * Bit 2 - OCF0B: Timer/Counter 0 Output Compare B Match Flag The OCF0B bit is set when a Compare Match occurs between the Timer/Counter and the data in OCR0B - Output Compare Register0 B. OCF0B is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, OCF0B is cleared by writing a logic one to the flag. When the I-bit in SREG, OCIE0B (Timer/Counter Compare B Match Interrupt Enable), and OCF0B are set, the Timer/Counter Compare Match Interrupt is executed. * Bit 1 - OCF0A: Timer/Counter 0 Output Compare A Match Flag The OCF0A bit is set when a Compare Match occurs between the Timer/Counter0 and the data in OCR0A - Output Compare Register0. OCF0A is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, OCF0A is cleared by writing a logic one to the flag. When the I-bit in SREG, OCIE0A (Timer/Counter0 Compare Match Interrupt Enable), and OCF0A are set, the Timer/Counter0 Compare Match Interrupt is executed. * Bit 0 - TOV0: Timer/Counter0 Overflow Flag The bit TOV0 is set when an overflow occurs in Timer/Counter0. TOV0 is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, TOV0 is cleared by writing a logic one to the flag. When the SREG I-bit, TOIE0 (Timer/Counter0 Overflow Interrupt Enable), and TOV0 are set, the Timer/Counter0 Overflow interrupt is executed. The setting of this flag is dependent of the WGM02:0 bit setting. Refer to Table 14-8, "Waveform Generation Mode Bit Description" on page 103.
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15. 16-bit Timer/Counter 1 with PWM
The 16-bit Timer/Counter 1 unit allows accurate program execution timing (event management), wave generation, and signal timing measurement. The main features are: * * * * * * * * * * *
True 16-bit Design (i.e., Allows 16-bit PWM) Three independent Output Compare Units Double Buffered Output Compare Registers One Input Capture Unit Input Capture Noise Canceler Clear Timer on Compare Match (Auto Reload) Glitch-free, Phase Correct Pulse Width Modulator (PWM) Variable PWM Period Frequency Generator External Event Counter Five independent interrupt sources (TOV1, OCF1A, OCF1B, OCF1C, ICF1)
15.1
Overview
Most register and bit references in this section are written in general form. A lower case "n" replaces the Timer/Counter number (for this product, only n=1 is available), and a lower case "x" replaces the Output Compare unit channel. However, when using the register or bit defines in a program, the precise form must be used, i.e., TCNT1 for accessing Timer/Counter1 counter value and so on. A simplified block diagram of the 16-bit Timer/Counter is shown in Figure 15-1. For the actual placement of I/O pins, see "Pinout AT90USB82/162" on page 3. CPU accessible I/O Registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O Register and bit locations are listed in the "16-bit Timer/Counter 1 with PWM" on page 107. The Power Reduction Timer/Counter1 bit, PRTIM1, in "Power Reduction Register 0 - PRR0" on page 43 must be written to zero to enable Timer/Counter1 module.
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Figure 15-1. 16-bit Timer/Counter Block Diagram(1)
Count Clear Direction Control Logic TOVn (Int.Req.) TCLK Clock Select Edge Detector TOP BOTTOM ( From Prescaler ) Timer/Counter TCNTn Tn
=
=0
OCFnA (Int.Req.)
=
OCRnA Fixed TOP Values
Waveform Generation
OCnA
OCFnB (Int.Req.) Waveform Generation OCnB
=
DATABUS
OCRnB OCFnC (Int.Req.)
=
OCRnC
Waveform Generation
OCnC
( From Analog Comparator Ouput ) ICFn (Int.Req.) ICRn Edge Detector Noise Canceler ICPn TCCRnA TCCRnB TCCRnC
Note:
1. Refer to Figure 1-1 on page 3, Table 11-3 on page 74, and Table 11-6 on page 77 for Timer/Counter1 pin placement and description.
15.1.1
Registers The Timer/Counter (TCNTn), Output Compare Registers (OCRnA/B/C), and Input Capture Register (ICRn) are all 16-bit registers. Special procedures must be followed when accessing the 16bit registers. These procedures are described in the section "Accessing 16-bit Registers" on page 109. The Timer/Counter Control Registers (TCCRnA/B/C) are 8-bit registers and have no CPU access restrictions. Interrupt requests (shorten as Int.Req.) signals are all visible in the Timer Interrupt Flag Register (TIFRn). All interrupts are individually masked with the Timer Interrupt Mask Register (TIMSKn). TIFRn and TIMSKn are not shown in the figure since these registers are shared by other timer units. The Timer/Counter can be clocked internally, via the prescaler, or by an external clock source on the Tn pin. The Clock Select logic block controls which clock source and edge the Timer/Counter uses to increment (or decrement) its value. The Timer/Counter is inactive when no clock source is selected. The output from the clock select logic is referred to as the timer clock (clkTn). The double buffered Output Compare Registers (OCRnA/B/C) are compared with the Timer/Counter value at all time. The result of the compare can be used by the Waveform Generator to generate a PWM or variable frequency output on the Output Compare pin (OCnA/B/C).
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See "Output Compare Units" on page 116.. The compare match event will also set the Compare Match Flag (OCFnA/B/C) which can be used to generate an Output Compare interrupt request. The Input Capture Register can capture the Timer/Counter value at a given external (edge triggered) event on either the Input Capture pin (ICPn) or on the Analog Comparator pins (See "Analog Comparator" on page 223.) The Input Capture unit includes a digital filtering unit (Noise Canceler) for reducing the chance of capturing noise spikes. The TOP value, or maximum Timer/Counter value, can in some modes of operation be defined by either the OCRnA Register, the ICRn Register, or by a set of fixed values. When using OCRnA as TOP value in a PWM mode, the OCRnA Register can not be used for generating a PWM output. However, the TOP value will in this case be double buffered allowing the TOP value to be changed in run time. If a fixed TOP value is required, the ICRn Register can be used as an alternative, freeing the OCRnA to be used as PWM output. 15.1.2 Definitions The following definitions are used extensively throughout the document:
BOTTOM MAX The counter reaches the BOTTOM when it becomes 0x0000. The counter reaches its MAXimum when it becomes 0xFFFF (decimal 65535). The counter reaches the TOP when it becomes equal to the highest value in the count sequence. The TOP value can be assigned to be one of the fixed values: 0x00FF, 0x01FF, or 0x03FF, or to the value stored in the OCRnA or ICRn Register. The assignment is dependent of the mode of operation.
TOP
15.2
Accessing 16-bit Registers
The TCNTn, OCRnA/B/C, and ICRn are 16-bit registers that can be accessed by the AVR CPU via the 8-bit data bus. The 16-bit register must be byte accessed using two read or write operations. Each 16-bit timer has a single 8-bit register for temporary storing of the high byte of the 16bit access. The same Temporary Register is shared between all 16-bit registers within each 16bit timer. Accessing the low byte triggers the 16-bit read or write operation. When the low byte of a 16-bit register is written by the CPU, the high byte stored in the Temporary Register, and the low byte written are both copied into the 16-bit register in the same clock cycle. When the low byte of a 16-bit register is read by the CPU, the high byte of the 16-bit register is copied into the Temporary Register in the same clock cycle as the low byte is read. Not all 16-bit accesses uses the Temporary Register for the high byte. Reading the OCRnA/B/C 16-bit registers does not involve using the Temporary Register. To do a 16-bit write, the high byte must be written before the low byte. For a 16-bit read, the low byte must be read before the high byte. The following code examples show how to access the 16-bit timer registers assuming that no interrupts updates the temporary register. The same principle can be used directly for accessing the OCRnA/B/C and ICRn Registers. Note that when using "C", the compiler handles the 16-bit access.
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Assembly Code Examples(1)
... ; Set TCNTn to 0x01FF ldi r17,0x01 ldi r16,0xFF out TCNTnH,r17 out TCNTnL,r16 ; Read TCNTn into r17:r16 in r16,TCNTnL in r17,TCNTnH ...
C Code Examples(1)
unsigned int i; ... /* Set TCNTn to 0x01FF */ TCNTn = 0x1FF; /* Read TCNTn into i */ i = TCNTn; ... Note: 1. See "About Code Examples" on page 7.
The assembly code example returns the TCNTn value in the r17:r16 register pair. It is important to notice that accessing 16-bit registers are atomic operations. If an interrupt occurs between the two instructions accessing the 16-bit register, and the interrupt code updates the temporary register by accessing the same or any other of the 16-bit Timer Registers, then the result of the access outside the interrupt will be corrupted. Therefore, when both the main code and the interrupt code update the temporary register, the main code must disable the interrupts during the 16-bit access. The following code examples show how to do an atomic read of the TCNTn Register contents. Reading any of the OCRnA/B/C or ICRn Registers can be done by using the same principle.
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Assembly Code Example(1)
TIM16_ReadTCNTn: ; Save global interrupt flag in r18,SREG ; Disable interrupts cli ; Read TCNTn into r17:r16 in r16,TCNTnL in r17,TCNTnH ; Restore global interrupt flag out SREG,r18 ret
C Code Example(1)
unsigned int TIM16_ReadTCNTn( void ) { unsigned char sreg; unsigned int i; /* Save global interrupt flag */ sreg = SREG; /* Disable interrupts */ __disable_interrupt(); /* Read TCNTn into i */ i = TCNTn; /* Restore global interrupt flag */ SREG = sreg; return i; } Note: 1. See "About Code Examples" on page 7.
The assembly code example returns the TCNTn value in the r17:r16 register pair.
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The following code examples show how to do an atomic write of the TCNTn Register contents. Writing any of the OCRnA/B/C or ICRn Registers can be done by using the same principle. Assembly Code Example(1)
TIM16_WriteTCNTn: ; Save global interrupt flag in r18,SREG ; Disable interrupts cli ; Set TCNTn to r17:r16 out TCNTnH,r17 out TCNTnL,r16 ; Restore global interrupt flag out SREG,r18 ret
C Code Example(1)
void TIM16_WriteTCNTn( unsigned int i ) { unsigned char sreg; unsigned int i; /* Save global interrupt flag */ sreg = SREG; /* Disable interrupts */ __disable_interrupt(); /* Set TCNTn to i */ TCNTn = i; /* Restore global interrupt flag */ SREG = sreg; } Note: 1. See "About Code Examples" on page 7.
The assembly code example requires that the r17:r16 register pair contains the value to be written to TCNTn. 15.2.1 Reusing the Temporary High Byte Register If writing to more than one 16-bit register where the high byte is the same for all registers written, then the high byte only needs to be written once. However, note that the same rule of atomic operation described previously also applies in this case.
15.3
Timer/Counter Clock Sources
The Timer/Counter can be clocked by an internal or an external clock source. The clock source is selected by the Clock Select logic which is controlled by the Clock Select (CSn2:0) bits located in the Timer/Counter control Register B (TCCRnB). For details on clock sources and prescaler, see "Timer/Counter0 and Timer/Counter1 Prescalers" on page 88.
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15.4 Counter Unit
The main part of the 16-bit Timer/Counter is the programmable 16-bit bi-directional counter unit. Figure 15-2 shows a block diagram of the counter and its surroundings. Figure 15-2. Counter Unit Block Diagram
DATA BUS
(8-bit) TOVn (Int.Req.) TEMP (8-bit) Clock Select Count TCNTnH (8-bit) TCNTnL (8-bit) Clear Direction Control Logic clkTn Edge Detector Tn
TCNTn (16-bit Counter)
( From Prescaler ) TOP BOTTOM
Signal description (internal signals): Count Direction Clear clkTn TOP BOTTOM Increment or decrement TCNTn by 1. Select between increment and decrement. Clear TCNTn (set all bits to zero). Timer/Counter clock. Signalize that TCNTn has reached maximum value. Signalize that TCNTn has reached minimum value (zero).
The 16-bit counter is mapped into two 8-bit I/O memory locations: Counter High (TCNTnH) containing the upper eight bits of the counter, and Counter Low (TCNTnL) containing the lower eight bits. The TCNTnH Register can only be indirectly accessed by the CPU. When the CPU does an access to the TCNTnH I/O location, the CPU accesses the high byte temporary register (TEMP). The temporary register is updated with the TCNTnH value when the TCNTnL is read, and TCNTnH is updated with the temporary register value when TCNTnL is written. This allows the CPU to read or write the entire 16-bit counter value within one clock cycle via the 8-bit data bus. It is important to notice that there are special cases of writing to the TCNTn Register when the counter is counting that will give unpredictable results. The special cases are described in the sections where they are of importance. Depending on the mode of operation used, the counter is cleared, incremented, or decremented at each timer clock (clkTn). The clkTn can be generated from an external or internal clock source, selected by the Clock Select bits (CSn2:0). When no clock source is selected (CSn2:0 = 0) the timer is stopped. However, the TCNTn value can be accessed by the CPU, independent of whether clkTn is present or not. A CPU write overrides (has priority over) all counter clear or count operations. The counting sequence is determined by the setting of the Waveform Generation mode bits (WGMn3:0) located in the Timer/Counter Control Registers A and B (TCCRnA and TCCRnB). There are close connections between how the counter behaves (counts) and how waveforms are generated on the Output Compare outputs OCnx. For more details about advanced counting sequences and waveform generation, see "Modes of Operation" on page 119.
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The Timer/Counter Overflow Flag (TOVn) is set according to the mode of operation selected by the WGMn3:0 bits. TOVn can be used for generating a CPU interrupt.
15.5
Input Capture Unit
The Timer/Counter incorporates an input capture unit that can capture external events and give them a time-stamp indicating time of occurrence. The external signal indicating an event, or multiple events, can be applied via the ICPn pin or alternatively, for the Timer/Counter1 only, via the Analog Comparator unit. The time-stamps can then be used to calculate frequency, duty-cycle, and other features of the signal applied. Alternatively the time-stamps can be used for creating a log of the events. The Input Capture unit is illustrated by the block diagram shown in Figure 15-3. The elements of the block diagram that are not directly a part of the input capture unit are gray shaded. The small "n" in register and bit names indicates the Timer/Counter number. Figure 15-3. Input Capture Unit Block Diagram
DATA BUS
(8-bit)
TEMP (8-bit)
ICRnH (8-bit) WRITE
ICRnL (8-bit)
TCNTnH (8-bit)
TCNTnL (8-bit)
ICRn (16-bit Register)
TCNTn (16-bit Counter)
ACO* Analog Comparator ICPn
ACIC*
ICNC
ICES
Noise Canceler
Edge Detector
ICFn (Int.Req.)
Note:
The Analog Comparator Output (ACO) can only trigger the Timer/Counter1 ICP - not Timer/Counter3, 4 or 5.
When a change of the logic level (an event) occurs on the Input Capture Pin (ICPn), alternatively on the analog Comparator output (ACO), and this change confirms to the setting of the edge detector, a capture will be triggered. When a capture is triggered, the 16-bit value of the counter (TCNTn) is written to the Input Capture Register (ICRn). The Input Capture Flag (ICFn) is set at the same system clock as the TCNTn value is copied into ICRn Register. If enabled (TICIEn = 1), the input capture flag generates an input capture interrupt. The ICFn flag is automatically cleared when the interrupt is executed. Alternatively the ICFn flag can be cleared by software by writing a logical one to its I/O bit location.
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Reading the 16-bit value in the Input Capture Register (ICRn) is done by first reading the low byte (ICRnL) and then the high byte (ICRnH). When the low byte is read the high byte is copied into the high byte Temporary Register (TEMP). When the CPU reads the ICRnH I/O location it will access the TEMP Register. The ICRn Register can only be written when using a Waveform Generation mode that utilizes the ICRn Register for defining the counter's TOP value. In these cases the Waveform Generation mode (WGMn3:0) bits must be set before the TOP value can be written to the ICRn Register. When writing the ICRn Register the high byte must be written to the ICRnH I/O location before the low byte is written to ICRnL. For more information on how to access the 16-bit registers refer to "Accessing 16-bit Registers" on page 109. 15.5.1 Input Capture Trigger Source The main trigger source for the input capture unit is the Input Capture Pin (ICPn). Timer/Counter1 can alternatively use the analog comparator output as trigger source for the input capture unit. The Analog Comparator is selected as trigger source by setting the analog Comparator Input Capture (ACIC) bit in the Analog Comparator Control and Status Register (ACSR). Be aware that changing trigger source can trigger a capture. The input capture flag must therefore be cleared after the change. Both the Input Capture Pin (ICPn) and the Analog Comparator output (ACO) inputs are sampled using the same technique as for the Tn pin (Figure 13-1 on page 88). The edge detector is also identical. However, when the noise canceler is enabled, additional logic is inserted before the edge detector, which increases the delay by four system clock cycles. Note that the input of the noise canceler and edge detector is always enabled unless the Timer/Counter is set in a Waveform Generation mode that uses ICRn to define TOP. An input capture can be triggered by software by controlling the port of the ICPn pin. 15.5.2 Noise Canceler The noise canceler improves noise immunity by using a simple digital filtering scheme. The noise canceler input is monitored over four samples, and all four must be equal for changing the output that in turn is used by the edge detector. The noise canceler is enabled by setting the Input Capture Noise Canceler (ICNCn) bit in Timer/Counter Control Register B (TCCRnB). When enabled the noise canceler introduces additional four system clock cycles of delay from a change applied to the input, to the update of the ICRn Register. The noise canceler uses the system clock and is therefore not affected by the prescaler. 15.5.3 Using the Input Capture Unit The main challenge when using the Input Capture unit is to assign enough processor capacity for handling the incoming events. The time between two events is critical. If the processor has not read the captured value in the ICRn Register before the next event occurs, the ICRn will be overwritten with a new value. In this case the result of the capture will be incorrect. When using the Input Capture interrupt, the ICRn Register should be read as early in the interrupt handler routine as possible. Even though the Input Capture interrupt has relatively high priority, the maximum interrupt response time is dependent on the maximum number of clock cycles it takes to handle any of the other interrupt requests.
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Using the Input Capture unit in any mode of operation when the TOP value (resolution) is actively changed during operation, is not recommended. Measurement of an external signal's duty cycle requires that the trigger edge is changed after each capture. Changing the edge sensing must be done as early as possible after the ICRn Register has been read. After a change of the edge, the Input Capture Flag (ICFn) must be cleared by software (writing a logical one to the I/O bit location). For measuring frequency only, the clearing of the ICFn Flag is not required (if an interrupt handler is used).
15.6
Output Compare Units
The 16-bit comparator continuously compares TCNTn with the Output Compare Register (OCRnx). If TCNT equals OCRnx the comparator signals a match. A match will set the Output Compare Flag (OCFnx) at the next timer clock cycle. If enabled (OCIEnx = 1), the Output Compare Flag generates an Output Compare interrupt. The OCFnx Flag is automatically cleared when the interrupt is executed. Alternatively the OCFnx Flag can be cleared by software by writing a logical one to its I/O bit location. The Waveform Generator uses the match signal to generate an output according to operating mode set by the Waveform Generation mode (WGMn3:0) bits and Compare Output mode (COMnx1:0) bits. The TOP and BOTTOM signals are used by the Waveform Generator for handling the special cases of the extreme values in some modes of operation (See "Modes of Operation" on page 119.) A special feature of Output Compare unit A allows it to define the Timer/Counter TOP value (i.e., counter resolution). In addition to the counter resolution, the TOP value defines the period time for waveforms generated by the Waveform Generator. Figure 15-4 shows a block diagram of the Output Compare unit. The small "n" in the register and bit names indicates the device number (n = n for Timer/Counter n), and the "x" indicates Output Compare unit (A/B/C). The elements of the block diagram that are not directly a part of the Output Compare unit are gray shaded. Figure 15-4. Output Compare Unit, Block Diagram
DATA BUS
(8-bit)
TEMP (8-bit)
OCRnxH Buf. (8-bit)
OCRnxL Buf. (8-bit)
TCNTnH (8-bit)
TCNTnL (8-bit)
OCRnx Buffer (16-bit Register)
TCNTn (16-bit Counter)
OCRnxH (8-bit)
OCRnxL (8-bit)
OCRnx (16-bit Register)
= (16-bit Comparator )
OCFnx (Int.Req.) TOP BOTTOM
Waveform Generator
OCnx
WGMn3:0
COMnx1:0
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The OCRnx Register is double buffered when using any of the twelve Pulse Width Modulation (PWM) modes. For the Normal and Clear Timer on Compare (CTC) modes of operation, the double buffering is disabled. The double buffering synchronizes the update of the OCRnx Compare Register to either TOP or BOTTOM of the counting sequence. The synchronization prevents the occurrence of odd-length, non-symmetrical PWM pulses, thereby making the output glitch-free. The OCRnx Register access may seem complex, but this is not case. When the double buffering is enabled, the CPU has access to the OCRnx Buffer Register, and if double buffering is disabled the CPU will access the OCRnx directly. The content of the OCR1x (Buffer or Compare) Register is only changed by a write operation (the Timer/Counter does not update this register automatically as the TCNT1 and ICR1 Register). Therefore OCR1x is not read via the high byte temporary register (TEMP). However, it is a good practice to read the low byte first as when accessing other 16-bit registers. Writing the OCRnx Registers must be done via the TEMP Register since the compare of all 16 bits is done continuously. The high byte (OCRnxH) has to be written first. When the high byte I/O location is written by the CPU, the TEMP Register will be updated by the value written. Then when the low byte (OCRnxL) is written to the lower eight bits, the high byte will be copied into the upper 8-bits of either the OCRnx buffer or OCRnx Compare Register in the same system clock cycle. For more information of how to access the 16-bit registers refer to "Accessing 16-bit Registers" on page 109. 15.6.1 Force Output Compare In non-PWM Waveform Generation modes, the match output of the comparator can be forced by writing a one to the Force Output Compare (FOCnx) bit. Forcing compare match will not set the OCFnx Flag or reload/clear the timer, but the OCnx pin will be updated as if a real compare match had occurred (the COMn1:0 bits settings define whether the OCnx pin is set, cleared or toggled). Compare Match Blocking by TCNTn Write All CPU writes to the TCNTn Register will block any compare match that occurs in the next timer clock cycle, even when the timer is stopped. This feature allows OCRnx to be initialized to the same value as TCNTn without triggering an interrupt when the Timer/Counter clock is enabled. Using the Output Compare Unit Since writing TCNTn in any mode of operation will block all compare matches for one timer clock cycle, there are risks involved when changing TCNTn when using any of the Output Compare channels, independent of whether the Timer/Counter is running or not. If the value written to TCNTn equals the OCRnx value, the compare match will be missed, resulting in incorrect waveform generation. Do not write the TCNTn equal to TOP in PWM modes with variable TOP values. The compare match for the TOP will be ignored and the counter will continue to 0xFFFF. Similarly, do not write the TCNTn value equal to BOTTOM when the counter is downcounting. The setup of the OCnx should be performed before setting the Data Direction Register for the port pin to output. The easiest way of setting the OCnx value is to use the Force Output Compare (FOCnx) strobe bits in Normal mode. The OCnx Register keeps its value even when changing between Waveform Generation modes. Be aware that the COMnx1:0 bits are not double buffered together with the compare value. Changing the COMnx1:0 bits will take effect immediately.
15.6.2
15.6.3
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15.7
Compare Match Output Unit
The Compare Output mode (COMnx1:0) bits have two functions. The Waveform Generator uses the COMnx1:0 bits for defining the Output Compare (OCnx) state at the next compare match. Secondly the COMnx1:0 bits control the OCnx pin output source. Figure 15-5 shows a simplified schematic of the logic affected by the COMnx1:0 bit setting. The I/O Registers, I/O bits, and I/O pins in the figure are shown in bold. Only the parts of the general I/O Port Control Registers (DDR and PORT) that are affected by the COMnx1:0 bits are shown. When referring to the OCnx state, the reference is for the internal OCnx Register, not the OCnx pin. If a system reset occur, the OCnx Register is reset to "0". Figure 15-5. Compare Match Output Unit, Schematic
COMnx1 COMnx0 FOCnx
Waveform Generator
D
Q
1 OCnx Pin
OCnx D
DATA BUS
0
Q
PORT D Q
DDR
clk I/O
The general I/O port function is overridden by the Output Compare (OCnx) from the Waveform Generator if either of the COMnx1:0 bits are set. However, the OCnx pin direction (input or output) is still controlled by the Data Direction Register (DDR) for the port pin. The Data Direction Register bit for the OCnx pin (DDR_OCnx) must be set as output before the OCnx value is visible on the pin. The port override function is generally independent of the Waveform Generation mode, but there are some exceptions. Refer to Table 15-1, Table 15-2 and Table 15-3 for details. The design of the Output Compare pin logic allows initialization of the OCnx state before the output is enabled. Note that some COMnx1:0 bit settings are reserved for certain modes of operation. See "16-bit Timer/Counter 1 with PWM" on page 107. The COMnx1:0 bits have no effect on the Input Capture unit. 15.7.1 Compare Output Mode and Waveform Generation The Waveform Generator uses the COMnx1:0 bits differently in normal, CTC, and PWM modes. For all modes, setting the COMnx1:0 = 0 tells the Waveform Generator that no action on the OCnx Register is to be performed on the next compare match. For compare output actions in the
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non-PWM modes refer to Table 15-1 on page 129. For fast PWM mode refer to Table 15-2 on page 129, and for phase correct and phase and frequency correct PWM refer to Table 15-3 on page 130. A change of the COMnx1:0 bits state will have effect at the first compare match after the bits are written. For non-PWM modes, the action can be forced to have immediate effect by using the FOCnx strobe bits.
15.8
Modes of Operation
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare pins, is defined by the combination of the Waveform Generation mode (WGMn3:0) and Compare Output mode (COMnx1:0) bits. The Compare Output mode bits do not affect the counting sequence, while the Waveform Generation mode bits do. The COMnx1:0 bits control whether the PWM output generated should be inverted or not (inverted or non-inverted PWM). For non-PWM modes the COMnx1:0 bits control whether the output should be set, cleared or toggle at a compare match (See "Compare Match Output Unit" on page 118.) For detailed timing information refer to "Timer/Counter Timing Diagrams" on page 126.
15.8.1
Normal Mode The simplest mode of operation is the Normal mode (WGMn3:0 = 0). In this mode the counting direction is always up (incrementing), and no counter clear is performed. The counter simply overruns when it passes its maximum 16-bit value (MAX = 0xFFFF) and then restarts from the BOTTOM (0x0000). In normal operation the Timer/Counter Overflow Flag (TOVn) will be set in the same timer clock cycle as the TCNTn becomes zero. The TOVn Flag in this case behaves like a 17th bit, except that it is only set, not cleared. However, combined with the timer overflow interrupt that automatically clears the TOVn Flag, the timer resolution can be increased by software. There are no special cases to consider in the Normal mode, a new counter value can be written anytime. The Input Capture unit is easy to use in Normal mode. However, observe that the maximum interval between the external events must not exceed the resolution of the counter. If the interval between events are too long, the timer overflow interrupt or the prescaler must be used to extend the resolution for the capture unit. The Output Compare units can be used to generate interrupts at some given time. Using the Output Compare to generate waveforms in Normal mode is not recommended, since this will occupy too much of the CPU time.
15.8.2
Clear Timer on Compare Match (CTC) Mode In Clear Timer on Compare or CTC mode (WGMn3:0 = 4 or 12), the OCRnA or ICRn Register are used to manipulate the counter resolution. In CTC mode the counter is cleared to zero when the counter value (TCNTn) matches either the OCRnA (WGMn3:0 = 4) or the ICRn (WGMn3:0 = 12). The OCRnA or ICRn define the top value for the counter, hence also its resolution. This mode allows greater control of the compare match output frequency. It also simplifies the operation of counting external events. The timing diagram for the CTC mode is shown in Figure 15-6. The counter value (TCNTn) increases until a compare match occurs with either OCRnA or ICRn, and then counter (TCNTn) is cleared.
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Figure 15-6. CTC Mode, Timing Diagram
OCnA Interrupt Flag Set or ICFn Interrupt Flag Set (Interrupt on TOP)
TCNTn
OCnA (Toggle) Period
1 2 3 4
(COMnA1:0 = 1)
An interrupt can be generated at each time the counter value reaches the TOP value by either using the OCFnA or ICFn Flag according to the register used to define the TOP value. If the interrupt is enabled, the interrupt handler routine can be used for updating the TOP value. However, changing the TOP to a value close to BOTTOM when the counter is running with none or a low prescaler value must be done with care since the CTC mode does not have the double buffering feature. If the new value written to OCRnA or ICRn is lower than the current value of TCNTn, the counter will miss the compare match. The counter will then have to count to its maximum value (0xFFFF) and wrap around starting at 0x0000 before the compare match can occur. In many cases this feature is not desirable. An alternative will then be to use the fast PWM mode using OCRnA for defining TOP (WGMn3:0 = 15) since the OCRnA then will be double buffered. For generating a waveform output in CTC mode, the OCnA output can be set to toggle its logical level on each compare match by setting the Compare Output mode bits to toggle mode (COMnA1:0 = 1). The OCnA value will not be visible on the port pin unless the data direction for the pin is set to output (DDR_OCnA = 1). The waveform generated will have a maximum frequency of fOCnA = fclk_I/O/2 when OCRnA is set to zero (0x0000). The waveform frequency is defined by the following equation: f clk_I/O f OCnA = -------------------------------------------------2 N ( 1 + OCRnA ) The N variable represents the prescaler factor (1, 8, 64, 256, or 1024). As for the Normal mode of operation, the TOVn Flag is set in the same timer clock cycle that the counter counts from MAX to 0x0000. 15.8.3 Fast PWM Mode The fast Pulse Width Modulation or fast PWM mode (WGMn3:0 = 5, 6, 7, 14, or 15) provides a high frequency PWM waveform generation option. The fast PWM differs from the other PWM options by its single-slope operation. The counter counts from BOTTOM to TOP then restarts from BOTTOM. In non-inverting Compare Output mode, the Output Compare (OCnx) is set on the compare match between TCNTn and OCRnx, and cleared at TOP. In inverting Compare Output mode output is cleared on compare match and set at TOP. Due to the single-slope operation, the operating frequency of the fast PWM mode can be twice as high as the phase correct and phase and frequency correct PWM modes that use dual-slope operation. This high frequency makes the fast PWM mode well suited for power regulation, rectification, and DAC applications. High frequency allows physically small sized external components (coils, capacitors), hence reduces total system cost.
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The PWM resolution for fast PWM can be fixed to 8-, 9-, or 10-bit, or defined by either ICRn or OCRnA. The minimum resolution allowed is 2-bit (ICRn or OCRnA set to 0x0003), and the maximum resolution is 16-bit (ICRn or OCRnA set to MAX). The PWM resolution in bits can be calculated by using the following equation: log ( TOP + 1 ) R FPWM = ---------------------------------log ( 2 ) In fast PWM mode the counter is incremented until the counter value matches either one of the fixed values 0x00FF, 0x01FF, or 0x03FF (WGMn3:0 = 5, 6, or 7), the value in ICRn (WGMn3:0 = 14), or the value in OCRnA (WGMn3:0 = 15). The counter is then cleared at the following timer clock cycle. The timing diagram for the fast PWM mode is shown in Figure 15-7. The figure shows fast PWM mode when OCRnA or ICRn is used to define TOP. The TCNTn value is in the timing diagram shown as a histogram for illustrating the single-slope operation. The diagram includes non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNTn slopes represent compare matches between OCRnx and TCNTn. The OCnx Interrupt Flag will be set when a compare match occurs. Figure 15-7. Fast PWM Mode, Timing Diagram
OCRnx / TOP Update and TOVn Interrupt Flag Set and OCnA Interrupt Flag Set or ICFn Interrupt Flag Set (Interrupt on TOP)
TCNTn
OCnx OCnx
(COMnx1:0 = 2)
(COMnx1:0 = 3)
Period
1
2
3
4
5
6
7
8
The Timer/Counter Overflow Flag (TOVn) is set each time the counter reaches TOP. In addition the OCnA or ICFn Flag is set at the same timer clock cycle as TOVn is set when either OCRnA or ICRn is used for defining the TOP value. If one of the interrupts are enabled, the interrupt handler routine can be used for updating the TOP and compare values. When changing the TOP value the program must ensure that the new TOP value is higher or equal to the value of all of the Compare Registers. If the TOP value is lower than any of the Compare Registers, a compare match will never occur between the TCNTn and the OCRnx. Note that when using fixed TOP values the unused bits are masked to zero when any of the OCRnx Registers are written. The procedure for updating ICRn differs from updating OCRnA when used for defining the TOP value. The ICRn Register is not double buffered. This means that if ICRn is changed to a low value when the counter is running with none or a low prescaler value, there is a risk that the new ICRn value written is lower than the current value of TCNTn. The result will then be that the counter will miss the compare match at the TOP value. The counter will then have to count to the MAX value (0xFFFF) and wrap around starting at 0x0000 before the compare match can occur. The OCRnA Register however, is double buffered. This feature allows the OCRnA I/O location 121
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to be written anytime. When the OCRnA I/O location is written the value written will be put into the OCRnA Buffer Register. The OCRnA Compare Register will then be updated with the value in the Buffer Register at the next timer clock cycle the TCNTn matches TOP. The update is done at the same timer clock cycle as the TCNTn is cleared and the TOVn Flag is set. Using the ICRn Register for defining TOP works well when using fixed TOP values. By using ICRn, the OCRnA Register is free to be used for generating a PWM output on OCnA. However, if the base PWM frequency is actively changed (by changing the TOP value), using the OCRnA as TOP is clearly a better choice due to its double buffer feature. In fast PWM mode, the compare units allow generation of PWM waveforms on the OCnx pins. Setting the COMnx1:0 bits to two will produce a non-inverted PWM and an inverted PWM output can be generated by setting the COMnx1:0 to three (see Table on page 129). The actual OCnx value will only be visible on the port pin if the data direction for the port pin is set as output (DDR_OCnx). The PWM waveform is generated by setting (or clearing) the OCnx Register at the compare match between OCRnx and TCNTn, and clearing (or setting) the OCnx Register at the timer clock cycle the counter is cleared (changes from TOP to BOTTOM). The PWM frequency for the output can be calculated by the following equation: f clk_I/O f OCnxPWM = ---------------------------------N ( 1 + TOP ) The N variable represents the prescaler divider (1, 8, 64, 256, or 1024). The extreme values for the OCRnx Register represents special cases when generating a PWM waveform output in the fast PWM mode. If the OCRnx is set equal to BOTTOM (0x0000) the output will be a narrow spike for each TOP+1 timer clock cycle. Setting the OCRnx equal to TOP will result in a constant high or low output (depending on the polarity of the output set by the COMnx1:0 bits.) A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved by setting OCnA to toggle its logical level on each compare match (COMnA1:0 = 1). This applies only if OCR1A is used to define the TOP value (WGM13:0 = 15). The waveform generated will have a maximum frequency of fOCnA = fclk_I/O/2 when OCRnA is set to zero (0x0000). This feature is similar to the OCnA toggle in CTC mode, except the double buffer feature of the Output Compare unit is enabled in the fast PWM mode. 15.8.4 Phase Correct PWM Mode The phase correct Pulse Width Modulation or phase correct PWM mode (WGMn3:0 = 1, 2, 3, 10, or 11) provides a high resolution phase correct PWM waveform generation option. The phase correct PWM mode is, like the phase and frequency correct PWM mode, based on a dualslope operation. The counter counts repeatedly from BOTTOM (0x0000) to TOP and then from TOP to BOTTOM. In non-inverting Compare Output mode, the Output Compare (OCnx) is cleared on the compare match between TCNTn and OCRnx while upcounting, and set on the compare match while downcounting. In inverting Output Compare mode, the operation is inverted. The dual-slope operation has lower maximum operation frequency than single slope operation. However, due to the symmetric feature of the dual-slope PWM modes, these modes are preferred for motor control applications. The PWM resolution for the phase correct PWM mode can be fixed to 8-, 9-, or 10-bit, or defined by either ICRn or OCRnA. The minimum resolution allowed is 2-bit (ICRn or OCRnA set to
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0x0003), and the maximum resolution is 16-bit (ICRn or OCRnA set to MAX). The PWM resolution in bits can be calculated by using the following equation:
log ( TOP + 1 ) R PCPWM = ---------------------------------log ( 2 ) In phase correct PWM mode the counter is incremented until the counter value matches either one of the fixed values 0x00FF, 0x01FF, or 0x03FF (WGMn3:0 = 1, 2, or 3), the value in ICRn (WGMn3:0 = 10), or the value in OCRnA (WGMn3:0 = 11). The counter has then reached the TOP and changes the count direction. The TCNTn value will be equal to TOP for one timer clock cycle. The timing diagram for the phase correct PWM mode is shown on Figure 15-8. The figure shows phase correct PWM mode when OCRnA or ICRn is used to define TOP. The TCNTn value is in the timing diagram shown as a histogram for illustrating the dual-slope operation. The diagram includes non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNTn slopes represent compare matches between OCRnx and TCNTn. The OCnx Interrupt Flag will be set when a compare match occurs. Figure 15-8. Phase Correct PWM Mode, Timing Diagram
OCRnx/TOP Update and OCnA Interrupt Flag Set or ICFn Interrupt Flag Set (Interrupt on TOP)
TOVn Interrupt Flag Set (Interrupt on Bottom)
TCNTn
OCnx OCnx Period
1 2 3 4
(COMnx1:0 = 2) (COMnx1:0 = 3)
The Timer/Counter Overflow Flag (TOVn) is set each time the counter reaches BOTTOM. When either OCRnA or ICRn is used for defining the TOP value, the OCnA or ICFn Flag is set accordingly at the same timer clock cycle as the OCRnx Registers are updated with the double buffer value (at TOP). The Interrupt Flags can be used to generate an interrupt each time the counter reaches the TOP or BOTTOM value. When changing the TOP value the program must ensure that the new TOP value is higher or equal to the value of all of the Compare Registers. If the TOP value is lower than any of the Compare Registers, a compare match will never occur between the TCNTn and the OCRnx. Note that when using fixed TOP values, the unused bits are masked to zero when any of the OCRnx Registers are written. As the third period shown in Figure 15-8 illustrates, changing the TOP actively while the Timer/Counter is running in the phase correct mode can result in an unsymmetrical output. The reason for this can be found in the time of update of the OCRnx Reg123
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ister. Since the OCRnx update occurs at TOP, the PWM period starts and ends at TOP. This implies that the length of the falling slope is determined by the previous TOP value, while the length of the rising slope is determined by the new TOP value. When these two values differ the two slopes of the period will differ in length. The difference in length gives the unsymmetrical result on the output. It is recommended to use the phase and frequency correct mode instead of the phase correct mode when changing the TOP value while the Timer/Counter is running. When using a static TOP value there are practically no differences between the two modes of operation. In phase correct PWM mode, the compare units allow generation of PWM waveforms on the OCnx pins. Setting the COMnx1:0 bits to two will produce a non-inverted PWM and an inverted PWM output can be generated by setting the COMnx1:0 to three (See Table 15-3 on page 130). The actual OCnx value will only be visible on the port pin if the data direction for the port pin is set as output (DDR_OCnx). The PWM waveform is generated by setting (or clearing) the OCnx Register at the compare match between OCRnx and TCNTn when the counter increments, and clearing (or setting) the OCnx Register at compare match between OCRnx and TCNTn when the counter decrements. The PWM frequency for the output when using phase correct PWM can be calculated by the following equation: f clk_I/O f OCnxPCPWM = --------------------------2 N TOP The N variable represents the prescaler divider (1, 8, 64, 256, or 1024). The extreme values for the OCRnx Register represent special cases when generating a PWM waveform output in the phase correct PWM mode. If the OCRnx is set equal to BOTTOM the output will be continuously low and if set equal to TOP the output will be continuously high for non-inverted PWM mode. For inverted PWM the output will have the opposite logic values. If OCR1A is used to define the TOP value (WGM13:0 = 11) and COM1A1:0 = 1, the OC1A output will toggle with a 50% duty cycle. 15.8.5 Phase and Frequency Correct PWM Mode The phase and frequency correct Pulse Width Modulation, or phase and frequency correct PWM mode (WGMn3:0 = 8 or 9) provides a high resolution phase and frequency correct PWM waveform generation option. The phase and frequency correct PWM mode is, like the phase correct PWM mode, based on a dual-slope operation. The counter counts repeatedly from BOTTOM (0x0000) to TOP and then from TOP to BOTTOM. In non-inverting Compare Output mode, the Output Compare (OCnx) is cleared on the compare match between TCNTn and OCRnx while upcounting, and set on the compare match while downcounting. In inverting Compare Output mode, the operation is inverted. The dual-slope operation gives a lower maximum operation frequency compared to the single-slope operation. However, due to the symmetric feature of the dual-slope PWM modes, these modes are preferred for motor control applications. The main difference between the phase correct, and the phase and frequency correct PWM mode is the time the OCRnx Register is updated by the OCRnx Buffer Register, (see Figure 158 and Figure 15-9). The PWM resolution for the phase and frequency correct PWM mode can be defined by either ICRn or OCRnA. The minimum resolution allowed is 2-bit (ICRn or OCRnA set to 0x0003), and
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the maximum resolution is 16-bit (ICRn or OCRnA set to MAX). The PWM resolution in bits can be calculated using the following equation: log ( TOP + 1 ) R PFCPWM = ---------------------------------log ( 2 ) In phase and frequency correct PWM mode the counter is incremented until the counter value matches either the value in ICRn (WGMn3:0 = 8), or the value in OCRnA (WGMn3:0 = 9). The counter has then reached the TOP and changes the count direction. The TCNTn value will be equal to TOP for one timer clock cycle. The timing diagram for the phase correct and frequency correct PWM mode is shown on Figure 15-9. The figure shows phase and frequency correct PWM mode when OCRnA or ICRn is used to define TOP. The TCNTn value is in the timing diagram shown as a histogram for illustrating the dual-slope operation. The diagram includes noninverted and inverted PWM outputs. The small horizontal line marks on the TCNTn slopes represent compare matches between OCRnx and TCNTn. The OCnx Interrupt Flag will be set when a compare match occurs. Figure 15-9. Phase and Frequency Correct PWM Mode, Timing Diagram
OCnA Interrupt Flag Set or ICFn Interrupt Flag Set (Interrupt on TOP)
OCRnx/TOP Updateand TOVn Interrupt Flag Set (Interrupt on Bottom)
TCNTn
OCnx OCnx Period
1 2 3 4
(COMnx1:0 = 2) (COMnx1:0 = 3)
The Timer/Counter Overflow Flag (TOVn) is set at the same timer clock cycle as the OCRnx Registers are updated with the double buffer value (at BOTTOM). When either OCRnA or ICRn is used for defining the TOP value, the OCnA or ICFn Flag set when TCNTn has reached TOP. The Interrupt Flags can then be used to generate an interrupt each time the counter reaches the TOP or BOTTOM value. When changing the TOP value the program must ensure that the new TOP value is higher or equal to the value of all of the Compare Registers. If the TOP value is lower than any of the Compare Registers, a compare match will never occur between the TCNTn and the OCRnx. As Figure 15-9 shows the output generated is, in contrast to the phase correct mode, symmetrical in all periods. Since the OCRnx Registers are updated at BOTTOM, the length of the rising and the falling slopes will always be equal. This gives symmetrical output pulses and is therefore frequency correct.
