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| m68hc08 microcontrollers freescale.com mc68hc908ap64a mc68hc908ap32a mc68hc908ap16a MC68HC908AP8A data sheet mc68hc908ap64a rev. 2 01/2007
mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 3 freescale and the freescale logo are trademarks of freescale semiconductor, inc. this product incorporates superflash?technology licensed from sst. freescale semiconductor, inc., 2005, 2007. all rights reserved. mc68hc908ap64a mc68hc908ap32a mc68hc908ap16a MC68HC908AP8A data sheet to provide the most up-to-date information, the revision of our documents on the world wide web will be the most current. your printed copy may be an earlier revision. to verify you have the latest information available, refer to: http://www.freescale.com the following revision history table summarizes changes contained in this document. for your convenience, the page number designators have been linked to the appropriate location. mc68hc908ap a-family data sheet, rev. 2 4 freescale semiconductor revision history date revision level description page number(s) january 2007 2 15.7.2 adc clock control register ?changed ?he adc clock should be set to between 500khz and 2mhz?to ?he adc clock should be set to between 500khz and 1mhz 250 mar 2005 1 first general release. mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 5 list of chapters chapter 1 general description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 chapter 2 memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 chapter 3 configuration & mask option registers (config & mor) . . . . . . . . . . . . . . . .49 chapter 4 central processor unit (cpu). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55 chapter 5 oscillator (osc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 chapter 6 clock generator module (cgm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79 chapter 7 system integration module (sim) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97 chapter 8 monitor rom (mon) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115 chapter 9 timer interface module (tim) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131 chapter 10 timebase module (tbm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147 chapter 11 serial communications interface module (sci) . . . . . . . . . . . . . . . . . . . . . . .151 chapter 12 infrared serial communications interface module (irsci) . . . . . . . . . . . . . .177 chapter 13 serial peripheral interface module (spi) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205 chapter 14 multi-master iic interface (mmiic) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225 chapter 15 analog-to-digital converter (adc). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .243 chapter 16 input/output (i/o) ports. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .255 chapter 17 external interrupt (irq) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .267 chapter 18 keyboard interrupt module (kbi) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .273 chapter 19 computer operating properly (cop) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279 chapter 20 low-voltage inhibit (lvi). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .283 chapter 21 break module (brk) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .287 chapter 22 electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293 chapter 23 mechanical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .307 chapter 24 ordering information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .311 list of chapters mc68hc908ap a-family data sheet, rev. 2 6 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 7 table of contents chapter 1 general description 1.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 1.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 1.3 mcu block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 1.4 pin assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.5 pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 1.6 power supply bypassing (vdd, vdda, vss, vssa) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 1.7 regulator power supply configuration (vreg) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 chapter 2 memory 2.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.2 input/output (i/o) section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.3 monitor rom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.4 random-access memory (ram) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 2.5 flash memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 2.5.1 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 2.5.2 flash control register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 2.5.3 flash page erase operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 2.5.4 flash mass erase operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 2.5.5 flash program operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4 2.5.6 flash protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 2.5.7 flash block protect register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 7 chapter 3 configuration & mask option registers (config & mor) 3.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.2 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.3 configuration register 1 (config1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 0 3.4 configuration register 2 (config2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 3.5 mask option register (mor). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 chapter 4 central processor unit (cpu) 4.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.3 cpu registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.3.1 accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 table of contents mc68hc908ap a-family data sheet, rev. 2 8 freescale semiconductor 4.3.2 index register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.3.3 stack pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.3.4 program counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.3.5 condition code register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.4 arithmetic/logic unit (alu) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.5 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.5.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.5.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.6 cpu during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.7 instruction set summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.8 opcode map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 chapter 5 oscillator (osc) 5.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 5.2 clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 5.2.1 cgm reference clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 5.2.2 tbm reference clock selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 5.3 internal oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 5.4 rc oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 5.5 x-tal oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 5.6 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 5.6.1 crystal amplifier input pin (osc1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6 5.6.2 crystal amplifier output pin (osc2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 5.6.3 oscillator enable signal (simoscen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 5.6.4 cgm oscillator clock (cgmxclk) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5.6.5 cgm reference clock (cgmrclk) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5.6.6 oscillator clock to time base module (oscclk) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5.7 low power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5.7.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5.7.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 5.8 oscillator during break mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 chapter 6 clock generator module (cgm) 6.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 6.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 6.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 6.3.1 oscillator module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 6.3.2 phase-locked loop circuit (pll) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 6.3.3 pll circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 6.3.4 acquisition and tracking modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 6.3.5 manual and automatic pll bandwidth modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 6.3.6 programming the pll . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 6.3.7 special programming exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 6.3.8 base clock selector circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 9 6.3.9 cgm external connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 6.4 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 6.4.1 external filter capacitor pin (cgmxfc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 6.4.2 pll analog power pin (v dda ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 6.4.3 pll analog ground pin (v ssa ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 6.4.4 oscillator output frequency signal (cgmxclk) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 6.4.5 cgm reference clock (cgmrclk) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 6.4.6 cgm vco clock output (cgmvclk) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 6.4.7 cgm base clock output (cgmout) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 6.4.8 cgm cpu interrupt (cgmint) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 6.5 cgm registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 6.5.1 pll control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 6.5.2 pll bandwidth control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 6.5.3 pll multiplier select registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92 6.5.4 pll vco range select register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 6.5.5 pll reference divider select register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 6.6 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 6.7 special modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 6.7.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 6.7.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 6.7.3 cgm during break interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 6.8 acquisition/lock time specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95 6.8.1 acquisition/lock time definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5 6.8.2 parametric influences on reaction time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 6.8.3 choosing a filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 chapter 7 system integration module (sim) 7.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 7.2 sim bus clock control and generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 7.2.1 bus timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 7.2.2 clock start-up from por or lvi reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7.2.3 clocks in stop mode and wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7.3 reset and system initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7.3.1 external pin reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 7.3.2 active resets from internal sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 7.3.2.1 power-on reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 7.3.2.2 computer operating properly (cop) reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 7.3.2.3 illegal opcode reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 7.3.2.4 illegal address reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.3.2.5 low-voltage inhibit (lvi) reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.3.2.6 monitor mode entry module reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.4 sim counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.4.1 sim counter during power-on reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.4.2 sim counter during stop mode recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.4.3 sim counter and reset states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 7.5 exception control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 table of contents mc68hc908ap a-family data sheet, rev. 2 10 freescale semiconductor 7.5.1 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 7.5.1.1 hardware interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 7.5.1.2 swi instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 7.5.2 interrupt status registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 7.5.2.1 interrupt status register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 7.5.2.2 interrupt status register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 7.5.2.3 interrupt status register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 7.5.3 reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7.5.4 break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7.5.5 status flag protection in break mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 7.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 7.7 sim registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 7.7.1 sim break status register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 7.7.2 sim reset status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 13 7.7.3 sim break flag control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 chapter 8 monitor rom (mon) 8.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 8.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 8.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 8.3.1 entering monitor mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 8.3.2 data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 8.3.3 break signal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 8.3.4 baud rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 8.3.5 commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 8.4 security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 8.5 rom-resident routines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 8.5.1 prgrnge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 8.5.2 erarnge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 8.5.3 ldrnge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 8.5.4 mon_prgrnge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 8.5.5 mon_erarnge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 chapter 9 timer interface module (tim) 9.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 9.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 9.3 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 9.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 9.4.1 tim counter prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 9.4.2 input capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 9.4.3 output compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 9.4.3.1 unbuffered output compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 9.4.3.2 buffered output compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 11 9.4.4 pulse width modulation (pwm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 9.4.4.1 unbuffered pwm signal generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 9.4.4.2 buffered pwm signal generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 9.4.4.3 pwm initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 9.5 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 9.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 9.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 9.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 9.7 tim during break interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 9.8 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 9.9 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 9.9.1 tim status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 9.9.2 tim counter registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 9.9.3 tim counter modulo registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 9.9.4 tim channel status and control registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 9.9.5 tim channel registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 chapter 10 timebase module (tbm) 10.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 10.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 10.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 10.4 timebase register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 10.5 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 10.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 10.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 10.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 chapter 11 serial communications interface module (sci) 11.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 11.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 11.3 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 11.