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Using the ICRn Register for defining TOP works well when using fixed TOP values. By using ICRn, the OCRnA Register is free to be used for generating a PWM output on OCnA. However, if the base PWM frequency is actively changed by changing the TOP value, using the OCRnA as TOP is clearly a better choice due to its double buffer feature. In phase and frequency correct PWM mode, the compare units allow generation of PWM waveforms on the OCnx pins. Setting the COMnx1:0 bits to two will produce a non-inverted PWM and an inverted PWM output can be generated by setting the COMnx1:0 to three (See Table 15-3 on page 130). The actual OCnx value will only be visible on the port pin if the data direction for the port pin is set as output (DDR_OCnx). The PWM waveform is generated by setting (or clearing) the OCnx Register at the compare match between OCRnx and TCNTn when the counter increments, and clearing (or setting) the OCnx Register at compare match between OCRnx and TCNTn when the counter decrements. The PWM frequency for the output when using phase and frequency correct PWM can be calculated by the following equation: f clk_I/O f OCnxPFCPWM = --------------------------2 N TOP The N variable represents the prescaler divider (1, 8, 64, 256, or 1024). The extreme values for the OCRnx Register represents special cases when generating a PWM waveform output in the phase correct PWM mode. If the OCRnx is set equal to BOTTOM the output will be continuously low and if set equal to TOP the output will be set to high for noninverted PWM mode. For inverted PWM the output will have the opposite logic values. If OCR1A is used to define the TOP value (WGM13:0 = 9) and COM1A1:0 = 1, the OC1A output will toggle with a 50% duty cycle.
15.9
Timer/Counter Timing Diagrams
The Timer/Counter is a synchronous design and the timer clock (clkTn) is therefore shown as a clock enable signal in the following figures. The figures include information on when Interrupt Flags are set, and when the OCRnx Register is updated with the OCRnx buffer value (only for modes utilizing double buffering). Figure 15-10 shows a timing diagram for the setting of OCFnx. Figure 15-10. Timer/Counter Timing Diagram, Setting of OCFnx, no Prescaling
clkI/O clkTn
(clkI/O /1)
TCNTn OCRnx OCFnx
OCRnx - 1
OCRnx OCRnx Value
OCRnx + 1
OCRnx + 2
Figure 15-11 shows the same timing data, but with the prescaler enabled.
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Figure 15-11. Timer/Counter Timing Diagram, Setting of OCFnx, with Prescaler (fclk_I/O/8)
clkI/O clkTn
(clkI/O /8)
TCNTn OCRnx OCFnx
OCRnx - 1
OCRnx OCRnx Value
OCRnx + 1
OCRnx + 2
Figure 15-12 shows the count sequence close to TOP in various modes. When using phase and frequency correct PWM mode the OCRnx Register is updated at BOTTOM. The timing diagrams will be the same, but TOP should be replaced by BOTTOM, TOP-1 by BOTTOM+1 and so on. The same renaming applies for modes that set the TOVn Flag at BOTTOM. Figure 15-12. Timer/Counter Timing Diagram, no Prescaling
clkI/O clkTn
(clkI/O /1)
(CTC and FPWM)
TCNTn TCNTn
TOP - 1 TOP - 1
TOP TOP
BOTTOM TOP - 1
BOTTOM + 1 TOP - 2
(PC and PFC PWM)
TOVn (FPWM) and ICFn (if used
as TOP)
(Update at TOP)
OCRnx
Old OCRnx Value
New OCRnx Value
Figure 15-13 shows the same timing data, but with the prescaler enabled.
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Figure 15-13. Timer/Counter Timing Diagram, with Prescaler (fclk_I/O/8)
clk I/O clk Tn
(clk /8) I/O
(CTC and FPWM)
TCNTn TCNTn
TOP - 1 TOP - 1
TOP TOP
BOTTOM TOP - 1
BOTTOM + 1 TOP - 2
(PC and PFC PWM)
TOVn (FPWM) and ICF n (if used
as TOP)
(Update at TOP)
OCRnx
Old OCRnx Value
New OCRnx Value
15.10 16-bit Timer/Counter Register Description
15.10.1 Timer/Counter1 Control Register A - TCCR1A
Bit Read/Write Initial Value 7 COM1A1 R/W 0 6 COM1A0 R/W 0 5 COM1B1 R/W 0 4 COM1B0 R/W 0 3 COM1C1 R/W 0 2 COM1C0 R/W 0 1 WGM11 R/W 0 0 WGM10 R/W 0 TCCR1A
* Bit 7:6 - COMnA1:0: Compare Output Mode for Channel A * Bit 5:4 - COMnB1:0: Compare Output Mode for Channel B * Bit 3:2 - COMnC1:0: Compare Output Mode for Channel C The COMnA1:0, COMnB1:0, and COMnC1:0 control the output compare pins (OCnA, OCnB, and OCnC respectively) behavior. If one or both of the COMnA1:0 bits are written to one, the OCnA output overrides the normal port functionality of the I/O pin it is connected to. If one or both of the COMnB1:0 bits are written to one, the OCnB output overrides the normal port functionality of the I/O pin it is connected to. If one or both of the COMnC1:0 bits are written to one, the OCnC output overrides the normal port functionality of the I/O pin it is connected to. However, note that the Data Direction Register (DDR) bit corresponding to the OCnA, OCnB or OCnC pin must be set in order to enable the output driver. When the OCnA, OCnB or OCnC is connected to the pin, the function of the COMnx1:0 bits is dependent of the WGMn3:0 bits setting. Table 15-1 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to a normal or a CTC mode (non-PWM).
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.
Table 15-1.
Compare Output Mode, non-PWM
COMnA0/COMnB0/ COMnC0 0 1 0 1 Description Normal port operation, OCnA/OCnB/OCnC disconnected. Toggle OCnA/OCnB/OCnC on compare match. Clear OCnA/OCnB/OCnC on compare match (set output to low level). Set OCnA/OCnB/OCnC on compare match (set output to high level).
COMnA1/COMnB1/ COMnC1 0 0 1 1
Table 15-2 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to the fast PWM mode. Table 15-2. Compare Output Mode, Fast PWM
COMnA0/COMnB0/ COMnC0 0 Description Normal port operation, OCnA/OCnB/OCnC disconnected. WGM13:0 = 14 or 15: Toggle OC1A on Compare Match, OC1B and OC1C disconnected (normal port operation). For all other WGM1 settings, normal port operation, OC1A/OC1B/OC1C disconnected. Clear OCnA/OCnB/OCnC on compare match, set OCnA/OCnB/OCnC at TOP Set OCnA/OCnB/OCnC on compare match, clear OCnA/OCnB/OCnC at TOP
COMnA1/COMnB1/ COMnC0 0
0
1
1 1 Note:
0 1
A special case occurs when OCRnA/OCRnB/OCRnC equals TOP and COMnA1/COMnB1/COMnC1 is set. In this case the compare match is ignored, but the set or clear is done at TOP. See "Fast PWM Mode" on page 96. for more details.
Table 15-3 shows the COMnx1:0 bit functionality when the WGMn3:0 bits are set to the phase correct and frequency correct PWM mode.
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Table 15-3.
Compare Output Mode, Phase Correct and Phase and Frequency Correct PWM
COMnA0/COMnB0/ COMnC0 0 Description Normal port operation, OCnA/OCnB/OCnC disconnected. WGM13:0 = 8, 9 10 or 11: Toggle OC1A on Compare Match, OC1B and OC1C disconnected (normal port operation). For all other WGM1 settings, normal port operation, OC1A/OC1B/OC1C disconnected. Clear OCnA/OCnB/OCnC on compare match when up-counting. Set OCnA/OCnB/OCnC on compare match when downcounting. Set OCnA/OCnB/OCnC on compare match when up-counting. Clear OCnA/OCnB/OCnC on compare match when downcounting.
COMnA1/COMnB/ COMnC1 0
0
1
1
0
1 Note:
1
A special case occurs when OCRnA/OCRnB/OCRnC equals TOP and COMnA1/COMnB1//COMnC1 is set. See "Phase Correct PWM Mode" on page 98. for more details.
* Bit 1:0 - WGMn1:0: Waveform Generation Mode Combined with the WGMn3:2 bits found in the TCCRnB Register, these bits control the counting sequence of the counter, the source for maximum (TOP) counter value, and what type of waveform generation to be used, see Table 15-4. Modes of operation supported by the Timer/Counter unit are: Normal mode (counter), Clear Timer on Compare match (CTC) mode, and three types of Pulse Width Modulation (PWM) modes. (See "Modes of Operation" on page 95.).
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Table 15-4. Waveform Generation Mode Bit Description(1)
WGM n2 (CTCn ) 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 WGM n1 (PWM n1) 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 WGM n0 (PWM n0) 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 Update of OCRnx at Immedi ate TOP TOP TOP Immedi ate TOP TOP TOP BOTTO M BOTTO M TOP TOP Immedi ate - TOP TOP TOVn Flag Set on MAX BOTTO M BOTTO M BOTTO M MAX TOP TOP TOP BOTTO M BOTTO M BOTTO M BOTTO M MAX - TOP TOP
Mo de 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Note:
WGM n3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1
Timer/Counter Mode of Operation Normal PWM, Phase Correct, 8-bit PWM, Phase Correct, 9-bit PWM, Phase Correct, 10-bit CTC Fast PWM, 8-bit Fast PWM, 9-bit Fast PWM, 10-bit PWM, Phase and Frequency Correct PWM, Phase and Frequency Correct PWM, Phase Correct PWM, Phase Correct CTC (Reserved) Fast PWM Fast PWM
TOP 0xFFF F 0x00F F 0x01F F 0x03F F OCRn A 0x00F F 0x01F F 0x03F F ICRn OCRn A ICRn OCRn A ICRn - ICRn OCRn A
1. The CTCn and PWMn1:0 bit definition names are obsolete. Use the WGMn2:0 definitions. However, the functionality and location of these bits are compatible with previous versions of the timer.
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15.10.2
Timer/Counter1 Control Register B - TCCR1B
Bit Read/Write Initial Value 7 ICNC1 R/W 0 6 ICES1 R/W 0 5 - R 0 4 WGM13 R/W 0 3 WGM12 R/W 0 2 CS12 R/W 0 1 CS11 R/W 0 0 CS10 R/W 0 TCCR1B
* Bit 7 - ICNCn: Input Capture Noise Canceler Setting this bit (to one) activates the Input Capture Noise Canceler. When the Noise Canceler is activated, the input from the Input Capture Pin (ICPn) is filtered. The filter function requires four successive equal valued samples of the ICPn pin for changing its output. The input capture is therefore delayed by four Oscillator cycles when the noise canceler is enabled. * Bit 6 - ICESn: Input Capture Edge Select This bit selects which edge on the Input Capture Pin (ICPn) that is used to trigger a capture event. When the ICESn bit is written to zero, a falling (negative) edge is used as trigger, and when the ICESn bit is written to one, a rising (positive) edge will trigger the capture. When a capture is triggered according to the ICESn setting, the counter value is copied into the Input Capture Register (ICRn). The event will also set the Input Capture Flag (ICFn), and this can be used to cause an Input Capture Interrupt, if this interrupt is enabled. When the ICRn is used as TOP value (see description of the WGMn3:0 bits located in the TCCRnA and the TCCRnB Register), the ICPn is disconnected and consequently the input capture function is disabled. * Bit 5 - Reserved Bit This bit is reserved for future use. For ensuring compatibility with future devices, this bit must be written to zero when TCCRnB is written. * Bit 4:3 - WGMn3:2: Waveform Generation Mode See TCCRnA Register description. * Bit 2:0 - CSn2:0: Clock Select The three clock select bits select the clock source to be used by the Timer/Counter, see Figure 14-1 and Figure 14-2.
Table 15-5.
CSn2 0 0 0 0 1 1 1 1
Clock Select Bit Description
CSn1 0 0 1 1 0 0 1 1 CSn0 0 1 0 1 0 1 0 1 Description No clock source. (Timer/Counter stopped) clkI/O/1 (No prescaling clkI/O/8 (From prescaler) clkI/O/64 (From prescaler) clkI/O/256 (From prescaler) clkI/O/1024 (From prescaler) External clock source on Tn pin. Clock on falling edge External clock source on Tn pin. Clock on rising edge
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If external pin modes are used for the Timer/Countern, transitions on the Tn pin will clock the counter even if the pin is configured as an output. This feature allows software control of the counting. 15.10.3 Timer/Counter1 Control Register C - TCCR1C
Bit Read/Write Initial Value 7 FOC1A W 0 6 FOC1B W 0 5 FOC1C W 0 4 - R 0 3 - R 0 2 - R 0 1 - R 0 0 - R 0 TCCR1C
* Bit 7 - FOCnA: Force Output Compare for Channel A * Bit 6 - FOCnB: Force Output Compare for Channel B * Bit 5 - FOCnC: Force Output Compare for Channel C The FOCnA/FOCnB/FOCnC bits are only active when the WGMn3:0 bits specifies a non-PWM mode. When writing a logical one to the FOCnA/FOCnB/FOCnC bit, an immediate compare match is forced on the waveform generation unit. The OCnA/OCnB/OCnC output is changed according to its COMnx1:0 bits setting. Note that the FOCnA/FOCnB/FOCnC bits are implemented as strobes. Therefore it is the value present in the COMnx1:0 bits that determine the effect of the forced compare. A FOCnA/FOCnB/FOCnC strobe will not generate any interrupt nor will it clear the timer in Clear Timer on Compare Match (CTC) mode using OCRnA as TOP. The FOCnA/FOCnB/FOCnB bits are always read as zero. * Bit 4:0 - Reserved Bits These bits are reserved for future use. For ensuring compatibility with future devices, these bits must be written to zero when TCCRnC is written. 15.10.4 Timer/Counter1 - TCNT1H and TCNT1L
Bit 7 TCNT1[7:0] Read/Write Initial Value R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 TCNT1H TCNT1L TCNT1[15:8]
The two Timer/Counter I/O locations (TCNTnH and TCNTnL, combined TCNTn) give direct access, both for read and for write operations, to the Timer/Counter unit 16-bit counter. To ensure that both the high and low bytes are read and written simultaneously when the CPU accesses these registers, the access is performed using an 8-bit temporary High Byte Register (TEMP). This temporary register is shared by all the other 16-bit registers. See "Accessing 16-bit Registers" on page 109. Modifying the counter (TCNTn) while the counter is running introduces a risk of missing a compare match between TCNTn and one of the OCRnx Registers. Writing to the TCNTn Register blocks (removes) the compare match on the following timer clock for all compare units.
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15.10.5
Output Compare Register 1 A - OCR1AH and OCR1AL
Bit 7 OCR1A[7:0] Read/Write Initial Value R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 OCR1AH OCR1AL OCR1A[15:8]
15.10.6
Output Compare Register 1 B - OCR1BH and OCR1BL
Bit 7 OCR1B[7:0] Read/Write Initial Value R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 OCR1BH OCR1BL OCR1B[15:8]
15.10.7
Output Compare Register 1 C - OCR1CH and OCR1CL
Bit 7 OCR1C[7:0] Read/Write Initial Value R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 OCR1CH OCR1CL OCR1C[15:8]
The Output Compare Registers contain a 16-bit value that is continuously compared with the counter value (TCNTn). A match can be used to generate an Output Compare interrupt, or to generate a waveform output on the OCnx pin. The Output Compare Registers are 16-bit in size. To ensure that both the high and low bytes are written simultaneously when the CPU writes to these registers, the access is performed using an 8-bit temporary High Byte Register (TEMP). This temporary register is shared by all the other 16-bit registers. See "Accessing 16-bit Registers" on page 109. 15.10.8 Input Capture Register 1 - ICR1H and ICR1L
Bit 7 ICR1[15:8] ICR1[7:0] Read/Write Initial Value R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 ICR1H ICR1L
IThe Input Capture is updated with the counter (TCNTn) value each time an event occurs on the ICPn pin (or optionally on the Analog Comparator output for Timer/Counter1). The Input Capture can be used for defining the counter TOP value. The Input Capture Register is 16-bit in size. To ensure that both the high and low bytes are read simultaneously when the CPU accesses these registers, the access is performed using an 8-bit temporary High Byte Register (TEMP). This temporary register is shared by all the other 16-bit registers. See "Accessing 16-bit Registers" on page 109. 15.10.9 Timer/Counter1 Interrupt Mask Register - TIMSK1
Bit Read/Write Initial Value 7 - R 0 6 - R 0 5 ICIE1 R/W 0 4 - R 0 3 OCIE1C R/W 0 2 OCIE1B R/W 0 1 OCIE1A R/W 0 0 TOIE1 R/W 0 TIMSK1
* Bit 5 - ICIEn: Timer/Countern, Input Capture Interrupt Enable 134
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When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the Timer/Countern Input Capture interrupt is enabled. The corresponding Interrupt Vector (See "Interrupts" on page 63.) is executed when the ICFn Flag, located in TIFRn, is set. Bit 3 - OCIEnC: Timer/Countern, Output Compare C Match Interrupt Enable When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the Timer/Countern Output Compare C Match interrupt is enabled. The corresponding Interrupt Vector (See "Interrupts" on page 63.) is executed when the OCFnC Flag, located in TIFRn, is set. * Bit 2 - OCIEnB: Timer/Countern, Output Compare B Match Interrupt Enable When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the Timer/Countern Output Compare B Match interrupt is enabled. The corresponding Interrupt Vector (See "Interrupts" on page 63.) is executed when the OCFnB Flag, located in TIFRn, is set. * Bit 1 - OCIEnA: Timer/Countern, Output Compare A Match Interrupt Enable When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the Timer/Countern Output Compare A Match interrupt is enabled. The corresponding Interrupt Vector (See "Interrupts" on page 63.) is executed when the OCFnA Flag, located in TIFRn, is set. * Bit 0 - TOIEn: Timer/Countern, Overflow Interrupt Enable When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the Timer/Countern Overflow interrupt is enabled. The corresponding Interrupt Vector (See "Interrupts" on page 63.) is executed when the TOVn Flag, located in TIFRn, is set. 15.10.10 Timer/Counter1 Interrupt Flag Register - TIFR1
Bit Read/Write Initial Value 7 - R 0 6 - R 0 5 ICF1 R/W 0 4 - R 0 3 OCF1C R/W 0 2 OCF1B R/W 0 1 OCF1A R/W 0 0 TOV1 R/W 0 TIFR1
* Bit 5 - ICFn: Timer/Countern, Input Capture Flag This flag is set when a capture event occurs on the ICPn pin. When the Input Capture Register (ICRn) is set by the WGMn3:0 to be used as the TOP value, the ICFn Flag is set when the counter reaches the TOP value. ICFn is automatically cleared when the Input Capture Interrupt Vector is executed. Alternatively, ICFn can be cleared by writing a logic one to its bit location. * Bit 3- OCFnC: Timer/Countern, Output Compare C Match Flag This flag is set in the timer clock cycle after the counter (TCNTn) value matches the Output Compare Register C (OCRnC). Note that a Forced Output Compare (FOCnC) strobe will not set the OCFnC Flag. OCFnC is automatically cleared when the Output Compare Match C Interrupt Vector is executed. Alternatively, OCFnC can be cleared by writing a logic one to its bit location. * Bit 2 - OCFnB: Timer/Counter1, Output Compare B Match Flag
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This flag is set in the timer clock cycle after the counter (TCNTn) value matches the Output Compare Register B (OCRnB). Note that a Forced Output Compare (FOCnB) strobe will not set the OCFnB Flag. OCFnB is automatically cleared when the Output Compare Match B Interrupt Vector is executed. Alternatively, OCFnB can be cleared by writing a logic one to its bit location. * Bit 1 - OCF1A: Timer/Counter1, Output Compare A Match Flag This flag is set in the timer clock cycle after the counter (TCNTn value matches the Output Compare Register A (OCRnA). Note that a Forced Output Compare (FOCnA) strobe will not set the OCFnA Flag. OCFnA is automatically cleared when the Output Compare Match A Interrupt Vector is executed. Alternatively, OCFnA can be cleared by writing a logic one to its bit location. * Bit 0 - TOVn: Timer/Countern, Overflow Flag The setting of this flag is dependent of the WGMn3:0 bits setting. In Normal and CTC modes, the TOVn Flag is set when the timer overflows. Refer to Table 15-4 on page 131 for the TOVn Flag behavior when using another WGMn3:0 bit setting. TOVn is automatically cleared when the Timer/Countern Overflow Interrupt Vector is executed. Alternatively, TOVn can be cleared by writing a logic one to its bit location.
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16. Serial Peripheral Interface - SPI
The Serial Peripheral Interface (SPI) allows high-speed synchronous data transfer between the A T90 US B 82 /1 62 an d p er i ph e r al de v ic e s o r be twe e n s ev e r al AV R d ev i c e s. The AT90USB82/162 SPI includes the following features: * * * * * * * *
Full-duplex, Three-wire Synchronous Data Transfer Master or Slave Operation LSB First or MSB First Data Transfer Seven Programmable Bit Rates End of Transmission Interrupt Flag Write Collision Flag Protection Wake-up from Idle Mode Double Speed (CK/2) Master SPI Mode
USART can also be used in Master SPI mode, see "USART in SPI Mode" on page 173. The Power Reduction SPI bit, PRSPI, in "Power Reduction Register 0 - PRR0" on page 43 on page 50 must be written to zero to enable SPI module. Figure 16-1. SPI Block Diagram(1)
DIVIDER /2/4/8/16/32/64/128
SPI2X
Note:
1. Refer to Figure 1-1 on page 3, and Table 11-6 on page 77 for SPI pin placement.
The interconnection between Master and Slave CPUs with SPI is shown in Figure 16-2. The system consists of two shift Registers, and a Master clock generator. The SPI Master initiates the communication cycle when pulling low the Slave Select SS pin of the desired Slave. Master and 137
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SPI2X
Slave prepare the data to be sent in their respective shift Registers, and the Master generates the required clock pulses on the SCK line to interchange data. Data is always shifted from Master to Slave on the Master Out - Slave In, MOSI, line, and from Slave to Master on the Master In - Slave Out, MISO, line. After each data packet, the Master will synchronize the Slave by pulling high the Slave Select, SS, line. When configured as a Master, the SPI interface has no automatic control of the SS line. This must be handled by user software before communication can start. When this is done, writing a byte to the SPI Data Register starts the SPI clock generator, and the hardware shifts the eight bits into the Slave. After shifting one byte, the SPI clock generator stops, setting the end of Transmission Flag (SPIF). If the SPI Interrupt Enable bit (SPIE) in the SPCR Register is set, an interrupt is requested. The Master may continue to shift the next byte by writing it into SPDR, or signal the end of packet by pulling high the Slave Select, SS line. The last incoming byte will be kept in the Buffer Register for later use. When configured as a Slave, the SPI interface will remain sleeping with MISO tri-stated as long as the SS pin is driven high. In this state, software may update the contents of the SPI Data Register, SPDR, but the data will not be shifted out by incoming clock pulses on the SCK pin until the SS pin is driven low. As one byte has been completely shifted, the end of Transmission Flag, SPIF is set. If the SPI Interrupt Enable bit, SPIE, in the SPCR Register is set, an interrupt is requested. The Slave may continue to place new data to be sent into SPDR before reading the incoming data. The last incoming byte will be kept in the Buffer Register for later use. Figure 16-2. SPI Master-slave Interconnection
SHIFT ENABLE
The system is single buffered in the transmit direction and double buffered in the receive direction. This means that bytes to be transmitted cannot be written to the SPI Data Register before the entire shift cycle is completed. When receiving data, however, a received character must be read from the SPI Data Register before the next character has been completely shifted in. Otherwise, the first byte is lost. In SPI Slave mode, the control logic will sample the incoming signal of the SCK pin. To ensure correct sampling of the clock signal, the frequency of the SPI clock should never exceed fosc/4.
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When the SPI is enabled, the data direction of the MOSI, MISO, SCK, and SS pins is overridden according to Table 16-1. For more details on automatic port overrides, refer to "Alternate Port Functions" on page 72. Table 16-1.
Pin MOSI MISO SCK SS Note:
SPI Pin Overrides(1)
Direction, Master SPI User Defined Input User Defined User Defined Direction, Slave SPI Input User Defined Input Input
1. See "Alternate Functions of Port B" on page 74 for a detailed description of how to define the direction of the user defined SPI pins.
The following code examples show how to initialize the SPI as a Master and how to perform a simple transmission. DDR_SPI in the examples must be replaced by the actual Data Direction Register controlling the SPI pins. DD_MOSI, DD_MISO and DD_SCK must be replaced by the actual data direction bits for these pins. E.g. if MOSI is placed on pin PB5, replace DD_MOSI with DDB5 and DDR_SPI with DDRB.
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Assembly Code Example(1)
SPI_MasterInit: ; Set MOSI and SCK output, all others input ldi out ldi out ret SPI_MasterTransmit: ; Start transmission of data (r16) out SPDR,r16 Wait_Transmit: ; Wait for transmission complete sbis SPSR,SPIF rjmp Wait_Transmit ret r17,(1<; Enable SPI, Master, set clock rate fck/16
C Code Example(1)
void SPI_MasterInit(void) { /* Set MOSI and SCK output, all others input */ DDR_SPI = (1<140
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The following code examples show how to initialize the SPI as a Slave and how to perform a simple reception. Assembly Code Example(1)
SPI_SlaveInit: ; Set MISO output, all others input ldi out ldi out ret SPI_SlaveReceive: ; Wait for reception complete sbis SPSR,SPIF rjmp SPI_SlaveReceive ; Read received data and return in ret r16,SPDR r17,(1<; Enable SPI
C Code Example(1)
void SPI_SlaveInit(void) { /* Set MISO output, all others input */ DDR_SPI = (1<16.1
16.1.1
SS Pin Functionality
Slave Mode When the SPI is configured as a Slave, the Slave Select (SS) pin is always input. When SS is held low, the SPI is activated, and MISO becomes an output if configured so by the user. All other pins are inputs. When SS is driven high, all pins are inputs, and the SPI is passive, which 141
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means that it will not receive incoming data. Note that the SPI logic will be reset once the SS pin is driven high. The SS pin is useful for packet/byte synchronization to keep the slave bit counter synchronous with the master clock generator. When the SS pin is driven high, the SPI slave will immediately reset the send and receive logic, and drop any partially received data in the Shift Register. 16.1.2 Master Mode When the SPI is configured as a Master (MSTR in SPCR is set), the user can determine the direction of the SS pin. If SS is configured as an output, the pin is a general output pin which does not affect the SPI system. Typically, the pin will be driving the SS pin of the SPI Slave. If SS is configured as an input, it must be held high to ensure Master SPI operation. If the SS pin is driven low by peripheral circuitry when the SPI is configured as a Master with the SS pin defined as an input, the SPI system interprets this as another master selecting the SPI as a slave and starting to send data to it. To avoid bus contention, the SPI system takes the following actions: 1. The MSTR bit in SPCR is cleared and the SPI system becomes a Slave. As a result of the SPI becoming a Slave, the MOSI and SCK pins become inputs. 2. The SPIF Flag in SPSR is set, and if the SPI interrupt is enabled, and the I-bit in SREG is set, the interrupt routine will be executed. Thus, when interrupt-driven SPI transmission is used in Master mode, and there exists a possibility that SS is driven low, the interrupt should always check that the MSTR bit is still set. If the MSTR bit has been cleared by a slave select, it must be set by the user to re-enable SPI Master mode. 16.1.3 SPI Control Register - SPCR
Bit Read/Write Initial Value 7 SPIE R/W 0 6 SPE R/W 0 5 DORD R/W 0 4 MSTR R/W 0 3 CPOL R/W 0 2 CPHA R/W 0 1 SPR1 R/W 0 0 SPR0 R/W 0 SPCR
* Bit 7 - SPIE: SPI Interrupt Enable This bit causes the SPI interrupt to be executed if SPIF bit in the SPSR Register is set and the if the Global Interrupt Enable bit in SREG is set. * Bit 6 - SPE: SPI Enable When the SPE bit is written to one, the SPI is enabled. This bit must be set to enable any SPI operations. * Bit 5 - DORD: Data Order When the DORD bit is written to one, the LSB of the data word is transmitted first. When the DORD bit is written to zero, the MSB of the data word is transmitted first. * Bit 4 - MSTR: Master/Slave Select This bit selects Master SPI mode when written to one, and Slave SPI mode when written logic zero. If SS is configured as an input and is driven low while MSTR is set, MSTR will be cleared,
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and SPIF in SPSR will become set. The user will then have to set MSTR to re-enable SPI Master mode. * Bit 3 - CPOL: Clock Polarity When this bit is written to one, SCK is high when idle. When CPOL is written to zero, SCK is low when idle. Refer to Figure 16-3 and Figure 16-4 for an example. The CPOL functionality is summarized below: Table 16-2. CPOL Functionality
CPOL 0 1 Leading Edge Rising Falling Trailing Edge Falling Rising
* Bit 2 - CPHA: Clock Phase The settings of the Clock Phase bit (CPHA) determine if data is sampled on the leading (first) or trailing (last) edge of SCK. Refer to Figure 16-3 and Figure 16-4 for an example. The CPOL functionality is summarized below: Table 16-3. CPHA Functionality
CPHA 0 1 Leading Edge Sample Setup Trailing Edge Setup Sample
* Bits 1, 0 - SPR1, SPR0: SPI Clock Rate Select 1 and 0 These two bits control the SCK rate of the device configured as a Master. SPR1 and SPR0 have no effect on the Slave. The relationship between SCK and the Oscillator Clock frequency fosc is shown in the following table: Table 16-4.
SPI2X 0 0 0 0 1 1 1 1
Relationship Between SCK and the Oscillator Frequency
SPR1 0 0 1 1 0 0 1 1 SPR0 0 1 0 1 0 1 0 1 SCK Frequency
fosc/4 fosc/16 fosc/64 fosc/128 fosc/2 fosc/8 fosc/32 fosc/64
16.1.4
SPI Status Register - SPSR
Bit Read/Write Initial Value 7 SPIF R 0 6 WCOL R 0 5 - R 0 4 - R 0 3 - R 0 2 - R 0 1 - R 0 0 SPI2X R/W 0 SPSR
* Bit 7 - SPIF: SPI Interrupt Flag
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When a serial transfer is complete, the SPIF Flag is set. An interrupt is generated if SPIE in SPCR is set and global interrupts are enabled. If SS is an input and is driven low when the SPI is in Master mode, this will also set the SPIF Flag. SPIF is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, the SPIF bit is cleared by first reading the SPI Status Register with SPIF set, then accessing the SPI Data Register (SPDR). * Bit 6 - WCOL: Write COLlision Flag The WCOL bit is set if the SPI Data Register (SPDR) is written during a data transfer. The WCOL bit (and the SPIF bit) are cleared by first reading the SPI Status Register with WCOL set, and then accessing the SPI Data Register. * Bit 5..1 - Res: Reserved Bits These bits are reserved bits in the AT90USB82/162 and will always read as zero. * Bit 0 - SPI2X: Double SPI Speed Bit When this bit is written logic one the SPI speed (SCK Frequency) will be doubled when the SPI is in Master mode (see Table 16-4). This means that the minimum SCK period will be two CPU clock periods. When the SPI is configured as Slave, the SPI is only guaranteed to work at fosc/4 or lower. The SPI interface on the AT90USB82/162 is also used for program memory and EEPROM downloading or uploading. See page 257 for serial programming and verification. 16.1.5 SPI Data Register - SPDR
Bit Read/Write Initial Value 7 MSB R/W X R/W X R/W X R/W X R/W X R/W X R/W X 6 5 4 3 2 1 0 LSB R/W X Undefined SPDR
The SPI Data Register is a read/write register used for data transfer between the Register File and the SPI Shift Register. Writing to the register initiates data transmission. Reading the register causes the Shift Register Receive buffer to be read.
16.2
Data Modes
There are four combinations of SCK phase and polarity with respect to serial data, which are determined by control bits CPHA and CPOL. The SPI data transfer formats are shown in Figure 16-3 and Figure 16-4. Data bits are shifted out and latched in on opposite edges of the SCK signal, ensuring sufficient time for data signals to stabilize. This is clearly seen by summarizing Table 16-2 and Table 16-3, as done below:
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Table 16-5. CPOL Functionality
Leading Edge CPOL=0, CPHA=0 CPOL=0, CPHA=1 CPOL=1, CPHA=0 CPOL=1, CPHA=1 Sample (Rising) Setup (Rising) Sample (Falling) Setup (Falling) Trailing eDge Setup (Falling) Sample (Falling) Setup (Rising) Sample (Rising) SPI Mode 0 1 2 3
Figure 16-3. SPI Transfer Format with CPHA = 0
SCK (CPOL = 0) mode 0 SCK (CPOL = 1) mode 2 SAMPLE I MOSI/MISO CHANGE 0 MOSI PIN CHANGE 0 MISO PIN SS
MSB first (DORD = 0) MSB LSB first (DORD = 1) LSB
Bit 6 Bit 1
Bit 5 Bit 2
Bit 4 Bit 3
Bit 3 Bit 4
Bit 2 Bit 5
Bit 1 Bit 6
LSB MSB
Figure 16-4. SPI Transfer Format with CPHA = 1
SCK (CPOL = 0) mode 1 SCK (CPOL = 1) mode 3 SAMPLE I MOSI/MISO CHANGE 0 MOSI PIN CHANGE 0 MISO PIN SS
MSB first (DORD = 0) LSB first (DORD = 1)
MSB LSB
Bit 6 Bit 1
Bit 5 Bit 2
Bit 4 Bit 3
Bit 3 Bit 4
Bit 2 Bit 5
Bit 1 Bit 6
LSB MSB
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17. USART
The Universal Synchronous and Asynchronous serial Receiver and Transmitter (USART) is a highly flexible serial communication device. The main features are: * * * * * * * * * * * * *
Full Duplex Operation (Independent Serial Receive and Transmit Registers) Asynchronous or Synchronous Operation Flow control CTS/RTS signals hardware management Master or Slave Clocked Synchronous Operation High Resolution Baud Rate Generator Supports Serial Frames with 5, 6, 7, 8, or 9 Data Bits and 1 or 2 Stop Bits Odd or Even Parity Generation and Parity Check Supported by Hardware Data OverRun Detection Framing Error Detection Noise Filtering Includes False Start Bit Detection and Digital Low Pass Filter Three Separate Interrupts on TX Complete, TX Data Register Empty and RX Complete Multi-processor Communication Mode Double Speed Asynchronous Communication Mode
17.1
Overview
A simplified block diagram of the USART Transmitter is shown in Figure 17-1 on page 147. CPU accessible I/O Registers and I/O pins are shown in bold.
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Figure 17-1. USART Block Diagram(1)
Clock Generator
UBRR[H:L] OSC
BAUD RATE GENERATOR
SYNC LOGIC
PIN CONTROL
XCK
Transmitter
UDR (Transmit) PARITY GENERATOR TRANSMIT SHIFT REGISTER PIN CONTROL TxD TX CONTROL
DATA BUS
Receiver
CLOCK RECOVERY RX CONTROL
RECEIVE SHIFT REGISTER
DATA RECOVERY
PIN CONTROL
RxD
UDR (Receive)
PARITY CHECKER
UCSRA
UCSRB
UCSRC
Note:
1. See Figure 1-1 on page 3, Table 11-9 on page 79 and for USART pin placement.
The dashed boxes in the block diagram separate the three main parts of the USART (listed from the top): Clock Generator, Transmitter and Receiver. Control Registers are shared by all units. The Clock Generation logic consists of synchronization logic for external clock input used by synchronous slave operation, and the baud rate generator. The XCKn (Transfer Clock) pin is only used by synchronous transfer mode. The Transmitter consists of a single write buffer, a serial Shift Register, Parity Generator and Control logic for handling different serial frame formats. The write buffer allows a continuous transfer of data without any delay between frames. The Receiver is the most complex part of the USART module due to its clock and data recovery units. The recovery units are used for asynchronous data reception. In addition to the recovery units, the Receiver includes a Parity Checker, Control logic, a Shift Register and a two level receive buffer (UDRn). The Receiver supports the same frame formats as the Transmitter, and can detect Frame Error, Data OverRun and Parity Errors.
17.2
Clock Generation
The Clock Generation logic generates the base clock for the Transmitter and Receiver. The USARTn supports four modes of clock operation: Normal asynchronous, Double Speed asynchronous, Master synchronous and Slave synchronous mode. The UMSELn bit in USART Control and Status Register C (UCSRnC) selects between asynchronous and synchronous operation. Double Speed (asynchronous mode only) is controlled by the U2Xn found in the UCSRnA Register. When using synchronous mode (UMSELn = 1), the Data Direction Register
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for the XCKn pin (DDR_XCKn) controls whether the clock source is internal (Master mode) or external (Slave mode). The XCKn pin is only active when using synchronous mode. Figure 17-2 shows a block diagram of the clock generation logic. Figure 17-2. Clock Generation Logic, Block Diagram
UBRR fosc Prescaling Down-Counter UBRR+1 /2 /4 /2 U2X
0 1
OSC DDR_XCK Sync Register Edge Detector
0 1
txclk
xcki XCK Pin xcko
0 1
UMSEL
DDR_XCK
UCPOL
1 0
rxclk
Signal description: txclk rxclk xcki operation. xcko fOSC 17.2.1 Transmitter clock (Internal Signal). Receiver base clock (Internal Signal). Input from XCK pin (internal Signal). Used for synchronous slave Clock output to XCK pin (Internal Signal). Used for synchronous master operation. XTAL pin frequency (System Clock).
Internal Clock Generation - The Baud Rate Generator Internal clock generation is used for the asynchronous and the synchronous master modes of operation. The description in this section refers to Figure 17-2. The USART Baud Rate Register (UBRRn) and the down-counter connected to it function as a programmable prescaler or baud rate generator. The down-counter, running at system clock (fosc), is loaded with the UBRRn value each time the counter has counted down to zero or when the UBRRLn Register is written. A clock is generated each time the counter reaches zero. This clock is the baud rate generator clock output (= fosc/(UBRRn+1)). The Transmitter divides the baud rate generator clock output by 2, 8 or 16 depending on mode. The baud rate generator output is used directly by the Receiver's clock and data recovery units. However, the recovery units use a state machine that uses 2, 8 or 16 states depending on mode set by the state of the UMSELn, U2Xn and DDR_XCKn bits.
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Table 17-1 contains equations for calculating the baud rate (in bits per second) and for calculating the UBRRn value for each mode of operation using an internally generated clock source. Table 17-1. Equations for Calculating Baud Rate Register Setting
Equation for Calculating Baud Rate(1) Equation for Calculating UBRR Value
Operating Mode
f OSC UBRRn = ----------------------- - 1 16BAUD
Asynchronous Normal mode (U2Xn = 0)
f OSC BAUD = ----------------------------------------16 ( UBRRn + 1 )
f OSC UBRRn = ------------------- - 1 8BAUD
Asynchronous Double Speed mode (U2Xn = 1)
f OSC BAUD = -------------------------------------8 ( UBRRn + 1 )
f OSC UBRRn = ------------------- - 1 2BAUD
Synchronous Master mode
f OSC BAUD = -------------------------------------2 ( UBRRn + 1 )
Note:
1. The baud rate is defined to be the transfer rate in bit per second (bps)
BAUD fOSC UBRRn
Baud rate (in bits per second, bps) System Oscillator clock frequency Contents of the UBRRHn and UBRRLn Registers, (0-4095)
Some examples of UBRRn values for some system clock frequencies are found in Table 17-9 on page 170. 17.2.2 Double Speed Operation (U2Xn) The transfer rate can be doubled by setting the U2Xn bit in UCSRnA. Setting this bit only has effect for the asynchronous operation. Set this bit to zero when using synchronous operation. Setting this bit will reduce the divisor of the baud rate divider from 16 to 8, effectively doubling the transfer rate for asynchronous communication. Note however that the Receiver will in this case only use half the number of samples (reduced from 16 to 8) for data sampling and clock recovery, and therefore a more accurate baud rate setting and system clock are required when this mode is used. For the Transmitter, there are no downsides.
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17.2.3
External Clock External clocking is used by the synchronous slave modes of operation. The description in this section refers to Figure 17-2 for details. External clock input from the XCKn pin is sampled by a synchronization register to minimize the chance of meta-stability. The output from the synchronization register must then pass through an edge detector before it can be used by the Transmitter and Receiver. This process introduces a two CPU clock period delay and therefore the maximum external XCKn clock frequency is limited by the following equation: f OSC f XCK < ---------4 Note that fosc depends on the stability of the system clock source. It is therefore recommended to add some margin to avoid possible loss of data due to frequency variations.
17.2.4
Synchronous Clock Operation When synchronous mode is used (UMSELn = 1), the XCKn pin will be used as either clock input (Slave) or clock output (Master). The dependency between the clock edges and data sampling or data change is the same. The basic principle is that data input (on RxDn) is sampled at the opposite XCKn clock edge of the edge the data output (TxDn) is changed. Figure 17-3. Synchronous Mode XCKn Timing.