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 11.4.1 data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 11.4.2 transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 11.4.2.1 character length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 11.4.2.2 character transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 11.4.2.3 break characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 11.4.2.4 idle characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 11.4.2.5 inversion of transmitted output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 11.4.2.6 transmitter interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 11.4.3 receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 11.4.3.1 character length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 11.4.3.2 character reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 11.4.3.3 data sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 table of contents mc68hc908ap a-family data sheet, rev. 2 12 freescale semiconductor 11.4.3.4 framing errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 11.4.3.5 baud rate tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 11.4.3.6 receiver wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 11.4.3.7 receiver interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 11.4.3.8 error interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 11.5 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 11.5.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 11.5.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 11.6 sci during break module interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 63 11.7 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 11.7.1 txd (transmit data). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 11.7.2 rxd (receive data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 11.8 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 11.8.1 sci control register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 11.8.2 sci control register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 11.8.3 sci control register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 11.8.4 sci status register 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 11.8.5 sci status register 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 11.8.6 sci data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 11.8.7 sci baud rate register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 chapter 12 infrared serial communications interface module (irsci) 12.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 12.2 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 12.3 irsci module overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 12.4 infrared functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 12.4.1 infrared transmit encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 12.4.2 infrared receive decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 12.5 sci functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 12.5.1 data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 12.5.2 transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 12.5.2.1 character length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 12.5.2.2 character transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 12.5.2.3 break characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 12.5.2.4 idle characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 12.5.2.5 transmitter interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 12.5.3 receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 12.5.3.1 character length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 12.5.3.2 character reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 12.5.3.3 data sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 12.5.3.4 framing errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 12.5.3.5 baud rate tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 12.5.3.6 receiver wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 12.5.3.7 receiver interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 12.5.3.8 error interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 12.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 13 12.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 12.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 12.7 sci during break module interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 91 12.8 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 12.8.1 ptc6/sctxd (transmit data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 12.8.2 ptc7/scrxd (receive data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 12.9 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 12.9.1 irsci control register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 12.9.2 irsci control register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 12.9.3 irsci control register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 12.9.4 irsci status register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 12.9.5 irsci status register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 12.9.6 irsci data register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 12.9.7 irsci baud rate register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 12.9.8 irsci infrared control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 04 chapter 13 serial peripheral interface module (spi) 13.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 13.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 13.3 pin name conventions and i/o register addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 13.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 13.4.1 master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 13.4.2 slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 13.5 transmission formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 13.5.1 clock phase and polarity controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 13.5.2 transmission format when cpha = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 13.5.3 transmission format when cpha = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 13.5.4 transmission initiation latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 13.6 queuing transmission data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 13.7 error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 13.7.1 overflow error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 13.7.2 mode fault error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 13.8 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 13.9 resetting the spi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 13.10 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 13.10.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 13.10.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 13.11 spi during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 13.12 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 13.12.1 miso (master in/slave out). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 13.12.2 mosi (master out/slave in). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 13.12.3 spsck (serial clock) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 13.12.4 ss (slave select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 13.12.5 cgnd (clock ground) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 13.13 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 table of contents mc68hc908ap a-family data sheet, rev. 2 14 freescale semiconductor 13.13.1 spi control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 13.13.2 spi status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 22 13.13.3 spi data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 chapter 14 multi-master iic interface (mmiic) 14.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 14.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 14.3 i/o pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 14.4 multi-master iic system configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 6 14.5 multi-master iic bus protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 14.5.1 start signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 14.5.2 slave address transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 27 14.5.3 data transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 14.5.4 repeated start signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 14.5.5 stop signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 14.5.6 arbitration procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 14.5.7 clock synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 14.5.8 handshaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 14.5.9 packet error code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 14.6 mmiic i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 14.6.1 mmiic address register (mmadr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 14.6.2 mmiic control register 1 (mmcr1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 14.6.3 mmiic control register 2 (mmcr2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 14.6.4 mmiic status register (mmsr). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 14.6.5 mmiic data transmit register (mmdtr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 14.6.6 mmiic data receive register (mmdrr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 14.6.7 mmiic crc data register (mmcrcdr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 14.6.8 mmiic frequency divider register (mmfdr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 14.7 program algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 14.7.1 data sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 14.8 smbus protocols with pec and without pec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 14.8.1 quick command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 14.8.2 send byte. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 14.8.3 receive byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 14.8.4 write byte/word . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 14.8.5 read byte/word. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 14.8.6 process call . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 14.8.7 block read/write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 14.9 smbus protocol implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 chapter 15 analog-to-digital converter (adc) 15.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 15.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 15.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 15.3.1 adc port i/o pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 15 15.3.2 voltage conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 15.3.3 conversion time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 15.3.4 continuous conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 15.3.5 auto-scan mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 15.3.6 result justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 15.3.7 data register interlocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 15.3.8 monotonicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 15.4 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 15.5 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 15.5.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 15.5.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 15.6 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 15.6.1 adc voltage in (v adin ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 15.6.2 adc analog power pin (v dda ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 15.6.3 adc analog ground pin (v ssa ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 15.6.4 adc voltage reference high pin (v refh ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 15.6.5 adc voltage reference low pin (v refl ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 15.7 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 15.7.1 adc status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 15.7.2 adc clock control register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 15.7.3 adc data register 0 (adrh0 and adrl0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 15.7.4 adc auto-scan mode data registers (adrl1?drl3) . . . . . . . . . . . . . . . . . . . . . . . . . 253 15.7.5 adc auto-scan control register (adascr) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 chapter 16 input/output (i/o) ports 16.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 16.2 port a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 16.2.1 port a data register (pta) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 16.2.2 data direction register (ddra) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 16.2.3 port-a led control register (leda) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 16.3 port b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 16.3.1 port b data register (ptb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 16.3.2 data direction register b (ddrb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 16.4 port c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 16.4.1 port c data register (ptc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 16.4.2 data direction register c (ddrc). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 16.5 port d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 16.5.1 port d data register (ptd) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 16.5.2 data direction register d (ddrd). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264 chapter 17 external interrupt (irq) 17.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 17.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 17.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 17.4 irq1 and irq2 pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 table of contents mc68hc908ap a-family data sheet, rev. 2 16 freescale semiconductor 17.5 irq module during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 70 17.6 irq registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 17.6.1 irq1 status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 17.6.2 irq2 status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 chapter 18 keyboard interrupt module (kbi) 18.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 18.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 18.3 i/o pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 18.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 18.4.1 keyboard initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 18.5 keyboard interrupt registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 18.5.1 keyboard status and control register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 18.5.2 keyboard interrupt enable register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 18.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 18.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 18.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 18.7 keyboard module during break interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 chapter 19 computer operating properly (cop) 19.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 19.2 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 19.3 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 19.3.1 iclk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 19.3.2 stop instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 19.3.3 copctl write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 19.3.4 power-on reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 19.3.5 internal reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 19.3.6 reset vector fetch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 19.3.7 copd (cop disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 19.3.8 coprs (cop rate select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 1 19.4 cop control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 19.5 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 19.6 monitor mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 19.7 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 19.7.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282 19.7.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282 19.8 cop module during break mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282 chapter 20 low-voltage inhibit (lvi) 20.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 20.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 20.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 17 20.3.1 low v dd detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 20.3.2 low v reg detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 20.3.3 polled lvi operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284 20.3.4 forced reset operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 20.3.5 voltage hysteresis protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 20.4 lvi status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 20.5 lvi interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 20.6 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286 20.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286 20.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286 chapter 21 break module (brk) 21.