UCPOL = 1 XCK
RxD / TxD Sample UCPOL = 0 XCK
RxD / TxD Sample
The UCPOLn bit UCRSC selects which XCKn clock edge is used for data sampling and which is used for data change. As Figure 17-3 shows, when UCPOLn is zero the data will be changed at rising XCKn edge and sampled at falling XCKn edge. If UCPOLn is set, the data will be changed at falling XCKn edge and sampled at rising XCKn edge.
17.3
Frame Formats
A serial frame is defined to be one character of data bits with synchronization bits (start and stop bits), and optionally a parity bit for error checking. The USART accepts all 30 combinations of the following as valid frame formats: * 1 start bit * 5, 6, 7, 8, or 9 data bits * no, even or odd parity bit * 1 or 2 stop bits
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A frame starts with the start bit followed by the least significant data bit. Then the next data bits, up to a total of nine, are succeeding, ending with the most significant bit. If enabled, the parity bit is inserted after the data bits, before the stop bits. When a complete frame is transmitted, it can be directly followed by a new frame, or the communication line can be set to an idle (high) state. Figure 17-4 illustrates the possible combinations of the frame formats. Bits inside brackets are optional. Figure 17-4. Frame Formats
FRAME
(IDLE)
St
0
1
2
3
4
[5]
[6]
[7]
[8]
[P]
Sp1 [Sp2]
(St / IDLE)
St (n) P Sp IDLE must be
Start bit, always low. Data bits (0 to 8). Parity bit. Can be odd or even. Stop bit, always high. No transfers on the communication line (RxDn or TxDn). An IDLE line high.
The frame format used by the USART is set by the UCSZn2:0, UPMn1:0 and USBSn bits in UCSRnB and UCSRnC. The Receiver and Transmitter use the same setting. Note that changing the setting of any of these bits will corrupt all ongoing communication for both the Receiver and Transmitter. The USART Character SiZe (UCSZn2:0) bits select the number of data bits in the frame. The USART Parity mode (UPMn1:0) bits enable and set the type of parity bit. The selection between one or two stop bits is done by the USART Stop Bit Select (USBSn) bit. The Receiver ignores the second stop bit. An FE (Frame Error) will therefore only be detected in the cases where the first stop bit is zero. 17.3.1 Parity Bit Calculation The parity bit is calculated by doing an exclusive-or of all the data bits. If odd parity is used, the result of the exclusive or is inverted. The relation between the parity bit and data bits is as follows:: P even = d n - 1 ... d 3 d 2 d 1 d 0 0 P odd = d n - 1 ... d 3 d 2 d 1 d 0 1 Peven P
odd
Parity bit using even parity Parity bit using odd parity Data bit n of the character
dn
If used, the parity bit is located between the last data bit and first stop bit of a serial frame.
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17.4
USART Initialization
The USART has to be initialized before any communication can take place. The initialization process normally consists of setting the baud rate, setting frame format and enabling the Transmitter or the Receiver depending on the usage. For interrupt driven USART operation, the Global Interrupt Flag should be cleared (and interrupts globally disabled) when doing the initialization. Before doing a re-initialization with changed baud rate or frame format, be sure that there are no ongoing transmissions during the period the registers are changed. The TXCn Flag can be used to check that the Transmitter has completed all transfers, and the RXC Flag can be used to check that there are no unread data in the receive buffer. Note that the TXCn Flag must be cleared before each transmission (before UDRn is written) if it is used for this purpose. The following simple USART initialization code examples show one assembly and one C function that are equal in functionality. The examples assume asynchronous operation using polling (no interrupts enabled) and a fixed frame format. The baud rate is given as a function parameter. For the assembly code, the baud rate parameter is assumed to be stored in the r17:r16 Registers. Assembly Code Example(1)
USART_Init: ; Set baud rate out out ldi out ldi out ret UBRRHn, r17 UBRRLn, r16 r16, (1<; Enable receiver and transmitter
; Set frame format: 8data, 2stop bit
C Code Example(1)
void USART_Init( unsigned int baud ) { /* Set baud rate */ UBRRHn = (unsigned char)(baud>>8); UBRRLn = (unsigned char)baud; /* Enable receiver and transmitter */ UCSRnB = (1<More advanced initialization routines can be made that include frame format as parameters, disable interrupts and so on. However, many applications use a fixed setting of the baud and control registers, and for these types of applications the initialization code can be placed directly in the main routine, or be combined with initialization code for other I/O modules.
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17.5 Data Transmission - The USART Transmitter
The USART Transmitter is enabled by setting the Transmit Enable (TXEN) bit in the UCSRnB Register. When the Transmitter is enabled, the normal port operation of the TxDn pin is overridden by the USART and given the function as the Transmitter's serial output. The baud rate, mode of operation and frame format must be set up once before doing any transmissions. If synchronous operation is used, the clock on the XCKn pin will be overridden and used as transmission clock. 17.5.1 Sending Frames with 5 to 8 Data Bit A data transmission is initiated by loading the transmit buffer with the data to be transmitted. The CPU can load the transmit buffer by writing to the UDRn I/O location. The buffered data in the transmit buffer will be moved to the Shift Register when the Shift Register is ready to send a new frame. The Shift Register is loaded with new data if it is in idle state (no ongoing transmission) or immediately after the last stop bit of the previous frame is transmitted. When the Shift Register is loaded with new data, it will transfer one complete frame at the rate given by the Baud Register, U2Xn bit or by XCKn depending on mode of operation. The following code examples show a simple USART transmit function based on polling of the Data Register Empty (UDREn) Flag. When using frames with less than eight bits, the most significant bits written to the UDRn are ignored. The USART has to be initialized before the function can be used. For the assembly code, the data to be sent is assumed to be stored in Register R16 Assembly Code Example(1)
USART_Transmit: ; Wait for empty transmit buffer sbis UCSRnA,UDREn rjmp USART_Transmit ; Put data (r16) into buffer, sends the data out ret UDRn,r16
C Code Example(1)
void USART_Transmit( unsigned char data ) { /* Wait for empty transmit buffer */ while ( !( UCSRnA & (1<The function simply waits for the transmit buffer to be empty by checking the UDREn Flag, before loading it with new data to be transmitted. If the Data Register Empty interrupt is utilized, the interrupt routine writes the data into the buffer. 17.5.2 Sending Frames with 9 Data Bit If 9-bit characters are used (UCSZn = 7), the ninth bit must be written to the TXB8 bit in UCSRnB before the low byte of the character is written to UDRn. The following code examples 153
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show a transmit function that handles 9-bit characters. For the assembly code, the data to be sent is assumed to be stored in registers R17:R16. Assembly Code Example(1)(2)
USART_Transmit: ; Wait for empty transmit buffer sbis UCSRnA,UDREn rjmp USART_Transmit ; Copy 9th bit from r17 to TXB8 cbi sbi out ret UCSRnB,TXB8 UCSRnB,TXB8 UDRn,r16 sbrc r17,0 ; Put LSB data (r16) into buffer, sends the data
C Code Example(1)(2)
void USART_Transmit( unsigned int data ) { /* Wait for empty transmit buffer */ while ( !( UCSRnA & (1<The ninth bit can be used for indicating an address frame when using multi processor communication mode or for other protocol handling as for example synchronization. 17.5.3 Transmitter Flags and Interrupts The USART Transmitter has two flags that indicate its state: USART Data Register Empty (UDREn) and Transmit Complete (TXCn). Both flags can be used for generating interrupts. The Data Register Empty (UDREn) Flag indicates whether the transmit buffer is ready to receive new data. This bit is set when the transmit buffer is empty, and cleared when the transmit buffer contains data to be transmitted that has not yet been moved into the Shift Register. For compatibility with future devices, always write this bit to zero when writing the UCSRnA Register. When the Data Register Empty Interrupt Enable (UDRIEn) bit in UCSRnB is written to one, the USART Data Register Empty Interrupt will be executed as long as UDREn is set (provided that global interrupts are enabled). UDREn is cleared by writing UDRn. When interrupt-driven data transmission is used, the Data Register Empty interrupt routine must either write new data to 154
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UDRn in order to clear UDREn or disable the Data Register Empty interrupt, otherwise a new interrupt will occur once the interrupt routine terminates. The Transmit Complete (TXCn) Flag bit is set one when the entire frame in the Transmit Shift Register has been shifted out and there are no new data currently present in the transmit buffer. The TXCn Flag bit is automatically cleared when a transmit complete interrupt is executed, or it can be cleared by writing a one to its bit location. The TXCn Flag is useful in half-duplex communication interfaces (like the RS-485 standard), where a transmitting application must enter receive mode and free the communication bus immediately after completing the transmission. When the Transmit Compete Interrupt Enable (TXCIEn) bit in UCSRnB is set, the USART Transmit Complete Interrupt will be executed when the TXCn Flag becomes set (provided that global interrupts are enabled). When the transmit complete interrupt is used, the interrupt handling routine does not have to clear the TXCn Flag, this is done automatically when the interrupt is executed. 17.5.4 Parity Generator The Parity Generator calculates the parity bit for the serial frame data. When parity bit is enabled (UPMn1 = 1), the transmitter control logic inserts the parity bit between the last data bit and the first stop bit of the frame that is sent. Disabling the Transmitter The disabling of the Transmitter (setting the TXEN to zero) will not become effective until ongoing and pending transmissions are completed, i.e., when the Transmit Shift Register and Transmit Buffer Register do not contain data to be transmitted. When disabled, the Transmitter will no longer override the TxDn pin.
17.5.5
17.6
Data Reception - The USART Receiver
The USART Receiver is enabled by writing the Receive Enable (RXENn) bit in the UCSRnB Register to one. When the Receiver is enabled, the normal pin operation of the RxDn pin is overridden by the USART and given the function as the Receiver's serial input. The baud rate, mode of operation and frame format must be set up once before any serial reception can be done. If synchronous operation is used, the clock on the XCKn pin will be used as transfer clock.
17.6.1
Receiving Frames with 5 to 8 Data Bits The Receiver starts data reception when it detects a valid start bit. Each bit that follows the start bit will be sampled at the baud rate or XCKn clock, and shifted into the Receive Shift Register until the first stop bit of a frame is received. A second stop bit will be ignored by the Receiver. When the first stop bit is received, i.e., a complete serial frame is present in the Receive Shift Register, the contents of the Shift Register will be moved into the receive buffer. The receive buffer can then be read by reading the UDRn I/O location. The following code example shows a simple USART receive function based on polling of the Receive Complete (RXCn) Flag. When using frames with less than eight bits the most significant
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bits of the data read from the UDRn will be masked to zero. The USART has to be initialized before the function can be used. Assembly Code Example(1)
USART_Receive: ; Wait for data to be received sbis UCSRnA, RXCn rjmp USART_Receive ; Get and return received data from buffer in ret r16, UDRn
C Code Example(1)
unsigned char USART_Receive( void ) { /* Wait for data to be received */ while ( !(UCSRnA & (1<The function simply waits for data to be present in the receive buffer by checking the RXCn Flag, before reading the buffer and returning the value. 17.6.2 Receiving Frames with 9 Data Bits If 9-bit characters are used (UCSZn=7) the ninth bit must be read from the RXB8n bit in UCSRnB before reading the low bits from the UDRn. This rule applies to the FEn, DORn and UPEn Status Flags as well. Read status from UCSRnA, then data from UDRn. Reading the UDRn I/O location will change the state of the receive buffer FIFO and consequently the TXB8n, FEn, DORn and UPEn bits, which all are stored in the FIFO, will change. The following code example shows a simple USART receive function that handles both nine bit characters and the status bits.
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Assembly Code Example(1)
USART_Receive: ; Wait for data to be received sbis UCSRnA, RXCn rjmp USART_Receive ; Get status and 9th bit, then data from buffer in in in r18, UCSRnA r17, UCSRnB r16, UDRn
; If error, return -1 andi r18,(1<USART_ReceiveNoError: ; Filter the 9th bit, then return lsr ret r17 andi r17, 0x01
C Code Example(1)
unsigned int USART_Receive( void ) { unsigned char status, resh, resl; /* Wait for data to be received */ while ( !(UCSRnA & (1<> 1) & 0x01; return ((resh << 8) | resl); } Note: 1. See "About Code Examples" on page 7.
The receive function example reads all the I/O Registers into the Register File before any computation is done. This gives an optimal receive buffer utilization since the buffer location read will be free to accept new data as early as possible.
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17.6.3
Receive Compete Flag and Interrupt The USART Receiver has one flag that indicates the Receiver state. The Receive Complete (RXCn) Flag indicates if there are unread data present in the receive buffer. This flag is one when unread data exist in the receive buffer, and zero when the receive buffer is empty (i.e., does not contain any unread data). If the Receiver is disabled (RXENn = 0), the receive buffer will be flushed and consequently the RXCn bit will become zero. When the Receive Complete Interrupt Enable (RXCIEn) in UCSRnB is set, the USART Receive Complete interrupt will be executed as long as the RXCn Flag is set (provided that global interrupts are enabled). When interrupt-driven data reception is used, the receive complete routine must read the received data from UDRn in order to clear the RXCn Flag, otherwise a new interrupt will occur once the interrupt routine terminates.
17.6.4
Receiver Error Flags The USART Receiver has three Error Flags: Frame Error (FEn), Data OverRun (DORn) and Parity Error (UPEn). All can be accessed by reading UCSRnA. Common for the Error Flags is that they are located in the receive buffer together with the frame for which they indicate the error status. Due to the buffering of the Error Flags, the UCSRnA must be read before the receive buffer (UDRn), since reading the UDRn I/O location changes the buffer read location. Another equality for the Error Flags is that they can not be altered by software doing a write to the flag location. However, all flags must be set to zero when the UCSRnA is written for upward compatibility of future USART implementations. None of the Error Flags can generate interrupts. The Frame Error (FEn) Flag indicates the state of the first stop bit of the next readable frame stored in the receive buffer. The FEn Flag is zero when the stop bit was correctly read (as one), and the FEn Flag will be one when the stop bit was incorrect (zero). This flag can be used for detecting out-of-sync conditions, detecting break conditions and protocol handling. The FEn Flag is not affected by the setting of the USBSn bit in UCSRnC since the Receiver ignores all, except for the first, stop bits. For compatibility with future devices, always set this bit to zero when writing to UCSRnA. The Data OverRun (DORn) Flag indicates data loss due to a receiver buffer full condition. A Data OverRun occurs when the receive buffer is full (two characters), it is a new character waiting in the Receive Shift Register, and a new start bit is detected. If the DORn Flag is set there was one or more serial frame lost between the frame last read from UDRn, and the next frame read from UDRn. For compatibility with future devices, always write this bit to zero when writing to UCSRnA. The DORn Flag is cleared when the frame received was successfully moved from the Shift Register to the receive buffer. The Parity Error (UPEn) Flag indicates that the next frame in the receive buffer had a Parity Error when received. If Parity Check is not enabled the UPEn bit will always be read zero. For compatibility with future devices, always set this bit to zero when writing to UCSRnA. For more details see "Parity Bit Calculation" on page 151 and "Parity Checker" on page 158.
17.6.5
Parity Checker The Parity Checker is active when the high USART Parity mode (UPMn1) bit is set. Type of Parity Check to be performed (odd or even) is selected by the UPMn0 bit. When enabled, the Parity Checker calculates the parity of the data bits in incoming frames and compares the result with the parity bit from the serial frame. The result of the check is stored in the receive buffer together with the received data and stop bits. The Parity Error (UPEn) Flag can then be read by software to check if the frame had a Parity Error.
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The UPEn bit is set if the next character that can be read from the receive buffer had a Parity Error when received and the Parity Checking was enabled at that point (UPMn1 = 1). This bit is valid until the receive buffer (UDRn) is read. 17.6.6 Disabling the Receiver In contrast to the Transmitter, disabling of the Receiver will be immediate. Data from ongoing receptions will therefore be lost. When disabled (i.e., the RXENn is set to zero) the Receiver will no longer override the normal function of the RxDn port pin. The Receiver buffer FIFO will be flushed when the Receiver is disabled. Remaining data in the buffer will be lost Flushing the Receive Buffer The receiver buffer FIFO will be flushed when the Receiver is disabled, i.e., the buffer will be emptied of its contents. Unread data will be lost. If the buffer has to be flushed during normal operation, due to for instance an error condition, read the UDRn I/O location until the RXCn Flag is cleared. The following code example shows how to flush the receive buffer. Assembly Code Example(1)
USART_Flush: sbis UCSRnA, RXCn ret in r16, UDRn rjmp USART_Flush
17.6.7
C Code Example(1)
void USART_Flush( void ) { unsigned char dummy; while ( UCSRnA & (1<17.7
Asynchronous Data Reception
The USART includes a clock recovery and a data recovery unit for handling asynchronous data reception. The clock recovery logic is used for synchronizing the internally generated baud rate clock to the incoming asynchronous serial frames at the RxDn pin. The data recovery logic samples and low pass filters each incoming bit, thereby improving the noise immunity of the Receiver. The asynchronous reception operational range depends on the accuracy of the internal baud rate clock, the rate of the incoming frames, and the frame size in number of bits.
17.7.1
Asynchronous Clock Recovery The clock recovery logic synchronizes internal clock to the incoming serial frames. Figure 17-5 illustrates the sampling process of the start bit of an incoming frame. The sample rate is 16 times the baud rate for Normal mode, and eight times the baud rate for Double Speed mode. The horizontal arrows illustrate the synchronization variation due to the sampling process. Note the larger time variation when using the Double Speed mode (U2Xn = 1) of operation. Samples denoted zero are samples done when the RxDn line is idle (i.e., no communication activity).
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Figure 17-5. Start Bit Sampling
RxD IDLE START BIT 0
Sample
(U2X = 0) 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 2 3
Sample
(U2X = 1) 0 1 2 3 4 5 6 7 8 1 2
When the clock recovery logic detects a high (idle) to low (start) transition on the RxDn line, the start bit detection sequence is initiated. Let sample 1 denote the first zero-sample as shown in the figure. The clock recovery logic then uses samples 8, 9, and 10 for Normal mode, and samples 4, 5, and 6 for Double Speed mode (indicated with sample numbers inside boxes on the figure), to decide if a valid start bit is received. If two or more of these three samples have logical high levels (the majority wins), the start bit is rejected as a noise spike and the Receiver starts looking for the next high to low-transition. If however, a valid start bit is detected, the clock recovery logic is synchronized and the data recovery can begin. The synchronization process is repeated for each start bit. 17.7.2 Asynchronous Data Recovery When the receiver clock is synchronized to the start bit, the data recovery can begin. The data recovery unit uses a state machine that has 16 states for each bit in Normal mode and eight states for each bit in Double Speed mode. Figure 17-6 shows the sampling of the data bits and the parity bit. Each of the samples is given a number that is equal to the state of the recovery unit. Figure 17-6. Sampling of Data and Parity Bit
RxD BIT n
Sample
(U2X = 0) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1
Sample
(U2X = 1) 1 2 3 4 5 6 7 8 1
The decision of the logic level of the received bit is taken by doing a majority voting of the logic value to the three samples in the center of the received bit. The center samples are emphasized on the figure by having the sample number inside boxes. The majority voting process is done as follows: If two or all three samples have high levels, the received bit is registered to be a logic 1. If two or all three samples have low levels, the received bit is registered to be a logic 0. This majority voting process acts as a low pass filter for the incoming signal on the RxDn pin. The recovery process is then repeated until a complete frame is received. Including the first stop bit. Note that the Receiver only uses the first stop bit of a frame. Figure 17-7 shows the sampling of the stop bit and the earliest possible beginning of the start bit of the next frame.
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Figure 17-7. Stop Bit Sampling and Next Start Bit Sampling
RxD STOP 1
(A) (B) (C)
Sample
(U2X = 0) 1 2 3 4 5 6 7 8 9 10 0/1 0/1 0/1
Sample
(U2X = 1) 1 2 3 4 5 6 0/1
The same majority voting is done to the stop bit as done for the other bits in the frame. If the stop bit is registered to have a logic 0 value, the Frame Error (FEn) Flag will be set. A new high to low transition indicating the start bit of a new frame can come right after the last of the bits used for majority voting. For Normal Speed mode, the first low level sample can be at point marked (A) in Figure 17-7. For Double Speed mode the first low level must be delayed to (B). (C) marks a stop bit of full length. The early start bit detection influences the operational range of the Receiver. 17.7.3 Asynchronous Operational Range The operational range of the Receiver is dependent on the mismatch between the received bit rate and the internally generated baud rate. If the Transmitter is sending frames at too fast or too slow bit rates, or the internally generated baud rate of the Receiver does not have a similar (see Table 17-2) base frequency, the Receiver will not be able to synchronize the frames to the start bit. The following equations can be used to calculate the ratio of the incoming data rate and internal receiver baud rate. ( D + 1 )S R slow = -----------------------------------------S - 1 + D S + SF D S SF SM Rslow ( D + 2 )S R fast = ----------------------------------( D + 1 )S + S M
Sum of character size and parity size (D = 5 to 10 bit) Samples per bit. S = 16 for Normal Speed mode and S = 8 for Double Speed mode. First sample number used for majority voting. SF = 8 for normal speed and SF = 4 for Double Speed mode. Middle sample number used for majority voting. SM = 9 for normal speed and SM = 5 for Double Speed mode. is the ratio of the slowest incoming data rate that can be accepted in relation to the receiver baud rate. Rfast is the ratio of the fastest incoming data rate that can be accepted in relation to the receiver baud rate.
Table 17-2 and Table 17-3 list the maximum receiver baud rate error that can be tolerated. Note that Normal Speed mode has higher toleration of baud rate variations.
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Table 17-2.
Recommended Maximum Receiver Baud Rate Error for Normal Speed Mode (U2Xn = 0)
Rslow (%) 93.20 94.12 94.81 95.36 95.81 96.17 Rfast (%) 106.67 105.79 105.11 104.58 104.14 103.78 Max Total Error (%) +6.67/-6.8 +5.79/-5.88 +5.11/-5.19 +4.58/-4.54 +4.14/-4.19 +3.78/-3.83 Recommended Max Receiver Error (%) 3.0 2.5 2.0 2.0 1.5 1.5
D # (Data+Parity Bit) 5 6 7 8 9 10
Table 17-3.
Recommended Maximum Receiver Baud Rate Error for Double Speed Mode (U2Xn = 1)
Rslow (%) 94.12 94.92 95.52 96.00 96.39 96.70 Rfast (%) 105.66 104.92 104,35 103.90 103.53 103.23 Max Total Error (%) +5.66/-5.88 +4.92/-5.08 +4.35/-4.48 +3.90/-4.00 +3.53/-3.61 +3.23/-3.30 Recommended Max Receiver Error (%) 2.5 2.0 1.5 1.5 1.5 1.0
D # (Data+Parity Bit) 5 6 7 8 9 10
The recommendations of the maximum receiver baud rate error was made under the assumption that the Receiver and Transmitter equally divides the maximum total error. There are two possible sources for the receivers baud rate error. The Receiver's system clock (XTAL) will always have some minor instability over the supply voltage range and the temperature range. When using a crystal to generate the system clock, this is rarely a problem, but for a resonator the system clock may differ more than 2% depending of the resonators tolerance. The second source for the error is more controllable. The baud rate generator can not always do an exact division of the system frequency to get the baud rate wanted. In this case an UBRR value that gives an acceptable low error can be used if possible.
17.8
Multi-processor Communication Mode
Setting the Multi-processor Communication mode (MPCMn) bit in UCSRnA enables a filtering function of incoming frames received by the USART Receiver. Frames that do not contain address information will be ignored and not put into the receive buffer. This effectively reduces the number of incoming frames that has to be handled by the CPU, in a system with multiple MCUs that communicate via the same serial bus. The Transmitter is unaffected by the MPCMn setting, but has to be used differently when it is a part of a system utilizing the Multi-processor Communication mode. If the Receiver is set up to receive frames that contain 5 to 8 data bits, then the first stop bit indicates if the frame contains data or address information. If the Receiver is set up for frames with nine data bits, then the ninth bit (RXB8n) is used for identifying address and data frames. When the frame type bit (the first stop or the ninth bit) is one, the frame contains an address. When the frame type bit is zero the frame is a data frame.
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The Multi-processor Communication mode enables several slave MCUs to receive data from a master MCU. This is done by first decoding an address frame to find out which MCU has been addressed. If a particular slave MCU has been addressed, it will receive the following data frames as normal, while the other slave MCUs will ignore the received frames until another address frame is received. 17.8.1 Using MPCMn For an MCU to act as a master MCU, it can use a 9-bit character frame format (UCSZn = 7). The ninth bit (TXB8n) must be set when an address frame (TXB8n = 1) or cleared when a data frame (TXB = 0) is being transmitted. The slave MCUs must in this case be set to use a 9-bit character frame format. The following procedure should be used to exchange data in Multi-processor Communication mode: 1. All Slave MCUs are in Multi-processor Communication mode (MPCMn in UCSRnA is set). 2. The Master MCU sends an address frame, and all slaves receive and read this frame. In the Slave MCUs, the RXCn Flag in UCSRnA will be set as normal. 3. Each Slave MCU reads the UDRn Register and determines if it has been selected. If so, it clears the MPCMn bit in UCSRnA, otherwise it waits for the next address byte and keeps the MPCMn setting. 4. The addressed MCU will receive all data frames until a new address frame is received. The other Slave MCUs, which still have the MPCMn bit set, will ignore the data frames. 5. When the last data frame is received by the addressed MCU, the addressed MCU sets the MPCMn bit and waits for a new address frame from master. The process then repeats from 2. Using any of the 5- to 8-bit character frame formats is possible, but impractical since the Receiver must change between using n and n+1 character frame formats. This makes fullduplex operation difficult since the Transmitter and Receiver uses the same character size setting. If 5- to 8-bit character frames are used, the Transmitter must be set to use two stop bit (USBSn = 1) since the first stop bit is used for indicating the frame type. Do not use Read-Modify-Write instructions (SBI and CBI) to set or clear the MPCMn bit. The MPCMn bit shares the same I/O location as the TXCn Flag and this might accidentally be cleared when using SBI or CBI instructions.
17.9
Hardware Flow Control
The hardware flow control can be enabled by software. CTS : (Clear to Send) RTS : (Request to Send)
HOST
TXD RXD CTS RTS TXD RXD CTS RTS
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17.9.1
Receiver Flow Control The reception flow can be controlled by hardware using the RTS pin. The aim of the flow control is to inform the external transmitter when the internal receive Fifo is full. Thus the transmitter can 163
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stop sending characters. RTS usage and so associated flow control is enabled using RTSEN bit in UCSRnD. Figure 17-8. shows a reception example. Figure 17-8. Reception Flow Control Waveform Example
FIFO Index
0 1 21 0 1
CPU Read
RXD
C1 C2
C3
RTS
Figure 17-9. RTS behavior
RXD
Start Byte0 Stop Start Byte1 Stop Start 1 additional byte may be sent if the transmitter misses the RTS trig Byte2
RTS Read from CPU
RTS will rise at 2/3 of the last received stop bit if the receive fifo is full. To ensure reliable transmissions, even after a RTS rise, an extra-data can still be received and stored in the Receive Shift Register. 17.9.2 Transmission Flow Control The transmission flow can be controlled by hardware using the CTS pin controlled by the external receiver. The aim of the flow control is to stop transmission when the receiver is full of data (CTS = 1). CTS usage and so associated flow control is enabled using CTSEN bit in UCSRnD. The CTS pin is sampled at each CPU write and at the middle of the last stop bit that is curently being sent. Figure 17-10. CTS behavior
Write from CPU TXD
sample Start Byte0 Stop sample Start Byte1 Stop sample Start Byte2
CTS
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17.10 USART Register Description
17.10.1 USART I/O Data Register n- UDRn
Bit 7 RXB[7:0] TXB[7:0] Read/Write Initial Value R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 6 5 4 3 2 1 0 UDRn (Read) UDRn (Write)
The USART Transmit Data Buffer Register and USART Receive Data Buffer Registers share the same I/O address referred to as USART Data Register or UDRn. The Transmit Data Buffer Register (TXB) will be the destination for data written to the UDRn Register location. Reading the UDRn Register location will return the contents of the Receive Data Buffer Register (RXB). For 5-, 6-, or 7-bit characters the upper unused bits will be ignored by the Transmitter and set to zero by the Receiver. The transmit buffer can only be written when the UDREn Flag in the UCSRnA Register is set. Data written to UDRn when the UDREn Flag is not set, will be ignored by the USART Transmitter. When data is written to the transmit buffer, and the Transmitter is enabled, the Transmitter will load the data into the Transmit Shift Register when the Shift Register is empty. Then the data will be serially transmitted on the TxDn pin. The receive buffer consists of a two level FIFO. The FIFO will change its state whenever the receive buffer is accessed. Due to this behavior of the receive buffer, do not use Read-ModifyWrite instructions (SBI and CBI) on this location. Be careful when using bit test instructions (SBIC and SBIS), since these also will change the state of the FIFO. 17.10.2 USART Control and Status Register A - UCSRnA
Bit Read/Write Initial Value 7 RXCn R 0 6 TXCn R/W 0 5 UDREn R 1 4 FEn R 0 3 DORn R 0 2 UPEn R 0 1 U2Xn R/W 0 0 MPCMn R/W 0 UCSRnA
* Bit 7 - RXCn: USART Receive Complete This flag bit is set when there are unread data in the receive buffer and cleared when the receive buffer is empty (i.e., does not contain any unread data). If the Receiver is disabled, the receive buffer will be flushed and consequently the RXCn bit will become zero. The RXCn Flag can be used to generate a Receive Complete interrupt (see description of the RXCIEn bit). * Bit 6 - TXCn: USART Transmit Complete This flag bit is set when the entire frame in the Transmit Shift Register has been shifted out and there are no new data currently present in the transmit buffer (UDRn). The TXCn Flag bit is automatically cleared when a transmit complete interrupt is executed, or it can be cleared by writing a one to its bit location. The TXCn Flag can generate a Transmit Complete interrupt (see description of the TXCIEn bit). * Bit 5 - UDREn: USART Data Register Empty The UDREn Flag indicates if the transmit buffer (UDRn) is ready to receive new data. If UDREn is one, the buffer is empty, and therefore ready to be written. The UDREn Flag can generate a Data Register Empty interrupt (see description of the UDRIEn bit). UDREn is set after a reset to indicate that the Transmitter is ready. 165
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* Bit 4 - FEn: Frame Error This bit is set if the next character in the receive buffer had a Frame Error when received. I.e., when the first stop bit of the next character in the receive buffer is zero. This bit is valid until the receive buffer (UDRn) is read. The FEn bit is zero when the stop bit of received data is one. Always set this bit to zero when writing to UCSRnA. * Bit 3 - DORn: Data OverRun This bit is set if a Data OverRun condition is detected. A Data OverRun occurs when the receive buffer is full (two characters), it is a new character waiting in the Receive Shift Register, and a new start bit is detected. This bit is valid until the receive buffer (UDRn) is read. Always set this bit to zero when writing to UCSRnA. * Bit 2 - UPEn: USART Parity Error This bit is set if the next character in the receive buffer had a Parity Error when received and the Parity Checking was enabled at that point (UPMn1 = 1). This bit is valid until the receive buffer (UDRn) is read. Always set this bit to zero when writing to UCSRnA. * Bit 1 - U2Xn: Double the USART Transmission Speed This bit only has effect for the asynchronous operation. Write this bit to zero when using synchronous operation. Writing this bit to one will reduce the divisor of the baud rate divider from 16 to 8 effectively doubling the transfer rate for asynchronous communication. * Bit 0 - MPCMn: Multi-processor Communication Mode This bit enables the Multi-processor Communication mode. When the MPCMn bit is written to one, all the incoming frames received by the USART Receiver that do not contain address information will be ignored. The Transmitter is unaffected by the MPCMn setting. For more detailed information see "Multi-processor Communication Mode" on page 162. 17.10.3 USART Control and Status Register n B - UCSRnB
Bit Read/Write Initial Value 7 RXCIEn R/W 0 6 TXCIEn R/W 0 5 UDRIEn R/W 0 4 RXENn R/W 0 3 TXENn R/W 0 2 UCSZn2 R/W 0 1 RXB8n R 0 0 TXB8n R/W 0 UCSRnB
* Bit 7 - RXCIEn: RX Complete Interrupt Enable n Writing this bit to one enables interrupt on the RXCn Flag. A USART Receive Complete interrupt will be generated only if the RXCIEn bit is written to one, the Global Interrupt Flag in SREG is written to one and the RXCn bit in UCSRnA is set. * Bit 6 - TXCIEn: TX Complete Interrupt Enable n Writing this bit to one enables interrupt on the TXCn Flag. A USART Transmit Complete interrupt will be generated only if the TXCIEn bit is written to one, the Global Interrupt Flag in SREG is written to one and the TXCn bit in UCSRnA is set. * Bit 5 - UDRIEn: USART Data Register Empty Interrupt Enable n Writing this bit to one enables interrupt on the UDREn Flag. A Data Register Empty interrupt will be generated only if the UDRIEn bit is written to one, the Global Interrupt Flag in SREG is written to one and the UDREn bit in UCSRnA is set.
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* Bit 4 - RXENn: Receiver Enable n Writing this bit to one enables the USART Receiver. The Receiver will override normal port operation for the RxDn pin when enabled. Disabling the Receiver will flush the receive buffer invalidating the FEn, DORn, and UPEn Flags. * Bit 3 - TXENn: Transmitter Enable n Writing this bit to one enables the USART Transmitter. The Transmitter will override normal port operation for the TxDn pin when enabled. The disabling of the Transmitter (writing TXENn to zero) will not become effective until ongoing and pending transmissions are completed, i.e., when the Transmit Shift Register and Transmit Buffer Register do not contain data to be transmitted. When disabled, the Transmitter will no longer override the TxDn port. * Bit 2 - UCSZn2: Character Size n The UCSZn2 bits combined with the UCSZn1:0 bit in UCSRnC sets the number of data bits (Character SiZe) in a frame the Receiver and Transmitter use. * Bit 1 - RXB8n: Receive Data Bit 8 n RXB8n is the ninth data bit of the received character when operating with serial frames with nine data bits. Must be read before reading the low bits from UDRn. * Bit 0 - TXB8n: Transmit Data Bit 8 n TXB8n is the ninth data bit in the character to be transmitted when operating with serial frames with nine data bits. Must be written before writing the low bits to UDRn. 17.10.4 USART Control and Status Register n C - UCSRnC
Bit Read/Write Initial Value 7 UMSELn1 R/W 0 6 UMSELn0 R/W 0 5 UPMn1 R/W 0 4 UPMn0 R/W 0 3 USBSn R/W 0 2 UCSZn1 R/W 1 1 UCSZn0 R/W 1 0 UCPOLn R/W 0 UCSRnC
* Bits 7:6 - UMSELn1:0 USART Mode Select These bits select the mode of operation of the USARTn as shown in Table 17-4.. Table 17-4.
0 0 1 1 Note:
UMSELn Bits Settings
UMSELn0 0 1 0 1 Mode Asynchronous USART Synchronous USART (Reserved) Master SPI (MSPIM)(1)
UMSELn1
1. See "USART in SPI Mode" on page 173 for full description of the Master SPI Mode (MSPIM) operation
* Bits 5:4 - UPMn1:0: Parity Mode These bits enable and set type of parity generation and check. If enabled, the Transmitter will automatically generate and send the parity of the transmitted data bits within each frame. The
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Receiver will generate a parity value for the incoming data and compare it to the UPMn setting. If a mismatch is detected, the UPEn Flag in UCSRnA will be set. Table 17-5.
0 0 1 1
UPMn Bits Settings
UPMn0 0 1 0 1 Parity Mode Disabled Reserved Enabled, Even Parity Enabled, Odd Parity
UPMn1
* Bit 3 - USBSn: Stop Bit Select This bit selects the number of stop bits to be inserted by the Transmitter. The Receiver ignores this setting. Table 17-6. USBS Bit Settings
USBSn 0 1 Stop Bit(s) 1-bit 2-bit
* Bit 2:1 - UCSZn1:0: Character Size The UCSZn1:0 bits combined with the UCSZn2 bit in UCSRnB sets the number of data bits (Character SiZe) in a frame the Receiver and Transmitter use. Table 17-7.
0 0 0 0 1 1 1 1
UCSZn Bits Settings
UCSZn1 0 0 1 1 0 0 1 1 UCSZn0 0 1 0 1 0 1 0 1 Character Size 5-bit 6-bit 7-bit 8-bit Reserved Reserved Reserved 9-bit
UCSZn2
* Bit 0 - UCPOLn: Clock Polarity This bit is used for synchronous mode only. Write this bit to zero when asynchronous mode is used. The UCPOLn bit sets the relationship between data output change and data input sample, and the synchronous clock (XCKn). Table 17-8.
UCPOLn 0 1
UCPOLn Bit Settings
Transmitted Data Changed (Output of TxDn Pin) Rising XCKn Edge Falling XCKn Edge Received Data Sampled (Input on RxDn Pin) Falling XCKn Edge Rising XCKn Edge
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17.10.5 USART Control and Status Register n D - UCSRnD
Bit Read/Write Initial Value 7 R/W 0 6 R/W 0 5 R/W 0 4 R/W 0 3 R/W 0 2 R/W 0 1 CTSEN R/W 0 0 RTSEN R/W 0 UCSRnD
* Bits 1 - CTSEN : USART CTS Enable Set this bit to one by firmware to enable the transmission flow control (CTS). Transmission is allowed if CTS = 0. Set this bit to zero by firmware to disable the transmission flow control (CTS). Transmission is always allowed. * Bits 0 - RTSEN : USART RTS Enable Set this bit to one by firmware to enable the receive flow control (RTS). Set this bit to zero by firmware to disable the receive flow control (RTS). 17.10.6 USART Baud Rate Registers - UBRRLn and UBRRHn
Bit 15 - UBRR[7:0] 7 Read/Write Initial Value R R/W 0 0 6 R R/W 0 0 5 R R/W 0 0 4 R R/W 0 0 3 R/W R/W 0 0 2 R/W R/W 0 0 1 R/W R/W 0 0 0 R/W R/W 0 0 14 - 13 - 12 - 11 UBRR[11:8] 10 9 8 UBRRHn UBRRLn
* Bit 15:12 - Reserved Bits These bits are reserved for future use. For compatibility with future devices, these bit must be written to zero when UBRRH is written. * Bit 11:0 - UBRR11:0: USART Baud Rate Register This is a 12-bit register which contains the USART baud rate. The UBRRH contains the four most significant bits, and the UBRRL contains the eight least significant bits of the USART baud rate. Ongoing transmissions by the Transmitter and Receiver will be corrupted if the baud rate is changed. Writing UBRRL will trigger an immediate update of the baud rate prescaler.
17.11 Examples of Baud Rate Setting
For standard crystal and resonator frequencies, the most commonly used baud rates for asynchronous operation can be generated by using the UBRR settings in Table 17-9 to Table 17-12. UBRR values which yield an actual baud rate differing less than 0.5% from the target baud rate, are bold in the table. Higher error ratings are acceptable, but the Receiver will have less noise resistance when the error ratings are high, especially for large serial frames (see "Asynchronous Operational Range" on page 161). The error values are calculated using the following equation:
BaudRate Closest Match Error[%] = ------------------------------------------------------- - 1 * 100% BaudRate
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Table 17-9.
Baud Rate (bps) 2400 4800 9600 14.4k 19.2k 28.8k 38.4k 57.6k 76.8k 115.2k 230.4k 250k Max. (1) 1.
Examples of UBRRn Settings for Commonly Used Oscillator Frequencies
fosc = 1.0000 MHz U2Xn = 0 U2Xn = 1 UBRR 51 25 12 8 6 3 2 1 1 0 - - 125 kbps Error 0.2% 0.2% 0.2% -3.5% -7.0% 8.5% 8.5% 8.5% -18.6% 8.5% - - fosc = 1.8432 MHz U2Xn = 0 UBRR 47 23 11 7 5 3 2 1 1 0 - - Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% -25.0% 0.0% - - U2Xn = 1 UBRR 95 47 23 15 11 7 5 3 2 1 0 - Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% - UBRR 51 25 12 8 6 3 2 1 1 0 - - 125 kbps fosc = 2.0000 MHz U2Xn = 0 Error 0.2% 0.2% 0.2% -3.5% -7.0% 8.5% 8.5% 8.5% -18.6% 8.5% - - U2Xn = 1 UBRR 103 51 25 16 12 8 6 3 2 1 - 0 Error 0.2% 0.2% 0.2% 2.1% 0.2% -3.5% -7.0% 8.5% 8.5% 8.5% - 0.0% 250 kbps
UBRR 25 12 6 3 2 1 1 0 - - - -
Error 0.2% 0.2% -7.0% 8.5% 8.5% 8.5% -18.6% 8.5% - - - -
62.5 kbps UBRR = 0, Error = 0.0%
115.2 kbps
230.4 kbps
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Table 17-10. Examples of UBRRn Settings for Commonly Used Oscillator Frequencies (Continued)
Baud Rate (bps) 2400 4800 9600 14.4k 19.2k 28.8k 38.4k 57.6k 76.8k 115.2k 230.4k 250k 0.5M 1M Max. 1.
(1)
fosc = 3.6864 MHz U2Xn = 0 UBRR 95 47 23 15 11 7 5 3 2 1 0 0 - - Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% -7.8% - - U2Xn = 1 UBRR 191 95 47 31 23 15 11 7 5 3 1 1 0 - Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% -7.8% -7.8% -
fosc = 4.0000 MHz U2Xn = 0 UBRR 103 51 25 16 12 8 6 3 2 1 0 0 - - Error 0.2% 0.2% 0.2% 2.1% 0.2% -3.5% -7.0% 8.5% 8.5% 8.5% 8.5% 0.0% - - 250 kbps U2Xn = 1 UBRR 207 103 51 34 25 16 12 8 6 3 1 1 0 - Error 0.2% 0.2% 0.2% -0.8% 0.2% 2.1% 0.2% -3.5% -7.0% 8.5% 8.5% 0.0% 0.0% -
fosc = 7.3728 MHz U2Xn = 0 UBRR 191 95 47 31 23 15 11 7 5 3 1 1 0 - Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% -7.8% -7.8% - U2Xn = 1 UBRR 383 191 95 63 47 31 23 15 11 7 3 3 1 0 Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% -7.8% -7.8% -7.8%
230.4 kbps UBRR = 0, Error = 0.0%
460.8 kbps
0.5 Mbps
460.8 kbps
921.6 kbps
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Table 17-11. Examples of UBRRn Settings for Commonly Used Oscillator Frequencies (Continued)
Baud Rate (bps) 2400 4800 9600 14.4k 19.2k 28.8k 38.4k 57.6k 76.8k 115.2k 230.4k 250k 0.5M 1M Max. 1.
(1)
fosc = 8.0000 MHz U2Xn = 0 UBRR 207 103 51 34 25 16 12 8 6 3 1 1 0 - Error 0.2% 0.2% 0.2% -0.8% 0.2% 2.1% 0.2% -3.5% -7.0% 8.5% 8.5% 0.0% 0.0% - U2Xn = 1 UBRR 416 207 103 68 51 34 25 16 12 8 3 3 1 0 Error -0.1% 0.2% 0.2% 0.6% 0.2% -0.8% 0.2% 2.1% 0.2% -3.5% 8.5% 0.0% 0.0% 0.0% 1 Mbps UBRR 287 143 71 47 35 23 17 11 8 5 2 2 - -
fosc = 11.0592 MHz U2Xn = 0 Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% -7.8% - - U2Xn = 1 UBRR 575 287 143 95 71 47 35 23 17 11 5 5 2 - Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% -7.8% -7.8% - UBRR 383 191 95 63 47 31 23 15 11 7 3 3 1 0
fosc = 14.7456 MHz U2Xn = 0 Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% -7.8% -7.8% -7.8% U2Xn = 1 UBRR 767 383 191 127 95 63 47 31 23 15 7 6 3 1 Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 5.3% -7.8% -7.8%
0.5 Mbps UBRR = 0, Error = 0.0%
691.2 kbps
1.3824 Mbps
921.6 kbps
1.8432 Mbps
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Table 17-12. Examples of UBRRn Settings for Commonly Used Oscillator Frequencies (Continued)
Baud Rate (bps) 2400 4800 9600 14.4k 19.2k 28.8k 38.4k 57.6k 76.8k 115.2k 230.4k 250k 0.5M 1M Max. 1.
(1)
fosc = 16.0000 MHz U2Xn = 0 UBRR 416 207 103 68 51 34 25 16 12 8 3 3 1 0 Error -0.1% 0.2% 0.2% 0.6% 0.2% -0.8% 0.2% 2.1% 0.2% -3.5% 8.5% 0.0% 0.0% 0.0% 1 Mbps UBRR = 0, Error = 0.0% U2Xn = 1 UBRR 832 416 207 138 103 68 51 34 25 16 8 7 3 1 Error 0.0% -0.1% 0.2% -0.1% 0.2% 0.6% 0.2% -0.8% 0.2% 2.1% -3.5% 0.0% 0.0% 0.0% 2 Mbps UBRR 479 239 119 79 59 39 29 19 14 9 4 4 - -
fosc = 18.4320 MHz U2Xn = 0 Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% -7.8% - - U2Xn = 1 UBRR 959 479 239 159 119 79 59 39 29 19 9 8 4 - Error 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 2.4% -7.8% - UBRR 520 259 129 86 64 42 32 21 15 10 4 4 - -
fosc = 20.0000 MHz U2Xn = 0 Error 0.0% 0.2% 0.2% -0.2% 0.2% 0.9% -1.4% -1.4% 1.7% -1.4% 8.5% 0.0% - - U2Xn = 1 UBRR 1041 520 259 173 129 86 64 42 32 21 10 9 4 - Error 0.0% 0.0% 0.2% -0.2% 0.2% -0.2% 0.2% 0.9% -1.4% -1.4% -1.4% 0.0% 0.0% -
1.152 Mbps
2.304 Mbps
1.25 Mbps
2.5 Mbps
18. USART in SPI Mode
The Universal Synchronous and Asynchronous serial Receiver and Transmitter (USART) can be set to a master SPI compliant mode of operation. The Master SPI Mode (MSPIM) has the following features: * * * * * * * *
Full Duplex, Three-wire Synchronous Data Transfer Master Operation Supports all four SPI Modes of Operation (Mode 0, 1, 2, and 3) LSB First or MSB First Data Transfer (Configurable Data Order) Queued Operation (Double Buffered) High Resolution Baud Rate Generator High Speed Operation (fXCKmax = fCK/2) Flexible Interrupt Generation
18.1
Overview
Setting both UMSELn1:0 bits to one enables the USART in MSPIM logic. In this mode of operation the SPI master control logic takes direct control over the USART resources. These resources include the transmitter and receiver shift register and buffers, and the baud rate generator. The parity generator and checker, the data and clock recovery logic, and the RX and TX 173
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control logic is disabled. The USART RX and TX control logic is replaced by a common SPI transfer control logic. However, the pin control logic and interrupt generation logic is identical in both modes of operation. The I/O register locations are the same in both modes. However, some of the functionality of the control registers changes when using MSPIM.
18.2
Clock Generation
The Clock Generation logic generates the base clock for the Transmitter and Receiver. For USART MSPIM mode of operation only internal clock generation (i.e. master operation) is supported. The Data Direction Register for the XCKn pin (DDR_XCKn) must therefore be set to one (i.e. as output) for the USART in MSPIM to operate correctly. Preferably the DDR_XCKn should be set up before the USART in MSPIM is enabled (i.e. TXENn and RXENn bit set to one). The internal clock generation used in MSPIM mode is identical to the USART synchronous master mode. The baud rate or UBRRn setting can therefore be calculated using the same equations, see Table 18-1:
Table 18-1.
Equations for Calculating Baud Rate Register Setting
Equation for Calculating Baud Rate(1) Equation for Calculating UBRRn Value
Operating Mode
Synchronous Master mode
f OSC BAUD = -------------------------------------2 ( UBRRn + 1 )
f OSC UBRRn = ------------------- - 1 2BAUD
Note:
1. The baud rate is defined to be the transfer rate in bit per second (bps)
BAUD fOSC UBRRn
Baud rate (in bits per second, bps) System Oscillator clock frequency Contents of the UBRRnH and UBRRnL Registers, (0-4095)
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18.3 SPI Data Modes and Timing
There are four combinations of XCKn (SCK) phase and polarity with respect to serial data, which are determined by control bits UCPHAn and UCPOLn. The data transfer timing diagrams are shown in Figure 18-1. Data bits are shifted out and latched in on opposite edges of the XCKn signal, ensuring sufficient time for data signals to stabilize. The UCPOLn and UCPHAn functionality is summarized in Table 18-2. Note that changing the setting of any of these bits will corrupt all ongoing communication for both the Receiver and Transmitter. Table 18-2.
UCPOLn 0 0 1 1
UCPOLn and UCPHAn FunctionalityUCPHAn 0 1 0 1 SPI Mode 0 1 2 3 Leading Edge Sample (Rising) Setup (Rising) Sample (Falling) Setup (Falling) Trailing Edge Setup (Falling) Sample (Falling) Setup (Rising) Sample (Rising)
Figure 18-1. UCPHAn and UCPOLn data transfer timing diagrams.
UCPOL=0
UCPHA=1
XCK Data setup (TXD) Data sample (RXD) XCK Data setup (TXD) Data sample (RXD)
UCPOL=1
UCPHA=0
XCK Data setup (TXD) Data sample (RXD)
XCK Data setup (TXD) Data sample (RXD)
18.4
Frame Formats
A serial frame for the MSPIM is defined to be one character of 8 data bits. The USART in MSPIM mode has two valid frame formats: * 8-bit data with MSB first * 8-bit data with LSB first A frame starts with the least or most significant data bit. Then the next data bits, up to a total of eight, are succeeding, ending with the most or least significant bit accordingly. When a complete frame is transmitted, a new frame can directly follow it, or the communication line can be set to an idle (high) state. The UDORDn bit in UCSRnC sets the frame format used by the USART in MSPIM mode. The Receiver and Transmitter use the same setting. Note that changing the setting of any of these bits will corrupt all ongoing communication for both the Receiver and Transmitter. 16-bit data transfer can be achieved by writing two data bytes to UDRn. A UART transmit complete interrupt will then signal that the 16-bit value has been shifted out.
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18.4.1
USART MSPIM Initialization The USART in MSPIM mode has to be initialized before any communication can take place. The initialization process normally consists of setting the baud rate, setting master mode of operation (by setting DDR_XCKn to one), setting frame format and enabling the Transmitter and the Receiver. Only the transmitter can operate independently. For interrupt driven USART operation, the Global Interrupt Flag should be cleared (and thus interrupts globally disabled) when doing the initialization.
Note: To ensure immediate initialization of the XCKn output the baud-rate register (UBRRn) must be zero at the time the transmitter is enabled. Contrary to the normal mode USART operation the UBRRn must then be written to the desired value after the transmitter is enabled, but before the first transmission is started. Setting UBRRn to zero before enabling the transmitter is not necessary if the initialization is done immediately after a reset since UBRRn is reset to zero.
Before doing a re-initialization with changed baud rate, data mode, or frame format, be sure that there is no ongoing transmissions during the period the registers are changed. The TXCn Flag can be used to check that the Transmitter has completed all transfers, and the RXCn Flag can be used to check that there are no unread data in the receive buffer. Note that the TXCn Flag must be cleared before each transmission (before UDRn is written) if it is used for this purpose. The following simple USART initialization code examples show one assembly and one C function that are equal in functionality. The examples assume polling (no interrupts enabled). The baud rate is given as a function parameter. For the assembly code, the baud rate parameter is assumed to be stored in the r17:r16 registers.
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Assembly Code Example(1)
USART_Init: clr r18 out UBRRnH,r18 out UBRRnL,r18 ; Setting the XCKn port pin as output, enables master mode. sbi XCKn_DDR, XCKn ; Set MSPI mode of operation and SPI data mode 0. ldi r18, (1<C Code Example(1)
void USART_Init( unsigned int baud ) { UBRRn = 0; /* Setting the XCKn port pin as output, enables master mode. */ XCKn_DDR |= (1<18.5
Data Transfer
Using the USART in MSPI mode requires the Transmitter to be enabled, i.e. the TXENn bit in the UCSRnB register is set to one. When the Transmitter is enabled, the normal port operation of the TxDn pin is overridden and given the function as the Transmitter's serial output. Enabling the receiver is optional and is done by setting the RXENn bit in the UCSRnB register to one. When the receiver is enabled, the normal pin operation of the RxDn pin is overridden and given the function as the Receiver's serial input. The XCKn will in both cases be used as the transfer clock. After initialization the USART is ready for doing data transfers. A data transfer is initiated by writing to the UDRn I/O location. This is the case for both sending and receiving data since the 177
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transmitter controls the transfer clock. The data written to UDRn is moved from the transmit buffer to the shift register when the shift register is ready to send a new frame.
Note: To keep the input buffer in sync with the number of data bytes transmitted, the UDRn register must be read once for each byte transmitted. The input buffer operation is identical to normal USART mode, i.e. if an overflow occurs the character last received will be lost, not the first data in the buffer. This means that if four bytes are transferred, byte 1 first, then byte 2, 3, and 4, and the UDRn is not read before all transfers are completed, then byte 3 to be received will be lost, and not byte 1.
The following code examples show a simple USART in MSPIM mode transfer function based on polling of the Data Register Empty (UDREn) Flag and the Receive Complete (RXCn) Flag. The USART has to be initialized before the function can be used. For the assembly code, the data to be sent is assumed to be stored in Register R16 and the data received will be available in the same register (R16) after the function returns. The function simply waits for the transmit buffer to be empty by checking the UDREn Flag, before loading it with new data to be transmitted. The function then waits for data to be present in the receive buffer by checking the RXCn Flag, before reading the buffer and returning the value.. Assembly Code Example(1)
USART_MSPIM_Transfer: ; Wait for empty transmit buffer sbis UCSRnA, UDREn rjmp USART_MSPIM_Transfer ; Put data (r16) into buffer, sends the data out UDRn,r16 ; Wait for data to be received USART_MSPIM_Wait_RXCn: sbis UCSRnA, RXCn rjmp USART_MSPIM_Wait_RXCn ; Get and return received data from buffer in r16, UDRn ret
C Code Example(1)
unsigned char USART_Receive( void ) { /* Wait for empty transmit buffer */ while ( !( UCSRnA & (1<178
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18.5.1 Transmitter and Receiver Flags and Interrupts The RXCn, TXCn, and UDREn flags and corresponding interrupts in USART in MSPIM mode are identical in function to the normal USART operation. However, the receiver error status flags (FE, DOR, and PE) are not in use and is always read as zero. Disabling the Transmitter or Receiver The disabling of the transmitter or receiver in USART in MSPIM mode is identical in function to the normal USART operation.
18.5.2
18.6
18.6.1
USART MSPIM Register Description
The following section describes the registers used for SPI operation using the USART. USART MSPIM I/O Data Register - UDRn The function and bit description of the USART data register (UDRn) in MSPI mode is identical to normal USART operation. See "USART I/O Data Register n- UDRn" on page 165. USART MSPIM Control and Status Register n A - UCSRnA *
Bit Read/Write Initial Value 7 RXCn R/W 0 6 TXCn R/W 0 5 UDREn R/W 0 4 R 0 3 R 0 2 R 1 1 R 1 0 R 0 UCSRnA
18.6.2
* Bit 7 - RXCn: USART Receive Complete This flag bit is set when there are unread data in the receive buffer and cleared when the receive buffer is empty (i.e., does not contain any unread data). If the Receiver is disabled, the receive buffer will be flushed and consequently the RXCn bit will become zero. The RXCn Flag can be used to generate a Receive Complete interrupt (see description of the RXCIEn bit). * Bit 6 - TXCn: USART Transmit Complete This flag bit is set when the entire frame in the Transmit Shift Register has been shifted out and there are no new data currently present in the transmit buffer (UDRn). The TXCn Flag bit is automatically cleared when a transmit complete interrupt is executed, or it can be cleared by writing a one to its bit location. The TXCn Flag can generate a Transmit Complete interrupt (see description of the TXCIEn bit). * Bit 5 - UDREn: USART Data Register Empty The UDREn Flag indicates if the transmit buffer (UDRn) is ready to receive new data. If UDREn is one, the buffer is empty, and therefore ready to be written. The UDREn Flag can generate a Data Register Empty interrupt (see description of the UDRIE bit). UDREn is set after a reset to indicate that the Transmitter is ready. * Bit 4:0 - Reserved Bits in MSPI mode When in MSPI mode, these bits are reserved for future use. For compatibility with future devices, these bits must be written to zero when UCSRnA is written.
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18.6.3
USART MSPIM Control and Status Register n B - UCSRnB
Bit Read/Write Initial Value 7 RXCIEn R/W 0 6 TXCIEn R/W 0 5 UDRIE R/W 0 4 RXENn R/W 0 3 TXENn R/W 0 2 R 1 1 R 1 0 R 0 UCSRnB
* Bit 7 - RXCIEn: RX Complete Interrupt Enable Writing this bit to one enables interrupt on the RXCn Flag. A USART Receive Complete interrupt will be generated only if the RXCIEn bit is written to one, the Global Interrupt Flag in SREG is written to one and the RXCn bit in UCSRnA is set. * Bit 6 - TXCIEn: TX Complete Interrupt Enable Writing this bit to one enables interrupt on the TXCn Flag. A USART Transmit Complete interrupt will be generated only if the TXCIEn bit is written to one, the Global Interrupt Flag in SREG is written to one and the TXCn bit in UCSRnA is set. * Bit 5 - UDRIE: USART Data Register Empty Interrupt Enable Writing this bit to one enables interrupt on the UDREn Flag. A Data Register Empty interrupt will be generated only if the UDRIE bit is written to one, the Global Interrupt Flag in SREG is written to one and the UDREn bit in UCSRnA is set. * Bit 4 - RXENn: Receiver Enable Writing this bit to one enables the USART Receiver in MSPIM mode. The Receiver will override normal port operation for the RxDn pin when enabled. Disabling the Receiver will flush the receive buffer. Only enabling the receiver in MSPI mode (i.e. setting RXENn=1 and TXENn=0) has no meaning since it is the transmitter that controls the transfer clock and since only master mode is supported. * Bit 3 - TXENn: Transmitter Enable Writing this bit to one enables the USART Transmitter. The Transmitter will override normal port operation for the TxDn pin when enabled. The disabling of the Transmitter (writing TXENn to zero) will not become effective until ongoing and pending transmissions are completed, i.e., when the Transmit Shift Register and Transmit Buffer Register do not contain data to be transmitted. When disabled, the Transmitter will no longer override the TxDn port. * Bit 2:0 - Reserved Bits in MSPI mode When in MSPI mode, these bits are reserved for future use. For compatibility with future devices, these bits must be written to zero when UCSRnB is written.
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18.6.4 USART MSPIM Control and Status Register n C - UCSRnC
Bit Read/Write Initial Value 7 UMSELn1 R/W 0 6 UMSELn0 R/W 0 5 R 0 4 R 0 3 R 0 2 UDORDn R/W 1 1 UCPHAn R/W 1 0 UCPOLn R/W 0 UCSRnC
* Bit 7:6 - UMSELn1:0: USART Mode Select These bits select the mode of operation of the USART as shown in Table 18-3. See "USART Control and Status Register n C - UCSRnC" on page 167 for full description of the normal USART operation. The MSPIM is enabled when both UMSELn bits are set to one. The UDORDn, UCPHAn, and UCPOLn can be set in the same write operation where the MSPIM is enabled. Table 18-3.
UMSELn1 0 0 1 1
UMSELn Bits Settings
UMSELn0 0 1 0 1 Mode Asynchronous USART Synchronous USART (Reserved) Master SPI (MSPIM)
* Bit 5:3 - Reserved Bits in MSPI mode When in MSPI mode, these bits are reserved for future use. For compatibility with future devices, these bits must be written to zero when UCSRnC is written. * Bit 2 - UDORDn: Data Order When set to one the LSB of the data word is transmitted first. When set to zero the MSB of the data word is transmitted first. Refer to the Frame Formats section page 4 for details. * Bit 1 - UCPHAn: Clock Phase The UCPHAn bit setting determine if data is sampled on the leasing edge (first) or tailing (last) edge of XCKn. Refer to the SPI Data Modes and Timing section page 4 for details. * Bit 0 - UCPOLn: Clock Polarity The UCPOLn bit sets the polarity of the XCKn clock. The combination of the UCPOLn and UCPHAn bit settings determine the timing of the data transfer. Refer to the SPI Data Modes and Timing section page 4 for details. 18.6.5 USART MSPIM Baud Rate Registers - UBRRnL and UBRRnH The function and bit description of the baud rate registers in MSPI mode is identical to normal USART operation. See "USART Baud Rate Registers - UBRRLn and UBRRHn" on page 169.
18.7
AVR USART MSPIM vs. AVR SPI
The USART in MSPIM mode is fully compatible with the AVR SPI regarding: * Master mode timing diagram. * The UCPOLn bit functionality is identical to the SPI CPOL bit. 181
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* The UCPHAn bit functionality is identical to the SPI CPHA bit. * The UDORDn bit functionality is identical to the SPI DORD bit. However, since the USART in MSPIM mode reuses the USART resources, the use of the USART in MSPIM mode is somewhat different compared to the SPI. In addition to differences of the control register bits, and that only master operation is supported by the USART in MSPIM mode, the following features differ between the two modules: * The USART in MSPIM mode includes (double) buffering of the transmitter. The SPI has no buffer. * The USART in MSPIM mode receiver includes an additional buffer level. * The SPI WCOL (Write Collision) bit is not included in USART in MSPIM mode. * The SPI double speed mode (SPI2X) bit is not included. However, the same effect is achieved by setting UBRRn accordingly. * Interrupt timing is not compatible. * Pin control differs due to the master only operation of the USART in MSPIM mode. A comparison of the USART in MSPIM mode and the SPI pins is shown in Table 18-4 on page 182.
Table 18-4.
Comparison of USART in MSPIM mode and SPI pins.
SPI MOSI MISO SCK SS Comment Master Out only Master In only (Functionally identical) Not supported by USART in MSPIM TxDn RxDn XCKn (N/A)
USART_MSPIM
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19. USB controller
19.1 Features
* Support full-speed * Support ping-pong mode (dual bank), with transparent switch * 176 bytes of DPRAM
- 1 endpoint of 64 bytes max, (default control endpoint) - 2 endpoints of 64 bytes max, (one bank) - 2 endpoints of 64 bytes max, (one or two banks)
19.2
Block Diagram
The USB controller provides the hardware to interface a USB link to a data flow stored in a double port memory (DPRAM). The USB controller requires a 48 MHz 0.25% reference clock (for Full-speed compliance), which is the output of an internal PLL. The PLL generates the internal high frequency (48 MHz) clock for USB interface, the PLL input is generated from an external lower frequency (the crystal oscillator or external clock input pin from XTAL1, to satisfy the USB frequency accuracy and jitter ; only this clock source allows proper functionnality of the USB controller). The 48MHz clock is used to generate a 12 MHz Full-speed bit clock from the received USB differential data and to transmit data according to full speed USB device tolerance. Clock recovery is done by a Digital Phase Locked Loop (DPLL) block, which is compliant with the jitter specification of the USB bus. To comply the USB Electrical characteristics, USB Pads (D+ or D-) should be powered within the 3.0 to 3.6V range. As AT90USB82/162 can be powered up to 5.5V, the internal regulator provides the USB pads power supply.
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Figure 19-1. USB controller Block Diagram overview
UVCC XTAL1
Regulator
UCAP
PLL 6x
clk 8MHz
PLL clock Prescaler
clk 48MHz
D-
CPU
DPLL Clock Recovery
D+
USB Interface
On-Chip USB DPRAM
19.3
Typical Application Implementation
Depending on the target application power supply, the AT90USB82/162 requires different hardware typical implementations. Figure 19-2. Operating modes versus frequency and power-supply
VCC (V) Max Operating Frequency (MHz)
5.5 16 MHz 4.5 USB compliant, with internal regulator
4.0 3.6 8 MHz USB compliant, without internal regulator 3.0 2.7 VCC min 0 USB not operational
2 MHz
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19.3.1 Bus Powered device Figure 19-3. Typical Bus powered application with 5V I/O
VCC
UCAP
1F
VBUS
UVCC
UDP
D+
UDM
D-
UVSS
UVSS
VSS
XTAL1
XTAL2
Figure 19-4. Typical Bus powered application with 3V I/O
VCC
UCAP
1F
VBUS UDM UDP UVSS
UVCC
D+
D-
UVSS
VSS
XTAL1
XTAL2
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19.3.2
Self Powered device Figure 19-5. Typical Self powered application with 3.4V to 5.5V I/O
External 3.4V - 5.5V Power Supply
UVCC
AVCC
VCC
UCAP
1F
UDP
Rs=22
D+
UDM
Rs=22
D-
UVSS
UGND
XTAL1
XTAL2
GND
GND
Typical Self powered application with 3.0V to 3.6 I/O
External 3.0V - 3.6V Power Supply
UVCC
AVCC
VCC
UCAP
1F
UDP
Rs=22
D+
UDM
Rs=22
D-
UVSS
UGND
XTAL1
XTAL2
GND
GND
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19.3.3 Design guidelines * Serial resistors on USB Data lines must have 22 Ohms value (+/- 5%). * Traces from the input USB receptable (or from the cable connection in the case of a tethered device) to the USB microcontroller pads should be as short as possibles, and follow differential traces routing rules (same length, as near as possible, avoid vias accumulation). * Voltage transcient / ESD suppressors may also be used to prevent USB pads to be damaged by external disturbances. * Ucap capacitor should be 1F (+/- 10%) for correct operation. * A 10F capacitor is highly recommended on VBUS line
19.4
19.4.1
General Operating Modes
Introduction The USB controller is disabled and reset after a hardware reset generated by: - Power on reset - External reset - Watchdog reset - Brown out reset - debugWIRE reset But another available and optionnal reset source is : - USB End Of Reset In this case, the USB controller is reset, but not disabled (so that the device remains attached).
19.4.2
Power-on and reset The next diagram explains the USB controller main states on power-on: Figure 19-6. USB controller states after reset
Clockstopped FRZCLK=1 Macrooff Reset USBE=0
HW RESET (exceptedfromEOR) USBE=0
USBE=1 USBE=0
Dev ice HW RESET from EOR
When the USB controller is in reset state: * USBE is not set
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* the USB controller clock is stopped in order to minimize the power consumption (FRZCLK=1), * the USB controller is disabled, * USB is in the suspend mode, * the Device USB controllers internal state is reset. * The DPACC bit and the DPADD10:0 field can be set by software. The DPRAM is not cleared. * The SPDCONF bits can be set by software. After setting USBE, the USB Controller enters in the Device state. The USB Controller can at any time be `stopped' by clearing USBE. In fact, clearing USBE acts as an hardware reset on the USB macro. 19.4.3 Interrupts Two interrupts vectors are assigned to USB controller. Figure 19-7. USB Interrupt System
USB Device Interrupt USB General Interrupt Vector
Endpoint Interrupt
USB Endpoint/Pipe Interrupt Vector
The macro distinguishes between USB General events in opposition with USB Endpoints events that are relevant with data transfers relatives to each endpoint.
Figure 19-8. USB General interrupt vector sources
UPRSMI UDINT.6
UPRSME UDIEN.6
EORSMI UDINT.5
EORSME UDIEN.5
WAKEUPI
UDINT.4
WAKEUPE
UDIEN.4 EORSTI UDINT.3
USB General Interrupt Vector
EORSTE UDIEN.3
SOFI UDINT.2
SOFE UDIEN.2 Asynchronous Interrupt source (allows the CPU to wake up from power down mode)
SUSPI UDINT.0
SUSPE UDIEN.0
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Each of these interupts are time-relative events that will be detected only if the USB clock is enabled (FRZCLK bit set), except for the WAKEUP interrupt that will trigger each time a state change is detected on the data lines. This asynchronous interrupt WAKEUP allows to wake-up a device that is in power-down mode, generally after that the USB has entered the Suspend state.
Figure 19-9. USB Endpoint Interrupt vector sources
Endpoint 4 Endpoint 3 Endpoint 2 Endpoint 1 Endpoint 0 OVERFI UESTAX.6 UNDERFI UESTAX.5 NAKINI UEINTX.6 FLERRE UEIENX.7
NAKINE UEIENX.6
NAKOUTI UEINTX.4
TXSTPE UEIENX.4 EPINT UEINT.X
RXSTPI UEINTX.3
USB Endpoint Interrupt Vector
TXOUTE UEIENX.3
RXOUTI UEINTX.2
RXOUTE UEIENX.2
STALLEDI
UEINTX.1
STALLEDE
UEIENX.1
TXINI
UEINTX.0
TXINE
UEIENX.0
Each endpoint has 8 interrupts sources associated with flags, and each source can be enabled or not to trigger the corresponding endpoint interrupt. If, for an endpoint, at least one of the sources is enabled to trigger interrupt, the corresponding event(s) will make the program branch to the USB Endpoint Interrupt vector. The user may determine the source (endpoint) of the interrupt by reading the UEINT register, and then handle the event detected by polling the different flags.
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19.5
19.5.1
Power modes
Idle mode In this mode, the CPU core is halted (CPU clock stopped). The Idle mode is taken wether the USB controller is running or not. The CPU can wake up on any USB interrupts.
19.5.2
Power down In this mode, the oscillator is stopped and halts all the clocks (CPU and peripherals). The USB controller "wakes up" when: * the WAKEUPI interrupt is triggered (single asynchronous interrupt)
19.5.3
Freeze clock The firmware has the ability to reduce the power consumption by setting the FRZCLK bit, which freeze the clock of USB controller. When FRZCLK is set, it is still possible to access to the following registers: * USBCON, * DPRAM direct access registers (DPADD7:0, UEDATX) * UDCON (detach, ...) * UDINT * UDIEN Moreover, when FRZCLK is set, only the asynchronous interrupt may be triggered : * WAKEUPI
19.6
Memory management
The controller does only support the following memory allocation management. The reservation of an Endpoint can only be made in the increasing order (Endpoint 0 to the last Endpoint). The firmware shall thus configure them in the same order. The reservation of an Endpoint "ki" is done when its ALLOC bit is set. Then, the hardware allocates the memory and insert it between the Endpoints "ki-1 " and "k i+1". The "k i+1 " Endpoint memory "slides" up and its data is lost. Note that the "ki+2" and upper Endpoint memory does not slide. Clearing an Endpoint enable (EPEN) does not clear either its ALLOC bit, or its configuration (EPSIZE/PSIZE, EPBK/PBK). To free its memory, the firmware should clear ALLOC. Then, the "ki+1" Endpoint memory automatically "slides" down. Note that the "k i+2" and upper Endpoint memory does not slide. The following figure illustrates the allocation and reorganization of the USB memory in a typical example:
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Table 19-1. Allocation and reorganization USB memory flow
Free memory 4 3 2 1 0
EPEN=1 ALLOC=1
Free memory 4 3
EPEN=0 (ALLOC=1)
Free memory 4 Lost memory 3 1 0
Free memory 4 3 2 (bigger size) 1 0 Conflict
1 0
Endpoints activation
Endpoint Disable
Free its memory (ALLOC=0)
Endpoint Activatation
* First, Endpoint 0 to Endpoint 4 are configured, in the growing order. The memory of each is reserved in the DPRAM. * Then, the Endpoint 2is disabled (EPEN=0), but its memory reservation is internally kept by the controller. * Its ALLOC bit is cleared: the Endpoint 3 "slides" down, but the Endpoint 4 does not "slide". * Finally, the firmware chooses to reconfigure the Endpoint 2, but with a bigger size. The controller reserved the memory after the endpoint 1 memory and automatically "slide" the Endpoint 3. The Endpoint 4 does not move and a memory conflict appear, in that both Endpoint 3 and 4 use a common area. The data of those endpoints are potentially lost. Note that : * the data of Endpoint 0 are never lost whatever the activation or deactivation of the higher Endpoint. Its data is lost if it is deactivated. * Deactivate and reactivate the same Endpoint with the same parameters does not lead to a "slide" of the higher endpoints. For those endpoints, the data are preserved. * CFGOK is set by hardware even in the case that there is a "conflict" in the memory allocation.
19.7
PAD suspend
The next figures illustrates the pad behaviour: * In the "idle" mode, the pad is put in low power consumption mode. * In the "active" mode, the pad is working.
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Figure 19-10. Pad behaviour
Idle mode
USBE=1 & DETACH=0 & suspend
USBE=0 | DETACH=1 | suspend
Active mode
The SUSPI flag indicated that a suspend state has been detected on the USB bus. This flag automatically put the USB pad in Idle. The detection of a non-idle event sets the WAKEUPI flag and wakes-up the USB pad.
SUSPI
Suspend detected = USB pad power down
Clear Suspend by software
WAKEUPI
Clear Resume by software Resume = USB pad wake-up
PAD status
Active Power Down Active
Moreover, the pad can also be put in the "idle" mode if the DETACH bit is set. It come back in the active mode when the DETACH bit is cleared.
19.8
D+/D- Read/write
The level of D+ and D- can be read and written using the UPOE register. The USB controller has to be enabled to write a value. For read operation, the USB controller can be enabled or disabled.
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19.9
19.9.1
Registers description
USB general registers
Bit Read/Writ e Initial Value 7 USBE R/W 0 6 R 0 5 FRZLK R/W 1 4 R 0 3 R 0 2 R 0 1 R 0 0 R 0 USBCON
* 7 - USBE: USB macro Enable Bit Set to enable the USB controller. Clear to disable and reset the USB controller, to disable the USB transceiver and to disable the USB controller clock inputs. * 6 - Reserved The value read from this bit is always 0. Do not set this bit. * 5 - FRZCLK: Freeze USB Clock Bit Set to disable the clock inputs (the "Resume Detection" is still active). This reduces the power consumption. Clear to enable the clock inputs. * 4-0 - Reserved The value read from these bits is always 0. Do not set these bits.
Bit
7 DPACC
6 R 0
5 R 0
4 R 0
3 R 0
2 R 0
1 R 0
0 R 0 UDPADDH
Read/Wr ite Initial Value
R/W 0
* 7 - DPACC: DPRAM Direct Access Bit Set this bit to directly read the content the Dual-Port RAM (DPR) data through the UEDATX or UPDATX registers. See Section 19.6, page 190 for more details. Clear this bit for normal operation and access the DPR through the endpoint FIFO. * 6-0 - Reserved The value read from these bits is always 0. Do not set these bits.
Bit
7 DPADD7:0
6
5
4
3
2
1
0 UDPADDL
Read/Wr ite Initial Value
R/W 0
R/W 0
R/W 0
R/W 0
R/W 0
R/W 0
R/W 0
R/W 0
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* 7-0 - DPADD7:0: DPRAM Address Low Bit DAPDD7:0 is the least significant part of DPADD.
19.9.2
USB/PS2 Software Output Enable register - UPOE
Bit 7 UPWE1 Read/Write Initial Value R/W 0 6 UPWE0 R/W 0 5 UPDRV 1 R/W 0 4 UPDRV 0 R/W 0 3 SCKI R 0 2 DATAI R 0 1 DPI R 0 0 DMI R 0 UPOE
* Bit 7:6 - UPOE[1:0]: USB/PS2 Output enable Set these bits with the following configuration to enable or disable the USB/PS2 software drive. UPOE1 - UPOE0 0 - 0 : Direct drive is disabled. 0 - 1 : Reserved 1 - 0 : Direct drive of DP/DM with USB levels (UPDRV[1:0] values) 1 - 1 : Direct drive of DP/DM with PS/2 levels (UPDRV[1:0] values) * Bit 5:4 - UPDRV[1:0] : USB/PS2 direct drive values Write in UPDRV1 the value to write on D+/SCK following the UPOE[1:0] configuration. Write in UPDRV0 the value to write on D-/DATA following the UPOE[1:0] configuration. * Bit 3 - SCKI : SCK Input value This bit is set to one by hardware if a `1' is read on SCK (PS/2 pad). This bit is set to zero by hardware if a `0' is read on SCK (PS/2 pad). * Bit 2 - DATAI : DATA Input value This bit is set to one by hardware if a `1' is read on DATA (PS/2 pad). This bit is set to zero by hardware if a `0' is read on DATA (PS/2 pad). * Bit 1 - DPI : D+ Input value This bit is set to one by hardware if a `1' is read on D+ (USB pad). This bit is set to zero by hardware if a `0' is read on D+ (USB pad). * Bit 0 - DMI : D- Input value This bit is set to one by hardware if a `1' is read on D- (USB pad). This bit is set to zero by hardware if a `0' is read on D- (USB pad).
19.10 USB Software Operating modes
Depending on the USB operating mode, the software should perform some the following operations: Power On the USB interface * Configure PLL interface * Enable PLL * Check PLL lock 194
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* Enable USB interface * Configure USB interface (USB Endpoint 0 configuration) * Attach USB device Power Off the USB interface * Detach USB device * Disable USB interface * Disable PLL Suspending the USB interface * Clear Suspend Bit * Set USB suspend clock * Disable PLL * Be sure to have interrupts enabled (WAKEUPE) to exit sleep mode * Put the MCU in sleep mode Resuming the USB interface * Enable PLL * Wait PLL lock * Clear USB suspend clock * Clear Resume information
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20. USB Device Operating modes
20.1 Introduction
The USB device controller supports full speed data transfers. In addition to the default control endpoint, it provides four other endpoints, which can be configured in control, bulk, interrupt or isochronous modes: * Endpoint 0:programmable size FIFO up to 64 bytes, default control endpoint * Endpoints 1and 2:programmable size FIFO up to 64 bytes. * Endpoints 3 and 4: programmable size FIFO up to 64 bytes with ping-pong mode. The controller starts in the "idle" mode. In this mode, the pad consumption is reduced to the minimum.
20.2
Power-on and reset
The next diagram explains the USB device controller main states on power-on: Figure 20-1. USB device controller states after reset

USBE=0
USBE=0 Reset HW RESET USBE=1 UID=1
Idle
The reset state of the Device controller is: * the macro clock is stopped in order to minimize the power consumption (FRZCLK set), * the USB device controller internal state is reset (all the registers are reset to their default value. Note that DETACH is set.) * the endpoint banks are reset * the D+ pull up are not activated (mode Detach) The D+ pull-up will be activated as soon as the DETACH bit is cleared. The macro is in the `Idle' state after reset with a minimum power consumption and does not need to have the PLL activated to enter in this state. The USB device controller can at any time be reset by clearing USBE.
20.3
Endpoint reset
An endpoint can be reset at any time by setting in the UERST register the bit corresponding to the endpoint (EPRSTx). This resets: * the internal state machine on that endpoint, * the Rx and Tx banks are cleared and their internal pointers are restored,
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* the UEINTX, UESTA0X and UESTA1X are restored to their reset value. The data toggle field remains unchanged. The other registers remain unchanged. The endpoint configuration remains active and the endpoint is still enabled. The endpoint reset may be associated with a clear of the data toggle command (RSTDT bit) as an answer to the CLEAR_FEATURE USB command.
20.4
USB reset
When an USB reset is detected on the USB line (SEO state with a minimal duration of 100s), the next operations are performed by the controller: * all the endpoints are disabled * the default control endpoint remains configured * The data toggle of the default control endpoint is cleared. If the hardware reset function is selected, a reset is generated to the CPU core without disabling the USB controller (that remains in the same state than after a USB Reset).
20.5
Endpoint selection
Prior to any operation performed by the CPU, the endpoint must first be selected. This is done by setting the EPNUM2:0 bits (in UENUM register) with the endpoint number which will be managed by the CPU. The CPU can then access to the various endpoint registers and data.
20.6
Endpoint activation
The endpoint is maintained under reset as long as the EPEN bit is not set. The following flow must be respected in order to activate an endpoint:
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Figure 20-2. Endpoint activation flow:
Endpoint Activation
UENUM
EPNUM=x
Select the endpoint
EPEN=1
Activate the endpoint
UECFG0X
EPDIR EPTYPE ...
Configure: - the endpoint direction - the endpoint type - the Not Yet Disable feature
UECFG1X
ALLOC EPSIZE EPBK
Configure: - the endpoint size - the bank parametrization Allocation and reorganization of the memory is made on-the-fly Test the correct endpoint configuration
CFGOK=1 Yes Endpoint activated
No
ERROR
As long as the endpoint is not correctly configured (CFGOK cleared), the hardware does not acknowledge the packets sent by the host. CFGOK will not be set if the Endpoint size parameter is bigger than the DPRAM size. A clear of EPEN acts as an endpoint reset (see Section 20.3, page 196 for more details). It also performs the next operation: * The configuration of the endpoint is kept (EPSIZE, EPBK, ALLOC kept) * It resets the data toggle field. * The DPRAM memory associated to the endpoint is still reserved. See Section 19.6, page 190 for more details about the memory allocation/reorganization.
20.7
Address Setup
The USB device address is set up according to the USB protocol: * the USB device, after power-up, responds at address 0 * the host sends a SETUP command (SET_ADDRESS(addr)), * the firmware records that address in UADD, but keep ADDEN cleared, * the USB device sends an IN command of 0 bytes (IN 0 Zero Length Packet) to acknowledge the transaction, * then, the firmware may enable the USB device address by setting ADDEN. The only accepted address by the controller is the one stored in UADD. ADDEN and UADD shall not be written at the same time. UADD contains the default address 00h after a power-up or an USB reset.
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ADDEN is cleared by hardware: * after a power-up reset, * when an USB reset is received, * or when the macro is disabled (USBE cleared) When this bit is cleared, the default device address 00h is used.
20.8
Suspend, Wake-up and Resume
After a period of 3 ms during which the USB line was inactive (J state), the controller setn the SUSPI flag and triggers the corresponding interrupt if enabled. The firmware may then set the FRZCLK bit. The CPU can also, depending on software architecture, disable the PLL and/or enter in the idle mode to reduce the power consumption (especially in a bus powered application). There are two ways to recover from the "Suspend" mode: * First one is to clear the FRZCLK bit. This is possible if the CPU is not in the Idle mode. * Second way, if the CPU is "idle", is to enable the WAKEUPI interrupt (WAKEUPE set). Then, as soon as an non-idle signal is seen by the controller, the WAKEUPI interrupt is triggered. The firmware shall then clear the FRZCLK bit to restart the transfer. There are no relationship between the SUSPI interrupt and the WAKEUPI interrupt: the WAKEUPI interrupt is triggered as soon as there are non-idle patterns on the data lines. Thus, the WAKEUPI interrupt can occurs even if the controller is not in the "suspend" mode. When the WAKEUPI interrupt is triggered, if the SUSPI interrupt bit was already set, it is cleared by hardware. When the SUSPI interrupt is triggered, if the WAKEUPI interrupt bit was already set, it is cleared by hardware.
20.9
Detach
The reset value of the DETACH bit is 1. It is possible to re-enumerate a device, simply by setting and clearing the DETACH bit (the line discharge time must be taken in account). * When the USB device controller is in full-speed mode, setting DETACH will disconnect the pull-up on the D+ . Then, clearing DETACH will connect the pull-up on the D+. Figure 20-3. Detach a device in Full-speed:
UVREF UVREF
D+ DEN=1 Detach, then Attach EN=1
D+ D-
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20.10 Remote Wake-up
The "Remote Wake-up" (or "upstream resume") request is the only operation allowed to be sent by the device on its own initiative. Anyway, to do that, the device should first have received a DEVICE_REMOTE_WAKEUP request from the host. * First, the USB controller must have detected the "suspend" state of the line: the remote wake-up can only be sent if the SUSPI bit is set. * The firmware has then the ability to set RMWKUP to send the "upstream resume" stream. This will automatically be done by the controller after 5ms of inactivity on the USB line. * When the controller starts to send the "upstream resume", the UPRSMI flag is set and interrupt is triggered (if enabled). If SUSPI was set, SUSPI is cleared by hardware. * RMWKUP is automatically cleared by hardware at the end of the "upstream resume". * After that, if the controller detects a good "End Of Resume" signal from the host, an EORSMI interrupt is triggered (if enabled).