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 21.2 features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 21.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 21.3.1 flag protection during break interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 21.3.2 cpu during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 88 21.3.3 timi and tim2 during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 21.3.4 cop during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 88 21.4 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288 21.4.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 21.4.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 21.5 break module registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 21.5.1 break status and control register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 21.5.2 break address registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 21.5.3 sim break status register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 21.5.4 sim break flag control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 chapter 22 electrical specifications 22.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 22.2 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 22.3 functional operating range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 22.4 thermal characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 22.5 5v dc electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 22.6 5v control timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 22.7 5v oscillator characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 22.8 5v adc electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298 22.9 mmiic electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 22.10 cgm electrical specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301 22.11 5v spi characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302 22.12 memory characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 table of contents mc68hc908ap a-family data sheet, rev. 2 18 freescale semiconductor chapter 23 mechanical specifications 23.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 23.2 48-pin low-profile quad flat pack (lqfp) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 23.3 44-pin quad flat pack (qfp) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 23.4 42-pin shrink dual in-line package (sdip) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 chapter 24 ordering information 24.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 24.2 mc order numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 19 chapter 1 general description 1.1 introduction the mc68hc908ap64a is a member of the low-cost, high-performance m68hc08 family of 8-bit microcontroller units (mcus). all mcus in the family use the enhanced m68hc08 central processor unit (cpu08) and are available with a variety of modules, memory sizes and types, and package types. 1.2 features features of the mc68hc908ap64a include the following: high-performance m68hc08 architecture fully upward-compatible object code with m6805, m146805, and m68hc05 families maximum internal bus frequency: 8-mhz at 5v operating voltage clock input options: rc-oscillator 1- to 8-mhz crystal-oscillator with 32mhz internal pll user program flash memory with security (1) feature 62,368 bytes for mc68hc908ap64a 32,768 bytes for mc68hc908ap32a 16,384 bytes for mc68hc908ap16a 8,192 bytes for MC68HC908AP8A on-chip ram 2,048 bytes for mc68hc908ap64a and mc68hc908ap32a 1,024 bytes for mc68hc908ap16a and MC68HC908AP8A two 16-bit, 2-channel timer interface modules (tim1 and tim2) with selectable input capture, output compare, and pwm capability on each channel table 1-1. summary of device variations device ram size (bytes) flash memory size (bytes) mc68hc908ap64a 2,048 62,368 mc68hc908ap32a 2,048 32,768 mc68hc908ap16a 1,024 16,384 MC68HC908AP8A 1,024 8,192 1. no security feature is absolutely secure. however, freescale? strategy is to make reading or copying the flash difficult for unauthorized users. general description mc68hc908ap a-family data sheet, rev. 2 20 freescale semiconductor timebase module serial communications interface module 1 (sci) serial communications interface module 2 (sci) with infrared (ir) encoder/decoder serial peripheral interface module (spi) system management bus (smbus), version 1.0/1.1 (multi-master iic bus) 8-channel, 10-bit analog-to-digital converter (adc) irq1 external interrupt pin with integrated pullup irq2 external interrupt pin with programmable pullup 8-bit keyboard wakeup port with integrated pullup 32 general-purpose input/output (i/o) pins: 31 shared-function i/o pins 8 led drivers (sink) ? 25ma open-drain i/o with pullup low-power design (fully static with stop and wait modes) master reset pin (with integrated pullup) and power-on reset system protection features optional computer operating properly (cop) reset, driven by internal rc oscillator low-voltage detection with optional reset or interrupt illegal opcode detection with reset illegal address detection with reset 48-pin low quad flat pack (lqfp), 44-pin quad flat pack (qfp), and 42-pin shrink dual-in-line package (sdip) specific features of the mc68hc908ap64a in 42-pin sdip are: 30 general-purpose l/os only external interrupt on irq1 only features of the cpu08 include the following: enhanced hc05 programming model extensive loop control functions 16 addressing modes (eight more than the hc05) 16-bit index register and stack pointer memory-to-memory data transfers fast 8 8 multiply instruction fast 16/8 divide instruction binary-coded decimal (bcd) instructions optimization for controller applications efficient c language support 1.3 mcu block diagram figure 1-1 shows the structure of the mc68hc908ap64a. mcu block diagram mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 21 figure 1-1. mc68hc908ap64a block diagram system integration module arithmetic/logic unit (alu) cpu registers m68hc08 cpu control and status registers ?96 bytes user flash ?(see table) user ram ?(see table) monitor rom ?959 bytes user flash vector space ?48 bytes external interrupt module ddrd portd internal bus * rst * irq1 computer operating properly module ptd7/kbi7 *** ptd6/kbi6 *** ptd5/kbi5 *** ptd4/kbi4 *** ptd3/kbi3 *** ptd2/kbi2 *** power-on reset module power ptd1/kbi1 *** ptd0/kbi0 *** serial communications interface module 1 2-channel timer interface module 1 2-channel timer interface module 2 serial peripheral interface module keyboard interrupt module 10-bit analog-to-digital converter module adc reference vrefl vrefh ddrb portb ptb7/t2ch1 ptb6/t2ch0 ptb5/t1ch1 ptb4/t1ch0 ptb3/rxd ? ptb2/txd ? ptb1/scl ? ptb0/sda ? ddrc portc ptc7/scrxd ? ptc6/sctxd ? ptc5/spsck ptc4/ ss ptc3/mosi ptc2/miso ptc1 # ptc0/ irq2 ** # ddra porta pta7/adc7 pta6/adc6 pta5/adc5 pta4/adc4 pta3/adc3 pta2/adc2 pta1/adc1 pta0/adc0 low-voltage inhibit module serial communications interface module 2 (with infrared modulator/demodulator) ? pin is open-drain when configured as output. led direct sink pin. # pin not bonded on 42-pin sdip. timebase module multi-master iic (smbus) interface module vdda vdd vssa vss vreg ** irq2 * pin contains integrated pullup device. ** pin contains configurable pullup device. *** pin contains integrated pullup device when configured as kbi. clock generator module osc1 osc2 cgmxfc phase-locked loop x-tal oscillator rc oscillator internal oscillator oscillators and . device user ram (bytes) user flash (bytes) mc68hc908ap64a 2,048 62,368 mc68hc908ap32a 2,048 32,768 mc68hc908ap16a 1,024 16,384 MC68HC908AP8A 1,024 8,192 general description mc68hc908ap a-family data sheet, rev. 2 22 freescale semiconductor 1.4 pin assignment figure 1-2. 48-pin lqfp pin assignments vssa 48 47 46 45 44 43 42 41 40 39 1 2 3 4 5 6 7 8 9 10 14 15 16 17 18 19 20 21 22 36 32 31 30 29 28 27 26 13 ptb6/t2ch0 irq1 ptb3/rxd rst vreg ptb5/t1ch1 vdd osc1 osc2 vss ptb4/t1ch0 ptc5/spsck ptc7/scrxd ptb0/sda ptb1/scl ptc6/sctxd ptc4/ ss ptc0/ irq2 ptc1 ptc2/miso pta7/adc7 ptc3/mosi nc vrefl vrefh pta1/adc1 nc pta5/adc5 pta4/adc4 pta2/adc2 pta0/adc0 nc pta3/adc3 cgmxfc 12 ptb2/txd 25 pta6/adc6 11 24 nc 23 35 34 33 vdda ptd2/kbi2 ptd1/kbi1 ptd0/kbi0 ptd7/kbi7 ptd6/kbi6 ptd5/kbi5 ptd4/kbi4 ptd3/kbi3 ptb7/t2ch1 37 38 nc: no connection pin assignment mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 23 figure 1-3. 44-pin qfp pin assignments 44 34 43 42 41 40 39 38 37 36 35 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 17 18 19 20 21 22 33 32 31 30 29 28 27 26 25 24 12 23 ptb6/t2ch0 irq1 ptb3/rxd rst vreg ptb5/t1ch1 vdd osc1 osc2 vss ptb4/t1ch0 ptc5/spsck ptc7/scrxd ptb0/sda ptb1/scl ptc6/sctxd ptc4/ ss ptc0/ irq2 ptc1 ptc2/miso ptc3/mosi ptb2/txd vrefl vrefh pta1/adc1 pta5/adc5 pta4/adc4 pta2/adc2 pta0/adc0 pta3/adc3 pta6/adc6 pta7/adc7 vssa cgmxfc vdda ptd2/kbi2 ptd1/kbi1 ptd0/kbi0 ptd6/kbi6 ptd5/kbi5 ptd4/kbi4 ptd3/kbi3 ptb7/t2ch1 ptd7/kbi7 general description mc68hc908ap a-family data sheet, rev. 2 24 freescale semiconductor figure 1-4. 42-pin sdip pin assignment 21 22 ptc6/sctxd ptc7/scrxd ptc2/miso 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 ptc3/mosi ptc4/ ss ptb1/scl ptb2/txd rst cgmxfc ptb4/t1ch0 irq1 ptb3/rxd vrefl vrefh ptd7/kbi7 ptd6/kbi6 ptd5/kbi5 ptd4/kbi4 ptd3/kbi3 vssa pta3/adc3 pta2/adc2 pta6/adc6 pta5/adc5 pta4/adc4 ptd2/kbi2 vdda pta1/adc1 pta0/adc0 ptd1/kbi1 ptd0/kbi0 ptb7/t2ch1 ptb6/t2ch0 vreg ptb5/t1ch1 vdd osc1 osc2 vss pta7/adc7 20 23 ptc5/spsck ptb0/sda pins not available on 42-pin package internal connection ptc0/ irq2 unconnected ptc1 unconnected pin functions mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 25 1.5 pin functions description of the pin functions are provided in table 1-2 . table 1-2. pin functions pin name pin description in/out voltage level v dd power supply. in 4.5 to 5.5 v ss power supply ground. out 0 v v dda power supply for analog circuits. in v dd v ssa power supply ground for analog circuits. out v ss v refh adc input reference high. in v dda v refl adc input reference low. out v ssa v reg internal (2.5v) regulator output. require external capacitors for decoupling. out 2.5v (1) rst reset input, active low; with internal pullup and schmitt trigger input. in v dd irq1 external irq1 pin; with internal pullup and schmitt trigger input. in v dd used for mode entry selection. in v dd to v tst osc1 crystal or rc oscillator input. in v reg osc2 crystal osc option: crystal oscillator output; inverted osc1. out v reg rc osc option: bus clock output. out v reg internal osc option: bus clock output. out v reg cgmxfc cgm external ?ter capacitor connection. in/out analog pta0/adc0 : pta7/adc7 8-bit general purpose i/o port. in/out v dd pins as adc inputs, adc0?dc7. in v refh each pin has high current sink for led. out v dd general description mc68hc908ap a-family data sheet, rev. 2 26 freescale semiconductor 1.6 power supply bypassing (vdd, vdda, vss, vssa) v dd and v ss are the power supply and ground pins, the mcu operates from a single power supply together with an on chip voltage regulator. fast signal transitions on mcu pins place high. short-duration current demands on the power supply. to prevent noise problems, take special care to provide power supply bypassing at the mcu as figure 1-5 shows. place the bypass capacitors as close to the mcu power pins as possible. use high-frequency-response ceramic capacitor for c bypass , c bulk are optional bulk current bypass capacitors for use in applications that require the port pins to source high current level. ptb0/sda ptb1/scl ptb2/txd ptb3/rxd ptb4/t1ch0 ptb5/t1ch1 ptb6/t2ch0 ptb7/t2ch1 8-bit general purpose i/o port; ptb0?tb3 are open drain when con?ured as output. ptb4?tb7 have schmitt trigger inputs. in/out v dd ptb0 as sda of mmiic. in/out v dd ptb1 as scl of mmiic. in/out v dd ptb2 as txd of sci; open drain output. out v dd ptb3 as rxd of sci. in v dd ptb4 as t1ch0 of tim1. in/out v dd ptb5 as t1ch1 of tim1. in/out v dd ptb6 as t2ch0 of tim2. in/out v dd ptb7 as t2ch1 of tim2. in/out v dd ptc0/ irq2 ptc1 ptc2/miso ptc3/mosi ptc4/ ss ptc5/spsck ptc6/sctxd ptc7/scrxd 8-bit general purpose i/o port; ptc6 and ptc7 are open drain when con?ured as output. in/out v dd ptc0 is shared with irq2 and has schmitt trigger input. in v dd ptc2 as miso of spi. in v dd ptc3 as mosi of spi. out v dd ptc4 as ss of spi. in v dd ptc5 as spsck of spi. in/out v dd ptc6 as sctxd of irsci; open drain output. out v dd ptc7 as scrxd of irsci. in v dd ptd0/kbi0 : ptd7/kbi7 8-bit general purpose i/o port with schmitt trigger inputs. in/out v dd pins as keyboard interrupts (with pullup), kbi0?bi7. in v dd 1. see chapter 22 electrical specifications for v reg tolerance. table 1-2. pin functions pin name pin description in/out voltage level regulator power supply configuration (vreg) mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 27 v dda and v ssa are the power supply and ground pins for the analog circuits of the mcu. these pins should be decoupled as per the digital power supply pins. figure 1-5. power supply bypassing 1.7 regulator power supply configuration (vreg) v reg is the output from the on-chip regulator. all internal logics, except for the i/o pads, are powered by v reg output. v reg requires an external ceramic bypass capacitor of 100 nf as figure 1-6 shows. place the bypass capacitor as close to the v reg pin as possible. figure 1-6. regulator power supply bypassing mcu v dd c2(a) c1(a) 0.1 f v ss v dd + note: component values shown represent typical applications. v dd c2(b) c1(b) 0.1 f v ssa v dda + mcu v ss v reg c vregbypass 100 nf general description mc68hc908ap a-family data sheet, rev. 2 28 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 29 chapter 2 memory 2.1 introduction the cpu08 can address 64k-bytes of memory space. the memory map, shown in figure 2-1 , includes: 62,368 bytes of user flash ?mc68hc908ap64a 32,768 bytes of user flash ?mc68hc908ap32a 16,384 bytes of user flash ?mc68hc908ap16a 8,192 bytes of user flash ?MC68HC908AP8A 2,048 bytes of ram ?mc68hc908ap64a and mc68hc908ap32a 1,024 bytes of ram ?mc68hc908ap16a and MC68HC908AP8A 48 bytes of user-defined vectors 959 bytes of monitor rom 2.2 input/output (i/o) section most of the control, status, and data registers are in the zero page area of $0000?005f. additional i/o registers have these addresses: $fe00; sim break status register, sbsr $fe01; sim reset status register, srsr $fe02; reserved $fe03; sim break flag control register, sbfcr $fe04; interrupt status register 1, int1 $fe05; interrupt status register 2, int2 $fe06; interrupt status register 3, int3 $fe07; reserved $fe08; flash control register, flcr $fe09; flash block protect register, flbpr $fe0a; reserved $fe0b; reserved $fe0c; break address register high, brkh $fe0d; break address register low, brkl $fe0e; break status and control register, brkscr $fe0f; lvi status register, lvisr $ffcf; mask option register, mor (flash register) $ffff; cop control register, copctl 2.3 monitor rom the 959 bytes at addresses $fc00?fdff and $fe10?ffce are reserved rom addresses that contain the instructions for the monitor functions. (see chapter 8 monitor rom (mon) .) memory mc68hc908ap a-family data sheet, rev. 2 30 freescale semiconductor $0000 $005f i/o registers 96 bytes mc68hc908ap32a mc68hc908ap16a MC68HC908AP8A $0060 $085f ram 2,048 bytes (mc68hc908ap64a) ram 2,048 bytes $0060 $085f ram 1,024 bytes $0060 $045f ram 1,024 bytes $0060 $045f unimplemented 1,024 bytes unimplemented 1,024 bytes $0860 $fbff flash memory 62,368 bytes (mc68hc908ap64a) flash memory 32,768 bytes $0860 $885f flash memory 16,384 bytes $0860 $485f flash memory 8,192 bytes $0860 $285f unimplemented 54,176 bytes $2860 $fbff unimplemented 45,984 bytes $4860 $fbff unimplemented 29,600 bytes $8860 $fbff $fc00 $fdff monitor rom 2 512 bytes $fe00 sim break status register $fe01 sim reset status register $fe02 reserved $fe03 sim break flag control register $fe04 interrupt status register 1 $fe05 interrupt status register 2 $fe06 interrupt status register 3 $fe07 reserved $fe08 flash control register $fe09 flash block protect register $fe0a reserved $fe0b reserved $fe0c break address register high $fe0d break address register low $fe0e break status and control register $fe0f lvi status register $fe10 $ffce monitor rom 1 447 bytes $ffcf mask option register $ffd0 $ffff flash vectors 48 bytes figure 2-1. memory map monitor rom mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 31 addr. register name bit 7 654321bit 0 $0000 port a data register (pta) read: pta7 pta6 pta5 pta4 pta3 pta2 pta1 pta0 write: reset: unaffected by reset $0001 port b data register (ptb) read: ptb7 ptb6 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 write: reset: unaffected by reset $0002 port c data register (ptc) read: ptc7 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1 ptc0 write: reset: unaffected by reset $0003 port d data register (ptd) read: ptd7 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 write: reset: unaffected by reset $0004 data direction register a (ddra) read: ddra7 ddra6 ddra5 ddra4 ddra3 ddra2 ddra1 ddra0 write: reset: 00000000 $0005 data direction register b (ddrb) read: ddrb7 ddrb6 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 write: reset: 00000000 $0006 data direction register c (ddrc) read: ddrc7 ddrc6 ddrc5 ddrc4 ddrc3 ddrc2 ddrc1 ddrc0 write: reset: 00000000 $0007 data direction register d (ddrd) read: ddrd7 ddrd6 ddrd5 ddrd4 ddrd3 ddrd2 ddrd1 ddrd0 write: reset: 00000000 $0008 unimplemented read: write: reset: $0009 unimplemented read: write: reset: $000a unimplemented read: write: reset: $000b unimplemented read: write: reset: $000c port-a led control register (leda) read: leda7 leda6 leda5 leda4 leda3 leda2 leda1 leda0 write: reset: 00000000 u = unaffected x = indeterminate = unimplemented r = reserved figure 2-2. control, status, and data registers (sheet 1 of 9) memory mc68hc908ap a-family data sheet, rev. 2 32 freescale semiconductor $000d unimplemented read: write: reset: $000e unimplemented read: write: reset: $000f unimplemented read: write: reset: $0010 spi control register (spcr) read: sprie r spmstr cpol cpha spwom spe sptie write: reset: 00101000 $0011 spi status and control register (spscr) read: sprf errie ovrf modf spte modfen spr1 spr0 write: reset: 00001000 $0012 spi data register (spdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset $0013 sci control register 1 (scc1) read: loops ensci txinv m wake ilty pen pty write: reset: 00000000 $0014 sci control register 2 (scc2) read: sctie tcie scrie ilie te re rwu sbk write: reset: 00000000 $0015 sci control register 3 (scc3) read: r8 t8 dmare dmate orie neie feie peie write: reset: u u 000000 $0016 sci status register 1 (scs1) read: scte tc scrf idle or nf fe pe write: reset: 11000000 $0017 sci status register 2 (scs2) read:000000bkfrpf write: reset: 00000000 $0018 sci data register (scdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset $0019 sci baud rate register (scbr) read: 0 0 scp1 scp0 r scr2 scr1 scr0 write: reset: 00000000 addr. register name bit 7 654321bit 0 u = unaffected x = indeterminate = unimplemented r = reserved figure 2-2. control, status, and data registers (sheet 2 of 9) monitor rom mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 33 $001a keyboard status and control register (kbscr) read:0000 keyf 0 imask mode write: ack reset: 00000000 $001b keyboard interrupt enable register (kbier) read: kbie7 kbie6 kbie5 kbie4 kbie3 kbie2 kbie1 kbie0 write: reset: 00000000 $001c irq2 status and control reg- ister (intscr2) read: 0 puc0enb 0 0 irq2f 0 imask2 mode2 write: ack2 reset: 00000000 $001d con?uration register 2 (config2) ? read: stop_ iclkdis stop_ rclken stop_ xclken oscclk1 oscclk0 00 scibdsrc write: reset: 00000000 ? one-time writable register after each reset. $001e irq1 status and control reg- ister (intscr1) read:0000i rq1f 0 imask1 mode1 write: ack1 reset: 00000000 $001f con?uration register 1 (config1) ? read: coprs lvistop lvirstd lvipwrd lviregd ssrec stop copd write: reset: 00000000 ? one-time writable register after each reset. $0020 timer 1 status and control register (t1sc) read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst reset: 00100000 $0021 timer 1 counter register high (t1cnth) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: 00000000 $0022 timer 1 counter register low (t1cntl) read:bit 7654321bit 0 write: reset: 00000000 $0023 timer 1 counter modulo reg- ister high (t1modh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: 11111111 $0024 timer 1 counter modulo register low (t1modl) read: bit 7654321bit 0 write: reset: 11111111 $0025 timer 1 channel 0 status and control register (t1sc0) read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset: 00000000 addr. register name bit 7 654321bit 0 u = unaffected x = indeterminate = unimplemented r = reserved figure 2-2. control, status, and data registers (sheet 3 of 9) memory mc68hc908ap a-family data sheet, rev. 2 34 freescale semiconductor $0026 timer 1 channel 0 register high (t1ch0h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $0027 timer 1 channel 0 register low (t1ch0l) read: bit 7654321bit 0 write: reset: indeterminate after reset $0028 timer 1 channel 1 status and control register (t1sc1) read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 reset: 00000000 $0029 timer 1 channel 1 register high (t1ch1h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $002a timer 1 channel 1 register low (t1ch1l) read: bit 7654321bit 0 write: reset: indeterminate after reset $002b timer 2 status and control register (t2sc) read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst reset: 00100000 $002c timer 2 counter register high (t2cnth) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: 00000000 $002d timer 2 counter register low (t2cntl) read:bit 7654321bit 0 write: reset: 00000000 $002e timer 2 counter modulo reg- ister high (t2modh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: 11111111 $002f timer 2 counter modulo register low (t2modl) read: bit 7654321bit 0 write: reset: 11111111 $0030 timer 2 channel 0 status and control register (t2sc0) read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset: 00000000 $0031 timer 2 channel 0 register high (t2ch0h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $0032 timer 2 channel 0 register low (t2ch0l) read: bit 7654321bit 0 write: reset: indeterminate after reset addr. register name bit 7 654321bit 0 u = unaffected x = indeterminate = unimplemented r = reserved figure 2-2. control, status, and data registers (sheet 4 of 9) monitor rom mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 35 $0033 timer 2 channel 1 status and control register (t2sc1) read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 reset: 00000000 $0034 timer 2 channel 1 register high (t2ch1h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $0035 timer 2 channel 1 register low (t2ch1l) read: bit 7654321bit 0 write: reset: indeterminate after reset $0036 pll control register (pctl) read: pllie pllf pllon bcs pre1 pre0 vpr1 vpr0 write: reset: 00100000 $0037 pll bandwidth control reg- ister (pbwc) read: auto lock acq 0000 r write: reset: 00000000 $0038 pll multiplier select register high (pmsh) read:0000 mul11 mul10 mul9 mul8 write: reset: 00000000 $0039 pll multiplier select register low (pmsl) read: mul7 mul6 mul5 mul4 mul3 mul2 mul1 mul0 write: reset: 01000000 $003a pll vco range select register (pmrs) read: vrs7 vrs6 vrs5 vrs4 vrs3 vrs2 vrs1 vrs0 write: reset: 01000000 $003b pll reference divider select register (pmds) read:0000 rds3 rds2 rds1 rds0 write: reset: 00000001 $003c unimplemented read: write: reset: $003d unimplemented read: write: reset: $003e unimplemented read: write: reset: $003f unimplemented read: write: reset: addr. register name bit 7 654321bit 0 u = unaffected x = indeterminate = unimplemented r = reserved figure 2-2. control, status, and data registers (sheet 5 of 9) memory mc68hc908ap a-family data sheet, rev. 2 36 freescale semiconductor $0040 irsci control register 1 (irscc1) read: loops ensci 0 m wake ilty pen pty write: reset: 00000000 $0041 irsci control register 2 (irscc2) read: sctie tcie scrie ilie te re rwu sbk write: reset: 00000000 $0042 irsci control register 3 (irscc3) read: r8 t8 dmare dmate orie neie feie peie write: reset: u u 000000 $0043 irsci status register 1 (irscs1) read: scte tc scrf idle or nf fe pe write: reset: 11000000 $0044 irsci status register 2 (irscs2) read: bkf rpf write: reset: 00000000 $0045 irsci data register (irscdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset $0046 irsci baud rate register (irscbr) read: cks 0 scp1 scp0 r scr2 scr1 scr0 write: reset: 00000000 $0047 irsci infrared control register (irscircr) read: r 0 0 0 r tnp1 tnp0 iren write: reset: 00000000 $0048 mmiic address register (mmadr) read: mmad7 mmad6 mmad5 mmad4 mmad3 mmad2 mmad1 mmextad write: reset: 10100000 $0049 mmiic control register 1 (mmcr1) read: mmen mmien 0 0 mmtxak repsen mmcrcby te 0 write: mmclrbb reset: 00000000 $004a mmiic control register 2 (mmcr2) read: mmalif mmnakif mmbb mmast mmrw 0 0 mmcrcef write: 0 0 reset: 0 0 0 0 0 0 0 unaffected $004b mmiic status register (mmsr) read: mmrxif mmtxif mmatch mmsrw mmrxak mmcrcbf mmtxbe mmrxbf write: 0 0 reset: 0 0 0 0 1010 $004c mmiic data transmit register (mmdtr) read: mmtd7 mmtd6 mmtd5 mmtd4 mmtd3 mmtd2 mmtd1 mmtd0 write: reset: 00000000 addr. register name bit 7 654321bit 0 u = unaffected x = indeterminate = unimplemented r = reserved figure 2-2. control, status, and data registers (sheet 6 of 9) monitor rom mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 37 $004d mmiic data receive register (mmdrr) read: mmrd7 mmrd6 mmrd5 mmrd4 mmrd3 mmrd2 mmrd1 mmrd0 write: reset: 00000000 $004e mmiic crc data register (mmcrdr) read: mmcrcd7 mmcrcd6 mmcrcd5 mmcrcd4 mmcrcd3 mmcrcd2 mmcrcd1 mmcrcd0 write: reset: 00000000 $004f mmiic frequency divider register (mmfdr) read: 0 0 0 0 0 mmbr2 mmbr1 mmbr0 write: reset: 00000100 $0050 reserved read: rrrrrrrr write: reset: $0051 timebase control register (tbcr) read: tbif tbr2 tbr1 tbr0 0 tbie tbon r write: tack reset: 00000000 $0052 unimplemented read: write: reset: $0053 unimplemented read: write: reset: $0054 unimplemented read: write: reset: $0055 unimplemented read: write: reset: $0056 unimplemented read: write: reset: $0057 adc status and control register (adscr) read: coco aien adco adch4 adch3 adch2 adch1 adch0 write: reset: 00011111 $0058 adc clock control register (adiclk) read: adiv2 adiv1 adiv0 adiclk mode1 mode0 0 0 write: r reset: 00000000 $0059 adc data register high 0 (adrh0) read: adx adx adx adx adx adx adx adx write: rrrrrrrr reset: 00000000 addr. register name bit 7 654321bit 0 u = unaffected x = indeterminate = unimplemented r = reserved figure 2-2. control, status, and data registers (sheet 7 of 9) memory mc68hc908ap a-family data sheet, rev. 2 38 freescale semiconductor $005a adc data register low 0 (adrl0) read: adx adx adx adx adx adx adx adx write: rrrrrrrr reset: 00000000 $005b adc data register low 1 (adrl1) read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write: rrrrrrrr reset: 00000000 $005c adc data register low 2 (adrl2) read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write: rrrrrrrr reset: 00000000 $005d adc data register low 3 (adrl3) read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write: rrrrrrrr reset: 00000000 $005e adc auto-scan control register (adascr) read: auto1 auto0 ascan write: reset: 00000000 $005f unimplemented read: write: reset: $fe00 sim break status register (sbsr) read: rrrrrr sbsw r write: note reset: 0 note: writing a logic 0 clears sbsw. $fe01 sim reset status register (srsr) read: por pin cop ilop ilad modrst lvi 0 write: reset: 10000000 $fe02 reserved read: rrrrrrrr write: reset: $fe03 sim break flag control reg- ister (sbfcr) read: bcfe rrrrrrr write: reset: 0 $fe04 interrupt status register 1 (int1) read: if6 if5 if4 if3 if2 if1 0 0 write: rrrrrrrr reset: 00000000 $fe05 interrupt status register 2 (int2) read: if14 if13 if12 if11 if10 if9 if8 if7 write: rrrrrrrr reset: 00000000 addr. register name bit 7 654321bit 0 u = unaffected x = indeterminate = unimplemented r = reserved figure 2-2. control, status, and data registers (sheet 8 of 9) monitor rom mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 39 $fe06 interrupt status register 3 (int3) read: 0 if21 if20 if19 if18 if17 if16 if15 write: rrrrrrrr reset: 00000000 $fe07 reserved read: rrrrrrrr write: reset: $fe08 flash control register (flcr) read:0000 hven mass erase pgm write: reset: 00000000 $fe09 flash block protect register (flbpr) read: bpr7 bpr6 bpr5 bpr4 bpr3 bpr2 bpr1 bpr0 write: reset: 00000000 $fe0a reserved read: rrrrrrrr write: reset: $fe0b reserved read: rrrrrrrr write: reset: $fe0c break address register high (brkh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: 00000000 $fe0d break address register low (brkl) read: bit 7654321bit 0 write: reset: 00000000 $fe0e break status and control register (brkscr) reset: brke brka 000000 read: write: 00000000 $fe0f lvi status register (lvisr) reset: lviout 0 000000 read: write: 00000000 $ffcf mask option register (mor) # read: oscsel1 oscsel0 rrrrrr write: erased:11111111 reset:uuuuuuuu $ffff cop control register (copctl) read: low byte of reset vector write: writing clears cop counter (any value) reset: unaffected by reset # mor is a non-volatile flash register; write by programming. addr. register name bit 7 654321bit 0 u = unaffected x = indeterminate = unimplemented r = reserved figure 2-2. control, status, and data registers (sheet 9 of 9) memory mc68hc908ap a-family data sheet, rev. 2 40 freescale semiconductor table 2-1. vector addresses priority int flag address vector lowest $ffd0 reserved $ffd1 reserved if21 $ffd2 tbm vector (high) $ffd3 tbm vector (low) if20 $ffd4 sci2 (irsci) transmit vector (high) $ffd5 sci2 (irsci) transmit vector (low) if19 $ffd6 sci2 (irsci) receive vector (high) $ffd7 sci2 (irsci) receive vector (low) if18 $ffd8 sci2 (irsci) error vector (high) $ffd9 sci2 (irsci) error vector (low) if17 $ffda spi transmit vector (high) $ffdb spi transmit vector (low) if16 $ffdc spi receive vector (high) $ffdd spi receive vector (low) if15 $ffde adc conversion complete vector (high) $ffdf adc conversion complete vector (low) if14 $ffe0 keyboard vector (high) $ffe1 keyboard vector (low) if13 $ffe2 sci transmit vector (high) $ffe3 sci transmit vector (low) if12 $ffe4 sci receive vector (high) $ffe5 sci receive vector (low) if11 $ffe6 sci error vector (high) $ffe7 sci error vector (low) if10 $ffe8 mmiic interrupt vector (high) $ffe9 mmiic interrupt vector (low) if9 $ffea tim2 over?w vector (high) $ffeb tim2 over?w vector (low) random-access memory (ram) mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 41 2.4 random-access memory (ram) addresses $0060 through $085f (or $045f) are ram locations. the location of the stack ram is programmable. the 16-bit stack pointer allows the stack to be anywhere in the 64k-byte memory space. note for correct operation, the stack pointer must point only to ram locations. within page zero are 160 bytes of ram. because the location of the stack ram is programmable, all page zero ram locations can be used for i/o control and user data or code. when the stack pointer is moved from its reset location at $00ff, direct addressing mode instructions can access efficiently all page zero ram locations. page zero ram, therefore, provides ideal locations for frequently accessed global variables. if8 $ffec tim2 channel 1 vector (high) $ffed tim2 channel 1 vector (low) if7 $ffee tim2 channel 0 vector (high) $ffef tim2 channel 0 vector (low) if6 $fff0 tim1 over?w vector (high) $fff1 tim1 over?w vector (low) if5 $fff2 tim1 channel 1 vector (high) $fff3 tim1 channel 1 vector (low) if4 $fff4 tim1 channel 0 vector (high) $fff5 tim1 channel 0 vector (low) if3 $fff6 pll vector (high) $fff7 pll vector (low) if2 $fff8 irq2 vector (high) $fff9 irq2 vector (low) if1 $fffa irq1 vector (high) $fffb irq1 vector (low) $fffc swi vector (high) $fffd swi vector (low) $fffe reset vector (high) highest $ffff reset vector (low) table 2-1. vector addresses (continued) priority int flag address vector memory mc68hc908ap a-family data sheet, rev. 2 42 freescale semiconductor before processing an interrupt, the cpu uses five bytes of the stack to save the contents of the cpu registers. note for m6805 compatibility, the h register is not stacked. during a subroutine call, the cpu uses two bytes of the stack to store the return address. the stack pointer decrements during pushes and increments during pulls. note be careful when using nested subroutines. the cpu may overwrite data in the ram during a subroutine or during the interrupt stacking operation. 2.5 flash memory this sub-section describes the operation of the embedded flash memory. this memory can be read, programmed, and erased from a single external supply. the program and erase operations are enabled through the use of an internal charge pump. 2.5.1 functional description the flash memory consists of an array of 62,368 bytes for user memory plus a block of 48 bytes for user interrupt vectors and one byte for the mask option register. an erased bit reads as logic 1 and a programmed bit reads as a logic 0. the flash memory page size is defined as 512 bytes, and is the minimum size that can be erased in a page erase operation. program and erase operations are facilitated through control bits in flash control register (flcr). the address ranges for the flash memory are: $0860?fbff; user memory, 62,368 bytes $ffd0?ffff; user interrupt vectors, 48 bytes $ffcf; mask option register programming tools are available from freescale. contact your local freescale representative for more information. note a security feature prevents viewing of the flash contents. (1) device flash memory size (bytes) memory address range mc68hc908ap64a 62,368 $0860?fbff mc68hc908ap32a 32,768 $0860?885f mc68hc908ap16a 16,384 $0860?485f MC68HC908AP8A 8,192 $0860?285f 1. no security feature is absolutely secure. however, freescale? strategy is to make reading or copying the flash difficult for unauthorized users. flash memory mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 43 2.5.2 flash control register the flash control register (flcr) controls flash program and erase operation. hven ?high voltage enable bit this read/write bit enables the charge pump to drive high voltages for program and erase operations in the array. hven can only be set if either pgm = 1 or erase = 1 and the proper sequence for program or erase is followed. 