20.11 STALL request
For each endpoint, the STALL management is performed using 2 bits: - STALLRQ (enable stall request) - STALLRQC (disable stall request) - STALLEDI (stall sent interrupt) To send a STALL handshake at the next request, the STALLRQ request bit has to be set. All following requests will be handshak'ed with a STALL until the STALLRQC bit is set. Setting STALLRQC automatically clears the STALLRQ bit. The STALLRQC bit is also immediately cleared by hardware after being set by software. Thus, the firmware will never read this bit as set. Each time the STALL handshake is sent, the STALLEDI flag is set by the USB controller and the EPINTx interrupt will be triggered (if enabled). The incoming packets will be discarded (RXOUTI and RWAL will not be set). The host will then send a command to reset the STALL: the firmware just has to set the STALLRQC bit and to reset the endpoint. 20.11.1 Special consideration for Control Endpoints A SETUP request is always ACK'ed. If a STALL request is set for a Control Endpoint and if a SETUP request occurs, the SETUP request has to be ACK'ed and the STALLRQ request and STALLEDI sent flags are automatically reset (RXSETUPI set, TXIN cleared, STALLED cleared, TXINI cleared...). This management simplifies the enumeration process management. If a command is not supported or contains an error, the firmware set the STALL request flag and can return to the main task, waiting for the next SETUP request. Th is fu nc t io n i s c o mp l ia nt wi th t he C ha pt er 8 t es t t ha t s en ds ex t r a s ta tu s fo r a GET_DESCRIPTOR. The firmware sets the STALL request just after receiving the status. All extra status will be automatically STALL'ed until the next SETUP request.
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20.11.2 STALL handshake and Retry mechanism The Retry mechanism has priority over the STALL handshake. A STALL handshake is sent if the STALLRQ request bit is set and if there is no retry required.
20.12 CONTROL endpoint management
A SETUP request is always ACK'ed. When a new setup packet is received, the RXSTPI interrupt is triggered (if enabled). The RXOUTI interrupt is not triggered. The FIFOCON and RWAL fields are irrelevant with CONTROL endpoints. The firmware shall thus never use them on that endpoints. When read, their value is always 0. CONTROL endpoints are managed by the following bits: * RXSTPI is set when a new SETUP is received. It shall be cleared by firmware to acknowledge the packet and to clear the endpoint bank. * RXOUTI is set when a new OUT data is received. It shall be cleared by firmware to acknowledge the packet and to clear the endpoint bank. * TXINI is set when the bank is ready to accept a new IN packet. It shall be cleared by firmware to send the packet and to clear the endpoint bank. CONTROL endpoints should not be managed by interrupts, but only by polling the status bits. 20.12.1 Control Write The next figure shows a control write transaction. During the status stage, the controller will not necessary send a NAK at the first IN token: * If the firmware knows the exact number of descriptor bytes that must be read, it can then anticipate on the status stage and send a ZLP for the next IN token, * or it can read the bytes and poll NAKINI, which tells that all the bytes have been sent by the host, and the transaction is now in the status stage.
SETUP
USB line RXSTPI RXOUTI TXINI SETUP
HW SW HW
DATA
OUT OUT IN NAK
SW HW SW
STATUS
IN
SW
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20.12.2
Control Read
The next figure shows a control read transaction. The USB controller has to manage the simultaneous write requests from the CPU and the USB host:
SETUP
USB line RXSTPI RXOUTI TXINI
Wr Enable HOST Wr Enable CPU SW HW
DATA
IN
SW
STATUS
IN OUT NAK
HW SW
SETUP
HW
OUT
SW
A NAK handshake is always generated at the first status stage command. When the controller detect the status stage, all the data writen by the CPU are erased, and clearing TXINI has no effects. The firmware checks if the transmission is complete or if the reception is complete. The OUT retry is always ack'ed. This reception: - set the RXOUTI flag (received OUT data) - set the TXINI flag (data sent, ready to accept new data) software algorithm:
set transmit ready wait (transmit complete OR Receive complete) if receive complete, clear flag and return if transmit complete, continue
Once the OUT status stage has been received, the USB controller waits for a SETUP request. The SETUP request have priority over any other request and has to be ACK'ed. This means that any other flag should be cleared and the fifo reset when a SETUP is received. WARNING: the byte counter is reset when a OUT Zero Length Packet is received. The firmware has to take care of this.
20.13 OUT endpoint management
OUT packets are sent by the host. All the data can be read by the CPU, which acknowledges or not the bank when it is empty.
20.13.1
Overview
The Endpoint must be configured first.
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20.13.1.1 "Manual" mode Each time the current bank is full, the RXOUTI and the FIFOCON bits are set. This triggers an interrupt if the RXOUTE bit is set. The firmware can acknowledge the USB interrupt by clearing the RXOUTI bit. The Firmware read the data and clear the FIFOCON bit in order to free the current bank. If the OUT Endpoint is composed of multiple banks, clearing the FIFOCON bit will switch to the next bank. The RXOUTI and FIFOCON bits are then updated by hardware in accordance with the status of the new bank. RXOUTI shall always be cleared before clearing FIFOCON. The RWAL bit always reflects the state of the current bank. This bit is set if the firmware can read data from the bank, and cleared by hardware when the bank is empty.
Example with 1 OUT data bank OUT DATA (to bank 0) ACK NAK OUT DATA (to bank 0) ACK
HW RXOUTI SW
HW SW
FIFOCON
read data from CPU BANK 0
SW
read data from CPU BANK 0
Example with 2 OUT data banks OUT DATA (to bank 0) ACK OUT DATA (to bank 1) ACK
HW RXOUTI SW
HW
SW
FIFOCON
read data from CPU BANK 0
SW
read data from CPU BANK 1
20.13.2
Detailed description The data are read by the CPU, following the next flow:
* When the bank is filled by the host, an endpoint interrupt (EPINTx) is triggered, if enabled (RXOUTE set) and RXOUTI is set. The CPU can also poll RXOUTI or FIFOCON, depending on the software architecture, * The CPU acknowledges the interrupt by clearing RXOUTI, * The CPU can read the number of byte (N) in the current bank (N=BYCT), * The CPU can read the data from the current bank ("N" read of UEDATX),
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* The CPU can free the bank by clearing FIFOCON when all the data is read, that is: * after "N" read of UEDATX, * as soon as RWAL is cleared by hardware. If the endpoint uses 2 banks, the second one can be filled by the HOST while the current one is being read by the CPU. Then, when the CPU clear FIFOCON, the next bank may be already ready and RXOUTI is set immediately.
20.14 IN endpoint management
IN packets are sent by the USB device controller, upon an IN request from the host. All the data can be written by the CPU, which acknowledge or not the bank when it is full.Overview The Endpoint must be configured first. 20.14.0.1 "Manual" mode The TXINI bit is set by hardware when the current bank becomes free. This triggers an interrupt if the TXINE bit is set. The FIFOCON bit is set at the same time. The CPU writes into the FIFO and clears the FIFOCON bit to allow the USB controller to send the data. If the IN Endpoint is composed of multiple banks, this also switches to the next data bank. The TXINI and FIFOCON bits are automatically updated by hardware regarding the status of the next bank. TXINI shall always be cleared before clearing FIFOCON.
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The RWAL bit always reflects the state of the current bank. This bit is set if the firmware can write data to the bank, and cleared by hardware when the bank is full.
Example with 1 IN data bank
NAK
IN
DATA (bank 0)
ACK
IN
HW TXINI SW SW
FIFOCON
write data from CPU BANK 0
SW
write data from CPU BANK 0
SW
Example with 2 IN data banks
IN
DATA (bank 0)
ACK
IN
DATA (bank 1)
ACK
HW TXINI SW SW SW
FIFOCON
write data from CPU BANK 0
SW
write data from CPU BANK 1
SW
write data from CPU BANK0
20.14.1
Detailed description The data are written by the CPU, following the next flow:
* When the bank is empty, an endpoint interrupt (EPINTx) is triggered, if enabled (TXINE set) and TXINI is set. The CPU can also poll TXINI or FIFOCON, depending the software architecture choice, * The CPU acknowledges the interrupt by clearing TXINI, * The CPU can write the data into the current bank (write in UEDATX), * The CPU can free the bank by clearing FIFOCON when all the data are written, that is: * after "N" write into UEDATX * as soon as RWAL is cleared by hardware. If the endpoint uses 2 banks, the second one can be read by the HOST while the current is being written by the CPU. Then, when the CPU clears FIFOCON, the next bank may be already ready (free) and TXINI is set immediately.
20.14.1.1
Abort An "abort" stage can be produced by the host in some situations:
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* In a control transaction: ZLP data OUT received during a IN stage, * In an isochronous IN transaction: ZLP data OUT received on the OUT endpoint during a IN stage on the IN endpoint * ... The KILLBK bit is used to kill the last "written" bank. The best way to manage this abort is to perform the following operations:
Table 20-1.
Abort flow
Endpoint Abort Clear UEIENX. TXINE NBUSYBK =0 Yes Endpoint reset Yes No
Disable the TXINI interrupt.
Abort is based on the fact that no banks are busy, meaning that nothing has to be sent. Kill the last written bank.
KILLBK=1
KILLBK=1 No
Wait for the end of the procedure.
Abort done
20.15 Isochronous mode
20.15.1 Underflow
An underflow can occur during IN stage if the host attempts to read a bank which is empty. In this situation, the UNDERFI interrupt is triggered. An underflow can also occur during OUT stage if the host send a packet while the banks are already full. Typically, he CPU is not fast enough. The packet is lost. It is not possible to have underflow error during OUT stage, in the CPU side, since the CPU should read only if the bank is ready to give data (RXOUTI=1 or RWAL=1)
20.15.2
CRC Error
A CRC error can occur during OUT stage if the USB controller detects a bad received packet. In this situation, the STALLEDI interrupt is triggered. This does not prevent the RXOUTI interrupt from being triggered.
20.16 Overflow
In Control, Isochronous, Bulk or Interrupt Endpoint, an overflow can occur during OUT stage, if the host attempts to write in a bank that is too small for the packet. In this situation, the OVERFI interrupt is triggered (if enabled). The packet is hacknowledged and the RXOUTI interrupt is also triggered (if enabled). The bank is filled with the first bytes of the packet.
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It is not possible to have overflow error during IN stage, in the CPU side, since the CPU should write only if the bank is ready to access data (TXINI=1 or RWAL=1).
20.17 Interrupts
The next figure shows all the interrupts sources:
Figure 20-4. USB Device Controller Interrupt System
UPRSMI UDINT.6 UPRSME UDIEN.6
EORSMI UDINT.5
EORSME UDIEN.5
WAKEUPI
UDINT.4
WAKEUPE
UDIEN.4 EORSTI UDINT.3
USB Device Interrupt
EORSTE UDIEN.3
SOFI UDINT.2
SOFE UDIEN.2
SUSPI UDINT.0
SUSPE UDIEN.0
There are 2 kind of interrupts: processing (i.e. their generation are part of the normal processing) and exception (errors). Processing interrupts are generated when: * Upstream resume(UPRSMI) * End of resume(EORSMI) * Wake up(WAKEUPI) * End of reset (Speed Initialization)(EORSTI) * Start of frame(SOFI, if FNCERR=0) * Suspend detected after 3 ms of inactivity(SUSPI) Exception Interrupts are generated when: * CRC error in frame number of SOF(SOFI, FNCERR=1)
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Figure 20-5. USB Device Controller Endpoint Interrupt System
Endpoint 4 Endpoint 3 Endpoint 2 Endpoint 1 Endpoint 0 OVERFI UESTAX.6 UNDERFI UESTAX.5 NAKINI UEINTX.6 FLERRE UEIENX.7
NAKINE UEIENX.6
NAKOUTI UEINTX.4
TXSTPE UEIENX.4 EPINT UEINT.X
Endpoint Interrupt
RXSTPI UEINTX.3
TXOUTE UEIENX.3
RXOUTI UEINTX.2
RXOUTE UEIENX.2
STALLEDI
UEINTX.1
STALLEDE
UEIENX.1
TXINI
UEINTX.0
TXINE
UEIENX.0
Processing interrupts are generated when: * Ready to accept IN data(EPINTx, TXINI=1) * Received OUT data(EPINTx, RXOUTI=1) * Received SETUP(EPINTx, RXSTPI=1) Exception Interrupts are generated when: * Stalled packet(EPINTx, STALLEDI=1) * CRC error on OUT in isochronous mode(EPINTx, STALLEDI=1) * Overflow(EPINTx, OVERFI=1) * Underflow in isochronous mode(EPINTx, UNDERFI=1) * NAK IN sent(EPINTx, NAKINI=1) * NAK OUT sent(EPINTx, NAKOUTI=1)
20.18 Registers
20.18.1 USB device general registers
Bit 7 Read/Wri R te Initial Value 0 6 R 0 5 R 0 4 R 0 3 R 0 2 RSTCPU R/W 0 1 RMWKUP R/W 0 0 DETACH R/W 1 UDCON
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* Bit 2- RSTCPU - USB Reset CPU Bit Set this bit to one by firmware in order to reset the CPU at the next USB reset (without disabling the USB controller). The value of this bit will not be affected by the reset of the CPU generated by a End Of Reset (remains set). This bit is reset when the USB controller is disabled.
Set this bit to zero by firmware otherwise.
* Bit 1- RMWKUP - Remote Wake-up Bit Set to send an "upstream-resume" to the host for a remote wake-up. The SUSPI bit must be set to allow the remote wake up to be sent.
Cleared by hardware. Clearing by software has no effect. See Section 20.10, page 200 for more details.
* Bit 0 - DETACH - Detach Bit Set to physically detach de device.
Clear to reconnect the device. See Section 20.9, page 199 for more details.
Bit
7 -
6 UPRSMI R/W 0
5 EORSMI R/W 0
4 WAKEUPI R/W 0
3 EORSTI R/W 0
2 SOFI R/W 0
1 R 0
0 SUSPI R/W 0 UDINT
Read/Wri R te Initial Value 0
* 7 - Reserved The value read from these bits is always 0. Do not set these bits. * 6 - UPRSMI - Upstream Resume Interrupt Flag Set by hardware when the USB controller is sending a resume signal called "Upstream Resume". This triggers an USB interrupt if UPRSME is set.
Shall be cleared by software (USB clocks must be enabled before). Setting by software has no effect.
* 5 - EORSMI - End Of Resume Interrupt Flag Set by hardware when the USB controller detects a good "End Of Resume" signal initiated by the host. This triggers an USB interrupt if EORSME is set.
Shall be cleared by software. Setting by software has no effect.
* 4 - WAKEUPI - Wake-up CPU Interrupt Flag Set by hardware when the USB controller is re-activated by a filtered non-idle signal from the lines (not by an upstream resume). This triggers an interrupt if WAKEUPE is set.
Shall be cleared by software (USB clock inputs must be enabled before). Setting by software has no effect. See Section 20.8, page 199 for more details.
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* 3 - EORSTI - End Of Reset Interrupt Flag Set by hardware when an "End Of Reset" has been detected by the USB controller. This triggers an USB interrupt if EORSTE is set.
Shall be cleared by software. Setting by software has no effect.
* 2 - SOFI - Start Of Frame Interrupt Flag Set by hardware when an USB "Start Of Frame" PID (SOF) has been detected (every 1 ms). This triggers an USB interrupt if SOFE is set.. * 1 - Reserved * 0 - SUSPI - Suspend Interrupt Flag Set by hardware when an USB "Suspend" `idle bus for 3 frame periods: a J state for 3 ms) is detected. This triggers an USB interrupt if SUSPE is set.
Shall be cleared by software. Setting by software has no effect. See Section 20.8, page 199 for more details. The interrupt flags bits are set even if their corresponding `Enable' bits is not set.
Bit
7 -
6 UPRSME R/W 0
5 EORSME R/W 0
4 WAKEUPE R/W 0
3 EORSTE R/W 0
2 SOFE R/W 0
1 R 0
0 SUSPE R/W 0 UDIEN
Read/Wri R te Initial Value 0
* 7 - Reserved The value read from these bits is always 0. Do not set these bits. * 6 - UPRSME - Upstream Resume Interrupt Enable Bit Set to enable the UPRSMI interrupt.
Clear to disable the UPRSMI interrupt.
* 5 - EORSME - End Of Resume Interrupt Enable Bit Set to enable the EORSMI interrupt.
Clear to disable the EORSMI interrupt.
* 4 - WAKEUPE - Wake-up CPU Interrupt Enable Bit Set to enable the WAKEUPI interrupt.
Clear to disable the WAKEUPI interrupt.
* 3 - EORSTE - End Of Reset Interrupt Enable Bit Set to enable the EORSTI interrupt. This bit is set after a reset.
Clear to disable the EORSTI interrupt.
* 2 - SOFE - Start Of Frame Interrupt Enable Bit Set to enable the SOFI interrupt.
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Clear to disable the SOFI interrupt.
* 1 - Reserved * 0 - SUSPE - Suspend Interrupt Enable Bit Set to enable the SUSPI interrupt.
Clear to disable the SUSPI interrupt.
Bit
7 ADDEN
6 UADD6:0 R/W 0
5 R 0
4 R 0
3 R 0
2 R 0
1 R 0
0 UDADDR R 0
Read/Wri R/W te Initial Value 0
* 7 - ADDEN - Address Enable Bit Set to activate the UADD (USB address).
Cleared by hardware. Clearing by software has no effect. See Section 20.7, page 198 for more details.
* 6-0 - UADD6:0 - USB Address Bits Set to configure the device address.
Shall not be cleared.
Bit
7 -
6 R 0
5 R 0
4 R 0
3 R 0
2 FNUM10:8 R 0
1 R 0
0 UDFNUMH R 0
Read/Wri R te Initial Value 0
* 7-3 - Reserved The value read from these bits is always 0. Do not set these bits. * 2-0 - FNUM10:8 - Frame Number Upper Flag Set by hardware. These bits are the 3 MSB of the 11-bits Frame Number information. They are provided in the last received SOF packet. FNUM is updated if a corrupted SOF is received.
Bit
7 FNUM7:0
6 R 0
5 R 0
4 R 0
3 R 0
2 R 0
1 R 0
0 UDFNUML R 0
Read/Wri R te Initial Value 0
* 7-0 Frame Number Lower Flag Set by hardware. These bits are the 8 LSB of the 11-bits Frame Number information.
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Bit
7 -
6 R 0
5 R 0
4 FNCERR R/W 0
3 R 0
2 R 0
1 R 0
0 R 0 UDMFN
Read/Wri R te Initial Value 0
* 7-5 - Reserved The value read from these bits is always 0. Do not set these bits. * 4 - FNCERR -Frame Number CRC Error Flag Set by hardware when a corrupted Frame Number in start of frame packet is received.
This bit and the SOFI interrupt are updated at the same time.
* 3-0 - Reserved The value read from these bits is always 0. Do not set these bits. 20.18.2 USB device endpoint registers
Bit 7 Read/Wri R te Initial Value 0 6 R 0 5 R 0 4 R 0 3 R 0 2 EPNUM2:0 R/W 0 R/W 0 R/W 0 1 0 UENUM
* 7-3 - Reserved The value read from these bits is always 0. Do not set these bits. * 2-0 - EPNUM2:0 Endpoint Number Bits Set to select the number of the endpoint which shall be accessed by the CPU. See Section 20.5, page 197 for more details.
Values greater than 100b are forbidden.
Bit
7 -
6 R 0
5 R 0
4 EPRST D4 R/W 0
3 EPRST D3 R/W 0
2 EPRST D2 R/W 0
1 EPRST D1 R/W 0
0 EPRST D0 R/W 0 UERST
Read/Wri R te Initial Value 0
* 7-5 - Reserved The value read from these bits is always 0. Do not set these bits. * 4-0 - EPRST4:0 - Endpoint FIFO Reset Bits Set to reset the selected endpoint FIFO prior to any other operation, upon hardware reset or when an USB bus reset has been received. See Section 20.3, page 196 for more information
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Then, cleared by software to complete the reset operation and start using the FIFO.
Bit
7 -
6 R 0
5 STALLRQ R/W 0
4 R/W 0
3 R/W 0
2 R 0
1 R 0
0 EPEN R/W 0 UECONX
STALLRQC RSTDT
Read/Wri R te Initial Value 0
* 7-6 - Reserved The value read from these bits is always 0. Do not set these bits. * 5 - STALLRQ - STALL Request Handshake Bit Set to request a STALL answer to the host for the next handshake.
Cleared by hardware when a new SETUP is received. Clearing by software has no effect. See Section 20.11, page 200 for more details.
* 4 - STALLRQC - STALL Request Clear Handshake Bit Set to disable the STALL handshake mechanism.
Cleared by hardware immediately after the set. Clearing by software has no effect. See Section 20.11, page 200 for more details.
3
* RSTDT - Reset Data Toggle Bit Set to automatically clear the data toggle sequence:
For OUT endpoint: the next received packet will have the data toggle 0. For IN endpoint: the next packet to be sent will have the data toggle 0. Cleared by hardware instantaneously. The firmware does not have to wait that the bit is cleared. Clearing by software has no effect.
* 2 - Reserved The value read from these bits is always 0. Do not set these bits. * 1 - Reserved The value read from these bits is always 0. Do not set these bits. * 0 - EPEN - Endpoint Enable Bit Set to enable the endpoint according to the device configuration. Endpoint 0 shall always be enabled after a hardware or USB reset and participate in the device configuration.
Clear this bit to disable the endpoint. See Section 20.6, page 197 for more details.
Bit
7 EPTYPE1:0
6 R/W
5 R
4 R
3 R
2 R
1 R
0 EPDIR R/W UECFG0X
Read/Wri R/W te
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Bit Initial Value
7 0
6 0
5 0
4 0
3 0
2 0
1 0
0 0
* 7-6 - EPTYPE1:0 - Endpoint Type Bits Set this bit according to the endpoint configuration:
00b: Control10b: Bulk 01b: Isochronous11b: Interrupt
* 5-1 - Reserved The value read from these bits is always 0. Do not set these bits. * 0 - EPDIR - Endpoint Direction Bit Set to configure an IN direction for bulk, interrupt or isochronous endpoints.
Clear to configure an OUT direction for bulk, interrupt, isochronous or control endpoints.
Bit
7 -
6 EPSIZE2:0 R/W 0
5 R/W 0
4 R/W 0
3 EPBK1:0 R/W 0
2 R/W 0
1 ALLOC R/W 0
0 R 0 UECFG1X
Read/Wri R te Initial Value 0
* 7 - Reserved The value read from these bits is always 0. Do not set these bits. * 6-4 - EPSIZE2:0 - Endpoint Size Bits Set this bit according to the endpoint size:
000b: 8 bytes 001b: 16 bytes 010b: 32 bytes 011b: 64 bytes Other : Reserved. Do not use this configuration.
* 3-2 - EPBK1:0 - Endpoint Bank Bits Set this field according to the endpoint size:
00b: One bank 01b: Double bank 1xb: Reserved. Do not use this configuration.
* 1 - ALLOC - Endpoint Allocation Bit Set this bit to allocate the endpoint memory.
Clear to free the endpoint memory. See Section 20.6, page 197 for more details.
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* 0 - Reserved The value read from these bits is always 0. Do not set these bits.
Bit
7 CFGOK
6 OVERFI R/W 0
5 UNDERFI R/W 0
4 R 0
3 DTSEQ1:0 R 0
2 R 0
1 NBUSYBK1:0 R 0
0 UESTA0X R 0
Read/Wri R te Initial Value 0
* 7 - CFGOK - Configuration Status Flag Set by hardware when the endpoint X size parameter (EPSIZE) and the bank parametrization (EPBK) are correct compared to the max FIFO capacity and the max number of allowed bank. This bit is updated when the bit ALLOC is set.
If this bit is cleared, the user should reprogram the UECFG1X register with correct EPSIZE and EPBK values.
* 6 - OVERFI - Overflow Error Interrupt Flag Set by hardware when an overflow error occurs in an isochronous endpoint. An interrupt (EPINTx) is triggered (if enabled).
See Section 20.15, page 206 for more details. Shall be cleared by software. Setting by software has no effect.
* 5 - UNDERFI - Flow Error Interrupt Flag Set by hardware when an underflow error occurs in an isochronous endpoint. An interrupt (EPINTx) is triggered (if enabled).
See Section 20.15, page 206 for more details. Shall be cleared by software. Setting by software has no effect.
* 4- Reserved The value read from these bits is always 0. Do not set these bits. * 3-2 - DTSEQ1:0 - Data Toggle Sequencing Flag Set by hardware to indicate the PID data of the current bank:
00b 01b 1xb Data0 Data1 Reserved.
For OUT transfer, this value indicates the last data toggle received on the current bank. For IN transfer, it indicates the Toggle that will be used for the next packet to be sent. This is not relative to the current bank.
* 1-0 - NBUSYBK1:0 - Busy Bank Flag Set by hardware to indicate the number of busy bank.
For IN endpoint, it indicates the number of busy bank(s), filled by the user, ready for IN transfer.
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For OUT endpoint, it indicates the number of busy bank(s) filled by OUT transaction from the host. 00b 01b 10b 11b All banks are free 1 busy bank 2 busy banks Reserved.
Bit
7 -
6 R 0
5 R 0
4 R 0
3 R 0
2 CTRLDIR R 0
1 CURRBK1:0 R 0
0 UESTA1X
Read/Wri R te Initial Value 0
0
* 7-3 - Reserved The value read from these bits is always 0. Do not set these bits. * 2 - CTRLDIR - Control Direction (Flag, and bit for debug purpose) Set by hardware after a SETUP packet, and gives the direction of the following packet:
- 1 for IN endpoint - 0 for OUT endpoint. Can not be set or cleared by software.
* 1-0 - CURRBK1:0 - Current Bank (all endpoints except Control endpoint) Flag Set by hardware to indicate the number of the current bank:
00b 01b 1xb Bank0 Bank1 Reserved.
Can not be set or cleared by software.
Bit
7 FIFOCON
6 NAKINI R/W 0
5 RWAL R/W 0
4 NAKOUTI R/W 0
3 RXSTPI R/W 0
2 RXOUTI R/W 0
1 STALLEDI R/W 0
0 TXINI R/W 0 UEINTX
Read/Wri R/W te Initial Value 0
* 7 - FIFOCON - FIFO Control Bit For OUT and SETUP Endpoint:
Set by hardware when a new OUT message is stored in the current bank, at the same time than RXOUT or RXSTP. Clear to free the current bank and to switch to the following bank. Setting by software has no effect.
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For IN Endpoint: Set by hardware when the current bank is free, at the same time than TXIN. Clear to send the FIFO data and to switch the bank. Setting by software has no effect.
* 6 - NAKINI - NAK IN Received Interrupt Flag Set by hardware when a NAK handshake has been sent in response of a IN request from the host. This triggers an USB interrupt if NAKINE is sent.
Shall be cleared by software. Setting by software has no effect.
* 5 - RWAL - Read/Write Allowed Flag Set by hardware to signal:
- for an IN endpoint: the current bank is not full i.e. the firmware can push data into the FIFO, - for an OUT endpoint: the current bank is not empty, i.e. the firmware can read data from the FIFO. The bit is never set if STALLRQ is set, or in case of error. Cleared by hardware otherwise. This bit shall not be used for the control endpoint.
* 4 - NAKOUTI - NAK OUT Received Interrupt Flag Set by hardware when a NAK handshake has been sent in response of a OUT/PING request from the host. This triggers an USB interrupt if NAKOUTE is sent.
Shall be cleared by software. Setting by software has no effect.
* 3 - RXSTPI - Received SETUP Interrupt Flag Set by hardware to signal that the current bank contains a new valid SETUP packet. An interrupt (EPINTx) is triggered (if enabled).
Shall be cleared by software to handshake the interrupt. Setting by software has no effect. This bit is inactive (cleared) if the endpoint is an IN endpoint.
* 2 - RXOUTI / KILLBK - Received OUT Data Interrupt Flag Set by hardware to signal that the current bank contains a new packet. An interrupt (EPINTx) is triggered (if enabled).
Shall be cleared by software to handshake the interrupt. Setting by software has no effect.
Kill Bank IN Bit
Set this bit to kill the last written bank. Cleared by hardware when the bank is killed. Clearing by software has no effect. See page 205 for more details on the Abort.
* 1 - STALLEDI - STALLEDI Interrupt Flag Set by hardware to signal that a STALL handshake has been sent, or that a CRC error has been detected in a OUT isochronous endpoint.
Shall be cleared by software. Setting by software has no effect.
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* 0 - TXINI - Transmitter Ready Interrupt Flag Set by hardware to signal that the current bank is free and can be filled. An interrupt (EPINTx) is triggered (if enabled).
Shall be cleared by software to handshake the interrupt. Setting by software has no effect. This bit is inactive (cleared) if the endpoint is an OUT endpoint.
Bit
7 FLERRE
6 NAKINE R/W 0
5 R 0
4 NAKOUTE R/W 0
3 RXSTPE R/W 0
2 RXOUTE R/W 0
1 STALLEDE R/W 0
0 TXINE R/W 0 UEIENX
Read/Wri R/W te Initial Value 0
* 7 - FLERRE - Flow Error Interrupt Enable Flag Set to enable an endpoint interrupt (EPINTx) when OVERFI or UNDERFI are sent.
Clear to disable an endpoint interrupt (EPINTx) when OVERFI or UNDERFI are sent.
* 6 - NAKINE - NAK IN Interrupt Enable Bit Set to enable an endpoint interrupt (EPINTx) when NAKINI is set.
Clear to disable an endpoint interrupt (EPINTx) when NAKINI is set.
* 5 - Reserved The value read from these bits is always 0. Do not set these bits. * 4 - NAKOUTE - NAK OUT Interrupt Enable Bit Set to enable an endpoint interrupt (EPINTx) when NAKOUTI is set.
Clear to disable an endpoint interrupt (EPINTx) when NAKOUTI is set.
* 3 - RXSTPE - Received SETUP Interrupt Enable Flag Set to enable an endpoint interrupt (EPINTx) when RXSTPI is sent.
Clear to disable an endpoint interrupt (EPINTx) when RXSTPI is sent.
* 2 - RXOUTE - Received OUT Data Interrupt Enable Flag Set to enable an endpoint interrupt (EPINTx) when RXOUTI is sent.
Clear to disable an endpoint interrupt (EPINTx) when RXOUTI is sent.
* 1 - STALLEDE - Stalled Interrupt Enable Flag Set to enable an endpoint interrupt (EPINTx) when STALLEDI is sent.
Clear to disable an endpoint interrupt (EPINTx) when STALLEDI is sent.
* 0 - TXINE - Transmitter Ready Interrupt Enable Flag Set to enable an endpoint interrupt (EPINTx) when TXINI is sent.
Clear to disable an endpoint interrupt (EPINTx) when TXINI is sent.
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Bit 7 DAT D7 Read/Wri R/W te Initial Value 0 6 DAT D6 R/W 0 5 DAT D5 R/W 0 4 DAT D4 R/W 0 3 DAT D3 R/W 0 2 DAT D2 R/W 0 1 DAT D1 R/W 0 0 DAT D0 R/W 0 UEDATX
* 7-0 - DAT7:0 -Data Bits Set by the software to read/write a byte from/to the endpoint FIFO selected by EPNUM.
Bit
7 BYCT D7
6 BYCT D6 R 0
5 BYCT D5 R 0
4 BYCT D4 R 0
3 BYCT D3 R 0
2 BYCT D2 R 0
1 BYCT D1 R 0
0 BYCT D0 R 0 UEBCLX R
Read/Wri R te Initial Value 0
* 7-0 - BYCT7:0 - Byte Count Bits Set by the hardware. BYCT7:0 is:
- (for IN endpoint) increased after each writing into the endpoint and decremented after each byte sent, - (for OUT endpoint) increased after each byte sent by the host, and decremented after each byte read by the software.
Bit
7 -
6 R 0
5 R 0
4 EPINT D4 R 0
3 EPINT D3 R 0
2 EPINT D2 R 0
1 EPINT D1 R 0
0 EPINT D0 R 0 UEINT R
Read/Wri R te Initial Value 0
* 7-5 - Reserved The value read from these bits is always 0. Do not set these bits. * 4-0 - EPINT4:0 - Endpoint Interrupts Bits Set by hardware when an interrupt is triggered by the UEINTX register and if the corresponding endpoint interrupt enable bit is set.
Cleared by hardware when the interrupt source is served.
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21. PS/2
21.1 Characteristics The PS/2 pad IO's characteristics are:
- support 5.5V (min: 4.5V, max: 5.5V) - open drain type - Output voltage level threshold, MCU driving low thru a 1k pull-up: VOLmax = 0,7V - fall time with 1k pull-up and 500pF load: 250ns < Tfall < 1s - internal 2.2k to 10k pull-up at Vcc (5V), controlled by firmware. - High impedance output when disabled.
Figure 21-1. USB pad and PS/2 pad multiplexing
PS/2 Pad
D+ / SCK
D- / SDATA
USB Pad
Bit Read/Write Initial Value
7 R 0
6 R 0
5 R 0
4 R 0
3 R 0
2 R 0
1 R 0
0 PS2EN R/W 0 PS2CON
* Bit 7:1 - Reserved bits Do not set these bits. * Bit 0 - PS2EN : PS/2 Pad Enable Set this bit to "1" to enable the PS/2 pad.
Set this bit to "0" to disable the PS/2 pad. For more information about pad driving, see "USB/PS2 Software Output Enable register - UPOE" on page 194.
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The UPOE register described in this section allows to read or writes values on the pad. PS/2 protocol must be entirely handled by software.
Figure 21-2. PS/2 Pad description
Vcc Z
4.7k
note: pull-up between 2.2k and 10k
Z
4.7k
SDATA SCK
Table 21-1.
PS/2 DC parameters
Symbol UVCC VIL VIH RIH
Parameter PS/2 power supply Input Low Voltage Input High Voltage Pull-up resistor
Condition UVCC = 4.5V - 5.5V UVCC = 4.5V - 5.5V UVCC = 4.5V - 5.5V
Min. 4.0V 2.4V 4.4k
Typ. 4.5V
Max. 5.5V 0.7V
5.1k
6.5k
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Table 21-2.
PS/2 AC parameters
Symbol Tfall_output Tspike
Parameter Fall time Spike width filtering
Condition UVCC = 4.5V - 5.5V 10% - 90% Rload = 1k, Cload = 500pF
Min. 330ns
Typ. 375ns
Max. 450ns 60ns
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22. Analog Comparator
The Analog Comparator compares the input values on the positive pin AIN0 and negative pin AIN1. When the voltage on the positive pin AIN0 is higher than the voltage on the negative pin AIN1, the Analog Comparator output, ACO, is set. The comparator's output can be set to trigger the Timer/Counter1 Input Capture function. In addition, the comparator can trigger a separate interrupt, exclusive to the Analog Comparator. The user can select Interrupt triggering on comparator output rise, fall or toggle. A block diagram of the comparator and its surrounding logic is shown in Figure 22-1. User can also replace by software the AIN0 input by the internal Bandgap reference.
Figure 22-1. Analog Comparator Block Diagram(1)
BANDGAP REFERENCE ACBG
Notes:
1. Refer to Figure 1-1 on page 3 and Table 11-9 on page 79 for Analog Comparator pin placement.
22.0.1
Analog Comparator Control and Status Register - ACSR
Bit Read/Write Initial Value 7 ACD R/W 0 6 ACBG R/W 0 5 ACO R N/A 4 ACI R/W 0 3 ACIE R/W 0 2 ACIC R/W 0 1 ACIS1 R/W 0 0 ACIS0 R/W 0 ACSR
* Bit 7 - ACD: Analog Comparator Disable When this bit is written logic one, the power to the Analog Comparator is switched off. This bit can be set at any time to turn off the Analog Comparator. This will reduce power consumption in Active and Idle mode. When changing the ACD bit, the Analog Comparator Interrupt must be disabled by clearing the ACIE bit in ACSR. Otherwise an interrupt can occur when the bit is changed. * Bit 6 - ACBG: Analog Comparator Bandgap Select When this bit is set, a fixed bandgap reference voltage replaces the positive input to the Analog Comparator. When this bit is cleared, AIN0 is applied to the positive input of the Analog Comparator. See "Internal Voltage Reference" on page 52. * Bit 5 - ACO: Analog Comparator Output The output of the Analog Comparator is synchronized and then directly connected to ACO. The synchronization introduces a delay of 1 - 2 clock cycles.
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* Bit 4 - ACI: Analog Comparator Interrupt Flag This bit is set by hardware when a comparator output event triggers the interrupt mode defined by ACIS1 and ACIS0. The Analog Comparator interrupt routine is executed if the ACIE bit is set and the I-bit in SREG is set. ACI is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, ACI is cleared by writing a logic one to the flag. * Bit 3 - ACIE: Analog Comparator Interrupt Enable When the ACIE bit is written logic one and the I-bit in the Status Register is set, the Analog Comparator interrupt is activated. When written logic zero, the interrupt is disabled. * Bit 2 - ACIC: Analog Comparator Input Capture Enable When written logic one, this bit enables the input capture function in Timer/Counter1 to be triggered by the Analog Comparator. The comparator output is in this case directly connected to the input capture front-end logic, making the comparator utilize the noise canceler and edge select features of the Timer/Counter1 Input Capture interrupt. When written logic zero, no connection between the Analog Comparator and the input capture function exists. To make the comparator trigger the Timer/Counter1 Input Capture interrupt, the ICIE1 bit in the Timer Interrupt Mask Register (TIMSK1) must be set. * Bits 1, 0 - ACIS1, ACIS0: Analog Comparator Interrupt Mode Select These bits determine which comparator events that trigger the Analog Comparator interrupt. The different settings are shown in Table 22-1. Table 22-1.
ACIS1 0 0 1 1
ACIS1/ACIS0 Settings
ACIS0 0 1 0 1 Interrupt Mode Comparator Interrupt on Output Toggle. Reserved Comparator Interrupt on Falling Output Edge. Comparator Interrupt on Rising Output Edge.
When changing the ACIS1/ACIS0 bits, the Analog Comparator Interrupt must be disabled by clearing its Interrupt Enable bit in the ACSR Register. Otherwise an interrupt can occur when the bits are changed.
22.0.2
Digital Input Disable Register 1 - DIDR1
Bit Read/Write Initial Value 7 - R 0 6 - R 0 5 - R 0 4 - R 0 3 - R 0 2 - R 0 1 AIN1D R/W 0 0 AIN0D R/W 0 DIDR1
* Bit 1, 0 - AIN1D, AIN0D: AIN1, AIN0 Digital Input Disable When this bit is written logic one, the digital input buffer on the AIN1/0 pin is disabled. The corresponding PIN Register bit will always read as zero when this bit is set. When an analog signal is applied to the AIN1/0 pin and the digital input from this pin is not needed, this bit should be written logic one to reduce power consumption in the digital input buffer.
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23. Boot Loader Support - Read-While-Write Self-Programming
The Boot Loader Support provides a real Read-While-Write Self-Programming mechanism for downloading and uploading program code by the MCU itself. This feature allows flexible application software updates controlled by the MCU using a Flash-resident Boot Loader program. The Boot Loader program can use any available data interface and associated protocol to read code and write (program) that code into the Flash memory, or read the code from the program memory. The program code within the Boot Loader section has the capability to write into the entire Flash, including the Boot Loader memory. The Boot Loader can thus even modify itself, and it can also erase itself from the code if the feature is not needed anymore. The size of the Boot Loader memory is configurable with fuses and the Boot Loader has two separate sets of Boot Lock bits which can be set independently. This gives the user a unique flexibility to select different levels of protection.
23.1
Boot Loader Features
* * * * * * *
Read-While-Write Self-Programming Flexible Boot Memory Size High Security (Separate Boot Lock Bits for a Flexible Protection) Separate Fuse to Select Reset Vector Optimized Page(1) Size Code Efficient Algorithm Efficient Read-Modify-Write Support 1. A page is a section in the Flash consisting of several bytes (see Table 25-11 on page 248) used during programming. The page organization does not affect normal operation.
Note:
23.2
Application and Boot Loader Flash Sections
The Flash memory is organized in two main sections, the Application section and the Boot Loader section (see Figure 23-2). The size of the different sections is configured by the BOOTSZ Fuses as shown in Table 23-8 on page 239 and Figure 23-2. These two sections can have different level of protection since they have different sets of Lock bits.
23.2.1
Application Section The Application section is the section of the Flash that is used for storing the application code. The protection level for the Application section can be selected by the application Boot Lock bits (Boot Lock bits 0), see Table 23-2 on page 229. The Application section can never store any Boot Loader code since the SPM instruction is disabled when executed from the Application section. BLS - Boot Loader Section While the Application section is used for storing the application code, the The Boot Loader software must be located in the BLS since the SPM instruction can initiate a programming when executing from the BLS only. The SPM instruction can access the entire Flash, including the BLS itself. The protection level for the Boot Loader section can be selected by the Boot Loader Lock bits (Boot Lock bits 1), see Table 23-3 on page 229.
23.2.2
23.3
Read-While-Write and No Read-While-Write Flash Sections
Whether the CPU supports Read-While-Write or if the CPU is halted during a Boot Loader software update is dependent on which address that is being programmed. In addition to the two sections that are configurable by the BOOTSZ Fuses as described above, the Flash is also
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divided into two fixed sections, the Read-While-Write (RWW) section and the No Read-WhileWrite (NRWW) section. The limit between the RWW- and NRWW sections is given in Table 231 and Figure 23-1 on page 227. The main difference between the two sections is: * When erasing or writing a page located inside the RWW section, the NRWW section can be read during the operation. * When erasing or writing a page located inside the NRWW section, the CPU is halted during the entire operation. Note that the user software can never read any code that is located inside the RWW section during a Boot Loader software operation. The syntax "Read-While-Write section" refers to which section that is being programmed (erased or written), not which section that actually is being read during a Boot Loader software update.