1 = high voltage enabled to array and charge pump on 0 = high voltage disabled to array and charge pump off mass ?mass erase control bit this read/write bit configures the memory for mass erase operation or page erase operation when the erase bit is set. 1 = mass erase operation selected 0 = page erase operation selected erase ?erase control bit this read/write bit configures the memory for erase operation. erase is interlocked with the pgm bit such that both bits cannot be equal to 1 or set to 1 at the same time. 1 = erase operation selected 0 = erase operation not selected pgm ?program control bit this read/write bit configures the memory for program operation. pgm is interlocked with the erase bit such that both bits cannot be equal to 1 or set to 1 at the same time. 1 = program operation selected 0 = program operation not selected 2.5.3 flash page erase operation use the following procedure to erase a page of flash memory. a page consists of 512 consecutive bytes starting from addresses $x000, $x200, $x400, $x600, $x800, $xa00, $xc00, or $xe00. the 48-byte user interrupt vectors cannot be erased by the page erase operation because of security reasons. mass erase is required to erase this page. 1. set the erase bit and clear the mass bit in the flash control register. 2. write any data to any flash location within the page address range desired. 3. wait for a time, t nvs (5 s). 4. set the hven bit. 5. wait for a time t erase (20 ms). 6. clear the erase bit. 7. wait for a time, t nvh (5 s). address: $fe08 bit 7654321bit 0 read: 0000 hven mass erase pgm write: reset:00000000 figure 2-3. flash control register (flcr) memory mc68hc908ap a-family data sheet, rev. 2 44 freescale semiconductor 8. clear the hven bit. 9. after time, t rcv (1 s), the memory can be accessed in read mode again. note programming and erasing of flash locations cannot be performed by code being executed from the flash memory. while these operations must be performed in the order as shown, but other unrelated operations may occur between the steps. 2.5.4 flash mass erase operation use the following procedure to erase the entire flash memory: 1. set both the erase bit and the mass bit in the flash control register. 2. write any data to any flash location within the flash memory address range. 3. wait for a time, t nvs (5 s). 4. set the hven bit. 5. wait for a time t me (200 ms). (see note below.) 6. clear the erase bit. 7. wait for a time, t nvh1 (100 s). 8. clear the hven bit. 9. after time, t rcv (1 s), the memory can be accessed in read mode again. note due to the relatively long mass erase time, user should take care in the code to prevent a cop reset from happening while the hven bit is set. programming and erasing of flash locations cannot be performed by code being executed from the flash memory. while these operations must be performed in the order as shown, but other unrelated operations may occur between the steps. 2.5.5 flash program operation programming of the flash memory is done on a row basis. a row consists of 64 consecutive bytes starting from addresses $xx00, $xx40, $xx80 or $xxc0. use the following procedure to program a row of flash memory. ( figure 2-4 shows a flowchart of the programming algorithm.) 1. set the pgm bit. this configures the memory for program operation and enables the latching of address and data for programming. 2. write any data to any flash location within the address range of the row to be programmed. 3. wait for a time, t nvs (5 s). 4. set the hven bit. 5. wait for a time, t pgs (10 s). 6. write data to the flash location to be programmed. 7. wait for time, t prog (20 s to 40 s). 8. repeat steps 6 and 7 until all bytes within the row are programmed. 9. clear the pgm bit. 10. wait for time, t nvh (5 s). 11. clear the hven bit. flash memory mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 45 12. after time, t rcv (1 s), the memory can be accessed in read mode again. this program sequence is repeated throughout the memory until all data is programmed. note the time between each flash address change (step 6 to step 6), or the time between the last flash addressed programmed to clearing the pgm bit (step 6 to step 9), must not exceed the maximum programming time, t prog max. note programming and erasing of flash locations cannot be performed by code being executed from the flash memory. while these operations must be performed in the order shown, other unrelated operations may occur between the steps. 2.5.6 flash protection due to the ability of the on-board charge pump to erase and program the flash memory in the target application, provision is made to protect pages of memory from unintentional erase or program operations due to system malfunction. this protection is done by use of a flash block protect register (flbpr). the flbpr determines the range of the flash memory which is to be protected. the range of the protected area starts from a location defined by flbpr and ends to the bottom of the flash memory ($ffff). when the memory is protected, the hven bit cannot be set in either erase or program operations. note the mask option register ($ffcf) and the 48 bytes of user interrupt vectors ($ffd0?ffff) are always protected, regardless of the value in the flash block protect register. a mass erase is required to erase these locations. memory mc68hc908ap a-family data sheet, rev. 2 46 freescale semiconductor figure 2-4. flash programming flowchart set hven bit write any data to any flash address within the row address range desired wait for a time, t nvs set pgm bit wait for a time, t pgs write data to the flash address to be programmed wait for a time, t prog clear pgm bit wait for a time, t nvh clear hven bit wait for a time, t rcv completed programming this row? y n end of programming the time between each flash address change (step 6 to step 6), or must not exceed the maximum programming time, t prog max. the time between the last flash address programmed to clearing pgm bit (step 6 to step 9) note: 1 2 3 4 5 6 7 9 10 11 12 algorithm for programming a row (64 bytes) of flash memory this row program algorithm assumes the row/s to be programmed are initially erased. flash memory mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 47 2.5.7 flash block protect register the flash block protect register is implemented as an 8-bit i/o register. the value in this register determines the starting address of the protected range within the flash memory. bpr[7:0] ?flash block protect bits bpr[7:1] represent bits [15:9] of a 16-bit memory address. bits [8:0] are logic 0?. bpr0 is used only for bpr[7:0] = $ff, for no block protection. the resultant 16-bit address is used for specifying the start address of the flash memory for block protection. the flash is protected from this start address to the end of flash memory, at $ffff. with this mechanism, the protect start address can be x000, x200, x400, x0600, x800, xa00, xc00, or xe00 (at page boundaries ?512 bytes) within the flash memory. examples of protect start address: address: $fe09 bit 7654321bit 0 read: bpr7 bpr6 bpr5 bpr4 bpr3 bpr2 bpr1 bpr0 write: reset:00000000 figure 2-5. flash block protect register (flbpr) 16-bit memory address start address of flash block protect 000000000 bpr[7:1] table 2-2 flash block protect range bpr[7:0] protected range $00 to $09 the entire flash memory is protected. $0a or $0b ( 0000 101x ) $0a00 to $ffff $0c or $0d ( 0000 110x ) $0c00 to $ffff and so on... $fa or $fb ( 1111 1101x ) $fa00 to $ffff $fc or $fd or $fe $ffcf to $ffff $ff the entire flash memory is not protected. (1) 1. except for the mask option register ($ffcf) and the 48-byte user vectors ($ffd0?ffff). these flash locations are always protected. memory mc68hc908ap a-family data sheet, rev. 2 48 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 49 chapter 3 configuration & mask option registers (config & mor) 3.1 introduction this section describes the configuration registers, config1 and config2; and the mask option register, mor. the configuration registers enable or disable these options: computer operating properly module (cop) cop timeout period (2 18 ?2 4 or 2 13 ?2 4 iclk cycles) low-voltage inhibit (lvi) on v dd lvi on v reg lvi module reset lvi module in stop mode stop instruction stop mode recovery time (32 iclk or 4096 iclk cycles) oscillator (internal, rc, and crystal) during stop mode serial communications interface clock source (cgmxclk or f bus ) the mask option register selects one of the following oscillator options: internal oscillator rc oscillator crystal oscillator addr. register name bit 7 654321bit 0 $001d con?uration register 2 (config2) ? read: stop_ iclkdis stop_ rclken stop_ xclken oscclk1 oscclk0 00 scibdsrc write: reset: 00000000 $001f con?uration register 1 (config1) ? read: coprs lvistop lvirstd lvipwrd lviregd ssrec stop copd write: reset: 00000000 $ffcf mask-option-register (mor) # read: oscsel1 oscsel0 rrrrrr write: erased:11111111 ? one-time writable register after each reset. # mor is a non-volatile flash register; write by programming. = unimplemented r = reserved figure 3-1. config and mor registers summary configuration & mask option registers (config & mor) mc68hc908ap a-family data sheet, rev. 2 50 freescale semiconductor 3.2 functional description the configuration registers and the mask option register are used in the initialization of various options. these two types of registers are configured differently: configuration registers ?write-once registers after reset mask option register ?flash register (write by programming) the configuration registers can be written once after each reset. all of the configuration register bits are cleared during reset. since the various options affect the operation of the mcu, it is recommended that these registers be written immediately after reset. the configuration registers are located at $001d and $001f. the configuration registers may be read at anytime. note the config registers are not in the flash memory but are special registers containing one-time writable latches after each reset. upon a reset, the config registers default to predetermined settings as shown in figure 3-2 and figure 3-3 . the mask option register (mor) is used for selecting one of the three clock options for the mcu. the mor is a byte located in flash memory, and is written to by a flash programming routine. 3.3 configuration register 1 (config1) coprs ?cop rate select bit coprs selects the cop time out period. reset clears coprs. (see chapter 19 computer operating properly (cop) .) 1 = cop time out period = 2 13 ?2 4 iclk cycles 0 = cop time out period = 2 18 ?2 4 iclk cycles lvistop ?lvi enable in stop mode bit when the lvipwrd or lviregd bit is clear, setting the lvistop bit enables the lvi to operate during stop mode. reset clears lvistop. (see chapter 20 low-voltage inhibit (lvi) .) 1 = lvi enabled during stop mode 0 = lvi disabled during stop mode note if lvistop=0, set lvirstd=1 before entering stop mode. lvirstd ?lvi reset disable bit lvirstd disables the reset signal from the lvi module. (see chapter 20 low-voltage inhibit (lvi) .) 1 = lvi module resets disabled 0 = lvi module resets enabled address: $001f bit 7654321bit 0 read: coprs lvistop lvirstd lvipwrd lviregd ssrec stop copd write: reset:00000000 figure 3-2. configuration register 1 (config1) configuration register 1 (config1) mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 51 lvipwrd ?v dd lvi circuit disable bit lvipwrd disables the v dd lvi circuit. (see chapter 20 low-voltage inhibit (lvi) .) 1 = v dd lvi circuit disabled 0 = v dd lvi circuit enabled lviregd ?v reg lvi circuit disable bit lviregd disables the v reg lvi circuit. (see chapter 20 low-voltage inhibit (lvi) .) 1 = v reg lvi circuit disabled 0 = v reg lvi circuit enabled note if lvipwrd=1 and lviregd=1, set lvirstd=1 before entering stop mode. ssrec ?short stop recovery bit ssrec enables the cpu to exit stop mode with a delay of 32 iclk cycles instead of a 4096 iclk cycle delay. 1 = stop mode recovery after 32 iclk cycles 0 = stop mode recovery after 4096 iclk cycles note exiting stop mode by pulling reset will result in the long stop recovery. if using an external crystal oscillator, do not set the ssrec bit. when the lvi is disabled in stop mode (lvistop=0), the system stabilization time for long stop recovery (4096 iclk cycles) gives a delay longer than the lvi? turn-on time. there is no period where the mcu is not protected from a low power condition. however, when using the short stop recovery configuration option, the 32 iclk delay is less than the lvi? turn-on time and there exists a period in start-up where the lvi is not protecting the mcu. stop ?stop instruction enable bit stop enables the stop instruction. 1 = stop instruction enabled 0 = stop instruction treated as illegal opcode copd ?cop disable bit copd disables the cop module. (see chapter 19 computer operating properly (cop) .) 1 = cop module disabled 0 = cop module enabled configuration & mask option registers (config & mor) mc68hc908ap a-family data sheet, rev. 2 52 freescale semiconductor 3.4 configuration register 2 (config2) stop_iclkdis ?internal oscillator stop mode disable stop_iclkdis disables the internal oscillator during stop mode. setting the stop_iclkdis bit disables the oscillator during stop mode. (see chapter 5 oscillator (osc) .) reset clears this bit. 1 = internal oscillator disabled during stop mode 0 = internal oscillator enabled to operate during stop mode stop_rclken ?rc oscillator stop mode enable bit stop_rclken enables the rc oscillator to continue operating during stop mode. setting the stop_rclken bit allows the oscillator to operate continuously even during stop mode. this is useful for driving the timebase module to allow it to generate periodic wake up while in stop mode. (see chapter 5 oscillator (osc) .) reset clears this bit. 1 = rc oscillator enabled to operate during stop mode 0 = rc oscillator disabled during stop mode stop_xclken ?x-tal oscillator stop mode enable bit stop_xclken enables the crystal (x-tal) oscillator to continue operating during stop mode. setting the stop_xclken bit allows the x-tal oscillator to operate continuously even during stop mode. this is useful for driving the timebase module to allow it to generate periodic wake up while in stop mode. (see chapter 5 oscillator (osc) .) reset clears this bit. 1 = x-tal oscillator enabled to operate during stop mode 0 = x-tal oscillator disabled during stop mode oscclk1, oscclk0 ?oscillator output control bits oscclk1 and oscclk0 select which oscillator output to be driven out as oscclk to the timebase module (tbm). reset clears these two bits. address: $001d bit 7654321bit 0 read: stop_ iclkdis stop_ rclken stop_ xclken oscclk1 oscclk0 00 scibd- src write: reset:00000000 figure 3-3. configuration register 2 (config2) oscclk1 oscclk0 timebase clock source 0 0 internal oscillator (iclk) 0 1 rc oscillator (rcclk) 1 0 x-tal oscillator (xtal) 1 1 not used mask option register (mor) mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 53 scibdsrc ?sci baud rate clock source scibdsrc selects the clock source used for the standard sci module (non-infrared sci). the setting of this bit affects the frequency at which the sci operates. 1 = internal data bus clock, f bus , is used as clock source for sci 0 = oscillator clock, cgmxclk, is used as clock source for sci 3.5 mask option register (mor) the mask option register (mor) is used for selecting one of the three clock options for the mcu. the mor is a byte located in flash memory, and is written to by a flash programming routine. oscsel1, oscsel0 ?oscillator selection bits oscsel1 and oscsel0 select which oscillator is used for the mcu cgmxclk clock. the erase state of these two bits is logic 1. these bits are unaffected by reset. (see table 3-1 ). bits 5? ?should be left as 1? note the internal oscillator is a free running oscillator and is available after each por or reset. it is turned-off in stop mode by setting the stop_iclkdis bit in config2. address: $ffcf bit 7654321bit 0 read: oscsel1 oscsel0 rrrrrr write: reset: unaffected by reset erased:11111111 r = reserved figure 3-4. mask option register (mor) table 3-1. cgmxclk clock selection oscsel1 oscsel0 cgmxclk osc2 pin comments 00 not used 0 1 iclk f bus internal oscillator generates the cgmxclk. 1 0 rcclk f bus rc oscillator generates the cgmxclk. internal oscillator is available after each por or reset. 1 1 x-tal inverting output of xtal x-tal oscillator generates the cgmxclk. internal oscillator is available after each por or reset. configuration & mask option registers (config & mor) mc68hc908ap a-family data sheet, rev. 2 54 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 55 chapter 4 central processor unit (cpu) 4.1 introduction the m68hc08 cpu (central processor unit) is an enhanced and fully object-code-compatible version of the m68hc05 cpu. the cpu08 reference manual (freescale document order number cpu08rm/ad) contains a description of the cpu instruction set, addressing modes, and architecture. 4.2 features object code fully upward-compatible with m68hc05 family 16-bit stack pointer with stack manipulation instructions 16-bit index register with x-register manipulation instructions 8-mhz cpu internal bus frequency 64-kbyte program/data memory space 16 addressing modes memory-to-memory data moves without using accumulator fast 8-bit by 8-bit multiply and 16-bit by 8-bit divide instructions enhanced binary-coded decimal (bcd) data handling modular architecture with expandable internal bus definition for extension of addressing range beyond 64 kbytes low-power stop and wait modes central processor unit (cpu) mc68hc908ap a-family data sheet, rev. 2 56 freescale semiconductor 4.3 cpu registers figure 4-1 shows the five cpu registers. cpu registers are not part of the memory map. figure 4-1. cpu registers 4.3.1 accumulator the accumulator is a general-purpose 8-bit register. the cpu uses the accumulator to hold operands and the results of arithmetic/logic operations. 4.3.2 index register the 16-bit index register allows indexed addressing of a 64-kbyte memory space. h is the upper byte of the index register, and x is the lower byte. h:x is the concatenated 16-bit index register. in the indexed addressing modes, the cpu uses the contents of the index register to determine the conditional address of the operand. the index register can serve also as a temporary data storage location. bit 7654321bit 0 read: write: reset: unaffected by reset figure 4-2. accumulator (a) accumulator (a) index register (h:x) stack pointer (sp) program counter (pc) condition code register (ccr) carry/borrow flag zero flag negative flag interrupt mask half-carry flag two? complement overflow flag v11hinzc h x 0 0 0 0 7 15 15 15 70 cpu registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 57 4.3.3 stack pointer the stack pointer is a 16-bit register that contains the address of the next location on the stack. during a reset, the stack pointer is preset to $00ff. the reset stack pointer (rsp) instruction sets the least significant byte to $ff and does not affect the most significant byte. the stack pointer decrements as data is pushed onto the stack and increments as data is pulled from the stack. in the stack pointer 8-bit offset and 16-bit offset addressing modes, the stack pointer can function as an index register to access data on the stack. the cpu uses the contents of the stack pointer to determine the conditional address of the operand. note the location of the stack is arbitrary and may be relocated anywhere in ram. moving the sp out of page 0 ($0000 to $00ff) frees direct address (page 0) space. for correct operation, the stack pointer must point only to ram locations. 4.3.4 program counter the program counter is a 16-bit register that contains the address of the next instruction or operand to be fetched. normally, the program counter automatically increments to the next sequential memory location every time an instruction or operand is fetched. jump, branch, and interrupt operations load the program counter with an address other than that of the next sequential location. during reset, the program counter is loaded with the reset vector address located at $fffe and $ffff. the vector address is the address of the first instruction to be executed after exiting the reset state. bit 15 1413121110987654321bit 0 read: write: reset:00000000 xxxxxxxx x = indeterminate figure 4-3. index register (h:x) bit 15 1413121110987654321bit 0 read: write: reset:0000000011111111 figure 4-4. stack pointer (sp) central processor unit (cpu) mc68hc908ap a-family data sheet, rev. 2 58 freescale semiconductor 4.3.5 condition code register the 8-bit condition code register contains the interrupt mask and five flags that indicate the results of the instruction just executed. bits 6 and 5 are set permanently to logic 1. the following paragraphs describe the functions of the condition code register. v ?overflow flag the cpu sets the overflow flag when a two's complement overflow occurs. the signed branch instructions bgt, bge, ble, and blt use the overflow flag. 1 = overflow 0 = no overflow h ?half-carry flag the cpu sets the half-carry flag when a carry occurs between accumulator bits 3 and 4 during an add-without-carry (add) or add-with-carry (adc) operation. the half-carry flag is required for binary-coded decimal (bcd) arithmetic operations. the daa instruction uses the states of the h and c flags to determine the appropriate correction factor. 1 = carry between bits 3 and 4 0 = no carry between bits 3 and 4 i ?interrupt mask when the interrupt mask is set, all maskable cpu interrupts are disabled. cpu interrupts are enabled when the interrupt mask is cleared. when a cpu interrupt occurs, the interrupt mask is set automatically after the cpu registers are saved on the stack, but before the interrupt vector is fetched. 1 = interrupts disabled 0 = interrupts enabled note to maintain m6805 family compatibility, the upper byte of the index register (h) is not stacked automatically. if the interrupt service routine modifies h, then the user must stack and unstack h using the pshh and pulh instructions. bit 15 1413121110987654321bit 0 read: write: reset: loaded with vector from $fffe and $ffff figure 4-5. program counter (pc) bit 7654321bit 0 read: v11hinzc write: reset: x 1 1 x 1 x x x x = indeterminate figure 4-6. condition code register (ccr) arithmetic/logic unit (alu) mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 59 after the i bit is cleared, the highest-priority interrupt request is serviced first. a return-from-interrupt (rti) instruction pulls the cpu registers from the stack and restores the interrupt mask from the stack. after any reset, the interrupt mask is set and can be cleared only by the clear interrupt mask software instruction (cli). n ?negative flag the cpu sets the negative flag when an arithmetic operation, logic operation, or data manipulation produces a negative result, setting bit 7 of the result. 1 = negative result 0 = non-negative result z ?zero flag the cpu sets the zero flag when an arithmetic operation, logic operation, or data manipulation produces a result of $00. 1 = zero result 0 = non-zero result c ?carry/borrow flag the cpu sets the carry/borrow flag when an addition operation produces a carry out of bit 7 of the accumulator or when a subtraction operation requires a borrow. some instructions such as bit test and branch, shift, and rotate ?also clear or set the carry/borrow flag. 1 = carry out of bit 7 0 = no carry out of bit 7 4.4 arithmetic/logic unit (alu) the alu performs the arithmetic and logic operations defined by the instruction set. refer to the cpu08 reference manual (freescale document order number cpu08rm/ad) for a description of the instructions and addressing modes and more detail about the architecture of the cpu. 4.5 low-power modes the wait and stop instructions put the mcu in low power-consumption standby modes. 4.5.1 wait mode the wait instruction: clears the interrupt mask (i bit) in the condition code register, enabling interrupts. after exit from wait mode by interrupt, the i bit remains clear. after exit by reset, the i bit is set. disables the cpu clock 4.5.2 stop mode the stop instruction: clears the interrupt mask (i bit) in the condition code register, enabling external interrupts. after exit from stop mode by external interrupt, the i bit remains clear. after exit by reset, the i bit is set. disables the cpu clock after exiting stop mode, the cpu clock begins running after the oscillator stabilization delay. central processor unit (cpu) mc68hc908ap a-family data sheet, rev. 2 60 freescale semiconductor 4.6 cpu during break interrupts if a break module is present on the mcu, the cpu starts a break interrupt by: loading the instruction register with the swi instruction loading the program counter with $fffc:$fffd or with $fefc:$fefd in monitor mode the break interrupt begins after completion of the cpu instruction in progress. if the break address register match occurs on the last cycle of a cpu instruction, the break interrupt begins immediately. a return-from-interrupt instruction (rti) in the break routine ends the break interrupt and returns the mcu to normal operation if the break interrupt has been deasserted. 4.7 instruction set summary table 4-1 provides a summary of the m68hc08 instruction set. 4.8 opcode map the opcode map is provided in table 4-2 . table 4-1. instruction set summary source form operation description effect on ccr address mode opcode operand cycles vh i nzc adc # opr adc opr adc opr adc opr ,x adc opr ,x adc ,x adc opr ,sp adc opr ,sp add with carry a (a) + (m) + (c) oo ooo imm dir ext ix2 ix1 ix sp1 sp2 a9 b9 c9 d9 e9 f9 9ee9 9ed9 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 add # opr add opr add opr add opr ,x add opr ,x add ,x add opr ,sp add opr ,sp add without carry a (a) + (m) oo ooo imm dir ext ix2 ix1 ix sp1 sp2 ab bb cb db eb fb 9eeb 9edb ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 ais # opr add immediate value (signed) to sp sp (sp) + (16 ?m) imm a7 ii 2 aix # opr add immediate value (signed) to h:x h:x (h:x) + (16 ?m) imm af ii 2 opcode map mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 61 and # opr and opr and opr and opr ,x and opr ,x and ,x and opr ,sp and opr ,sp logical and a (a) & (m) 0 oo imm dir ext ix2 ix1 ix sp1 sp2 a4 b4 c4 d4 e4 f4 9ee4 9ed4 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 asl opr asla aslx asl opr ,x asl ,x asl opr ,sp arithmetic shift left (same as lsl) o ooo dir inh inh ix1 ix sp1 38 48 58 68 78 9e68 dd ff ff 4 1 1 4 3 5 asr opr asra asrx asr opr ,x asr opr ,x asr opr ,sp arithmetic shift right o ooo dir inh inh ix1 ix sp1 37 47 57 67 77 9e67 dd ff ff 4 1 1 4 3 5 bcc rel branch if carry bit clear pc (pc) + 2 + rel ? (c) = 0 rel 24 rr 3 bclr n , opr clear bit n in m mn 0 dir (b0) dir (b1) dir (b2) dir (b3) dir (b4) dir (b5) dir (b6) dir (b7) 11 13 15 17 19 1b 1d 1f dd dd dd dd dd dd dd dd 4 4 4 4 4 4 4 4 bcs rel branch if carry bit set (same as blo) pc (pc) + 2 + rel ? (c) = 1 rel 25 rr 3 beq rel branch if equal pc (pc) + 2 + rel ? (z) = 1 rel 27 rr 3 bge opr branch if greater than or equal to (signed operands) pc (pc) + 2 + rel ? (n v) = 0 rel 90 rr 3 bgt opr branch if greater than (signed operands) pc (pc) + 2 + rel ? (z) | (n v)=0 rel 92 rr 3 bhcc rel branch if half carry bit clear pc (pc) + 2 + rel ? (h) = 0 rel 28 rr 3 bhcs rel branch if half carry bit set pc (pc) + 2 + rel ? (h) = 1 rel 29 rr 3 bhi rel branch if higher pc (pc) + 2 + rel ? (c) | (z) = 0 rel 22 rr 3 bhs rel branch if higher or same (same as bcc) pc (pc) + 2 + rel ? (c) = 0 rel 24 rr 3 bih rel branch if irq pin high pc (pc) + 2 + rel ? irq = 1 rel 2f rr 3 bil rel branch if irq pin low pc (pc) + 2 + rel ? irq = 0 rel 2e rr 3 table 4-1. instruction set summary source form operation description effect on ccr address mode opcode operand cycles vh i nzc c b0 b7 0 b0 b7 c central processor unit (cpu) mc68hc908ap a-family data sheet, rev. 2 62 freescale semiconductor bit # opr bit opr bit opr bit opr ,x bit opr ,x bit ,x bit opr ,sp bit opr ,sp bit test (a) & (m) 0 oo imm dir ext ix2 ix1 ix sp1 sp2 a5 b5 c5 d5 e5 f5 9ee5 9ed5 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 ble opr branch if less than or equal to (signed operands) pc (pc) + 2 + rel ? (z) | (n v)=1 rel 93 rr 3 blo rel branch if lower (same as bcs) pc (pc) + 2 + rel ? (c) = 1 rel 25 rr 3 bls rel branch if lower or same pc (pc) + 2 + rel ? (c) | (z) = 1 rel 23 rr 3 blt opr branch if less than (signed operands) pc (pc) + 2 + rel ? (n v) = 1 rel 91 rr 3 bmc rel branch if interrupt mask clear pc (pc) + 2 + rel ? (i) = 0 rel 2c rr 3 bmi rel branch if minus pc (pc) + 2 + rel ? (n) = 1 rel 2b rr 3 bms rel branch if interrupt mask set pc (pc) + 2 + rel ? (i) = 1 rel 2d rr 3 bne rel branch if not equal pc (pc) + 2 + rel ? (z) = 0 rel 26 rr 3 bpl rel branch if plus pc (pc) + 2 + rel ? (n) = 0 rel 2a rr 3 bra rel branch always pc (pc) + 2 + rel rel 20 rr 3 brclr n , opr , rel branch if bit n in m clear pc (pc) + 3 + rel ? (mn) = 0 o dir (b0) dir (b1) dir (b2) dir (b3) dir (b4) dir (b5) dir (b6) dir (b7) 01 03 05 07 09 0b 0d 0f dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr 5 5 5 5 5 5 5 5 brn rel branch never pc (pc) + 2 rel 21 rr 3 brset n , opr , rel branch if bit n in m set pc (pc) + 3 + rel ? (mn) = 1 o dir (b0) dir (b1) dir (b2) dir (b3) dir (b4) dir (b5) dir (b6) dir (b7) 00 02 04 06 08 0a 0c 0e dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr 5 5 5 5 5 5 5 5 bset n , opr set bit n in m mn 1 dir (b0) dir (b1) dir (b2) dir (b3) dir (b4) dir (b5) dir (b6) dir (b7) 10 12 14 16 18 1a 1c 1e dd dd dd dd dd dd dd dd 4 4 4 4 4 4 4 4 table 4-1. instruction set summary source form operation description effect on ccr address mode opcode operand cycles vh i nzc opcode map mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 63 bsr rel branch to subroutine pc (pc) + 2; push (pcl) sp (sp) ?1; push (pch) sp (sp) ?1 pc (pc) + rel rel ad rr 4 cbeq opr,rel cbeqa # opr,rel cbeqx # opr,rel cbeq opr, x+ ,rel cbeq x+ ,rel cbeq opr, sp ,rel compare and branch if equal pc (pc) + 3 + rel ? (a) (m) = $00 pc (pc) + 3 + rel ? (a) (m) = $00 pc (pc) + 3 + rel ? (x) (m) = $00 pc (pc) + 3 + rel ? (a) (m) = $00 pc (pc) + 2 + rel ? (a) (m) = $00 pc (pc) + 4 + rel ? (a) (m) = $00 dir imm imm ix1+ ix+ sp1 31 41 51 61 71 9e61 dd rr ii rr ii rr ff rr rr ff rr 5 4 4 5 4 6 clc clear carry bit c 0 0 inh 98 1 cli clear interrupt mask i 0 0 inh 9a 2 clr opr clra clrx clrh clr opr ,x clr ,x clr opr ,sp clear m $00 a $00 x $00 h $00 m $00 m $00 m $00 001 dir inh inh inh ix1 ix sp1 3f 4f 5f 8c 6f 7f 9e6f dd ff ff 3 1 1 1 3 2 4 cmp # opr cmp opr cmp opr cmp opr ,x cmp opr ,x cmp ,x cmp opr ,sp cmp opr ,sp compare a with m (a) ?(m) o ooo imm dir ext ix2 ix1 ix sp1 sp2 a1 b1 c1 d1 e1 f1 9ee1 9ed1 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 com opr coma comx com opr ,x com ,x com opr ,sp complement (one s complement) m ( m) = $ff ?(m) a ( a) = $ff ?(m) x ( x) = $ff ?(m) m ( m) = $ff ?(m) m ( m) = $ff ?(m) m ( m) = $ff ?(m) 0 oo 1 dir inh inh ix1 ix sp1 33 43 53 63 73 9e63 dd ff ff 4 1 1 4 3 5 cphx # opr cphx opr compare h:x with m (h:x) ?(m:m + 1) o ooo imm dir 65 75 ii ii+1 dd 3 4 cpx # opr cpx opr cpx opr cpx ,x cpx opr ,x cpx opr ,x cpx opr ,sp cpx opr ,sp compare x with m (x) ?(m) o ooo imm dir ext ix2 ix1 ix sp1 sp2 a3 b3 c3 d3 e3 f3 9ee3 9ed3 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 daa decimal adjust a (a) 10 u ooo inh 72 2 table 4-1. instruction set summary source form operation description effect on ccr address mode opcode operand cycles vh i nzc central processor unit (cpu) mc68hc908ap a-family data sheet, rev. 2 64 freescale semiconductor dbnz opr,rel dbnza rel dbnzx rel dbnz opr, x ,rel dbnz x ,rel dbnz opr, sp ,rel decrement and branch if not zero a (a) 1 or m (m) 1 or x (x) 1 pc (pc) + 3 + rel ? (result) 0 pc (pc) + 2 + rel ? (result) 0 pc (pc) + 2 + rel ? (result) 0 pc (pc) + 3 + rel ? (result) 0 pc (pc) + 2 + rel ? (result) 0 pc (pc) + 4 + rel ? (result) 0 dir inh inh ix1 ix sp1 3b 4b 5b 6b 7b 9e6b dd rr rr rr ff rr rr ff rr 5 3 3 5 4 6 dec opr deca decx dec opr ,x dec ,x dec opr ,sp decrement m (m) ?1 a (a) ?1 x (x) ?1 m (m) ?1 m (m) ?1 m (m) ?1 o oo dir inh inh ix1 ix sp1 3a 4a 5a 6a 7a 9e6a dd ff ff 4 1 1 4 3 5 div divide a (h:a)/(x) h remainder oo inh 52 7 eor # opr eor opr eor opr eor opr ,x eor opr ,x eor ,x eor opr ,sp eor opr ,sp exclusive or m with a a (a m) 0 oo imm dir ext ix2 ix1 ix sp1 sp2 a8 b8 c8 d8 e8 f8 9ee8 9ed8 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 inc opr inca incx inc opr ,x inc ,x inc opr ,sp increment m (m) + 1 a (a) + 1 x (x) + 1 m (m) + 1 m (m) + 1 m (m) + 1 o oo dir inh inh ix1 ix sp1 3c 4c 5c 6c 7c 9e6c dd ff ff 4 1 1 4 3 5 jmp opr jmp opr jmp opr ,x jmp opr ,x jmp ,x jump pc jump address dir ext ix2 ix1 ix bc cc dc ec fc dd hh ll ee ff ff 2 3 4 3 2 jsr opr jsr opr jsr opr ,x jsr opr ,x jsr ,x jump to subroutine pc (pc) + n ( n = 1, 2, or 3) push (pcl); sp (sp) ?1 push (pch); sp (sp) ?1 pc unconditional address dir ext ix2 ix1 ix bd cd dd ed fd dd hh ll ee ff ff 4 5 6 5 4 lda # opr lda opr lda opr lda opr ,x lda opr ,x lda ,x lda opr ,sp lda opr ,sp load a from m a (m) 0 oo imm dir ext ix2 ix1 ix sp1 sp2 a6 b6 c6 d6 e6 f6 9ee6 9ed6 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 ldhx # opr ldhx opr load h:x from m h:x (m:m + 1) 0 oo imm dir 45 55 ii jj dd 3 4 table 4-1. instruction set summary source form operation description effect on ccr address mode opcode operand cycles vh i nzc opcode map mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 65 ldx # opr ldx opr ldx opr ldx opr ,x ldx opr ,x ldx ,x ldx opr ,sp ldx opr ,sp load x from m x (m) 0 oo imm dir ext ix2 ix1 ix sp1 sp2 ae be ce de ee fe 9eee 9ede ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 lsl opr lsla lslx lsl opr ,x lsl ,x lsl opr ,sp logical shift left (same as asl) o ooo dir inh inh ix1 ix sp1 38 48 58 68 78 9e68 dd ff ff 4 1 1 4 3 5 lsr opr lsra lsr x lsr opr ,x lsr ,x lsr opr ,sp logical shift right o 0 oo dir inh inh ix1 ix sp1 34 44 54 64 74 9e64 dd ff ff 4 1 1 4 3 5 mov opr,opr mov opr, x+ mov # opr,opr mov x+ ,opr move (m) destination (m) source h:x (h:x) + 1 (ix+d, dix+) 0 oo dd dix+ imd ix+d 4e 5e 6e 7e dd dd dd ii dd dd 5 4 4 4 mul unsigned multiply x:a (x) (a) 0 0 inh 42 5 neg opr nega negx neg opr ,x neg ,x neg opr ,sp negate (two s complement) m ?m) = $00 ?(m) a ?a) = $00 ?(a) x ?x) = $00 ?(x) m ?m) = $00 ?(m) m ?m) = $00 ?