23.3.1
RWW - Read-While-Write Section If a Boot Loader software update is programming a page inside the RWW section, it is possible to read code from the Flash, but only code that is located in the NRWW section. During an ongoing programming, the software must ensure that the RWW section never is being read. If the user software is trying to read code that is located inside the RWW section (i.e., by load program memory, call, or jump instructions or an interrupt) during programming, the software might end up in an unknown state. To avoid this, the interrupts should either be disabled or moved to the Boot Loader section. The Boot Loader section is always located in the NRWW section. The RWW Section Busy bit (RWWSB) in the Store Program Memory Control and Status Register (SPMCSR) will be read as logical one as long as the RWW section is blocked for reading. After a programming is completed, the RWWSB must be cleared by software before reading code located in the RWW section. See "Store Program Memory Control and Status Register - SPMCSR" on page 231. for details on how to clear RWWSB. NRWW - No Read-While-Write Section The code located in the NRWW section can be read when the Boot Loader software is updating a page in the RWW section. When the Boot Loader code updates the NRWW section, the CPU is halted during the entire Page Erase or Page Write operation. Table 23-1.
Read-While-Write Features
Which Section Can be Read During Programming? NRWW Section None Is the CPU Halted? No Yes Read-While-Write Supported? Yes No
23.3.2
Which Section does the Z-pointer Address During the Programming? RWW Section NRWW Section
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Figure 23-1. Read-While-Write vs. No Read-While-Write
Read-While-Write (RWW) Section
Z-pointer Addresses RWW Section
Z-pointer Addresses NRWW Section
No Read-While-Write (NRWW) Section
CPU is Halted During the Operation Code Located in NRWW Section Can be Read During the Operation
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Figure 23-2. Memory Sections
Program Memory BOOTSZ = '11' 0x0000
Read-While-Write Section Read-While-Write Section
Program Memory BOOTSZ = '10' 0x0000
Application Flash Section
Application Flash Section
No Read-While-Write Section
End RWW Start NRWW Application Flash Section
No Read-While-Write Section
End RWW Start NRWW Application Flash Section End Application Start Boot Loader Boot Loader Flash Section Flashend Program Memory BOOTSZ = '00'
Boot Loader Flash Section
End Application Start Boot Loader Flashend
Program Memory BOOTSZ = '01' 0x0000
Read-While-Write Section Read-While-Write Section
0x0000
Application Flash Section
Application Flash Section
No Read-While-Write Section
End RWW Start NRWW Application Flash Section End Application Start Boot Loader Boot Loader Flash Section Flashend
No Read-While-Write Section
End RWW, End Application Start NRWW, Start Boot Loader
Boot Loader Flash Section
Flashend
Note:
1. The parameters in the figure above are given in Table 23-8 on page 239.
23.4
Boot Loader Lock Bits
If no Boot Loader capability is needed, the entire Flash is available for application code. The Boot Loader has two separate sets of Boot Lock bits which can be set independently. This gives the user a unique flexibility to select different levels of protection. The user can select: * To protect the entire Flash from a software update by the MCU. * To protect only the Boot Loader Flash section from a software update by the MCU. * To protect only the Application Flash section from a software update by the MCU. * Allow software update in the entire Flash. See Table 23-2 and Table 23-3 for further details. The Boot Lock bits can be set in software and in Serial or Parallel Programming mode, but they can be cleared by a Chip Erase command only. The general Write Lock (Lock Bit mode 2) does not control the programming of the Flash memory by SPM instruction. Similarly, the general Read/Write Lock (Lock Bit mode 1) does not control reading nor writing by (E)LPM/SPM, if it is attempted.
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Table 23-2.
BLB0 Mode 1 2
Boot Lock Bit0 Protection Modes (Application Section)(1)
BLB02 1 1 BLB01 1 0 Protection No restrictions for SPM or (E)LPM accessing the Application section. SPM is not allowed to write to the Application section. SPM is not allowed to write to the Application section, and (E)LPM executing from the Boot Loader section is not allowed to read from the Application section. If Interrupt Vectors are placed in the Boot Loader section, interrupts are disabled while executing from the Application section. (E)LPM executing from the Boot Loader section is not allowed to read from the Application section. If Interrupt Vectors are placed in the Boot Loader section, interrupts are disabled while executing from the Application section.
3
0
0
4 Note:
0
1
1. "1" means unprogrammed, "0" means programmed
Table 23-3.
BLB1 Mode 1 2
Boot Lock Bit1 Protection Modes (Boot Loader Section)(1)
BLB12 1 1 BLB11 1 0 Protection No restrictions for SPM or (E)LPM accessing the Boot Loader section. SPM is not allowed to write to the Boot Loader section. SPM is not allowed to write to the Boot Loader section, and (E)LPM executing from the Application section is not allowed to read from the Boot Loader section. If Interrupt Vectors are placed in the Application section, interrupts are disabled while executing from the Boot Loader section. (E)LPM executing from the Application section is not allowed to read from the Boot Loader section. If Interrupt Vectors are placed in the Application section, interrupts are disabled while executing from the Boot Loader section.
3
0
0
4 Note:
0
1
1. "1" means unprogrammed, "0" means programmed
23.5
23.5.1
Entering the Boot Loader Program
The bootloader can be executed with three different conditions:
Regular application conditions. A jump or call from the application program. This may be initiated by a trigger such as a command received via USART, or SPI interface. Boot Reset Fuse The Boot Reset Fuse (BOOTRST) can be programmed so that the Reset Vector is pointing to the Boot Flash start address after a reset. In this case, the Boot Loader is started after a reset. After the application code is loaded, the program can start executing the application code. Note that the fuses cannot be changed by the MCU itself. This means that once the Boot Reset Fuse
23.5.2
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is programmed, the Reset Vector will always point to the Boot Loader Reset and the fuse can only be changed through the serial or parallel programming interface.
Table 23-4.
BOOTRST 1 0 Note:
Boot Reset Fuse(1)
Reset Address Reset Vector = Application Reset (address 0x0000) Reset Vector = Boot Loader Reset (see Table 23-8 on page 239)
1. "1" means unprogrammed, "0" means programmed
23.5.3
External Hardware conditions The Hardware Boot Enable Fuse (HWBE) can be programmed (See Table 23-5) so that upon special hardware conditions under reset, the bootloader execution is forced after reset. Table 23-5.
HWBE 1 0 Note:
Hardware Boot Enable Fuse(1)
Reset Address PD7/HWB pin can not be used to force Boot Loader execution after reset PD7/HWB pin is used during reset to force bootloader execution after reset
1. "1" means unprogrammed, "0" means programmed
When the HWBE fuse is enable the PD7/HWB pin is configured as input during reset and sampled during reset rising edge. When PD7/HWB pin is `0' during reset rising edge, the reset vector will be set as the Boot Loader Reset address and the Boot Loader will be executed (See Figures 23-3).
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Figure 23-3. Boot Process Description
RESET
tSHRH
PD7/HWB
tHHRH
HWBE ?
Ext. Hardware Conditions ?
BOOTRST ?
Reset Vector = Application Reset
Reset Vector =Boot Lhoader Reset
23.5.4
Store Program Memory Control and Status Register - SPMCSR The Store Program Memory Control and Status Register contains the control bits needed to control the Boot Loader operations.
Bit Read/Write Initial Value 7 SPMIE R/W 0 6 RWWSB R 0 5 SIGRD R/W 0 4 RWWSRE R/W 0 3 BLBSET R/W 0 2 PGWRT R/W 0 1 PGERS R/W 0 0 SPMEN R/W 0 SPMCSR
* Bit 7 - SPMIE: SPM Interrupt Enable When the SPMIE bit is written to one, and the I-bit in the Status Register is set (one), the SPM ready interrupt will be enabled. The SPM ready Interrupt will be executed as long as the SPMEN bit in the SPMCSR Register is cleared. * Bit 6 - RWWSB: Read-While-Write Section Busy When a Self-Programming (Page Erase or Page Write) operation to the RWW section is initiated, the RWWSB will be set (one) by hardware. When the RWWSB bit is set, the RWW section cannot be accessed. The RWWSB bit will be cleared if the RWWSRE bit is written to one after a Self-Programming operation is completed. Alternatively the RWWSB bit will automatically be cleared if a page load operation is initiated. * Bit 5 - SIGRD: Signature Row Read If this bit is written to one at the same time as SPMEN, the next LPM instruction within three clock cycles will read a byte from the signature row into the destination register. see "Reading the Signature Row from Software" on page 236 for details. An SPM instruction within four cycles
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after SIGRD and SPMEN are set will have no effect. This operation is reserved for future use and should not be used.
* Bit 4 - RWWSRE: Read-While-Write Section Read Enable When programming (Page Erase or Page Write) to the RWW section, the RWW section is blocked for reading (the RWWSB will be set by hardware). To re-enable the RWW section, the user software must wait until the programming is completed (SPMEN will be cleared). Then, if the RWWSRE bit is written to one at the same time as SPMEN, the next SPM instruction within four clock cycles re-enables the RWW section. The RWW section cannot be re-enabled while the Flash is busy with a Page Erase or a Page Write (SPMEN is set). If the RWWSRE bit is written while the Flash is being loaded, the Flash load operation will abort and the data loaded will be lost. * Bit 3 - BLBSET: Boot Lock Bit Set If this bit is written to one at the same time as SPMEN, the next SPM instruction within four clock cycles sets Boot Lock bits, according to the data in R0. The data in R1 and the address in the Zpointer are ignored. The BLBSET bit will automatically be cleared upon completion of the Lock bit set, or if no SPM instruction is executed within four clock cycles.
An (E)LPM instruction within three cycles after BLBSET and SPMEN are set in the SPMCSR Register, will read either the Lock bits or the Fuse bits (depending on Z0 in the Z-pointer) into the destination register. See "Reading the Fuse and Lock Bits from Software" on page 235 for details.
* Bit 2 - PGWRT: Page Write If this bit is written to one at the same time as SPMEN, the next SPM instruction within four clock cycles executes Page Write, with the data stored in the temporary buffer. The page address is taken from the high part of the Z-pointer. The data in R1 and R0 are ignored. The PGWRT bit will auto-clear upon completion of a Page Write, or if no SPM instruction is executed within four clock cycles. The CPU is halted during the entire Page Write operation if the NRWW section is addressed. * Bit 1 - PGERS: Page Erase If this bit is written to one at the same time as SPMEN, the next SPM instruction within four clock cycles executes Page Erase. The page address is taken from the high part of the Z-pointer. The data in R1 and R0 are ignored. The PGERS bit will auto-clear upon completion of a Page Erase, or if no SPM instruction is executed within four clock cycles. The CPU is halted during the entire Page Write operation if the NRWW section is addressed. * Bit 0 - SPMEN: Store Program Memory Enable This bit enables the SPM instruction for the next four clock cycles. If written to one together with either RWWSRE, BLBSET, PGWRT' or PGERS, the following SPM instruction will have a special meaning, see description above. If only SPMEN is written, the following SPM instruction will store the value in R1:R0 in the temporary page buffer addressed by the Z-pointer. The LSB of the Z-pointer is ignored. The SPMEN bit will auto-clear upon completion of an SPM instruction, or if no SPM instruction is executed within four clock cycles. During Page Erase and Page Write, the SPMEN bit remains high until the operation is completed.
Writing any other combination than "10001", "01001", "00101", "00011" or "00001" in the lower five bits will have no effect.
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Note: Only one SPM instruction should be active at any time.
23.6
Addressing the Flash During Self-Programming
The Z-pointer is used to address the SPM commands. The Z pointer consists of the Z-registers ZL and ZH in the register file. The number of bits actually used is implementation dependent. Since the Flash is organized in pages (see Table 25-11 on page 248), the Program Counter can be treated as having two different sections. One section, consisting of the least significant bits, is addressing the words within a page, while the most significant bits are addressing the pages. This is shown in Figure 23-4. Note that the Page Erase and Page Write operations are addressed independently. Therefore it is of major importance that the Boot Loader software addresses the same page in both the Page Erase and Page Write operation. Once a programming operation is initiated, the address is latched and the Z-pointer can be used for other operations. The (E)LPM instruction use the Z-pointer to store the address. Since this instruction addresses the Flash byte-by-byte, also bit Z0 of the Z-pointer is used.
Figure 23-4. Addressing the Flash During SPM(1)
BIT Z - REGISTER PCMSB PROGRAM COUNTER
PCPAGE
15
ZPCMSB
ZPAGEMSB
10 0
PAGEMSB
PCWORD
PAGE ADDRESS WITHIN THE FLASH PROGRAM MEMORY
PAGE
WORD ADDRESS WITHIN A PAGE
PAGE INSTRUCTION WORD PCWORD[PAGEMSB:0]: 00 01 02
PAGEEND
Note:
1. The different variables used in Figure 23-4 are listed in Table 23-10 on page 240.
23.7
Self-Programming the Flash
The program memory is updated in a page by page fashion. Before programming a page with the data stored in the temporary page buffer, the page must be erased. The temporary page buffer is filled one word at a time using SPM and the buffer can be filled either before the Page Erase command or between a Page Erase and a Page Write operation: Alternative 1, fill the buffer before a Page Erase * Fill temporary page buffer
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* Perform a Page Erase * Perform a Page Write Alternative 2, fill the buffer after Page Erase * Perform a Page Erase * Fill temporary page buffer * Perform a Page Write If only a part of the page needs to be changed, the rest of the page must be stored (for example in the temporary page buffer) before the erase, and then be rewritten. When using alternative 1, the Boot Loader provides an effective Read-Modify-Write feature which allows the user software to first read the page, do the necessary changes, and then write back the modified data. If alternative 2 is used, it is not possible to read the old data while loading since the page is already erased. The temporary page buffer can be accessed in a random sequence. It is essential that the page address used in both the Page Erase and Page Write operation is addressing the same page. See "Simple Assembly Code Example for a Boot Loader" on page 237 for an assembly code example.
23.7.1
Performing Page Erase by SPM To execute Page Erase, set up the address in the Z-pointer, write "X0000011" to SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The data in R1 and R0 is ignored. The page address must be written to PCPAGE in the Z-register. Other bits in the Z-pointer will be ignored during this operation.
* Page Erase to the RWW section: The NRWW section can be read during the Page Erase. * Page Erase to the NRWW section: The CPU is halted during the operation.
23.7.2
Filling the Temporary Buffer (Page Loading) To write an instruction word, set up the address in the Z-pointer and data in R1:R0, write "00000001" to SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The content of PCWORD in the Z-register is used to address the data in the temporary buffer. The temporary buffer will auto-erase after a Page Write operation or by writing the RWWSRE bit in SPMCSR. It is also erased after a system reset. Note that it is not possible to write more than one time to each address without erasing the temporary buffer.
If the EEPROM is written in the middle of an SPM Page Load operation, all data loaded will be lost.
23.7.3
Performing a Page Write To execute Page Write, set up the address in the Z-pointer, write "X0000101" to SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The data in R1 and R0 is ignored. The page address must be written to PCPAGE. Other bits in the Z-pointer must be written to zero during this operation.
* Page Write to the RWW section: The NRWW section can be read during the Page Write. * Page Write to the NRWW section: The CPU is halted during the operation.
23.7.4
Using the SPM Interrupt If the SPM interrupt is enabled, the SPM interrupt will generate a constant interrupt when the SPMEN bit in SPMCSR is cleared. This means that the interrupt can be used instead of polling the SPMCSR Register in software. When using the SPM interrupt, the Interrupt Vectors should
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be moved to the BLS section to avoid that an interrupt is accessing the RWW section when it is blocked for reading. How to move the interrupts is described in "Interrupts" on page 63.
23.7.5
Consideration While Updating BLS Special care must be taken if the user allows the Boot Loader section to be updated by leaving Boot Lock bit11 unprogrammed. An accidental write to the Boot Loader itself can corrupt the entire Boot Loader, and further software updates might be impossible. If it is not necessary to change the Boot Loader software itself, it is recommended to program the Boot Lock bit11 to protect the Boot Loader software from any internal software changes. Prevent Reading the RWW Section During Self-Programming During Self-Programming (either Page Erase or Page Write), the RWW section is always blocked for reading. The user software itself must prevent that this section is addressed during the self programming operation. The RWWSB in the SPMCSR will be set as long as the RWW section is busy. During Self-Programming the Interrupt Vector table should be moved to the BLS as described in "Interrupts" on page 63, or the interrupts must be disabled. Before addressing the RWW section after the programming is completed, the user software must clear the RWWSB by writing the RWWSRE. See "Simple Assembly Code Example for a Boot Loader" on page 237 for an example. Setting the Boot Loader Lock Bits by SPM To set the Boot Loader Lock bits, write the desired data to R0, write "X0001001" to SPMCSR and execute SPM within four clock cycles after writing SPMCSR. The only accessible Lock bits are the Boot Lock bits that may prevent the Application and Boot Loader section from any software update by the MCU.
Bit R0 7 1 6 1 5 BLB12 4 BLB11 3 BLB02 2 BLB01 1 1 0 1
23.7.6
23.7.7
See Table 23-2 and Table 23-3 for how the different settings of the Boot Loader bits affect the Flash access. If bits 5..2 in R0 are cleared (zero), the corresponding Boot Lock bit will be programmed if an SPM instruction is executed within four cycles after BLBSET and SPMEN are set in SPMCSR. The Z-pointer is don't care during this operation, but for future compatibility it is recommended to load the Z-pointer with 0x0001 (same as used for reading the lOck bits). For future compatibility it is also recommended to set bits 7, 6, 1, and 0 in R0 to "1" when writing the Lock bits. When programming the Lock bits the entire Flash can be read during the operation.
23.7.8
EEPROM Write Prevents Writing to SPMCSR Note that an EEPROM write operation will block all software programming to Flash. Reading the Fuses and Lock bits from software will also be prevented during the EEPROM write operation. It is recommended that the user checks the status bit (EEPE) in the EECR Register and verifies that the bit is cleared before writing to the SPMCSR Register. Reading the Fuse and Lock Bits from Software It is possible to read both the Fuse and Lock bits from software. To read the Lock bits, load the Z-pointer with 0x0001 and set the BLBSET and SPMEN bits in SPMCSR. When an (E)LPM instruction is executed within three CPU cycles after the BLBSET and SPMEN bits are set in SPMCSR, the value of the Lock bits will be loaded in the destination register. The BLBSET and SPMEN bits will auto-clear upon completion of reading the Lock bits or if no (E)LPM instruction
23.7.9
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is executed within three CPU cycles or no SPM instruction is executed within four CPU cycles. When BLBSET and SPMEN are cleared, (E)LPM will work as described in the Instruction set Manual.
Bit Rd 7 - 6 - 5 BLB12 4 BLB11 3 BLB02 2 BLB01 1 LB2 0 LB1
The algorithm for reading the Fuse Low byte is similar to the one described above for reading the Lock bits. To read the Fuse Low byte, load the Z-pointer with 0x0000 and set the BLBSET and SPMEN bits in SPMCSR. When an (E)LPM instruction is executed within three cycles after the BLBSET and SPMEN bits are set in the SPMCSR, the value of the Fuse Low byte (FLB) will be loaded in the destination register as shown below. Refer to Table 25-5 on page 245 for a detailed description and mapping of the Fuse Low byte.
Bit Rd 7 FLB7 6 FLB6 5 FLB5 4 FLB4 3 FLB3 2 FLB2 1 FLB1 0 FLB0
Similarly, when reading the Fuse High byte, load 0x0003 in the Z-pointer. When an (E)LPM instruction is executed within three cycles after the BLBSET and SPMEN bits are set in the SPMCSR, the value of the Fuse High byte (FHB) will be loaded in the destination register as shown below. Refer to Table 25-4 on page 245 for detailed description and mapping of the Fuse High byte.
Bit Rd 7 FHB7 6 FHB6 5 FHB5 4 FHB4 3 FHB3 2 FHB2 1 FHB1 0 FHB0
When reading the Extended Fuse byte, load 0x0002 in the Z-pointer. When an (E)LPM instruction is executed within three cycles after the BLBSET and SPMEN bits are set in the SPMCSR, the value of the Extended Fuse byte (EFB) will be loaded in the destination register as shown below. Refer to Table 25-3 on page 244 for detailed description and mapping of the Extended Fuse byte.
Bit Rd 7 - 6 - 5 - 4 - 3 - 2 EFB2 1 EFB1 0 EFB0
Fuse and Lock bits that are programmed, will be read as zero. Fuse and Lock bits that are unprogrammed, will be read as one.
23.7.10
Reading the Signature Row from Software To read the Signature Row from software, load the Z-pointer with the signature byte address given in Table 23-6 on page 236 and set the SIGRD and SPMEN bits in SPMCSR. When an LPM instruction is executed within three CPU cycles after the SIGRD and SPMEN bits are set in SPMCSR, the signature byte value will be loaded in the destination register. The SIGRD and SPMEN bits will auto-clear upon completion of reading the Signature Row Lock bits or if no LPM instruction is executed within three CPU cycles. When SIGRD and SPMEN are cleared, LPM will work as described in the Instruction set Manual. Table 23-6.
Signature Row Addressing
Z-Pointer Address 0x0000 0x0002 0x0004 0x0001
Signature Byte Device Signature Byte 1 Device Signature Byte 2 Device Signature Byte 3 RC Oscillator Calibration Byte
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Note: All other addresses are reserved for future use.
23.7.11
Preventing Flash Corruption During periods of low VCC, the Flash program can be corrupted because the supply voltage is too low for the CPU and the Flash to operate properly. These issues are the same as for board level systems using the Flash, and the same design solutions should be applied.
A Flash program corruption can be caused by two situations when the voltage is too low. First, a regular write sequence to the Flash requires a minimum voltage to operate correctly. Secondly, the CPU itself can execute instructions incorrectly, if the supply voltage for executing instructions is too low. Flash corruption can easily be avoided by following these design recommendations (one is sufficient): 1. If there is no need for a Boot Loader update in the system, program the Boot Loader Lock bits to prevent any Boot Loader software updates. 2. Keep the AVR RESET active (low) during periods of insufficient power supply voltage. This can be done by enabling the internal Brown-out Detector (BOD) if the operating voltage matches the detection level. If not, an external low VCC reset protection circuit can be used. If a reset occurs while a write operation is in progress, the write operation will be completed provided that the power supply voltage is sufficient. 3. Keep the AVR core in Power-down sleep mode during periods of low VCC. This will prevent the CPU from attempting to decode and execute instructions, effectively protecting the SPMCSR Register and thus the Flash from unintentional writes.
23.7.12
Programming Time for Flash when Using SPM The calibrated RC Oscillator is used to time Flash accesses. Table 23-7 shows the typical programming time for Flash accesses from the CPU. Table 23-7.
SPM Programming Time
Symbol Flash write (Page Erase, Page Write, and write Lock bits by SPM) Min Programming Time 3.7 ms Max Programming Time 4.5 ms
23.7.13
Simple Assembly Code Example for a Boot Loader
;-the routine writes one page of data from RAM to Flash ; the first data location in RAM is pointed to by the Y pointer ; the first data location in Flash is pointed to by the Z-pointer ;-error handling is not included ;-the routine must be placed inside the Boot space ; (at least the Do_spm sub routine). Only code inside NRWW section can ; be read during Self-Programming (Page Erase and Page Write). ;-registers used: r0, r1, temp1 (r16), temp2 (r17), looplo (r24), ; loophi (r25), spmcrval (r20) ; storing and restoring of registers is not included in the routine ; register usage can be optimized at the expense of code size ;-It is assumed that either the interrupt table is moved to the Boot ; loader section or that the interrupts are disabled. .equ PAGESIZEB = PAGESIZE*2 ;PAGESIZEB is page size in BYTES, not words .org SMALLBOOTSTART Write_page: ; Page Erase ldi spmcrval, (1<237
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; disable interrupts if enabled, store status in temp2, SREG cli ; check that no EEPROM write access is present Wait_ee: sbic EECR, EEPE rjmp Wait_ee ; SPM timed sequence out SPMCSR, spmcrval spm ; restore SREG (to enable interrupts if originally enabled) out SREG, temp2 ret
23.7.14
AT90USB82/162 Boot Loader Parameters In Table 23-8 through Table 23-10, the parameters used in the description of the Self-Programming are given. Table 23-8.
Boot Size Configuration() (16k)
Boot Reset Address (Start Boot Loader Section) 0x3E00 0x3C00 0x3800 0x3000 0x1E00 0x1C00 0x1800 0x1000 Boot Size (in bytes)
1 1 16K b 0 0 1 1 8Kb 0 0
1 0 1 0 1 0 1 0
512 bytes 1024 bytes 2048 bytes 4096 bytes 512 bytes 1024 bytes 2048 bytes 4096 bytes
4 8 16 32 4 8 16 32
0x0000 0x3DFF 0x0000 0x3BFF 0x0000 0x37FF 0x0000 0x2FFF 0x0000 0x1DFF 0x0000 0x1BFF 0x0000 0x17FF 0x0000 0x0FFF
0x3E00 0x3FFF 0x3C00 0x3FFF 0x3800 0x3FFF 0x3000 0x3FFF 0x1E00 0x1FFF 0x1C00 0x1FFF 0x1800 0x1FFF 0x1000 0x1FFF
0x3DFF 0x3BFF 0x37FF 0x2FFF 0x1DFF 0x1BFF 0x17FF 0x0FFF
(Page size = 64 words = 128 bytes)
End Application Section
Application Flash Section (byte address)
Boot Loader Flash Section (byte address)
BOOTSZ1
BOOTSZ0
DEVICE
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The different BOOTSZ Fuse configurations are shown in Figure 23-2.
Table 23-9.
Device 16K 8K Note:
Read-While-Write Limit(1)
Section Read-While-Write section (RWW) No Read-While-Write section (NRWW) Read-While-Write section (RWW) No Read-While-Write section (NRWW) Pages 96 32 32 32 Address 0x0000 - 0x2FFF 0x3000 - 0x3FFF 0x0000 - 0x0FFF 0x1000 - 0x1FFF
1. For details about these two section, see "NRWW - No Read-While-Write Section" on page 226 and "RWW - Read-While-Write Section" on page 226.
Table 23-10. Explanation of different variables used in Figure 23-4 and the mapping to the Zpointer
Variable PCMSB PAGEMSB 12 5 Corresponding Z-value Description(1) Most significant bit in the Program Counter. (The Program Counter is 13 bits PC[12:0]) Most significant bit which is used to address the words within one page (64 words in a page requires six bits PC [5:0]). Z13 Bit in Z-pointer that is mapped to PCMSB. Because Z0 is not used, the ZPCMSB equals PCMSB + 1. Bit in Z-pointer that is mapped to PCMSB. Because Z0 is not used, the ZPAGEMSB equals PAGEMSB + 1. Program Counter page address: Page select, for Page Erase and Page Write Program Counter word address: Word select, for filling temporary buffer (must be zero during Page Write operation)
ZPCMSB
ZPAGEMSB PCPAGE PCWORD Note: PC[12:6] PC[5:0]
Z6 Z13:Z7 Z6:Z1
1. Z0: should be zero for all SPM commands, byte select for the (E)LPM instruction.
See "Addressing the Flash During Self-Programming" on page 233 for details about the use of Z-pointer during Self-Programming.
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24. debugWIRE On-chip Debug System
24.1 Features
* * * * * * * * * *
Complete Program Flow Control Emulates All On-chip Functions, Both Digital and Analog, except RESET Pin Real-time Operation Symbolic Debugging Support (Both at C and Assembler Source Level, or for Other HLLs) Unlimited Number of Program Break Points (Using Software Break Points) Non-intrusive Operation Electrical Characteristics Identical to Real Device Automatic Configuration System High-Speed Operation Programming of Non-volatile Memories
24.2
Overview
The debugWIRE On-chip debug system uses a One-wire, bi-directional interface to control the program flow, execute AVR instructions in the CPU and to program the different non-volatile memories.
24.3
Physical Interface
When the debugWIRE Enable (DWEN) Fuse is programmed and Lock bits are unprogrammed, the debugWIRE system within the target device is activated. The RESET port pin is configured as a wire-AND (open-drain) bi-directional I/O pin and becomes the communication gateway between target and emulator.
Figure 24-1. The debugWIRE Setup
2.7 - 5.5
VCC
(See Note)
dW
dW(RESET)
GND
Figure 24-1 shows the schematic of a target MCU, with debugWIRE enabled, and the emulator connector. The system clock is not affected by debugWIRE and will always be the clock source selected by the CKSEL Fuses.
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When designing a system where debugWIRE will be used, the following observations must be made for correct operation: * Connecting the RESET pin directly to VCC will not work. * Any capacitors (or additionnal circuitry) connected to the RESET pin must be disconnected when using debugWire. * All external reset sources must be disconnected.
Note: some releases of JTAG Ice mkII firmware may require a pull-up resistor with a value between 8 and 14 kOhms when operating at 5V.
24.4
Software Break Points
debugWIRE supports Program memory Break Points by the AVR Break instruction. Setting a Break Point in AVR Studio(R) will insert a BREAK instruction in the Program memory. The instruction replaced by the BREAK instruction will be stored. When program execution is continued, the stored instruction will be executed before continuing from the Program memory. A break can be inserted manually by putting the BREAK instruction in the program. The Flash must be re-programmed each time a Break Point is changed. This is automatically handled by AVR Studio through the debugWIRE interface. The use of Break Points will therefore reduce the Flash Data retention. Devices used for debugging purposes should not be shipped to end customers.
24.5
Limitations of debugWIRE
The debugWIRE communication pin (dW) is physically located on the same pin as External Reset (RESET). An External Reset source is therefore not supported when the debugWIRE is enabled. The debugWIRE system accurately emulates all I/O functions when running at full speed, i.e., when the program in the CPU is running. When the CPU is stopped, care must be taken while accessing some of the I/O Registers via the debugger (AVR Studio). A programmed DWEN Fuse enables some parts of the clock system to be running in all sleep modes. This will increase the power consumption while in sleep. Thus, the DWEN Fuse should be disabled when debugWire is not used.
24.6
24.6.1
debugWIRE Related Register in I/O Memory
The following section describes the registers used with the debugWire.
debugWire Data Register - DWDR
Bit Read/Write Initial Value 7 R/W 0 6 R/W 0 5 R/W 0 4 R/W 0 3 R/W 0 2 R/W 0 1 R/W 0 0 DWDR R/W 0 DWDR[7:0]
The DWDR Register provides a communication channel from the running program in the MCU to the debugger. This register is only accessible by the debugWIRE and can therefore not be used as a general purpose register in the normal operations.
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25. Memory Programming
25.1 Program And Data Memory Lock Bits
The AT90USB82/162 provides six Lock bits which can be left unprogrammed ("1") or can be programmed ("0") to obtain the additional features listed in Table 25-2. The Lock bits can only be erased to "1" with the Chip Erase command.
Table 25-1.
Lock Bit Byte(1)
Bit No 7 6 Description - - Boot Lock bit Boot Lock bit Boot Lock bit Boot Lock bit Lock bit Lock bit Default Value 1 (unprogrammed) 1 (unprogrammed) 1 (unprogrammed) 0 (programmed) 1 (unprogrammed) 1 (unprogrammed) 0 (programmed) 0 (programmed)
Lock Bit Byte
BLB12 BLB11 BLB02 BLB01 LB2 LB1 Note:
5 4 3 2 1 0
1. "1" means unprogrammed, "0" means programmed
Table 25-2.
LB Mode 1 2
Lock Bit Protection Modes(1)(2)
Protection Type LB1 1 0 No memory lock features enabled. Further programming of the Flash and EEPROM is disabled in Parallel and Serial Programming mode. The Fuse bits are locked in both Serial and Parallel Programming mode.(1) Further programming and verification of the Flash and EEPROM is disabled in Parallel and Serial Programming mode. The Boot Lock bits and Fuse bits are locked in both Serial and Parallel Programming mode.(1) No restrictions for SPM or (E)LPM accessing the Application section. SPM is not allowed to write to the Application section. SPM is not allowed to write to the Application section, and (E)LPM executing from the Boot Loader section is not allowed to read from the Application section. If Interrupt Vectors are placed in the Boot Loader section, interrupts are disabled while executing from the Application section. (E)LPM executing from the Boot Loader section is not allowed to read from the Application section. If Interrupt Vectors are placed in the Boot Loader section, interrupts are disabled while executing from the Application section. LB2 1 1
Memory Lock Bits
3 BLB0 Mode 1 2
0 BLB02 1 1
0 BLB01 1 0
3
0
0
4
0
1
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Table 25-2.
BLB1 Mode 1 2
Lock Bit Protection Modes(1)(2) (Continued)
Protection Type BLB11 1 0 No restrictions for SPM or (E)LPM accessing the Boot Loader section. SPM is not allowed to write to the Boot Loader section. SPM is not allowed to write to the Boot Loader section, and (E)LPM executing from the Application section is not allowed to read from the Boot Loader section. If Interrupt Vectors are placed in the Application section, interrupts are disabled while executing from the Boot Loader section. (E)LPM executing from the Application section is not allowed to read from the Boot Loader section. If Interrupt Vectors are placed in the Application section, interrupts are disabled while executing from the Boot Loader section. BLB12 1 1
Memory Lock Bits
3
0
0
4 Notes:
0
1
1. Program the Fuse bits and Boot Lock bits before programming the LB1 and LB2. 2. "1" means unprogrammed, "0" means programmed
25.2
Fuse Bits
The AT90USB82/162 has four Fuse bytes. Table 25-3 - Table 25-5 describe briefly the functionality of all the fuses and how they are mapped into the Fuse bytes. Note that the fuses are read as logical zero, "0", if they are programmed.
Table 25-3.
- - - - HWBE BODLEVEL2 BODLEVEL1
Extended Fuse Byte
Bit No 7 6 5 4 3
(1) (1)
Fuse Low Byte
Description - - - - Hardware Boot Enable Brown-out Detector trigger level Brown-out Detector trigger level Brown-out Detector trigger level
Default Value : 0xF4 1 1 1 1 0 (programmed) 1 (unprogrammed) 0 (programmed) 0 (programmed)
2 1 0
BODLEVEL0(1) Note:
1. See Table 9-2 on page 49 for BODLEVEL Fuse decoding.
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Table 25-4.
Fuse High Byte
Bit No 7 6 5 4 3 2 1 0 Description Enable debugWIRE (and disable Reset capability Disable Reset (pin can be used as general purpose I/O) Enable Serial Program and Data Downloading Watchdog Timer always ON EEPROM memory is preserved through the Chip Erase Select Boot Size (see Table 25-6 for details) Select Boot Size (see Table 25-6 for details) Select Bootloader Address as Reset Vector Default Value : 0xD9 1 (unprogrammed, debugWIRE disabled) 1 (unprogrammed, Reset enabled) 0 (programmed, SPI prog. enabled) 1 (unprogrammed)(3) 1 (unprogrammed, EEPROM not preserved) 0 (programmed)(2) 0 (programmed)(2) 1 (unprogrammed, Reset vector @0x0000)
Fuse High Byte DWEN(4) RSTDSBL SPIEN(1) WDTON(3) EESAVE BOOTSZ1 BOOTSZ0 BOOTRST Note:
1. The SPIEN Fuse is not accessible in serial programming mode. 2. The default value of BOOTSZ1..0 results in maximum Boot Size. See Table 23-8 on page 239 for details. 3. See "Watchdog Timer Control Register - WDTCSR" on page 56 for details. 4. Never ship a product with the DWEN Fuse programmed regardless of the setting of Lock bits and RSTDSBL Fuse. A programmed DWEN Fuse enables some parts of the clock system to be running in all sleep modes. This may increase the power consumption.
Table 25-5.
CKDIV8 CKOUT SUT1 SUT0 CKSEL3 CKSEL2 CKSEL1 CKSEL0 Note:
(4)
Fuse Low Byte
Fuse Low Byte
(3)
Bit No 7 6 5 4 3 2 1 0
Description Divide clock by 8 Clock output Select start-up time Select start-up time Select Clock source Select Clock source Select Clock source Select Clock source
Default Value : 0x5E 0 (programmed) 1 (unprogrammed) 0 (programmed)(1) 1 (unprogrammed)(1) 1 (unprogrammed)(2) 1 (unprogrammed)(2) 1 (unprogrammed)(2) 0 (programmed)(2)
1. The default value of SUT1..0 results in maximum start-up time for the default clock source. See Table 9-1 on page 47 for details. 2. The default setting of CKSEL3..0 results in external Oscillator. See Table 6-1 on page 29 for details. 3. The CKOUT Fuse allow the system clock to be output on PORTC7. See "Clock Output Buffer" on page 34 for details. 4. See "System Clock Prescaler" on page 34 for details.
The status of the Fuse bits is not affected by Chip Erase. Note that the Fuse bits are locked if Lock bit1 (LB1) is programmed. Program the Fuse bits before programming the Lock bits.
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25.2.1
Latching of Fuses The fuse values are latched when the device enters programming mode and changes of the fuse values will have no effect until the part leaves Programming mode. This does not apply to the EESAVE Fuse which will take effect once it is programmed. The fuses are also latched on Power-up in Normal mode.
25.3
Signature Bytes
All Atmel microcontrollers have a three-byte signature code which identifies the device. This code can be read in both serial and parallel mode, also when the device is locked. The three bytes reside in a separate address space. AT90USB82/162 Signature Bytes: 1. 0x000: 0x1E (indicates manufactured by Atmel). 2. 0x001: 0x94 (indicates 16KB Flash memory). 3. 0x002: 0x82 (indicates AT90USB82/162 device).
25.4
Calibration Byte
The AT90USB82/162 has a byte calibration value for the internal RC Oscillator. This byte resides in the high byte of address 0x000 in the signature address space. During reset, this byte is automatically written into the OSCCAL Register to ensure correct frequency of the calibrated RC Oscillator.
25.5
Parallel Programming Parameters, Pin Mapping, and Commands
This section describes how to parallel program and verify Flash Program memory, EEPROM Data memory, Memory Lock bits, and Fuse bits in the AT90USB82/162. Pulses are assumed to be at least 250 ns unless otherwise noted.
25.5.1
Signal Names
In this section, some pins of the AT90USB82/162 are referenced by signal names describing their functionality during parallel programming, see Figure 25-1 and Table 25-6. Pins not described in the following table are referenced by pin names. The XA1/XA0 pins determine the action executed when the XTAL1 pin is given a positive pulse. The bit coding is shown in Table 25-9. When pulsing WR or OE, the command loaded determines the action executed. The different commands are shown in Table 25-10.
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Figure 25-1. Parallel Programming(1)
+5V RDY/BSY OE WR BS1 XA0 XA1 PAGEL +12 V BS2 PD1 PD2 PD3 PD4 PD5 PD6 PD7 RESET PC6 XTAL1 GND
PB7:0
VCC +5V AVCC DATA
Note:
1. Unused Pins should be left floating.
Table 25-6.
Pin Name Mapping
Pin Name PD1 PD2 PD3 PD4 PD5 PD6 PD7 PC6 PB7-0 I/O O I I I I I I I I/O Function 0: Device is busy programming, 1: Device is ready for new command. Output Enable (Active low). Write Pulse (Active low). Byte Select 1. XTAL Action Bit 0 XTAL Action Bit 1 Program Memory and EEPROM data Page Load. Byte Select 2. Bi-directional Data bus (Output when OE is low).
Signal Name in Programming Mode RDY/BSY OE WR BS1 XA0 XA1 PAGEL BS2 DATA
Table 25-7.
BS2 and BS1 Encoding
Flash / EEPROM Address Low Byte High Byte Extended High Byte Reserved Flash Data Loading / Reading Low Byte High Byte Reserved Reserved Fuse Programming Low Byte High Byte Extended Byte Reserved Reading Fuse and Lock Bits Fuse Low Byte Lockbits Extended Fuse Byte Fuse High Byte
BS2 0 0 1 1
BS1 0 1 0 1
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Table 25-8.
Pin Values Used to Enter Programming Mode
Pin PAGEL XA1 XA0 BS1 Symbol Prog_enable[3] Prog_enable[2] Prog_enable[1] Prog_enable[0] Value 0 0 0 0
Table 25-9.
XA1 0 0 1 1
XA1 and XA0 Encoding
XA0 0 1 0 1 Action when XTAL1 is Pulsed Load Flash or EEPROM Address (High or low address byte determined by BS2 and BS1). Load Data (High or Low data byte for Flash determined by BS1). Load Command No Action, Idle
Table 25-10. Command Byte Bit Encoding
Command Byte 1000 0000 0100 0000 0010 0000 0001 0000 0001 0001 0000 1000 0000 0100 0000 0010 0000 0011 Command Executed Chip Erase Write Fuse bits Write Lock bits Write Flash Write EEPROM Read Signature Bytes and Calibration byte Read Fuse and Lock bits Read Flash Read EEPROM
Table 25-11. No. of Words in a Page and No. of Pages in the Flash
Flash Size 4/8K words (8/16Kbytes) Page Size 64 words PCWORD PC[5:0] No. of Pages 128 PCPAGE PC[12:6] PCMSB 12
Table 25-12. No. of Bytes in a Page and No. of Pages in the EEPROM
EEPROM Size 512 bytes Page Size 4 bytes PCWORD EEA[1:0] No. of Pages 128 PCPAGE EEA[8:2] EEAMSB 8
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25.6
25.6.1
Parallel Programming
Enter Programming Mode The following algorithm puts the device in parallel programming mode:
1. Apply 4.5 - 5.5V between VCC and GND. 2. Set RESET to "0" and toggle XTAL1 at least six times. 3. Set the Prog_enable pins listed in Table 25-8 on page 248 to "0000" and wait at least 100 ns. 4. Apply 11.5 - 12.5V to RESET. Any activity on Prog_enable pins within 100 ns after +12V has been applied to RESET, will cause the device to fail entering programming mode. 5. Wait at least 50 s before sending a new command.
25.6.2
Considerations for Efficient Programming The loaded command and address are retained in the device during programming. For efficient programming, the following should be considered.