(m) o ooo dir inh inh ix1 ix sp1 30 40 50 60 70 9e60 dd ff ff 4 1 1 4 3 5 nop no operation none inh 9d 1 nsa nibble swap a a (a[3:0]:a[7:4]) inh 62 3 ora # opr ora opr ora opr ora opr ,x ora opr ,x ora ,x ora opr ,sp ora opr ,sp inclusive or a and m a (a) | (m) 0 oo imm dir ext ix2 ix1 ix sp1 sp2 aa ba ca da ea fa 9eea 9eda ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 psha push a onto stack push (a); sp (sp) ?1 inh 87 2 pshh push h onto stack push (h); sp (sp) ?1 inh 8b 2 pshx push x onto stack push (x); sp (sp) ?1 inh 89 2 pula pull a from stack sp (sp + 1); pull ( a ) inh 86 2 table 4-1. instruction set summary source form operation description effect on ccr address mode opcode operand cycles vh i nzc c b0 b7 0 b0 b7 c 0 central processor unit (cpu) mc68hc908ap a-family data sheet, rev. 2 66 freescale semiconductor pulh pull h from stack sp (sp + 1); pull ( h ) inh 8a 2 pulx pull x from stack sp (sp + 1); pull ( x ) inh 88 2 rol opr rola rolx rol opr ,x rol ,x rol opr ,sp rotate left through carry o ooo dir inh inh ix1 ix sp1 39 49 59 69 79 9e69 dd ff ff 4 1 1 4 3 5 ror opr rora rorx ror opr ,x ror ,x ror opr ,sp rotate right through carry o ooo dir inh inh ix1 ix sp1 36 46 56 66 76 9e66 dd ff ff 4 1 1 4 3 5 rsp reset stack pointer sp $ff inh 9c 1 rti return from interrupt sp (sp) + 1; pull (ccr) sp (sp) + 1; pull (a) sp (sp) + 1; pull (x) sp (sp) + 1; pull (pch) sp (sp) + 1; pull (pcl) oooooo inh 80 7 rts return from subroutine sp sp + 1 ; pull ( pch) sp sp + 1; pull (pcl) inh 81 4 sbc # opr sbc opr sbc opr sbc opr ,x sbc opr ,x sbc ,x sbc opr ,sp sbc opr ,sp subtract with carry a (a) ?(m) ?(c) o ooo imm dir ext ix2 ix1 ix sp1 sp2 a2 b2 c2 d2 e2 f2 9ee2 9ed2 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 sec set carry bit c 1 1 inh 99 1 sei set interrupt mask i 1 1 inh 9b 2 sta opr sta opr sta opr ,x sta opr ,x sta ,x sta opr ,sp sta opr ,sp store a in m m (a) 0 oo dir ext ix2 ix1 ix sp1 sp2 b7 c7 d7 e7 f7 9ee7 9ed7 dd hh ll ee ff ff ff ee ff 3 4 4 3 2 4 5 sthx opr store h:x in m (m:m + 1) (h:x) 0 oo dir 35 dd 4 stop enable irq pin; stop processing i 0; stop processing 0 inh 8e 1 table 4-1. instruction set summary source form operation description effect on ccr address mode opcode operand cycles vh i nzc c b0 b7 b0 b7 c opcode map mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 67 stx opr stx opr stx opr ,x stx opr ,x stx ,x stx opr ,sp stx opr ,sp store x in m m (x) 0 oo dir ext ix2 ix1 ix sp1 sp2 bf cf df ef ff 9eef 9edf dd hh ll ee ff ff ff ee ff 3 4 4 3 2 4 5 sub # opr sub opr sub opr sub opr ,x sub opr ,x sub ,x sub opr ,sp sub opr ,sp subtract a (a) ?(m) o ooo imm dir ext ix2 ix1 ix sp1 sp2 a0 b0 c0 d0 e0 f0 9ee0 9ed0 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 swi software interrupt pc (pc) + 1; push (pcl) sp (sp) ?1; push (pch) sp (sp) ?1; push (x) sp (sp) ?1; push (a) sp (sp) ?1; push (ccr) sp (sp) ?1; i 1 pch interrupt vector high byte pcl interrupt vector low byte 1 inh 83 9 tap transfer a to ccr ccr (a) oooooo inh 84 2 tax transfer a to x x (a) inh 97 1 tpa transfer ccr to a a (ccr) inh 85 1 tst opr tsta tstx tst opr ,x tst ,x tst opr ,sp test for negative or zero (a) ?$00 or (x) ?$00 or (m) ?$00 0 oo dir inh inh ix1 ix sp1 3d 4d 5d 6d 7d 9e6d dd ff ff 3 1 1 3 2 4 tsx transfer sp to h:x h:x (sp) + 1 inh 95 2 txa transfer x to a a (x) inh 9f 1 txs transfer h:x to sp (sp) (h:x) ?1 inh 94 2 wait enable interrupts; wait for interrupt i 0; inhibit cpu clocking until interrupted 0 inh 8f 1 table 4-1. instruction set summary source form operation description effect on ccr address mode opcode operand cycles vh i nzc central processor unit (cpu) mc68hc908ap a-family data sheet, rev. 2 68 freescale semiconductor a accumulator n any bit c carry/borrow bit opr operand (one or two bytes) ccr condition code register pc program counter dd direct address of operand pch program counter high byte dd rr direct address of operand and relative offset of branch instruction pcl program counter low byte dd direct to direct addressing mode rel relative addressing mode dir direct addressing mode rel relative program counter offset byte dix+ direct to indexed with post increment addressing mode rr relative program counter offset byte ee ff high and low bytes of offset in indexed, 16-bit offset addressing sp1 stack pointer, 8-bit offset addressing mode ext extended addressing mode sp2 stack pointer 16-bit offset addressing mode ff offset byte in indexed, 8-bit offset addressing sp stack pointer h half-carry bit u unde?ed h index register high byte v over?w bit hh ll high and low bytes of operand address in extended addressing x index register low byte i interrupt mask z zero bit ii immediate operand byte & logical and imd immediate source to direct destination addressing mode | logical or imm immediate addressing mode logical exclusive or inh inherent addressing mode ( ) contents of ix indexed, no offset addressing mode ? ) negation (two s complement) ix+ indexed, no offset, post increment addressing mode # immediate value ix+d indexed with post increment to direct addressing mode sign extend ix1 indexed, 8-bit offset addressing mode loaded with ix1+ indexed, 8-bit offset, post increment addressing mode ? if ix2 indexed, 16-bit offset addressing mode : concatenated with m memory location o set or cleared n negative bit not affected table 4-1. instruction set summary source form operation description effect on ccr address mode opcode operand cycles vh i nzc mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 69 opcode map table 4-2. opcode map bit manipulation branch read-modify-write control register/memory dir dir rel dir inh inh ix1 sp1 ix inh inh imm dir ext ix2 sp2 ix1 sp1 ix 0 1234569e6789 abcd9ede9eef 0 5 brset0 3 dir 4 bset0 2 dir 3 bra 2 rel 4 neg 2 dir 1 nega 1 inh 1 negx 1 inh 4 neg 2 ix1 5 neg 3 sp1 3 neg 1ix 7 rti 1 inh 3 bge 2 rel 2 sub 2 imm 3 sub 2 dir 4 sub 3 ext 4 sub 3 ix2 5 sub 4 sp2 3 sub 2 ix1 4 sub 3 sp1 2 sub 1ix 1 5 brclr0 3 dir 4 bclr0 2 dir 3 brn 2 rel 5 cbeq 3 dir 4 cbeqa 3 imm 4 cbeqx 3 imm 5 cbeq 3 ix1+ 6 cbeq 4 sp1 4 cbeq 2 ix+ 4 rts 1 inh 3 blt 2 rel 2 cmp 2 imm 3 cmp 2 dir 4 cmp 3 ext 4 cmp 3 ix2 5 cmp 4 sp2 3 cmp 2 ix1 4 cmp 3 sp1 2 cmp 1ix 2 5 brset1 3 dir 4 bset1 2 dir 3 bhi 2 rel 5 mul 1 inh 7 div 1 inh 3 nsa 1 inh 2 daa 1 inh 3 bgt 2 rel 2 sbc 2 imm 3 sbc 2 dir 4 sbc 3 ext 4 sbc 3 ix2 5 sbc 4 sp2 3 sbc 2 ix1 4 sbc 3 sp1 2 sbc 1ix 3 5 brclr1 3 dir 4 bclr1 2 dir 3 bls 2 rel 4 com 2 dir 1 coma 1 inh 1 comx 1 inh 4 com 2 ix1 5 com 3 sp1 3 com 1ix 9 swi 1 inh 3 ble 2 rel 2 cpx 2 imm 3 cpx 2 dir 4 cpx 3 ext 4 cpx 3 ix2 5 cpx 4 sp2 3 cpx 2 ix1 4 cpx 3 sp1 2 cpx 1ix 4 5 brset2 3 dir 4 bset2 2 dir 3 bcc 2 rel 4 lsr 2 dir 1 lsra 1 inh 1 lsrx 1 inh 4 lsr 2 ix1 5 lsr 3 sp1 3 lsr 1ix 2 ta p 1 inh 2 txs 1 inh 2 and 2 imm 3 and 2 dir 4 and 3 ext 4 and 3 ix2 5 and 4 sp2 3 and 2 ix1 4 and 3 sp1 2 and 1ix 5 5 brclr2 3 dir 4 bclr2 2 dir 3 bcs 2 rel 4 sthx 2 dir 3 ldhx 3 imm 4 ldhx 2 dir 3 cphx 3 imm 4 cphx 2 dir 1 tpa 1 inh 2 tsx 1 inh 2 bit 2 imm 3 bit 2 dir 4 bit 3 ext 4 bit 3 ix2 5 bit 4 sp2 3 bit 2 ix1 4 bit 3 sp1 2 bit 1ix 6 5 brset3 3 dir 4 bset3 2 dir 3 bne 2 rel 4 ror 2 dir 1 rora 1 inh 1 rorx 1 inh 4 ror 2 ix1 5 ror 3 sp1 3 ror 1ix 2 pula 1 inh 2 lda 2 imm 3 lda 2 dir 4 lda 3 ext 4 lda 3 ix2 5 lda 4 sp2 3 lda 2 ix1 4 lda 3 sp1 2 lda 1ix 7 5 brclr3 3 dir 4 bclr3 2 dir 3 beq 2 rel 4 asr 2 dir 1 asra 1 inh 1 asrx 1 inh 4 asr 2 ix1 5 asr 3 sp1 3 asr 1ix 2 psha 1 inh 1 ta x 1 inh 2 ais 2 imm 3 sta 2 dir 4 sta 3 ext 4 sta 3 ix2 5 sta 4 sp2 3 sta 2 ix1 4 sta 3 sp1 2 sta 1ix 8 5 brset4 3 dir 4 bset4 2 dir 3 bhcc 2 rel 4 lsl 2 dir 1 lsla 1 inh 1 lslx 1 inh 4 lsl 2 ix1 5 lsl 3 sp1 3 lsl 1ix 2 pulx 1 inh 1 clc 1 inh 2 eor 2 imm 3 eor 2 dir 4 eor 3 ext 4 eor 3 ix2 5 eor 4 sp2 3 eor 2 ix1 4 eor 3 sp1 2 eor 1ix 9 5 brclr4 3 dir 4 bclr4 2 dir 3 bhcs 2 rel 4 rol 2 dir 1 rola 1 inh 1 rolx 1 inh 4 rol 2 ix1 5 rol 3 sp1 3 rol 1ix 2 pshx 1 inh 1 sec 1 inh 2 adc 2 imm 3 adc 2 dir 4 adc 3 ext 4 adc 3 ix2 5 adc 4 sp2 3 adc 2 ix1 4 adc 3 sp1 2 adc 1ix a 5 brset5 3 dir 4 bset5 2 dir 3 bpl 2 rel 4 dec 2 dir 1 deca 1 inh 1 decx 1 inh 4 dec 2 ix1 5 dec 3 sp1 3 dec 1ix 2 pulh 1 inh 2 cli 1 inh 2 ora 2 imm 3 ora 2 dir 4 ora 3 ext 4 ora 3 ix2 5 ora 4 sp2 3 ora 2 ix1 4 ora 3 sp1 2 ora 1ix b 5 brclr5 3 dir 4 bclr5 2 dir 3 bmi 2 rel 5 dbnz 3 dir 3 dbnza 2 inh 3 dbnzx 2 inh 5 dbnz 3 ix1 6 dbnz 4 sp1 4 dbnz 2ix 2 pshh 1 inh 2 sei 1 inh 2 add 2 imm 3 add 2 dir 4 add 3 ext 4 add 3 ix2 5 add 4 sp2 3 add 2 ix1 4 add 3 sp1 2 add 1ix c 5 brset6 3 dir 4 bset6 2 dir 3 bmc 2 rel 4 inc 2 dir 1 inca 1 inh 1 incx 1 inh 4 inc 2 ix1 5 inc 3 sp1 3 inc 1ix 1 clrh 1 inh 1 rsp 1 inh 2 jmp 2 dir 3 jmp 3 ext 4 jmp 3 ix2 3 jmp 2 ix1 2 jmp 1ix d 5 brclr6 3 dir 4 bclr6 2 dir 3 bms 2 rel 3 tst 2 dir 1 tsta 1 inh 1 tstx 1 inh 3 tst 2 ix1 4 tst 3 sp1 2 tst 1ix 1 nop 1 inh 4 bsr 2 rel 4 jsr 2 dir 5 jsr 3 ext 6 jsr 3 ix2 5 jsr 2 ix1 4 jsr 1ix e 5 brset7 3 dir 4 bset7 2 dir 3 bil 2 rel 5 mov 3dd 4 mov 2 dix+ 4 mov 3 imd 4 mov 2 ix+d 1 stop 1 inh * 2 ldx 2 imm 3 ldx 2 dir 4 ldx 3 ext 4 ldx 3 ix2 5 ldx 4 sp2 3 ldx 2 ix1 4 ldx 3 sp1 2 ldx 1ix f 5 brclr7 3 dir 4 bclr7 2 dir 3 bih 2 rel 3 clr 2 dir 1 clra 1 inh 1 clrx 1 inh 3 clr 2 ix1 4 clr 3 sp1 2 clr 1ix 1 wait 1 inh 1 txa 1 inh 2 aix 2 imm 3 stx 2 dir 4 stx 3 ext 4 stx 3 ix2 5 stx 4 sp2 3 stx 2 ix1 4 stx 3 sp1 2 stx 1ix inh inherent rel relative sp1 stack pointer, 8-bit offset imm immediate ix indexed, no offset sp2 stack pointer, 16-bit offset dir direct ix1 indexed, 8-bit offset ix+ indexed, no offset with ext extended ix2 indexed, 16-bit offset post increment dd direct-direct imd immediate-direct ix1+ indexed, 1-byte offset with ix+d indexed-direct dix+ direct-indexed post increment * pre-byte for stack pointer indexed instructions 0 high byte of opcode in hexadecimal low byte of opcode in hexadecimal 0 5 brset0 3 dir cycles opcode mnemonic number of bytes / addressing mode msb lsb msb lsb central processor unit (cpu) mc68hc908ap a-family data sheet, rev. 2 70 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 71 chapter 5 oscillator (osc) 5.1 introduction the oscillator module consist of three types of oscillator circuits: internal oscillator rc oscillator 1mhz to 8mhz crystal (x-tal) oscillator the reference clock for the cgm and other mcu sub-systems is selected by programming the mask option register located at $ffcf. the reference clock for the timebase module (tbm) is selected by the two bits, oscclk1 and oscclk0, in the config2 register. the internal oscillator runs continuously after a por or reset, and is always available. the rc and crystal oscillator cannot run concurrently; one is disabled while the other is selected; because the rc and x-tal circuits share the same osc1 pin. note the oscillator circuits are powered by the on-chip v reg regulator, therefore, the output swing on osc1 and osc2 is from v ss to v reg . figure 5-1 . shows the block diagram of the oscillator module. 5.2 clock selection reference clocks are selectable for the following sub-systems: cgmxclk and cgmrclk reference clock for clock generator module (cgm) and other mcu sub-systems other than tbm and cop. this is the main reference clock for the mcu. oscclk ?reference clock for timebase module (tbm). oscillator (osc) mc68hc908ap a-family data sheet, rev. 2 72 freescale semiconductor figure 5-1. oscillator module block diagram 5.2.1 cgm reference clock selection the clock generator module (cgm) reference clock (cgmxclk) is the reference clock input to the mcu. it is selected by programming two bits in a flash memory location; the mask option register (mor), at $ffcf. see 3.5 mask option register (mor) . address: $ffcf bit 7654321bit 0 read: oscsel1 oscsel0 rrrrrr write: reset: unaffected by reset erased:11111111 r = reserved figure 5-2. mask option register (mor) x-tal oscillator rc oscillator internal oscillator mux osc1 osc2 bus clock from sim mux xclk rcclk iclk oscclk0 oscclk1 oscsel0 oscsel1 oscclk to tbm cgmxclk cgmrclk to cgm and others mor config2 to cgm pll xrci xrci to sim (and cop) clock selection mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 73 note the internal oscillator is a free running oscillator and is available after each por or reset. it is turned-off in stop mode by setting the stop_iclkdis bit in config2. 5.2.2 tbm reference clock selection the timebase module reference clock (oscclk) is selected by configuring two bits in the config2 register, at $001d. see chapter 3 configuration & mask option registers (config & mor) . note the rcclk or xclk is only available if that clock is selected as the cgm reference clock, whereas the iclk is always available. table 5-1. cgmxclk clock selection oscsel1 oscsel0 cgmxclk osc2 pin comments 0 0 not used 0 1 iclk f bus internal oscillator generates the cgmxclk. 1 0 rcclk f bus rc oscillator generates the cgmxclk. internal oscillator is available after each por or reset. 1 1 xclk inverting output of x-tal x-tal oscillator generates the cgmxclk. internal oscillator is available after each por or reset. address: $001d bit 7654321bit 0 read: stop_ iclkdis stop_ rclken stop_ xclken oscclk1 oscclk0 00 scibd- src write: reset:00000000 figure 5-3. configuration register 2 (config2) table 5-2. timebase module reference clock selection oscclk1 oscclk0 timebase clock source 0 0 internal oscillator (iclk) 0 1 rc oscillator (rcclk) 1 0 x-tal oscillator (xclk) 1 1 not used oscillator (osc) mc68hc908ap a-family data sheet, rev. 2 74 freescale semiconductor 5.3 internal oscillator the internal oscillator clock (iclk), with a frequency of f iclk , is a free running clock that requires no external components. it can be selected as the cgmxclk for the cgm and mcu sub-systems; and the oscclk clock for the tbm. the iclk is also the reference clock input to the computer operating properly (cop) module. due to the simplicity of the internal oscillator, it does not have the accuracy and stability of the rc oscillator or the x-tal oscillator. therefore, the iclk is not suitable where an accurate bus clock is required and it should not be used as the cgmrclk to the cgm pll. the internal oscillator by default is always available and is free running after por or reset. it can be turned-off in stop mode by setting the stop_iclkdis bit before executing the stop instruction. figure 5-4 shows the logical representation of components of the internal oscillator circuitry. figure 5-4. internal oscillator internal oscillator en simoscen stop_iclkdis config2 iclk mcu from sim to clock selection mux bus clock from sim osc2 and cop rc oscillator mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 75 5.4 rc oscillator the rc oscillator circuit is designed for use with an external resistor and a capacitor. in its typical configuration, the rc oscillator requires two external components, one r and one c. component values should have a tolerance of 1% or less, to obtain a clock source with less than 10% tolerance. the oscillator configuration uses two components: ? ext ? ext figure 5-5. rc oscillator 5.5 x-tal oscillator the crystal (x-tal) oscillator circuit is designed for use with an external 1?mhz crystal to provide an accurate clock source. in its typical configuration, the x-tal oscillator is connected in a pierce oscillator configuration, as shown in figure 5-6 . this figure shows only the logical representation of the internal components and may not represent actual circuitry. the oscillator configuration uses five components: crystal, x 1 fixed capacitor, c 1 tuning capacitor, c 2 (can also be a fixed capacitor) feedback resistor, r b series resistor, r s (optional) r ext c ext v reg mcu osc1 simoscen from sim stop_rclken config2 rc oscillator en see chapter 22 for component value requirements. bus clock from sim osc2 rcclk to clock selection mux oscillator (osc) mc68hc908ap a-family data sheet, rev. 2 76 freescale semiconductor figure 5-6. crystal oscillator the series resistor (r s ) is included in the diagram to follow strict pierce oscillator guidelines and may not be required for all ranges of operation, especially with high frequency crystals. refer to the crystal manufacturer? data for more information. 5.6 i/o signals the following paragraphs describe the oscillator i/o signals. 5.6.1 crystal amplifier input pin (osc1) osc1 pin is an input to the crystal oscillator amplifier or the input to the rc oscillator circuit. 5.6.2 crystal amplifier output pin (osc2) when the x-tal oscillator is selected, osc2 pin is the output of the crystal oscillator inverting amplifier. when the rc oscillator or internal oscillator is selected, osc2 pin is the output of the internal bus clock. 5.6.3 oscillator enable signal (simoscen) the simoscen signal from the system integration module (sim) enables/disables the x-tal oscillator, the rc-oscillator, or the internal oscillator circuit. c 1 c 2 r b x 1 r s mcu osc2 osc1 see chapter 22 for component value requirements. simoscen from sim stop_xclken config2 xclk to clock selection mux 1?mhz low power modes mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 77 5.6.4 cgm oscillator clock (cgmxclk) the cgmxclk clock is output from the x-tal oscillator, rc oscillator or the internal oscillator. this clock drives to cgm and other mcu sub-systems. 5.6.5 cgm reference clock (cgmrclk) this is buffered signal of cgmxclk, it is used by the cgm as the phase-locked-loop (pll) reference clock. 5.6.6 oscillator clock to time base module (oscclk) the oscclk is the reference clock that drives the timebase module. see chapter 10 timebase module (tbm) . 5.7 low power modes the wait and stop instructions put the mcu in low-power consumption standby modes. 5.7.1 wait mode the wait instruction has no effect on the oscillator module. cgmxclk continues to drive to the clock generator module, and oscclk continues to drive the timebase module. 