* The command needs only be loaded once when writing or reading multiple memory locations. * Skip writing the data value 0xFF, that is the contents of the entire EEPROM (unless the EESAVE Fuse is programmed) and Flash after a Chip Erase. * Address high byte needs only be loaded before programming or reading a new 256 word window in Flash or 256 byte EEPROM. This consideration also applies to Signature bytes reading.
25.6.3
Chip Erase
The Chip Erase will erase the Flash and EEPROM(1) memories plus Lock bits. The Lock bits are not reset until the program memory has been completely erased. The Fuse bits are not changed. A Chip Erase must be performed before the Flash and/or EEPROM are reprogrammed.
Note: 1. The EEPRPOM memory is preserved during Chip Erase if the EESAVE Fuse is programmed.
Load Command "Chip Erase" 1. Set XA1, XA0 to "10". This enables command loading. 2. Set BS1 to "0". 3. Set DATA to "1000 0000". This is the command for Chip Erase. 4. Give XTAL1 a positive pulse. This loads the command. 5. Give WR a negative pulse. This starts the Chip Erase. RDY/BSY goes low. 6. Wait until RDY/BSY goes high before loading a new command.
25.6.4
Programming the Flash The Flash is organized in pages, see Table 25-11 on page 248. When programming the Flash, the program data is latched into a page buffer. This allows one page of program data to be programmed simultaneously. The following procedure describes how to program the entire Flash memory:
A. Load Command "Write Flash"
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1. Set XA1, XA0 to "10". This enables command loading. 2. Set BS1 to "0". 3. Set DATA to "0001 0000". This is the command for Write Flash. 4. Give XTAL1 a positive pulse. This loads the command. B. Load Address Low byte (Address bits 7..0) 1. Set XA1, XA0 to "00". This enables address loading. 2. Set BS2, BS1 to "00". This selects the address low byte. 3. Set DATA = Address low byte (0x00 - 0xFF). 4. Give XTAL1 a positive pulse. This loads the address low byte. C. Load Data Low Byte 1. Set XA1, XA0 to "01". This enables data loading. 2. Set DATA = Data low byte (0x00 - 0xFF). 3. Give XTAL1 a positive pulse. This loads the data byte. D. Load Data High Byte 1. Set BS1 to "1". This selects high data byte. 2. Set XA1, XA0 to "01". This enables data loading. 3. Set DATA = Data high byte (0x00 - 0xFF). 4. Give XTAL1 a positive pulse. This loads the data byte. E. Latch Data 1. Set BS1 to "1". This selects high data byte. 2. Give PAGEL a positive pulse. This latches the data bytes. (See Figure 25-3 for signal waveforms) F. Repeat B through E until the entire buffer is filled or until all data within the page is loaded. While the lower bits in the address are mapped to words within the page, the higher bits address the pages within the FLASH. This is illustrated in Figure 25-2 on page 251. Note that if less than eight bits are required to address words in the page (pagesize < 256), the most significant bit(s) in the address low byte are used to address the page when performing a Page Write. G. Load Address High byte (Address bits15..8) 1. Set XA1, XA0 to "00". This enables address loading. 2. Set BS2, BS1 to "01". This selects the address high byte. 3. Set DATA = Address high byte (0x00 - 0xFF). 4. Give XTAL1 a positive pulse. This loads the address high byte. H. Load Address Extended High byte (Address bits 23..16) 1. Set XA1, XA0 to "00". This enables address loading. 2. Set BS2, BS1 to "10". This selects the address extended high byte. 3. Set DATA = Address extended high byte (0x00 - 0xFF). 4. Give XTAL1 a positive pulse. This loads the address high byte. I. Program Page 1. Set BS2, BS1 to "00" 2. Give WR a negative pulse. This starts programming of the entire page of data. RDY/BSY goes low.
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3. Wait until RDY/BSY goes high (See Figure 25-3 for signal waveforms). J. Repeat B through I until the entire Flash is programmed or until all data has been programmed. K. End Page Programming 1. 1. Set XA1, XA0 to "10". This enables command loading. 2. Set DATA to "0000 0000". This is the command for No Operation. 3. Give XTAL1 a positive pulse. This loads the command, and the internal write signals are reset.
Figure 25-2. Addressing the Flash Which is Organized in Pages(1)
PCMSB PROGRAM COUNTER
PCPAGE
PAGEMSB
PCWORD
PAGE ADDRESS WITHIN THE FLASH PROGRAM MEMORY
PAGE
WORD ADDRESS WITHIN A PAGE
PAGE INSTRUCTION WORD PCWORD[PAGEMSB:0]: 00 01 02
PAGEEND
Note:
1. PCPAGE and PCWORD are listed in Table 25-11 on page 248.
Figure 25-3. Programming the Flash Waveforms(1)
F A
DATA XA1 XA0 BS1 0x10
B
ADDR. LOW
C
DATA LOW
D
DATA HIGH
E
XX
B
ADDR. LOW
C
DATA LOW
D
DATA HIGH
E
XX
G
H
I
XX
ADDR. HIGH ADDR. EXT.H
BS2 XTAL1 WR RDY/BSY RESET +12V OE PAGEL
Note:
1. "XX" is don't care. The letters refer to the programming description above.
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25.6.5
Programming the EEPROM The EEPROM is organized in pages, see Table 25-12 on page 248. When programming the EEPROM, the program data is latched into a page buffer. This allows one page of data to be programmed simultaneously. The programming algorithm for the EEPROM data memory is as follows (refer to "Programming the Flash" on page 249 for details on Command, Address and Data loading):
1. A: Load Command "0001 0001". 2. G: Load Address High Byte (0x00 - 0xFF). 3. B: Load Address Low Byte (0x00 - 0xFF). 4. C: Load Data (0x00 - 0xFF). 5. E: Latch data (give PAGEL a positive pulse). K: Repeat 3 through 5 until the entire buffer is filled. L: Program EEPROM page 1. Set BS2, BS1 to "00". 2. Give WR a negative pulse. This starts programming of the EEPROM page. RDY/BSY goes low. 3. Wait until to RDY/BSY goes high before programming the next page (See Figure 25-4 for signal waveforms).
Figure 25-4. Programming the EEPROM Waveforms
K A
DATA XA1 XA0 BS1 XTAL1 WR RDY/BSY RESET +12V OE PAGEL BS2 0x11
G
ADDR. HIGH
B
ADDR. LOW
C
DATA
E
XX
B
ADDR. LOW
C
DATA
E
XX
L
25.6.6
Reading the Flash The algorithm for reading the Flash memory is as follows (refer to "Programming the Flash" on page 249 for details on Command and Address loading):
1. A: Load Command "0000 0010". 2. H: Load Address Extended Byte (0x00- 0xFF). 3. G: Load Address High Byte (0x00 - 0xFF). 4. B: Load Address Low Byte (0x00 - 0xFF). 5. Set OE to "0", and BS1 to "0". The Flash word low byte can now be read at DATA. 6. Set BS to "1". The Flash word high byte can now be read at DATA. 7. Set OE to "1".
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25.6.7 Reading the EEPROM The algorithm for reading the EEPROM memory is as follows (refer to "Programming the Flash" on page 249 for details on Command and Address loading):
1. A: Load Command "0000 0011". 2. G: Load Address High Byte (0x00 - 0xFF). 3. B: Load Address Low Byte (0x00 - 0xFF). 4. Set OE to "0", and BS1 to "0". The EEPROM Data byte can now be read at DATA. 5. Set OE to "1".
25.6.8
Programming the Fuse Low Bits The algorithm for programming the Fuse Low bits is as follows (refer to "Programming the Flash" on page 249 for details on Command and Data loading):
1. A: Load Command "0100 0000". 2. C: Load Data Low Byte. Bit n = "0" programs and bit n = "1" erases the Fuse bit. 3. Give WR a negative pulse and wait for RDY/BSY to go high.
25.6.9
Programming the Fuse High Bits The algorithm for programming the Fuse High bits is as follows (refer to "Programming the Flash" on page 249 for details on Command and Data loading):
1. A: Load Command "0100 0000". 2. C: Load Data Low Byte. Bit n = "0" programs and bit n = "1" erases the Fuse bit. 3. Set BS2, BS1 to "01". This selects high data byte. 4. Give WR a negative pulse and wait for RDY/BSY to go high. 5. Set BS2, BS1 to "00". This selects low data byte.
25.6.10
Programming the Extended Fuse Bits The algorithm for programming the Extended Fuse bits is as follows (refer to "Programming the Flash" on page 249 for details on Command and Data loading):
1. 1. A: Load Command "0100 0000". 2. 2. C: Load Data Low Byte. Bit n = "0" programs and bit n = "1" erases the Fuse bit. 3. 3. Set BS2, BS1 to "10". This selects extended data byte. 4. 4. Give WR a negative pulse and wait for RDY/BSY to go high. 5. 5. Set BS2, BS1 to "00". This selects low data byte.
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Figure 25-5. Programming the FUSES Waveforms
Write Fuse Low byte A
DATA
0x40
Write Fuse high byte A C
DATA XX
Write Extended Fuse byte A
0x40
C
DATA XX
C
DATA XX
0x40
XA1
XA0
BS1
BS2
XTAL1
WR
RDY/BSY
RESET +12V
OE
PAGEL
25.6.11
Programming the Lock Bits The algorithm for programming the Lock bits is as follows (refer to "Programming the Flash" on page 249 for details on Command and Data loading):
1. A: Load Command "0010 0000". 2. C: Load Data Low Byte. Bit n = "0" programs the Lock bit. If LB mode 3 is programmed (LB1 and LB2 is programmed), it is not possible to program the Boot Lock bits by any External Programming mode. 3. Give WR a negative pulse and wait for RDY/BSY to go high. The Lock bits can only be cleared by executing Chip Erase.
25.6.12
Reading the Fuse and Lock Bits The algorithm for reading the Fuse and Lock bits is as follows (refer to "Programming the Flash" on page 249 for details on Command loading):
1. A: Load Command "0000 0100". 2. Set OE to "0", and BS2, BS1 to "00". The status of the Fuse Low bits can now be read at DATA ("0" means programmed). 3. Set OE to "0", and BS2, BS1 to "11". The status of the Fuse High bits can now be read at DATA ("0" means programmed). 4. Set OE to "0", and BS2, BS1 to "10". The status of the Extended Fuse bits can now be read at DATA ("0" means programmed). 5. Set OE to "0", and BS2, BS1 to "01". The status of the Lock bits can now be read at DATA ("0" means programmed). 6. Set OE to "1".
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Figure 25-6. Mapping Between BS1, BS2 and the Fuse and Lock Bits During Read
Fuse Low Byte 0
0 Extended Fuse Byte BS2 Lock Bits 0 1 1 DATA
Fuse High Byte BS2
1
BS1
25.6.13
Reading the Signature Bytes The algorithm for reading the Signature bytes is as follows (refer to "Programming the Flash" on page 249 for details on Command and Address loading):
1. A: Load Command "0000 1000". 2. B: Load Address Low Byte (0x00 - 0x02). 3. Set OE to "0", and BS to "0". The selected Signature byte can now be read at DATA. 4. Set OE to "1".
25.6.14
Reading the Calibration Byte The algorithm for reading the Calibration byte is as follows (refer to "Programming the Flash" on page 249 for details on Command and Address loading):
1. A: Load Command "0000 1000". 2. B: Load Address Low Byte, 0x00. 3. Set OE to "0", and BS1 to "1". The Calibration byte can now be read at DATA. 4. Set OE to "1".
25.6.15
Parallel Programming Characteristics Figure 25-7. Parallel Programming Timing, Including some General Timing Requirements
tXLWL XTAL1 Data & Contol (DATA, XA0/1, BS1, BS2) PAGEL WR RDY/BSY tWLRH tXHXL tDVXH tBVPH tPHPL tPLWL tXLDX tPLBX t BVWL tWLWH
WLRL
tWLBX
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Figure 25-8. Parallel Programming Timing, Loading Sequence with Timing Requirements(1)
LOAD ADDRESS (LOW BYTE) LOAD DATA (LOW BYTE)
t XLXH
LOAD DATA LOAD DATA (HIGH BYTE)
tXLPH tPLXH
LOAD ADDRESS (LOW BYTE)
XTAL1
BS1
PAGEL
DATA
ADDR0 (Low Byte)
DATA (Low Byte)
DATA (High Byte)
ADDR1 (Low Byte)
XA0
XA1
Note:
1. The timing requirements shown in Figure 25-7 (i.e., tDVXH, tXHXL, and tXLDX) also apply to loading operation.
Figure 25-9. Parallel Programming Timing, Reading Sequence (within the Same Page) with Timing Requirements(1)
LOAD ADDRESS (LOW BYTE)
tXLOL
READ DATA (LOW BYTE)
READ DATA (HIGH BYTE)
LOAD ADDRESS (LOW BYTE)
XTAL1
tBVDV
BS1
tOLDV
OE
tOHDZ
DATA
ADDR0 (Low Byte)
DATA (Low Byte)
DATA (High Byte)
ADDR1 (Low Byte)
XA0
XA1
Note:
1. The timing requirements shown in Figure 25-7 (i.e., tDVXH, tXHXL, and tXLDX) also apply to reading operation.
Table 25-13. Parallel Programming Characteristics, VCC = 5V 10%
Symbol VPP IPP tDVXH tXLXH tXHXL tXLDX Parameter Programming Enable Voltage Programming Enable Current Data and Control Valid before XTAL1 High XTAL1 Low to XTAL1 High XTAL1 Pulse Width High Data and Control Hold after XTAL1 Low 67 200 150 67 Min 11.5 Typ Max 12.5 250 Units V A ns ns ns ns
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Table 25-13. Parallel Programming Characteristics, VCC = 5V 10% (Continued)
Symbol tXLWL tXLPH tPLXH tBVPH tPHPL tPLBX tWLBX tPLWL tBVWL tWLWH tWLRL tWLRH tWLRH_CE tXLOL tBVDV tOLDV tOHDZ Notes: 1. 2. Parameter XTAL1 Low to WR Low XTAL1 Low to PAGEL high PAGEL low to XTAL1 high BS1 Valid before PAGEL High PAGEL Pulse Width High BS1 Hold after PAGEL Low BS2/1 Hold after WR Low PAGEL Low to WR Low BS2/1 Valid to WR Low WR Pulse Width Low WR Low to RDY/BSY Low WR Low to RDY/BSY High(1) WR Low to RDY/BSY High for Chip Erase XTAL1 Low to OE Low BS1 Valid to DATA valid OE Low to DATA Valid OE High to DATA Tri-stated
(2)
Min 0 0 150 67 150 67 67 67 67 150 0 3.7 7.5 0 0
Typ
Max
Units ns ns ns ns ns ns ns ns ns ns
1 4.5 9 250 250 250
s ms ms ns ns ns ns
tWLRH is valid for the Write Flash, Write EEPROM, Write Fuse bits and Write Lock bits commands. tWLRH_CE is valid for the Chip Erase command.
25.7
Serial Downloading
Both the Flash and EEPROM memory arrays can be programmed using a serial programming bus while RESET is pulled to GND. The serial programming interface consists of pins SCK, PDI (input) and PDO (output). After RESET is set low, the Programming Enable instruction needs to be executed first before program/erase operations can be executed. NOTE, in Table 25-14 on page 257, the pin mapping for serial programming is listed. Not all packages use the SPI pins dedicated for the internal Serial Peripheral Interface - SPI.
25.8
Serial Programming Pin Mapping
Table 25-14. Pin Mapping Serial Programming
Symbol PDI PDO SCK Pins PB2 PB3 PB1 I/O I O I Description Serial Data in Serial Data out Serial Clock
Figure 25-10. Serial Programming and Verify(1)
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+1.8 - 5.5V VCC +1.8 - 5.5V(2) PDI PDO SCK XTAL1 AVCC
RESET
GND
Notes:
1. If the device is clocked by the internal Oscillator, it is no need to connect a clock source to the XTAL1 pin. 2. VCC - 0.3V < AVCC < VCC + 0.3V, however, AVCC should always be within 1.8 - 5.5V
When programming the EEPROM, an auto-erase cycle is built into the self-timed programming operation (in the Serial mode ONLY) and there is no need to first execute the Chip Erase instruction. The Chip Erase operation turns the content of every memory location in both the Program and EEPROM arrays into 0xFF. Depending on CKSEL Fuses, a valid clock must be present. The minimum low and high periods for the serial clock (SCK) input are defined as follows: Low: > 2 CPU clock cycles for fck < 12 MHz, 3 CPU clock cycles for fck >= 12 MHz High: > 2 CPU clock cycles for fck < 12 MHz, 3 CPU clock cycles for fck >= 12 MHz
25.8.1
Serial Programming Algorithm When writing serial data to the AT90USB82/162, data is clocked on the rising edge of SCK.
When reading data from the AT90USB82/162, data is clocked on the falling edge of SCK. See Figure 25-11 for timing details. To program and verify the AT90USB82/162 in the serial programming mode, the following sequence is recommended (See four byte instruction formats in Table 25-16): 1. Power-up sequence: Apply power between VCC and GND while RESET and SCK are set to "0". In some systems, the programmer can not guarantee that SCK is held low during power-up. In this case, RESET must be given a positive pulse of at least two CPU clock cycles duration after SCK has been set to "0". 2. Wait for at least 20 ms and enable serial programming by sending the Programming Enable serial instruction to pin PDI. 3. The serial programming instructions will not work if the communication is out of synchronization. When in sync. the second byte (0x53), will echo back when issuing the third byte of the Programming Enable instruction. Whether the echo is correct or not, all four bytes of the instruction must be transmitted. If the 0x53 did not echo back, give RESET a positive pulse and issue a new Programming Enable command. 4. The Flash is programmed one page at a time. The memory page is loaded one byte at a time by supplying the 7 LSB of the address and data together with the Load Program
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Memory Page instruction. To ensure correct loading of the page, the data low byte must be loaded before data high byte is applied for a given address. The Program Memory Page is stored by loading the Write Program Memory Page instruction with the address lines 15..8. Before issuing this command, make sure the instruction Load Extended Address Byte has been used to define the MSB of the address. The extended address byte is stored until the command is re-issued, i.e., the command needs only to be issued for the first page, since the memory size is not larger than 64KWord. If polling (RDY/BSY) is not used, the user must wait at least tWD_FLASH before issuing the next page. (See Table 25-15.) Accessing the serial programming interface before the Flash write operation completes can result in incorrect programming. 5. The EEPROM array is programmed one byte at a time by supplying the address and data together with the appropriate Write instruction. An EEPROM memory location is first automatically erased before new data is written. If polling is not used, the user must wait at least tWD_EEPROM before issuing the next byte. (See Table 25-15.) In a chip erased device, no 0xFFs in the data file(s) need to be programmed. 6. Any memory location can be verified by using the Read instruction which returns the content at the selected address at serial output PDO. When reading the Flash memory, use the instruction Load Extended Address Byte to define the upper address byte, which is not included in the Read Program Memory instruction. The extended address byte is stored until the command is re-issued, i.e., the command needs only to be issued for the first page, since the memory size is not larger than 64KWord. 7. At the end of the programming session, RESET can be set high to commence normal operation. 8. Power-off sequence (if needed): Set RESET to "1". Turn VCC power off.
Table 25-15. Minimum Wait Delay Before Writing the Next Flash or EEPROM Location
Symbol tWD_FLASH tWD_EEPROM tWD_ERASE Minimum Wait Delay 4.5 ms 9.0 ms 9.0 ms
Figure 25-11. Serial Programming Waveforms
SERIAL DATA INPUT (MOSI) SERIAL DATA OUTPUT (MISO) SERIAL CLOCK INPUT (SCK)
SAMPLE
MSB
LSB
MSB
LSB
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Table 25-16. Serial Programming Instruction Set
Instruction Format Instruction Programming Enable Chip Erase Load Extended Address Byte 0010 H000 Read Program Memory 0100 H000 Load Program Memory Page xxxx xxxx xxbb bbbb iiii iiii aaaa aaaa bbbb bbbb oooo oooo Byte 1 1010 1100 1010 1100 0100 1101 Byte 2 0101 0011 100x xxxx 0000 0000 Byte 3 xxxx xxxx xxxx xxxx cccc cccc Byte4 xxxx xxxx xxxx xxxx xxxx xxxx Operation Enable Serial Programming after RESET goes low. Chip Erase EEPROM and Flash. Defines Extended Address Byte for Read Program Memory and Write Program Memory Page. Read H (high or low) data o from Program memory at word address c:a:b. Write H (high or low) data i to Program Memory page at word address b. Data low byte must be loaded before Data high byte is applied within the same address. Write Program Memory Page at address c:a:b. Read data o from EEPROM memory at address a:b. Write data i to EEPROM memory at address a:b. Load data i to EEPROM memory page buffer. After data is loaded, program EEPROM page. Write EEPROM page at address a:b. Read Lock bits. "0" = programmed, "1" = unprogrammed. See Table 25-1 on page 243 for details. Write Lock bits. Set bits = "0" to program Lock bits. See Table 25-1 on page 243 for details. Read Signature Byte o at address b. Set bits = "0" to program, "1" to unprogram. Set bits = "0" to program, "1" to unprogram. Set bits = "0" to program, "1" to unprogram. See Table 25-3 on page 244 for details. Read Fuse bits. "0" = programmed, "1" = unprogrammed. Read Fuse High bits. "0" = programmed, "1" = unprogrammed.
Write Program Memory Page Read EEPROM Memory Write EEPROM Memory Load EEPROM Memory Page (page access) Write EEPROM Memory Page (page access) Read Lock bits
0100 1100 1010 0000 1100 0000 1100 0001
aaaa aaaa 0000 aaaa 0000 aaaa 0000 0000
bbxx xxxx bbbb bbbb bbbb bbbb 0000 00bb
xxxx xxxx oooo oooo iiii iiii iiii iiii
1100 0010 0101 1000
0000 aaaa 0000 0000
bbbb bb00 xxxx xxxx
xxxx xxxx xxoo oooo
1010 1100 Write Lock bits Read Signature Byte Write Fuse bits Write Fuse High bits Write Extended Fuse Bits Read Fuse bits Read Fuse High bits 0101 0000 0101 1000 0011 0000 1010 1100 1010 1100 1010 1100
111x xxxx
xxxx xxxx
11ii iiii
000x xxxx 1010 0000 1010 1000 1010 0100
xxxx xxbb xxxx xxxx xxxx xxxx xxxx xxxx
oooo oooo iiii iiii iiii iiii iiii iiii
0000 0000 0000 1000
xxxx xxxx xxxx xxxx
oooo oooo oooo oooo
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Table 25-16. Serial Programming Instruction Set (Continued)
Instruction Format Instruction Read Extended Fuse Bits Read Calibration Byte Poll RDY/BSY Note: 0011 1000 1111 0000 000x xxxx 0000 0000 0000 0000 xxxx xxxx oooo oooo xxxx xxxo Byte 1 0101 0000 Byte 2 0000 1000 Byte 3 xxxx xxxx Byte4 oooo oooo Operation Read Extended Fuse bits. "0" = programmed, "1" = unprogrammed. See Table 25-3 on page 244 for details. Read Calibration Byte If o = "1", a programming operation is still busy. Wait until this bit returns to "0" before applying another command.
a = address high bits, b = address low bits, c = address extended bits, H = 0 - Low byte, 1 - High Byte, o = data out, i = data in, x = don't care
25.8.2
Serial Programming Characteristics For characteristics of the Serial Programming module see "SPI Timing Characteristics" on page 265.
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26. Electrical Characteristics
26.1 Absolute Maximum Ratings*
*NOTICE: Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Operating Temperature....................................-55C to +125C Storage Temperature ..................................... -65C to +150C Voltage on any Pin except RESET & UVcc with respect to Ground(7) .............................-0.5V to VCC+0.5V Voltage on RESET with respect to Ground......-0.5V to +13.0V Voltage on UVcc with respect to Ground ...........-0.5V to +6.0V Maximum Operating Voltage ............................................ 6.0V DC Current per I/O Pin ............................................... 40.0 mA DC Current VCC and GND Pins................................ 200.0 mA
26.2
DC Characteristics
Parameter Input Low Voltage, Standard IOs(8) Input Low Voltage, XTAL1 pin Input Low Voltage, RESET pin Input Low Voltage, MOSI/MISO pins Input Low Voltage, PS2 pins Input High Voltage, Standard IOs(8) Input High Voltage, XTAL1 pin Input High Voltage, RESET pin Input High Voltage, MOSI/MISO pins Input High Voltage, PS2 pins Output Low Voltage(3), Standard IOs(8), MOSI/MISO pins Condition VCC = 2.7V - 5.5V VCC = 2.7V - 5.5V VCC = 2.7V - 5.5V VCC = 2.7V - 5.5V VCC = 4.5V - 5.5V VCC = 2.7V - 5.5V VCC = 2.7V - 5.5V VCC = 2.7V - 5.5V VCC = 2.7V - 5.5V VCC = 4.5V - 5.5V IOL = 10mA, VCC = 5V IOL = 5mA, VCC = 3V Min.(5) -0.5 -0.5 -0.5 -0.5 -0.5 0.6VCC(2) 0.7VCC(2) 0.9VCC(2) 2 2.4 Typ. Max.(5) 0.2VCC(1) 0.1VCC(1) 0.1VCC(1) 0.8 0.7 VCC + 0.5 VCC + 0.5 VCC + 0.5 VCC + 0.5 VCC + 0.5 0.7 0.5 Units V V V V V V V V V V V
TA = -40C to 85C, VCC = 2.7V to 5.5V (unless otherwise noted)
Symbol VIL VIL1 VIL2 VIL3 VIL4 VIH VIH1 VIH2 VIH3 VIH4 VOL
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TA = -40C to 85C, VCC = 2.7V to 5.5V (unless otherwise noted) (Continued)
Symbol VOL1 VOH IIL IIH RRST RPU RPUDP RPUPS2 Parameter Output Low Voltage, PS2 pins Output High Voltage(4), Standard IOs(8), MOSI/MISO pins Input Leakage Current I/O Pin Input Leakage Current I/O Pin Reset Pull-up Resistor I/O Pin Pull-up Resistor USD D+ Internal Pull-Up PS2 Pull-up Resistor VCC = 5V Active 8MHz, VCC = 3V Power Supply Current(6) Active 16MHz, VCC = 5V Idle 8MHz, VCC = 3V Idle 16MHz, VCC = 5V WDT disabled, Regulator Disabled,VCC = 3V ICC Power-down mode WDT enabled, Regulator Disabled,VCC = 3V WDT, BOD, Regulator Enabled, Vcc = 5V WDT, BOD Enabled, Regulator Disabled, Vcc = 3V WDT, BOD, Regulator Enabled, Vcc = 5V VACIO IACLK tACID Rusb Vreg Note: Analog Comparator Input Offset Voltage Analog Comparator Input Leakage Current Analog Comparator Propagation Delay USB Series resistor (external) Vcc 4.0V, I100mA, 3.0 CUCAP=1F20% 1. "Max" means the highest value where the pin is guaranteed to be read as low Regulator Output Voltage VCC = 5V Vin = VCC/2 VCC = 5V Vin = VCC/2 VCC = 2.7V VCC = 4.0V -50 750 500 225% 3.3 3.6 Condition IOL = 5mA, VCC = 4.5 - 5.5V IOH = -20mA, VCC = 5V IOH = -10mA, VCC = 3V VCC = 5.5V, pin low (absolute value) VCC = 5.5V, pin high (absolute value) 30 20 900 3.2 4.7 7 13.5 3.5 4 5 10 41 70 120 <10 4.5 10 15 65 100 150 40 50 4.2 2.3 1 1 60 50 1500 6.5 8.5 25 Min.(5) Typ. Max.(5) 0.7 Units V V A A k k k mA mA mA mA A A A A A mV nA ns V
Standby mode
2. "Min" means the lowest value where the pin is guaranteed to be read as high 3. Although each I/O port can sink more than the test conditions (20mA at VCC = 5V, 10mA at VCC = 3V) under steady state conditions (non-transient), the following must be observed: 1.)The sum of all IOL, for ports B0-B7, C0-C7, D0-D7 should not exceed 150 mA.
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4.
5. 6. 7. 8.
If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test condition. Although each I/O port can source more than the test conditions (20mA at VCC = 5V, 10mA at VCC = 3V) under steady state conditions (non-transient), the following must be observed: 1.)The sum of all IOL, for ports B0-B7, C0-C7, D0-D7 should not exceed 150 mA. If IOH exceeds the test condition, VOH may exceed the related specification. Pins are not guaranteed to source current greater than the listed test condition. All DC Characteristics contained in this datasheet are based on simulation and characterization of other AVR microcontrollers manufactured in the same process technology. These values are preliminary values representing design targets, and will be updated after characterization of actual silicon Values with "Power Reduction Register 1 - PRR1" disabled (0x00). As specified in the USB Electrical chapter, the D+/D- pads can withstand voltages down to -1V applied through a 39 resistor (in series with the external 22 resistor). All IOs Except XTAL1, MOSI, MISO, PS2 and Reset pins
26.3
External Clock Drive Waveforms
Figure 26-1. External Clock Drive Waveforms
V IH1 V IL1
26.4
External Clock Drive
Table 26-1.
Symbol 1/tCLCL tCLCL tCHCX tCLCX tCLCH tCHCL
External Clock Drive
VCC=2.7-5.5V Parameter Oscillator Frequency Clock Period High Time Low Time Rise Time Fall Time Change in period from one clock cycle to the next Min. 0 125 50 50 1.6 1.6 2 Max. 8 VCC=4.5-5.5V Min. 0 62.5 25 25 0.5 0.5 2 Max. 16 Units MHz ns ns ns s s %
tCLCL
Note:
All DC Characteristics contained in this datasheet are based on simulation and characterization of other AVR microcontrollers manufactured in the same process technology. These values are preliminary values representing design targets, and will be updated after characterization of actual silicon.
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26.5 Maximum speed vs. VCC
Maximum frequency is depending on VCC. As shown in Figure 26-2, the Maximum Frequency vs. VCC curve is linear between 2.7V < VCC < 4.5V.
Figure 26-2. Maximum Frequency vs. VCC, AT90USB82/162
16 MHz
8 MHz
Safe Operating Area
2.7V
4.5V
5.5V
26.6
SPI Timing Characteristics
See Figure 26-3 and Figure 26-3 for details.
Table 26-2.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
SPI Timing Parameters
Description SCK period SCK high/low Rise/Fall time Setup Hold Out to SCK SCK to out Mode Master Master Master Master Master Master Master Master Slave Slave Slave Slave Slave Slave Slave Slave Slave Slave 20 20 10 10 tck 15 4 * tck 2 * tck TBD Min Typ See Table 16-4 50% duty cycle TBD 10 10 0.5 * tsck 10 10 15 ns Max
SCK to out high SS low to out SCK period SCK high/low(1) Rise/Fall time Setup Hold SCK to out SCK to SS high SS high to tri-state SS low to SCK
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Note:
1. In SPI Programming mode the minimum SCK high/low period is: - 2 tCLCL for fCK < 12 MHz - 3 tCLCL for fCK > 12 MHz
Figure 26-3. SPI Interface Timing Requirements (Master Mode)
SS
6 1
SCK (CPOL = 0) SCK (CPOL = 1) MISO (Data Input) MOSI (Data Output)
2
2
4 MSB
5 ... 7 MSB ... LSB LSB
3
8
Table 26-3.
SPI Interface Timing Requirements (Slave Mode)
SS
9 10 16
SCK (CPOL = 0) SCK (CPOL = 1) MOSI (Data Input) MISO (Data Output)
11
11
13
14 MSB 15 MSB ... LSB ... LSB
12
17 X
26.7
Hardware Boot EntranceTiming Characteristics
Figure 26-4. Hardware Boot Timing Requirements
RESET
tSHRH
ALE/HWB
tHHRH
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Table 26-4.
Symbol
tSHRH
Hardware Boot Timings
Parameter HWB low Setup before Reset High HWB low Hold after Reset High
Min Max
0
StartUpTime(SUT) + Time Out Delay(TOUT)
tHHRH
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27. AT90USB82/162 Typical Characteristics - Preliminary Data
The following charts show typical behavior. These figures are not tested during manufacturing. All current consumption measurements are performed with all I/O pins configured as inputs and with internal pull-ups enabled. A sine wave generator with rail-to-rail output is used as clock source. All Active- and Idle current consumption measurements are done with all bits in the PRR registers set and thus, the corresponding I/O modules are turned off. Also the Analog Comparator is disabled during these measurements. The power consumption in Power-down mode is independent of clock selection. The current consumption is a function of several factors such as: operating voltage, operating frequency, loading of I/O pins, switching rate of I/O pins, code executed and ambient temperature. The dominating factors are operating voltage and frequency. The current drawn from capacitive loaded pins may be estimated (for one pin) as CL*VCC*f where CL = load capacitance, VCC = operating voltage and f = average switching frequency of I/O pin. The parts are characterized at frequencies higher than test limits. Parts are not guaranteed to function properly at frequencies higher than the ordering code indicates. The difference between current consumption in Power-down mode with Watchdog Timer enabled and Power-down mode with Watchdog Timer disabled represents the differential current drawn by the Watchdog Timer.
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27.1 Input Voltage Levels
Figure 27-1. Input Low Voltage vs. Vcc, all I/Os excluding DP/DM and MOSI/MISO
2.5
2
Threshold (V)
1.5
1
0.5
0 2 2.5 3 3.5 V CC (V) 4 4.5 5 5.5
Figure 27-2. Input High Voltage vs. Vcc, all I/Os excluding DP/DM and MOSI/MISO
2.5
2
Threshold (V)
1.5
1
0.5
0 2.5 3 3.5 4 V CC (V) 4.5 5 5.5
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Figure 27-3. Input Low Voltage vs. Vcc for MOSI/MISO I/Os
2.5
2
Threshold (V)
1.5
85C 25C -40C
1
0.5
0 2.5 3 3.5 4 V CC (V) 4.5 5 5.5
Figure 27-4. Input High Voltage vs. Vcc, MOSI/MISO I/Os
2.5 2.5
2 2
Threshold (V) Threshold (V)
1.5 1.5
85C 85 25C 25 -40C -40
1 1
0.5 0.5
0 0
2.5 2.5
3 3
3.5 3.5
4 4 V CC (V) V CC (V)
4.5 4.5
5 5
5.5 5.5
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27.2 Output Voltage Levels
Figure 27-5. Output Low Voltage vs. Output Current, all I/Os excluding DP/DM, Vcc=3V
1 0.9 0.8 0.7 0.6 V OL (V) 0.5 0.4 0.3 0.2 0.1 0 0 5 10 IOL (mA) 15 20 25
85 25 -40
Figure 27-6. Output Low Voltage vs. Output Current, all I/Os excluding DP/DM, Vcc=5V
0.7 0.6 0.5 0.4 V OL (V) 0.3 0.2 0.1 0 0 -0.1 IOL (mA) 5 10 15 20 25
85 25 -40
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Figure 27-7. Output Low Voltage vs. Output Current, PS2 I/Os, Vcc=5V
1.2 1.2 1 1
0.8 0.8 V OL (V) V OL (V) 0.6 0.6 0.4 0.4 0.2 0.2 0 0 0 -0.2
85C 85C 25C 25C -40C -40C
5 0 2 4 6
10 8 10 IOL (mA) IOL (mA)
15 12 14
20 16 18
25 20
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Figure 27-8. Output High Voltage vs. Output Current, all I/Os excluding DP/DM, Vcc=3V
3.5 3 2.5 2 1.5 1 0.5 0 0 5 10 IOH (mA) 15 20 25
85 25 -40
V OH (V)
Figure 27-9. Output High Voltage vs. Output Current, all I/Os excluding DP/DM, Vcc=5V
5 4.9 4.8 4.7 V OH (V) 4.6 4.5 4.4 4.3 4.2 0 5 10 IOH (mA) 15 20 25
85 25 -40
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27.3
I/O Pull-up Current
Figure 27-10. Standard I/O Pull-Up Current vs. Pin Voltage, Vcc=5V
140 140 120 120 100 100 IOP (uA) IOP (uA) 80 80 60 60 40 40 20 20 0 0 -20 0 0
85 25 -40
1
1
2
2 V OP (V) V OP (V)
3
3
4
4
5
5
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27.4 Power-down Supply Current
Figure 27-11. Power-down Supply Current vs. Vcc, with BOD Disabled, WDT Disabled, Regulator Disabled
20 18 16 14 12 ICC (uA) 10 8 6 4 2 0 2 2.5 3 3.5 4 V CC (V) 4.5 5 5.5 6
85 25
Figure 27-12. Power-down Supply Current vs. Vcc, with BOD Disabled, WDT Enabled, Regulator Disabled
50 45 40 35 30 ICC (uA) 25 20 15 10 5 0 2 2.5 3 3.5 4 V CC (V) 4.5 5 5.5 6 6.5
85 25
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Figure 27-13. Power-down Supply Current vs. Vcc, with BOD Enabled, Watchdog Disabled
70 60 50 ICC (uA) 40 30 20 10 0 3 3.5 4 V CC (V) 4.5 5 5.5
85C 25C
Figure 27-14. Power-down Supply Current vs. Vcc, with BOD Enabled, WDT Enabled, Regulator Disabled
WATCHDOG TIMER ENABLED, BODEN 100 90 80 70 60
ICC (uA) 70 60 50 40 30 20 10 0 3 3.5 4 4.5 V CC (V) 5 5.5
85 25
ICC (uA)
50 40 30 20 10 0 3
3.5
4
4.5 V CC (V)
5
5.5
6
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Figure 27-15. Power-down Supply Current vs. Vcc, with BOD Enabled, Regulator Enabled
100 90 80 70
ICC (uA)
75 65 55 45 35 25 15 5 -5 2 2.5 3 3.5 4 V CC 4.5 (V) 4.5 5 5.5 6
60 ICC (uA) 50 40 30 20 10 0 2
85 25 -40
2.5
3
3.5 V
4 (V)
5
5.5
6
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27.5
Idle Supply Current
Figure 27-16. Idle Supply Current vs. Frequency and Vcc, T=25C, Regulator Disabled (below 4V)
6
5
4 ICC (mA)
5.5 5 4.5 4 3.3
3
2
1
0 0 2 4 6 8 Frequency (MHz) 10 12 14 16
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27.6 Active Supply Current
Figure 27-17. Active Supply Current vs Frequency and Vcc, T=25C
20 18 16 14 12 ICC (mA) 10 8 6 4 2 0 0 2 4 6 8 Frequency (MHz) 10 12 14 16
5.5 5 4.5 3.6 2.7
27.7
Reset Supply Current
Figure 27-18. Reset Supply Current vs Frequency and Vcc
12 10 8 ICC (mA) 6 4 2 0 4 6 8 10 Frequency (MHz) 12 14 16
5.5 5 4.5 3.3 2.7
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Figure 27-19. Reset Pull-Up Current vs. Pin Voltage, Vcc=5V
120
100
80 IRESET (uA)
85C
60
-40C
40
20
0 0 1 2 3 V RESET (V) 4 5 6
27.8
Bandgap Voltage
Figure 27-20. Bandgap voltage vs. Vcc, vs. Temperature
1.15 1.14 1.13 Bandgap Voltage (V) 1.12 1.11 1.1 1.09 1.08 1.07 1.06 1.05 2 2.5 3 3.5 Vcc (V) 4 4.5 5 5.5
85 25 -40
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27.9 USB Regulator
Figure 27-21. USB Regulator Output Voltage vs. Input Voltage, No Load
3.4 3.4 3.3 3.3 3.2 3.2 Current (V) Output Volage(V) 3.1 3.1 3 3 2.9 2.9 2.8 2.8 2.7 2.7 3 3 3.5 3.5 4 4 4.5 4.5 Voltage (V) Voltage (V) 5 5 5.5 5.5 6 6
85C 85C -40C -40C
Figure 27-22. USB Regulator Output Voltage vs. Input Voltage, Load=75 Ohms
3.4 3.4 3.23.2 33 Current (V) Voltage (V) 2.82.8 2.62.6 2.42.4 2.22.2 22 33
85 85 25 25 -40 -40
3.5 3.5
44
4.5 4.5 Voltage (V) Voltage (V)
55
5.5 5.5
6 6
Note:
The 75 Ohms load is equivalent to the maximum average consumption of the USB peripheral in operation (full bus load)
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27.10 Power-On Reset
Figure 27-23. Power-On Reset Level vs. Temperature
1.7 1.6 1.5 POR Voltage (V) 1.4 1.3 1.2 1.1 1 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 Temperature
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27.11 BOD Levels
Figure 27-24. BOD Voltage (2.7V level) vs. Temperature
2.8 2.79 2.78 2.77 Threshold (V) 2.76 2.75 2.74 2.73 2.72 2.71 2.7 2.69 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100
Vcc Rise Vcc Fall
Temperature (C)
Figure 27-25. BOD Voltage (2.9V level) vs. Temperature
3
2.98
2.96 Threshold (V)
V c c Ris e
2.94
V c c Fall
2.92
2.9
2.88 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 Temperature (C)
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Figure 27-26. BOD Voltage (3.0V level) vs. Temperature
3.12 3.1 3.08 Threshold (V) 3.06 3.04 3.02 3 2.98 -50
Vcc Rise Vcc Fall
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
Temperature (C)
Figure 27-27. BOD Voltage (3.5V level) vs. TemperatureBOD Voltage (3.0V level) vs. Temperature
3.12 3.1 3.08 Threshold (V) 3.06 3.04 3.02 3 2.98 -50
Vcc Rise Vcc Fall
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
Temperature (C)
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Figure 27-28. BOD Voltage (3.6V level) vs. Temperature
3.58 3.69 3.57 3.68 3.56 3.67 3.55 3.66 Threshold (V) Threshold (V) 3.65 3.54 3.64 3.53 3.63 3.52 3.62 3.51 3.61 3.5 3.6 3.49 3.59 3.48 3.58 -50 -40 -30 -20 -10 -50 -40 -30 -20 -10
Vcc Rise Vcc Rise Vcc Fall Vcc Fall
0
0
10 20 30 40 10 20 30 40 Temperature (C) Temperature (C)
50 50
60 60
70 70
80 80
90 100 90 100
Figure 27-29. BOD Voltage (4.0V level) vs. Temperature
3.58 3.69 4.1 3.57 3.68 4.08 3.56 3.67 3.55 3.66 4.06 3.65 3.54 3.64 3.53 4.04 3.63 3.52 3.62 4.02 3.51 3.61 3.5 3.64 3.49 3.59 3.48 3.58 3.98 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 -50 00 10 20 30 40 50 60 70 80 90 -50 -40 -40 -30 -30 -20 -20 -10 -10 10 20 30 40 50 60 70 80 90 100 100 Temperature (C) Temperature (C) Temperature (C)
Threshold (V) Threshold (V) Threshold (V)
Vcc Rise Vcc Rise Vcc Rise Vcc Fall Vcc Fall Vcc Fall
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Figure 27-30. BOD Voltage (4.3V level) vs. Temperature
3.58 3.69 4.1 4.42 3.57 3.68 4.4 4.08 3.56 3.67 3.55 3.66 4.38 4.06 3.65 3.54 4.36 3.64 3.53 4.04 3.63 4.34 3.52 3.62 4.02 3.51 4.32 3.61 3.5 3.64 3.49 4.3 3.59 3.48 3.58 3.98 4.28 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 -50 00 10 -50 -40 -40 -30 -30 -20 -20 -10 -10 10 20 30 40 50 60 70 80 90 100 100 -50 -40 -30 -20 -10 0 10 20 20 30 30 40 40 50 50 60 60 70 70 80 80 90 90 100 Temperature (C) Temperature (C) Temperature (C) Temperature (C)
Threshold (V) Threshold (V) Threshold (V)
Vcc Rise Vcc Rise Vcc Rise Vcc Rise Vcc Fall Vcc Fall Vcc Fall Vcc Fall
27.12 Watchdog Timer Frequency
Figure 27-31. WDT Oscillator Frequency vs. Vcc
128 126 124 FRC (kHz) 122 120 118 116 114 2 2.5 3 3.5 V CC (V) 4 4.5 5 5.5
85 25 -40
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27.13 Internal RC Oscillator Frequency
Figure 27-32. RC Oscillator Frequency vs. OSCCAL, T=25C
20
15 FRC (MHz)
10
5
0 -1 15 31 47 63 79 95 111 127 143 159 175 191 207 223 239 255 OSCCAL (X1)
Figure 27-33. RC Oscillator Frequency vs. Vcc
8.7 8.6 8.5 8.4 FRC (MHz) 8.3 8.2 8.1 8 7.9 7.8 7.7 2 2.5 3 3.5 V CC (V) 4 4.5 5 5.5
85C 25C -40C
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28. Register Summary
Address
(0xFF) (0xFE) (0xFD) (0xFC) (0xFB) (0xFA) (0xF9) (0xF8) (0xF7) (0xF6) (0xF5) (0xF4) (0xF3) (0xF2) (0xF1) (0xF0) (0xEF) (0xEE) (0xED) (0xEC) (0xEB) (0xEA) (0xE9) (0xE8) (0xE7) (0xE6) (0xE5) (0xE4) (0xE3) (0xE2) (0xE1) (0xE0) (0xDF) (0xDE) (0xDD) (0xDC) (0xDB) (0xDA) (0xD9) (0xD8) (0xD7) (0xD6) (0xD5) (0xD4) (0xD3) (0xD2) (0xD1) (0xD0) (0xCF) (0xCE) (0xCD) (0xCC) (0xCB) (0xCA) (0xC9) (0xC8) (0xC7) (0xC6) (0xC5) (0xC4) (0xC3) (0xC2) (0xC1) (0xC0) (0xBF)
Name
Reserved Reserved Reserved Reserved UPOE PS2CON Reserved Reserved Reserved Reserved Reserved UEINT Reserved UEBCLX UEDATX UEIENX UESTA1X UESTA0X UECFG1X UECFG0X UECONX UERST UENUM UEINTX Reserved UDMFN UDFNUMH UDFNUML UDADDR UDIEN UDINT UDCON Reserved Reserved Reserved Reserved Reserved Reserved Reserved USBCON Reserved Reserved Reserved Reserved Reserved CLKSTA CLKSEL1 CLKSEL0 Reserved UDR1 UBRR1H UBRR1L UCSR1D UCSR1C UCSR1B UCSR1A Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved
Bit 7
UPWE1 -
Bit 6
UPWE0 -
Bit 5
UPDRV1 -
Bit 4
UPDRV0 -
Bit 3
SCKI BYCT7:0 DAT7:0
Bit 2
DATAI EPINT4:0 -
Bit 1
DPI -
Bit 0
DMI PS2EN -
Page
FLERRE CFGOK -
NAKINE OVERFI
UNDERFI EPSIZE2:0 -
NAKOUTE STALLRQC NAKOUTI FNCERR -
RXSTPE -
RXOUTE CTRLDIR
STALLEDE
TXINE
CURRBK1:0 NBUSYBK1:0 ALLOC EPDIR EPEN
DTSEQ1:0 EPBK1:0 RSTDT RXSTPI FNUM7:0 UADD6:0 RXOUTI EPRST4:0 -
EPTYPE1:0 FIFOCON ADDEN USBE RCCKSEL3 RCSUT1 UMSEL11 RXCIE1 RXC1 UPRSME UPRSMI RCCKSEL2 RCSUT0 UMSEL10 TXCIE1 TXC1 NAKINI -
STALLRQ RWAL -
EPNUM2:0 STALLEDI FNUM10:8 TXINI -
EORSME EORSMI FRZCLK RCCKSEL1 EXSUT1 UPM11 UDRIE1 UDRE1 -
WAKEUPE WAKEUPI RCCKSEL0 EXSUT0 UPM10 RXEN1 FE1 -
EORSTE EORSTI EXCKSEL3 RCE -
SOFE SOFI RSTCPU EXCKSEL2 EXTE -
RMWKUP RCON EXCKSEL1 -
SUSPE SUSPI DETACH EXTON EXCKSEL0 CLKS -
USART1 I/O Data Register USART1 Baud Rate Register High Byte USBS1 TXEN1 DOR1 UCSZ11 UCSZ12 PE1 CTSEN UCSZ10 RXB81 U2X1 RTSEN UCPOL1 TXB81 MPCM1 USART1 Baud Rate Register Low Byte
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AT90USB82/162
Address
(0xBE) (0xBD) (0xBC) (0xBB) (0xBA) (0xB9) (0xB8) (0xB7) (0xB6) (0xB5) (0xB4) (0xB3) (0xB2) (0xB1) (0xB0) (0xAF) (0xAE) (0xAD) (0xAC) (0xAB) (0xAA) (0xA9) (0xA8) (0xA7) (0xA6) (0xA5) (0xA4) (0xA3) (0xA2) (0xA1) (0xA0) (0x9F) (0x9E) (0x9D) (0x9C) (0x9B) (0x9A) (0x99) (0x98) (0x97) (0x96) (0x95) (0x94) (0x93) (0x92) (0x91) (0x90) (0x8F) (0x8E) (0x8D) (0x8C) (0x8B) (0x8A) (0x89) (0x88) (0x87) (0x86) (0x85) (0x84) (0x83) (0x82) (0x81) (0x80) (0x7F) (0x7E) (0x7D)
Name
Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved OCR1CH OCR1CL OCR1BH OCR1BL OCR1AH OCR1AL ICR1H ICR1L TCNT1H TCNT1L Reserved TCCR1C TCCR1B TCCR1A Reserved Reserved Reserved
Bit 7
-
Bit 6
-
Bit 5
-
Bit 4
-
Bit 3
-
Bit 2
-
Bit 1
-
Bit 0
-
Page
Timer/Counter1 - Output Compare Register C High Byte Timer/Counter1 - Output Compare Register C Low Byte Timer/Counter1 - Output Compare Register B High Byte Timer/Counter1 - Output Compare Register B Low Byte Timer/Counter1 - Output Compare Register A High Byte Timer/Counter1 - Output Compare Register A Low Byte Timer/Counter1 - Input Capture Register High Byte Timer/Counter1 - Input Capture Register Low Byte Timer/Counter1 - Counter Register High Byte Timer/Counter1 - Counter Register Low Byte FOC1A ICNC1 COM1A1 FOC1B ICES1 COM1A0 FOC1C COM1B1 WGM13 COM1B0 WGM12 COM1C1 CS12 COM1C0 CS11 WGM11 CS10 WGM10 -
289
7707E-AVR-11/08
Address
(0x7C) (0x7B) (0x7A) (0x79) (0x78) (0x77) (0x76) (0x75) (0x74) (0x73) (0x72) (0x71) (0x70) (0x6F) (0x6E) (0x6D) (0x6C) (0x6B) (0x6A) (0x69) (0x68) (0x67) (0x66) (0x65) (0x64) (0x63) (0x62) (0x61) (0x60) 0x3F (0x5F) 0x3E (0x5E) 0x3D (0x5D) 0x3C (0x5C) 0x3B (0x5B) 0x3A (0x5A) 0x39 (0x59) 0x38 (0x58) 0x37 (0x57) 0x36 (0x56) 0x35 (0x55) 0x34 (0x54) 0x33 (0x53) 0x32 (0x52) 0x31 (0x51) 0x30 (0x50) 0x2F (0x4F) 0x2E (0x4E) 0x2D (0x4D) 0x2C (0x4C) 0x2B (0x4B) 0x2A (0x4A) 0x29 (0x49) 0x28 (0x48) 0x27 (0x47) 0x26 (0x46) 0x25 (0x45) 0x24 (0x44) 0x23 (0x43) 0x22 (0x42) 0x21 (0x41) 0x20 (0x40) 0x1F (0x3F) 0x1E (0x3E) 0x1D (0x3D) 0x1C (0x3C) 0x1B (0x3B)
Name
Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved TIMSK1 TIMSK0 Reserved PCMSK1 PCMSK0 EICRB EICRA PCICR Reserved OSCCAL PRR1 PRR0 REGCR WDTCKD CLKPR WDTCSR SREG SPH SPL Reserved Reserved Reserved Reserved Reserved SPMCSR Reserved MCUCR MCUSR SMCR Reserved DWDR ACSR Reserved SPDR SPSR SPCR GPIOR2 GPIOR1 PLLCSR OCR0B OCR0A TCNT0 TCCR0B TCCR0A GTCCR EEARH EEARL EEDR EECR GPIOR0 EIMSK EIFR PCIFR
Bit 7
PCINT7 ISC71 ISC31 PRUSB CLKPCE WDIF I SP15 SP7 SPMIE ACD SPIF SPIE
Bit 6
PCINT6 ISC70 ISC30 WDIE T SP14 SP6 RWWSB ACBG WCOL SPE
Bit 5
ICIE1 PCINT5 ISC61 ISC21 PRTIM0 WDP3 H SP13 SP5 SIGRD USBRF ACO DORD
Bit 4
PCINT12 PCINT4 ISC60 ISC20 WDCE S SP12 SP4 RWWSRE ACI MSTR
Bit 3
OCIE1C PCINT11 PCINT3 ISC51 ISC11 PRTIM1 WDEWIF CLKPS3 WDE V SP11 SP3 BLBSET WDRF SM2 ACIE -
Bit 2
OCIE1B OCIE0B PCINT10 PCINT2 ISC50 ISC10 PRSPI WDEWIE CLKPS2 WDP2 N SP10 SP2 PGWRT BORF SM1 ACIC CPHA
Bit 1
OCIE1A OCIE0A PCINT9 PCINT1 ISC41 ISC01 PCIE1 WCLKD1 CLKPS1 WDP1 Z SP9 SP1 PGERS IVSEL EXTRF SM0 ACIS1 SPR1
Bit 0
TOIE1 TOIE0 PCINT8 PCINT0 ISC40 ISC00 PCIE0 PRUSART1 REGDIS WCLKD0 CLKPS0 WDP0 C SP8 SP0 SPMEN IVCE PORF SE ACIS0 SPI2X SPR0
Page
Oscillator Calibration Register
debugWIRE Data Register
SPI Data Register CPOL
General Purpose I/O Register 2 General Purpose I/O Register 1 PLLP2 PLLP1 PLLP0 PLLE PLOCK Timer/Counter0 Output Compare Register B Timer/Counter0 Output Compare Register A Timer/Counter0 (8 Bit) FOC0A COM0A1 TSM FOC0B COM0A0 COM0B1 COM0B0 EEPROM Data Register INT7 INTF7 INT6 INTF6 EEPM1 INT5 INTF5 EEPM0 INT4 INTF4 EERIE INT3 INTF3 EEMPE INT2 INTF2 EEPE INT1 INTF1 PCIF1 EERE INT0 INTF0 PCIF0 General Purpose I/O Register 0 WGM02 CS02 CS01 WGM01 PSRASY CS00 WGM00 PSRSYNC
EEPROM Address Register High Byte
EEPROM Address Register Low Byte
290
AT90USB82/162
7707E-AVR-11/08
AT90USB82/162
Address
0x1A (0x3A) 0x19 (0x39) 0x18 (0x38) 0x17 (0x37) 0x16 (0x36) 0x15 (0x35) 0x14 (0x34) 0x13 (0x33) 0x12 (0x32) 0x11 (0x31) 0x10 (0x30) 0x0F (0x2F) 0x0E (0x2E) 0x0D (0x2D) 0x0C (0x2C) 0x0B (0x2B) 0x0A (0x2A) 0x09 (0x29) 0x08 (0x28) 0x07 (0x27) 0x06 (0x26) 0x05 (0x25) 0x04 (0x24) 0x03 (0x23) 0x02 (0x22) 0x01 (0x21) 0x00 (0x20)
Name
Reserved Reserved Reserved Reserved TIFR1 TIFR0 Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved PORTD DDRD PIND PORTC DDRC PINC PORTB DDRB PINB Reserved Reserved Reserved
Bit 7
PORTD7 DDD7 PIND7 PORTC7 DDC7 PINC7 PORTB7 DDB7 PINB7 -
Bit 6
PORTD6 DDD6 PIND6 PORTC6 DDC6 PINC6 PORTB6 DDB6 PINB6 -
Bit 5
ICF1 PORTD5 DDD5 PIND5 PORTC5 DDC5 PINC5 PORTB5 DDB5 PINB5 -
Bit 4
PORTD4 DDD4 PIND4 PORTC4 DDC4 PINC4 PORTB4 DDB4 PINB4 -
Bit 3
OCF1C PORTD3 DDD3 PIND3 PORTB3 DDB3 PINB3 -
Bit 2
OCF1B OCF0B PORTD2 DDD2 PIND2 PORTC2 DDC2 PINC2 PORTB2 DDB2 PINB2 -
Bit 1
OCF1A OCF0A PORTD1 DDD1 PIND1 PORTC1 DDC1 PINC1 PORTB1 DDB1 PINB1 -
Bit 0
TOV1 TOV0 PORTD0 DDD0 PIND0 PORTC0 DDC0 PINC0 PORTB0 DDB0 PINB0 -
Page
Note:
1. For compatibility with future devices, reserved bits should be written to zero if accessed. Moreover reserved bits are not guaranteed to be read as "0". Reserved I/O memory addresses should never be written. 2. I/O registers within the address range $00 - $1F are directly bit-accessible using the SBI and CBI instructions. In these registers, the value of single bits can be checked by using the SBIS and SBIC instructions. 3. Some of the status flags are cleared by writing a logical one to them. Note that the CBI and SBI instructions will operate on all bits in the I/O register, writing a one back into any flag read as set, thus clearing the flag. The CBI and SBI instructions work with registers 0x00 to 0x1F only. 4. When using the I/O specific commands IN and OUT, the I/O addresses $00 - $3F must be used. When addressing I/O registers as data space using LD and ST instructions, $20 must be added to these addresses. The AT90USB82/162 is a complex microcontroller with more peripheral units than can be supported within the 64 location reserved in Opcode for the IN and OUT instructions. For the Extended I/O space from $60 - $1FF in SRAM, only the ST/STS/STD and LD/LDS/LDD instructions can be used.
291
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29. Instruction Set Summary
Mnemonics
ADD ADC ADIW SUB SUBI SBC SBCI SBIW AND ANDI OR ORI EOR COM NEG SBR CBR INC DEC TST CLR SER RJMP IJMP JMP RCALL ICALL CALL RET RETI CPSE CP CPC CPI SBRC SBRS SBIC SBIS BRBS BRBC BREQ BRNE BRCS BRCC BRSH BRLO BRMI BRPL BRGE BRLT BRHS BRHC BRTS BRTC BRVS BRVC BRIE BRID SBI CBI LSL LSR Rd,Rr Rd,Rr Rd,Rr Rd,K Rr, b Rr, b P, b P, b s, k s, k k k k k k k k k k k k k k k k k k k P,b P,b Rd Rd k k k
Operands
Rd, Rr Rd, Rr Rdl,K Rd, Rr Rd, K Rd, Rr Rd, K Rdl,K Rd, Rr Rd, K Rd, Rr Rd, K Rd, Rr Rd Rd Rd,K Rd,K Rd Rd Rd Rd Rd BRANCH INSTRUCTIONS k
Description
Add two Registers Add with Carry two Registers Add Immediate to Word Subtract two Registers Subtract Constant from Register Subtract with Carry two Registers Subtract with Carry Constant from Reg. Subtract Immediate from Word Logical AND Registers Logical AND Register and Constant Logical OR Registers Logical OR Register and Constant Exclusive OR Registers One's Complement Two's Complement Set Bit(s) in Register Clear Bit(s) in Register Increment Decrement Test for Zero or Minus Clear Register Set Register Relative Jump Indirect Jump to (Z) Direct Jump Relative Subroutine Call Indirect Call to (Z) Direct Subroutine Call Subroutine Return Interrupt Return Compare, Skip if Equal Compare Compare with Carry Compare Register with Immediate Skip if Bit in Register Cleared Skip if Bit in Register is Set Skip if Bit in I/O Register Cleared Skip if Bit in I/O Register is Set Branch if Status Flag Set Branch if Status Flag Cleared Branch if Equal Branch if Not Equal Branch if Carry Set Branch if Carry Cleared Branch if Same or Higher Branch if Lower Branch if Minus Branch if Plus Branch if Greater or Equal, Signed Branch if Less Than Zero, Signed Branch if Half Carry Flag Set Branch if Half Carry Flag Cleared Branch if T Flag Set Branch if T Flag Cleared Branch if Overflow Flag is Set Branch if Overflow Flag is Cleared Branch if Interrupt Enabled Branch if Interrupt Disabled
Operation
Rd Rd + Rr Rd Rd + Rr + C Rdh:Rdl Rdh:Rdl + K Rd Rd - Rr Rd Rd - K Rd Rd - Rr - C Rd Rd - K - C Rdh:Rdl Rdh:Rdl - K Rd Rd * Rr Rd Rd * K Rd Rd v Rr Rd Rd v K Rd Rd Rr Rd 0xFF - Rd Rd 0x00 - Rd Rd Rd v K Rd Rd * (0xFF - K) Rd Rd + 1 Rd Rd - 1 Rd Rd * Rd Rd Rd Rd Rd 0xFF PC PC + k + 1 PC Z PC k PC PC + k + 1 PC Z PC k PC STACK PC STACK if (Rd = Rr) PC PC + 2 or 3 Rd - Rr Rd - Rr - C Rd - K if (Rr(b)=0) PC PC + 2 or 3 if (Rr(b)=1) PC PC + 2 or 3 if (P(b)=0) PC PC + 2 or 3 if (P(b)=1) PC PC + 2 or 3 if (SREG(s) = 1) then PCPC+k + 1 if (SREG(s) = 0) then PCPC+k + 1 if (Z = 1) then PC PC + k + 1 if (Z = 0) then PC PC + k + 1 if (C = 1) then PC PC + k + 1 if (C = 0) then PC PC + k + 1 if (C = 0) then PC PC + k + 1 if (C = 1) then PC PC + k + 1 if (N = 1) then PC PC + k + 1 if (N = 0) then PC PC + k + 1 if (N V= 0) then PC PC + k + 1 if (N V= 1) then PC PC + k + 1 if (H = 1) then PC PC + k + 1 if (H = 0) then PC PC + k + 1 if (T = 1) then PC PC + k + 1 if (T = 0) then PC PC + k + 1 if (V = 1) then PC PC + k + 1 if (V = 0) then PC PC + k + 1 if ( I = 1) then PC PC + k + 1 if ( I = 0) then PC PC + k + 1 I/O(P,b) 1 I/O(P,b) 0 Rd(n+1) Rd(n), Rd(0) 0 Rd(n) Rd(n+1), Rd(7) 0
Flags
Z,C,N,V,H Z,C,N,V,H Z,C,N,V,S Z,C,N,V,H Z,C,N,V,H Z,C,N,V,H Z,C,N,V,H Z,C,N,V,S Z,N,V Z,N,V Z,N,V Z,N,V Z,N,V Z,C,N,V Z,C,N,V,H Z,N,V Z,N,V Z,N,V Z,N,V Z,N,V Z,N,V None None None None None None None None I None Z, N,V,C,H Z, N,V,C,H Z, N,V,C,H None None None None None None None None None None None None None None None None None None None None None None None None None None Z,C,N,V Z,C,N,V
#Clocks
1 1 2 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 3 4 4 5 5 5 1/2/3 1 1 1 1/2/3 1/2/3 1/2/3 1/2/3 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 2 2 1 1
ARITHMETIC AND LOGIC INSTRUCTIONS
BIT AND BIT-TEST INSTRUCTIONS Set Bit in I/O Register Clear Bit in I/O Register Logical Shift Left Logical Shift Right
292
AT90USB82/162
7707E-AVR-11/08
AT90USB82/162
Mnemonics
ROL ROR ASR SWAP BSET BCLR BST BLD SEC CLC SEN CLN SEZ CLZ SEI CLI SES CLS SEV CLV SET CLT SEH CLH MOV MOVW LDI LD LD LD LD LD LD LDD LD LD LD LDD LDS ST ST ST ST ST ST STD ST ST ST STD STS LPM LPM LPM SPM IN OUT PUSH POP NOP SLEEP WDR BREAK Rd, P P, Rr Rr Rd Rd, Z Rd, Z+ Rd, Rr Rd, Rr Rd, K Rd, X Rd, X+ Rd, - X Rd, Y Rd, Y+ Rd, - Y Rd,Y+q Rd, Z Rd, Z+ Rd, -Z Rd, Z+q Rd, k X, Rr X+, Rr - X, Rr Y, Rr Y+, Rr - Y, Rr Y+q,Rr Z, Rr Z+, Rr -Z, Rr Z+q,Rr k, Rr
Operands
Rd Rd Rd Rd s s Rr, b Rd, b
Description
Rotate Left Through Carry Rotate Right Through Carry Arithmetic Shift Right Swap Nibbles Flag Set Flag Clear Bit Store from Register to T Bit load from T to Register Set Carry Clear Carry Set Negative Flag Clear Negative Flag Set Zero Flag Clear Zero Flag Global Interrupt Enable Global Interrupt Disable Set Signed Test Flag Clear Signed Test Flag Set Twos Complement Overflow. Clear Twos Complement Overflow Set T in SREG Clear T in SREG Set Half Carry Flag in SREG Clear Half Carry Flag in SREG
Operation
Rd(0)C,Rd(n+1) Rd(n),CRd(7) Rd(7)C,Rd(n) Rd(n+1),CRd(0) Rd(n) Rd(n+1), n=0..6 Rd(3..0)Rd(7..4),Rd(7..4)Rd(3..0) SREG(s) 1 SREG(s) 0 T Rr(b) Rd(b) T C1 C0 N1 N0 Z1 Z0 I1 I0 S1 S0 V1 V0 T1 T0 H1 H0 Rd Rr Rd+1:Rd Rr+1:Rr Rd K Rd (X) Rd (X), X X + 1 X X - 1, Rd (X) Rd (Y) Rd (Y), Y Y + 1 Y Y - 1, Rd (Y) Rd (Y + q) Rd (Z) Rd (Z), Z Z+1 Z Z - 1, Rd (Z) Rd (Z + q) Rd (k) (X) Rr (X) Rr, X X + 1 X X - 1, (X) Rr (Y) Rr (Y) Rr, Y Y + 1 Y Y - 1, (Y) Rr (Y + q) Rr (Z) Rr (Z) Rr, Z Z + 1 Z Z - 1, (Z) Rr (Z + q) Rr (k) Rr R0 (Z) Rd (Z) Rd (Z), Z Z+1 (Z) R1:R0 Rd P P Rr STACK Rr Rd STACK
Flags
Z,C,N,V Z,C,N,V Z,C,N,V None SREG(s) SREG(s) T None C C N N Z Z I I S S V V T T H H None None None None None None None None None None None None None None None None None None None None None None None None None None None None None None None None None None None None
#Clocks
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 1 1 2 2 1 1 1 N/A
DATA TRANSFER INSTRUCTIONS Move Between Registers Copy Register Word Load Immediate Load Indirect Load Indirect and Post-Inc. Load Indirect and Pre-Dec. Load Indirect Load Indirect and Post-Inc. Load Indirect and Pre-Dec. Load Indirect with Displacement Load Indirect Load Indirect and Post-Inc. Load Indirect and Pre-Dec. Load Indirect with Displacement Load Direct from SRAM Store Indirect Store Indirect and Post-Inc. Store Indirect and Pre-Dec. Store Indirect Store Indirect and Post-Inc. Store Indirect and Pre-Dec. Store Indirect with Displacement Store Indirect Store Indirect and Post-Inc. Store Indirect and Pre-Dec. Store Indirect with Displacement Store Direct to SRAM Load Program Memory Load Program Memory Load Program Memory and Post-Inc Store Program Memory In Port Out Port Push Register on Stack Pop Register from Stack MCU CONTROL INSTRUCTIONS No Operation Sleep Watchdog Reset Break (see specific descr. for Sleep function) (see specific descr. for WDR/timer) For On-chip Debug Only None None None
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30. Ordering Information
Part Number 90USB82-16MU 90USB162-16MU 90USB162-16AU
Temp. Range Industrial Green Industrial Green Industrial Green
Flash Memory Size 8K 16K 16K
Package QFN32 QFN32 TQFP32
Product Marking 90USB82-16MU 90USB162-16MU 90USB162-16AU
31. Packaging Information
Package Type QFN32 PN, 32-Lead 5.0 x 5.0 mm Body, 0.50 mm Pitch Quad Flat No Lead Package (QFN) MA, 32-Lead 7 x 7 mm Body size, 1.00 mm Bodu Thickness 0.8 mm Lead Pitch, Thin Profile Plastic Quad Flat Package (TQFP) Note: If ultrasonic process is used for assembly, we recommend that frequency to be applied should be either below or above the 12 to 26kHz range.
TQFP32
294
AT90USB82/162
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AT90USB82/162
31.1 QFN32
295
7707E-AVR-11/08
31.2
TQFP32
296
AT90USB82/162
7707E-AVR-11/08
AT90USB82/162
32. Errata
32.1 AT90USB162 Errata History
Silicon Release First Release QFP32 `DateCode LotNumber' marking `0705 6J4972' `0709 J4973-2' `0709 J5597-1' Second Release Third Release `0709 F3150-1' All date codes after 0709 QFN32 `DateCode LotNumber' marking all lots marked 90USB162-16MES `0714 50-2' `0722 50-3' `0735 3151' All other lots
32.1.1
AT90USB162 First Release 1. High current consumption in sleep mode If a pending interrupt cannot wake the part up from the selected mode, the current consumption will increase during sleep when executing the SLEEP instruction directly after a SEI instruction. Problem Fix/workaround Before entering sleep, interrupts not used to wake up the part from the sleep mode should be disabled. 2. PS2 high level clamped to UCAP When configured in PS2 mode, the output high level is clamped to the UCAP voltage level. Problem Fix/workaround None. 3. Transient perturbation in USB suspend mode generates overconsumption In device mode and when the USB is suspended, transient perturbation received on the USB lines generates a wake up state. However the idle state following the perturbation does not set the SUSPI bit anymore. The internal USB engine remains in suspend mode but the USB differential receiver is still enabled and generates a typical 300A extra-power consumption. Detection of the suspend state after the transient perturbation should be performed by software (instead of reading the SUSPI bit). Problem fix/workaround USB waiver allows bus powered devices to consume up to 2.5mA in suspend state.
32.1.2
AT90USB162 Second Release 1. High current consumption in sleep mode If a pending interrupt cannot wake the part up from the selected mode, the current consumption will increase during sleep when executing the SLEEP instruction directly after a SEI instruction. Problem Fix/workaround
297
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Before entering sleep, interrupts not used to wake up the part from the sleep mode should be disabled.
2. Extra power consumption The typical power comsumption is increased by 90A at 5V and by 160A in worst case conditions. Problem Fix/workaround None. 3. Transient perturbation in USB suspend mode generates overconsumption In device mode and when the USB is suspended, transient perturbation received on the USB lines generates a wake up state. However the idle state following the perturbation does not set the SUSPI bit anymore. The internal USB engine remains in suspend mode but the USB differential receiver is still enabled and generates a typical 300A extra-power consumption. Detection of the suspend state after the transient perturbation should be performed by software (instead of reading the SUSPI bit). Problem fix/workaround USB waiver allows bus powered devices to consume up to 2.5mA in suspend state. 32.1.3 AT90USB162 Third Release 1. High current consumption in sleep mode If a pending interrupt cannot wake the part up from the selected mode, the current consumption will increase during sleep when executing the SLEEP instruction directly after a SEI instruction. Problem Fix/workaround Before entering sleep, interrupts not used to wake up the part from the sleep mode should be disabled. 2. Transient perturbation in USB suspend mode generates overconsumption In device mode and when the USB is suspended, transient perturbation received on the USB lines generates a wake up state. However the idle state following the perturbation does not set the SUSPI bit anymore. The internal USB engine remains in suspend mode but the USB differential receiver is still enabled and generates a typical 300A extra-power consumption. Detection of the suspend state after the transient perturbation should be performed by software (instead of reading the SUSPI bit). Problem fix/workaround USB waiver allows bus powered devices to consume up to 2.5mA in suspend state.
32.2
32.2.1
AT90USB82 Errata History
AT90USB82 Initial Release (all lots) 1. High current consumption in sleep mode If a pending interrupt cannot wake the part up from the selected mode, the current consumption will increase during sleep when executing the SLEEP instruction directly after a SEI instruction.
298
AT90USB82/162
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AT90USB82/162
Problem Fix/workaround Before entering sleep, interrupts not used to wake up the part from the sleep mode should be disabled. 2. Transient perturbation in USB suspend mode generates overconsumption In device mode and when the USB is suspended, transient perturbation received on the USB lines generates a wake up state. However the idle state following the perturbation does not set the SUSPI bit anymore. The internal USB engine remains in suspend mode but the USB differential receiver is still enabled and generates a typical 300A extra-power consumption. Detection of the suspend state after the transient perturbation should be performed by software (instead of reading the SUSPI bit). Problem fix/workaround USB waiver allows bus powered devices to consume up to 2.5mA in suspend state.
33. Datasheet Revision History for AT90USB82/162
Please note that the referring page numbers in this section are referred to this document. The referring revision in this section are referring to the document revision.
33.1
Changes from 7707A to 7707B
1. Removed all references to Timer/Counter 2, A/D Converter. 2. Clarified information in Power Reduction Mode and Timer/Counter 1 sections. 3. Added USB design guidelines and schematics. 4. Updated default fuse configuration & EEPROM page size. 5. Updated AC/DC parameters. 6. Updated Errata section.
33.2 33.3 33.4
Changes from 7707B to 7707C
1. Updated Errata section.
Changes from 7707C to 7707D
1. Correction to Oscillator description, page 245.
Changes from 7707D to 7707E
1. Updated package descriptions. 2. Added recomendation for ultrasonic assembly. 3. Updated typical self powered applications.
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Features ..................................................................................................... 1 1 Pin Configurations ................................................................................... 3
1.1 Disclaimer ................................................................................................................3
2
Overview ................................................................................................... 4
2.1 Block Diagram .........................................................................................................4 2.2 Pin Descriptions .......................................................................................................5
3 4
About Code Examples ............................................................................. 7 AVR CPU Core .......................................................................................... 8
4.1 Introduction ..............................................................................................................8 4.2 Architectural Overview .............................................................................................8 4.3 ALU - Arithmetic Logic Unit .....................................................................................9 4.4 Status Register ........................................................................................................9 4.5 General Purpose Register File ..............................................................................11 4.6 Stack Pointer .........................................................................................................12 4.7 Instruction Execution Timing .................................................................................12 4.8 Reset and Interrupt Handling .................................................................................13
5
AVR AT90USB82/162 Memories ........................................................... 16
5.1 In-System Reprogrammable Flash Program Memory ...........................................16 5.2 SRAM Data Memory ..............................................................................................17 5.3 EEPROM Data Memory ........................................................................................18 5.4 I/O Memory ............................................................................................................24
6
System Clock and Clock Options ......................................................... 25
6.1 Clock Systems and their Distribution .....................................................................25 6.2 Clock Switch ..........................................................................................................26 6.3 Clock Sources .......................................................................................................29 6.4 Low Power Crystal Oscillator .................................................................................30 6.5 Calibrated Internal RC Oscillator ...........................................................................32 6.6 External Clock .......................................................................................................34 6.7 Clock Output Buffer ...............................................................................................34 6.8 System Clock Prescaler ........................................................................................34 6.9 PLL ........................................................................................................................36
7 8
Power Distribution ................................................................................. 39 Power Management and Sleep Modes ................................................. 41
1
AT90USB82/162
7707E-AVR-11/08
AT90USB82/162
8.1 Idle Mode ...............................................................................................................42 8.2 Power-down Mode .................................................................................................42 8.3 Power-save Mode ..................................................................................................42 8.4 Standby Mode .......................................................................................................42 8.5 Extended Standby Mode .......................................................................................42 8.6 Power Reduction Register .....................................................................................43 8.7 Minimizing Power Consumption ............................................................................44
9
System Control and Reset .................................................................... 46
9.1 Resetting the AVR .................................................................................................46 9.2 Reset Sources .......................................................................................................46 9.3 Power-on Reset .....................................................................................................47 9.4 External Reset .......................................................................................................48 9.5 Brown-out Detection ..............................................................................................49 9.6 Watchdog Reset ....................................................................................................50 9.7 USB Reset .............................................................................................................50 9.8 Internal Voltage Reference ....................................................................................52 9.9 Watchdog Timer ....................................................................................................52
10 Interrupts ................................................................................................ 63
10.1 Interrupt Vectors in AT90USB82/162 ..................................................................63
11 I/O-Ports .................................................................................................. 67
11.1 Introduction ..........................................................................................................67 11.2 Ports as General Digital I/O .................................................................................68 11.3 Alternate Port Functions ......................................................................................72 11.4 Register Description for I/O-Ports ........................................................................82
12 External Interrupts ................................................................................. 84 13 Timer/Counter0 and Timer/Counter1 Prescalers ................................ 88 14 8-bit Timer/Counter0 with PWM ............................................................ 90
14.1 Overview ..............................................................................................................90 14.2 Timer/Counter Clock Sources .............................................................................91 14.3 Counter Unit ........................................................................................................91 14.4 Output Compare Unit ...........................................................................................92 14.5 Compare Match Output Unit ................................................................................94 14.6 Modes of Operation .............................................................................................95 14.7 Timer/Counter Timing Diagrams .........................................................................99
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14.8 8-bit Timer/Counter Register Description ..........................................................100
15 16-bit Timer/Counter 1 with PWM ....................................................... 107
15.1 Overview ............................................................................................................107 15.2 Accessing 16-bit Registers ................................................................................109 15.3 Timer/Counter Clock Sources ...........................................................................112 15.4 Counter Unit ......................................................................................................113 15.5 Input Capture Unit .............................................................................................114 15.6 Output Compare Units .......................................................................................116 15.7 Compare Match Output Unit ..............................................................................118 15.8 Modes of Operation ...........................................................................................119 15.9 Timer/Counter Timing Diagrams .......................................................................126 15.10 16-bit Timer/Counter Register Description ......................................................128
16 Serial Peripheral Interface - SPI ......................................................... 137
16.1 SS Pin Functionality ..........................................................................................141 16.2 Data Modes .......................................................................................................144
17 USART ................................................................................................... 146
17.1 Overview ............................................................................................................146 17.2 Clock Generation ...............................................................................................147 17.3 Frame Formats ..................................................................................................150 17.4 USART Initialization ...........................................................................................152 17.5 Data Transmission - The USART Transmitter ..................................................153 17.6 Data Reception - The USART Receiver ...........................................................155 17.7 Asynchronous Data Reception ..........................................................................159 17.8 Multi-processor Communication Mode ..............................................................162 17.9 Hardware Flow Control ......................................................................................163 17.10 USART Register Description ...........................................................................165 17.11 Examples of Baud Rate Setting .......................................................................169
18 USART in SPI Mode ............................................................................. 173
18.1 Overview ............................................................................................................173 18.2 Clock Generation ...............................................................................................174 18.3 SPI Data Modes and Timing ..............................................................................175 18.4 Frame Formats ..................................................................................................175 18.5 Data Transfer .....................................................................................................177 18.6 USART MSPIM Register Description ................................................................179 18.7 AVR USART MSPIM vs.
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AT90USB82/162
AVR SPI 181
19 USB controller ...................................................................................... 183
19.1 Features ............................................................................................................183 19.2 Block Diagram ...................................................................................................183 19.3 Typical Application Implementation ...................................................................184 19.4 General Operating Modes .................................................................................187 19.5 Power modes .....................................................................................................190 19.6 Memory management ........................................................................................190 19.7 PAD suspend .....................................................................................................191 19.8 D+/D- Read/write ...............................................................................................192 19.9 Registers description .........................................................................................193 19.10 USB Software Operating modes .....................................................................194
20 USB Device Operating modes ............................................................ 196
20.1 Introduction ........................................................................................................196 20.2 Power-on and reset ...........................................................................................196 20.3 Endpoint reset ...................................................................................................196 20.4 USB reset ..........................................................................................................197 20.5 Endpoint selection .............................................................................................197 20.6 Endpoint activation ............................................................................................197 20.7 Address Setup ...................................................................................................198 20.8 Suspend, Wake-up and Resume .......................................................................199 20.9 Detach ...............................................................................................................199 20.10 Remote Wake-up .............................................................................................200 20.11 STALL request .................................................................................................200 20.12 CONTROL endpoint management ..................................................................201 20.13 OUT endpoint management ............................................................................202 20.14 IN endpoint management ................................................................................204 20.15 Isochronous mode ...........................................................................................206 20.16 Overflow ..........................................................................................................206 20.17 Interrupts .........................................................................................................207 20.18 Registers .........................................................................................................208
21 PS/2 ....................................................................................................... 220
21.1 Characteristics ...................................................................................................220
22 Analog Comparator .............................................................................. 223
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23 Boot Loader Support - Read-While-Write Self-Programming ......... 225
23.1 Boot Loader Features ........................................................................................225 23.2 Application and Boot Loader Flash Sections .....................................................225 23.3 Read-While-Write and No Read-While-Write Flash Sections ............................225 23.4 Boot Loader Lock Bits .......................................................................................228 23.5 Entering the Boot Loader Program ....................................................................229 23.6 Addressing the Flash During Self-Programming ...............................................233 23.7 Self-Programming the Flash ..............................................................................233
24 debugWIRE On-chip Debug System .................................................. 241
24.1 Features ............................................................................................................241 24.2 Overview ............................................................................................................241 24.3 Physical Interface ..............................................................................................241 24.4 Software Break Points .......................................................................................242 24.5 Limitations of debugWIRE .................................................................................242 24.6 debugWIRE Related Register in I/O Memory ....................................................242
25 Memory Programming ......................................................................... 243
25.1 Program And Data Memory Lock Bits ...............................................................243 25.2 Fuse Bits ............................................................................................................244 25.3 Signature Bytes .................................................................................................246 25.4 Calibration Byte .................................................................................................246 25.5 Parallel Programming Parameters, Pin Mapping, and Commands ...................246 25.6 Parallel Programming ........................................................................................249 25.7 Serial Downloading ............................................................................................257 25.8 Serial Programming Pin Mapping ......................................................................257
26 Electrical Characteristics .................................................................... 262
26.1 Absolute Maximum Ratings* .............................................................................262 26.2 DC Characteristics .............................................................................................262 26.3 External Clock Drive Waveforms .......................................................................264 26.4 External Clock Drive ..........................................................................................264 26.5 Maximum speed vs. VCC ...........................................................................................................................265 26.6 SPI Timing Characteristics ................................................................................265 26.7 Hardware Boot EntranceTiming Characteristics ................................................266
27 AT90USB82/162 Typical Characteristics - Preliminary Data ........... 268
27.1 Input Voltage Levels ..........................................................................................269 27.2 Output Voltage Levels .......................................................................................271
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27.3 I/O Pull-up Current .............................................................................................274 27.4 Power-down Supply Current ..............................................................................275 27.5 Idle Supply Current ............................................................................................278 27.6 Active Supply Current ........................................................................................279 27.7 Reset Supply Current ........................................................................................279 27.8 Bandgap Voltage ...............................................................................................280 27.9 USB Regulator ...................................................................................................281 27.10 Power-On Reset ..............................................................................................282 27.11 BOD Levels .....................................................................................................283 27.12 Watchdog Timer Frequency ............................................................................286 27.13 Internal RC Oscillator Frequency ....................................................................287
28 Register Summary ............................................................................... 288 29 Instruction Set Summary ..................................................................... 292 30 Ordering Information ........................................................................... 294 31 Packaging Information ........................................................................ 294
31.1 QFN32 ...............................................................................................................295 31.2 TQFP32 .............................................................................................................296
32 Errata ..................................................................................................... 297
32.1 AT90USB162 Errata History ..............................................................................297 32.2 AT90USB82 Errata History ................................................................................298
33 Datasheet Revision History for AT90USB82/162 .............................. 299
33.1 Changes from 7707A to 7707B .........................................................................299 33.2 Changes from 7707B to 7707C .........................................................................299 33.3 Changes from 7707C to 7707D .........................................................................299 33.4 Changes from 7707D to 7707E .........................................................................299
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