5.7.2 stop mode the stop instruction disables the x-tal or the rc oscillator circuit, and hence the cgmxclk clock stops running. for continuous x-tal or rc oscillator operation in stop mode, set the stop_xclken (for x-tal) or stop_rclken (for rc) bit to logic 1 before entering stop mode. the internal oscillator clock continues operation in stop mode. it can be disabled by setting the stop_iclkdis bit to logic 1 before entering stop mode. 5.8 oscillator during break mode the oscillator continues to drive cgmxclk when the device enters the break state. oscillator (osc) mc68hc908ap a-family data sheet, rev. 2 78 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 79 chapter 6 clock generator module (cgm) 6.1 introduction this section describes the clock generator module (cgm). the cgm generates the base clock signal, cgmout, which is based on either the oscillator clock divided by two or the divided phase-locked loop (pll) clock, cgmpclk, divided by two. cgmout is the clock from which the sim derives the system clocks, including the bus clock, which is at a frequency of cgmout 2. the pll is a frequency generator designed for use with a crystal (1 to 8 mhz) to generate a base frequency and dividing to a maximum bus frequency of 8mhz. 6.2 features features of the cgm include: phase-locked loop with output frequency in integer multiples of an integer dividend of the crystal reference low-frequency crystal operation with low-power operation and high-output frequency resolution programmable prescaler for power-of-two increases in frequency programmable hardware voltage-controlled oscillator (vco) for low-jitter operation automatic bandwidth control mode for low-jitter operation automatic frequency lock detector cpu interrupt on entry or exit from locked condition configuration register bit to allow oscillator operation during stop mode 6.3 functional description the cgm consists of three major sub-modules: oscillator module ?the oscillator module generates the constant reference frequency clock, cgmrclk (buffered cgmxclk). phase-locked loop (pll) ?the pll generates the programmable vco frequency clock, cgmvclk, and the divided vco clock, cgmpclk. base clock selector circuit this software-controlled circuit selects either cgmxclk divided by two or the divided vco clock, cgmpclk, divided by two as the base clock, cgmout. the sim derives the system clocks from either cgmout or cgmxclk. figure 6-1 shows the structure of the cgm. figure 6-2 is a summary of the cgm registers. clock generator module (cgm) mc68hc908ap a-family data sheet, rev. 2 80 freescale semiconductor figure 6-1. cgm block diagram bcs phase detector loop filter frequency divider voltage controlled oscillator automatic mode control lock detector clock cgmxclk cgmout cgmvdv interrupt control cgmint cgmrdv pll analog 2 cgmrclk select circuit v dda cgmxfc v ssa lock auto acq vpr[1:0] pllie pllf mul[11:0] reference divider vrs[7:0] frequency divider pre[1:0] to adc phase-locked loop (pll) a b 1 s* *when s = 1, cgmout = b simdiv2 from sim to sim to sim rds[3:0] r cgmpclk simoscen oscillator (osc) module osc2 oscsel[1:0] oscclk[1:0] osc1 from sim iclk cgmrclk internal oscillator rc oscillator crystal oscillator mux see chapter 5 oscillator (osc) . n oscclk to timebase module (tbm) to sim (and cop) l 2 p 2 e cgmvclk functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 81 6.3.1 oscillator module the oscillator module provides two clock outputs cgmxclk and cgmrclk to the cgm module. cgmxclk when selected, is driven to sim module to generate the system bus clock. cgmrclk is used by the phase-lock-loop to provide a higher frequency system bus clock. the oscillator module also provides the reference clock for the timebase module (tbm). see chapter 5 oscillator (osc) for detailed oscillator circuit description. see chapter 10 timebase module (tbm) for detailed description on tbm. 6.3.2 phase-locked loop circuit (pll) the pll is a frequency generator that can operate in either acquisition mode or tracking mode, depending on the accuracy of the output frequency. the pll can change between acquisition and tracking modes either automatically or manually. 6.3.3 pll circuits the pll consists of these circuits: voltage-controlled oscillator (vco) reference divider frequency pre-scaler modulo vco frequency divider addr. register name bit 7 654321bit 0 $0036 pll control register (ptcl) read: pllie pllf pllon bcs pre1 pre0 vpr1 vpr0 write: reset:00100000 $0037 pll bandwidth control register (pbwc) read: auto lock acq 0000 r write: reset:0000000 $0038 pll multiplier select register high (pmsh) read: 0000 mul11 mul10 mul9 mul8 write: reset:00000000 $0039 pll multiplier select register low (pmsl) read: mul7 mul6 mul5 mul4 mul3 mul2 mul1 mul0 write: reset:01000000 $003a pll vco range select register (pmrs) read: vrs7 vrs6 vrs5 vrs4 vrs3 vrs2 vrs1 vrs0 write: reset:01000000 $003b pll reference divider select register (pmds) read: 0000 rds3 rds2 rds1 rds0 write: reset:00000001 = unimplemented r = reserved notes: 1. when auto = 0, pllie is forced clear and is read-only. 2. when auto = 0, pllf and lock read as clear. 3. when auto = 1, acq is read-only. 4. when pllon = 0 or vrs7:vrs0 = $0, bcs is forced clear and is read-only. 5. when pllon = 1, the pll programming register is read-only. 6. when bcs = 1, pllon is forced set and is read-only. figure 6-2. cgm i/o register summary clock generator module (cgm) mc68hc908ap a-family data sheet, rev. 2 82 freescale semiconductor phase detector loop filter lock detector the operating range of the vco is programmable for a wide range of frequencies and for maximum immunity to external noise, including supply and cgmxfc noise. the vco frequency is bound to a range from roughly one-half to twice the center-of-range frequency, f vrs . modulating the voltage on the cgmxfc pin changes the frequency within this range. by design, f vrs is equal to the nominal center-of-range frequency, f nom , (125 khz) times a linear factor, l, and a power-of-two factor, e, or (l 2 e )f nom . cgmrclk is the pll reference clock, a buffered version of cgmxclk. cgmrclk runs at a frequency, f rclk , and is fed to the pll through a programmable modulo reference divider, which divides f rclk by a factor, r. the divider? output is the final reference clock, cgmrdv, running at a frequency, f rdv =f rclk /r. with an external crystal (1mhz?mhz), always set r = 1 for specified performance. with an external high-frequency clock source, use r to divide the external frequency to between 1mhz and 8mhz. the vco? output clock, cgmvclk, running at a frequency, f vclk , is fed back through a programmable pre-scaler divider and a programmable modulo divider. the pre-scaler divides the vco clock by a power-of-two factor p (the cgmpclk) and the modulo divider reduces the vco clock by a factor, n. the dividers output is the vco feedback clock, cgmvdv, running at a frequency, f vdv =f vclk /(n 2 p ). (see 6.3.6 programming the pll for more information.) the phase detector then compares the vco feedback clock, cgmvdv, with the final reference clock, cgmrdv. a correction pulse is generated based on the phase difference between the two signals. the loop filter then slightly alters the dc voltage on the external capacitor connected to cgmxfc based on the width and direction of the correction pulse. the filter can make fast or slow corrections depending on its mode, described in 6.3.4 acquisition and tracking modes . the value of the external capacitor and the reference frequency determines the speed of the corrections and the stability of the pll. the lock detector compares the frequencies of the vco feedback clock, cgmvdv, and the final reference clock, cgmrdv. therefore, the speed of the lock detector is directly proportional to the final reference frequency, f rdv . the circuit determines the mode of the pll and the lock condition based on this comparison. 6.3.4 acquisition and tracking modes the pll filter is manually or automatically configurable into one of two operating modes: acquisition mode ?in acquisition mode, the filter can make large frequency corrections to the vco. this mode is used at pll start up or when the pll has suffered a severe noise hit and the vco frequency is far off the desired frequency. when in acquisition mode, the acq bit is clear in the pll bandwidth control register. (see 6.5.2 pll bandwidth control register .) tracking mode in tracking mode, the filter makes only small corrections to the frequency of the vco. pll jitter is much lower in tracking mode, but the response to noise is also slower. the pll enters tracking mode when the vco frequency is nearly correct, such as when the pll is selected as the base clock source. (see 6.3.8 base clock selector circuit .) the pll is automatically in tracking mode when not in acquisition mode or when the acq bit is set. functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 83 6.3.5 manual and automatic pll bandwidth modes the pll can change the bandwidth or operational mode of the loop filter manually or automatically. automatic mode is recommended for most users. in automatic bandwidth control mode (auto = 1), the lock detector automatically switches between acquisition and tracking modes. automatic bandwidth control mode also is used to determine when the vco clock, cgmvclk, is safe to use as the source for the base clock, cgmout. (see 6.5.2 pll bandwidth control register .) if pll interrupts are enabled, the software can wait for a pll interrupt request and then check the lock bit. if interrupts are disabled, software can poll the lock bit continuously (during pll start-up, usually) or at periodic intervals. in either case, when the lock bit is set, the vco clock is safe to use as the source for the base clock. (see 6.3.8 base clock selector circuit .) if the vco is selected as the source for the base clock and the lock bit is clear, the pll has suffered a severe noise hit and the software must take appropriate action, depending on the application. (see 6.6 interrupts for information and precautions on using interrupts.) the following conditions apply when the pll is in automatic bandwidth control mode: the acq bit (see 6.5.2 pll bandwidth control register .) is a read-only indicator of the mode of the filter. (see 6.3.4 acquisition and tracking modes .) the acq bit is set when the vco frequency is within a certain tolerance and is cleared when the vco frequency is out of a certain tolerance. (see 6.8 acquisition/lock time specifications for more information.) the lock bit is a read-only indicator of the locked state of the pll. the lock bit is set when the vco frequency is within a certain tolerance and is cleared when the vco frequency is out of a certain tolerance. (see 6.8 acquisition/lock time specifications for more information.) cpu interrupts can occur if enabled (pllie = 1) when the pll? lock condition changes, toggling the lock bit. (see 6.5.1 pll control register .) the pll also may operate in manual mode (auto = 0). manual mode is used by systems that do not require an indicator of the lock condition for proper operation. such systems typically operate well below f busmax . the following conditions apply when in manual mode: acq is a writable control bit that controls the mode of the filter. before turning on the pll in manual mode, the acq bit must be clear. before entering tracking mode ( acq = 1), software must wait a given time, t acq (see 6.8 acquisition/lock time specifications .), after turning on the pll by setting pllon in the pll control register (pctl). software must wait a given time, t al , after entering tracking mode before selecting the pll as the clock source to cgmout (bcs = 1). the lock bit is disabled. cpu interrupts from the cgm are disabled. 6.3.6 programming the pll the following procedure shows how to program the pll. note the round function in the following equations means that the real number should be rounded to the nearest integer number. clock generator module (cgm) mc68hc908ap a-family data sheet, rev. 2 84 freescale semiconductor 1. choose the desired bus frequency, f busdes , or the desired vco frequency, f vclkdes ; and then solve for the other. the relationship between f bus and f vclk is governed by the equation: where p is the power of two multiplier, and can be 0, 1, 2, or 3 2. choose a practical pll reference frequency, f rclk , and the reference clock divider, r. typically, the reference is 4mhz and r = 1. frequency errors to the pll are corrected at a rate of f rclk /r. for stability and lock time reduction, this rate must be as fast as possible. the vco frequency must be an integer multiple of this rate. the relationship between the vco frequency, f vclk , and the reference frequency, f rclk ,is where n is the integer range multiplier, between 1 and 4095. in cases where desired bus frequency has some tolerance, choose f rclk to a value determined either by other module requirements (such as modules which are clocked by cgmxclk), cost requirements, or ideally, as high as the specified range allows. see chapter 22 electrical specifications . choose the reference divider, r = 1. when the tolerance on the bus frequency is tight, choose f rclk to an integer divisor of f busdes , and r = 1. if f rclk cannot meet this requirement, use the following equation to solve for r with practical choices of f rclk , and choose the f rclk that gives the lowest r. 3. calculate n: 4. calculate and verify the adequacy of the vco and bus frequencies f vclk and f bus . f vclk 2 p f cgmpclk 2 p 4 f bus == f vclk 2 p n r ----------- f rclk () = r round r max f vclkdes f rclk -------------------------- ?? ?? ?? integer f vclkdes f rclk -------------------------- ?? ?? ?? ?? ?? ?? = n round rf vclkdes f rclk 2 p ------------------------------------ - ?? ?? ?? = f bus f vclk 2 p 4 ----------- = f vclk 2 p n r ----------- f rclk () = functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 85 5. select the vco? power-of-two range multiplier e, according to this table: 6. select a vco linear range multiplier, l, where f nom = 125khz 7. calculate and verify the adequacy of the vco programmed center-of-range frequency, f vrs . the center-of-range frequency is the midpoint between the minimum and maximum frequencies attainable by the pll. for proper operation, 8. verify the choice of p, r, n, e, and l by comparing f vclk to f vrs and f vclkdes . for proper operation, f vclk must be within the application? tolerance of f vclkdes , and f vrs must be as close as possible to f vclk. note exceeding the recommended maximum bus frequency or vco frequency can crash the mcu. 9. program the pll registers accordingly: a. in the pre bits of the pll control register (pctl), program the binary equivalent of p. b. in the vpr bits of the pll control register (pctl), program the binary equivalent of e. c. in the pll multiplier select register low (pmsl) and the pll multiplier select register high (pmsh), program the binary equivalent of n. d. in the pll vco range select register (pmrs), program the binary coded equivalent of l. e. in the pll reference divider select register (pmds), program the binary coded equivalent of r. note the values for p, e, n, l, and r can only be programmed when the pll is off (pllon = 0). table 6-1 provides numeric examples (numbers are in hexadecimal notation): frequency range e 0 < f vclk < 9,830,400 0 9,830,400 f vclk < 19,660,800 1 19,660,800 f vclk < 39,321,600 2 note: do not program e to a value of 3. l round f vclk 2 e f nom -------------------------- ?? ?? ?? = f vrs l2 e () f nom = f vrs f vclk f nom 2 e 2 -------------------------- clock generator module (cgm) mc68hc908ap a-family data sheet, rev. 2 86 freescale semiconductor 6.3.7 special programming exceptions the programming method described in 6.3.6 programming the pll does not account for three possible exceptions. a value of 0 for r, n, or l is meaningless when used in the equations given. to account for these exceptions: a 0 value for r or n is interpreted exactly the same as a value of 1. a 0 value for l disables the pll and prevents its selection as the source for the base clock. (see 6.3.8 base clock selector circuit .) 6.3.8 base clock selector circuit this circuit is used to select either the oscillator clock, cgmxclk, or the divided vco clock, cgmpclk, as the source of the base clock, cgmout. the two input clocks go through a transition control circuit that waits up to three cgmxclk cycles and three cgmpclk cycles to change from one clock source to the other. during this time, cgmout is held in stasis. the output of the transition control circuit is then divided by two to correct the duty cycle. therefore, the bus clock frequency, which is one-half of the base clock frequency, is one-fourth the frequency of the selected clock (cgmxclk or cgmpclk). the bcs bit in the pll control register (pctl) selects which clock drives cgmout. the divided vco clock cannot be selected as the base clock source if the pll is not turned on. the pll cannot be turned off if the divided vco clock is selected. the pll cannot be turned on or off simultaneously with the selection or deselection of the divided vco clock. the divided vco clock also cannot be selected as the base clock source if the factor l is programmed to a 0. this value would set up a condition inconsistent with the operation of the pll, so that the pll would be disabled and the oscillator clock would be forced as the source of the base clock. 6.3.9 cgm external connections in its typical configuration, the cgm requires up to four external components. figure 6-3 shows the external components for the pll: bypass capacitor, c byp filter network table 6-1. numeric examples cgmvclk cgmpclk f bus f rclk rnpel 32 mhz 32 mhz 8.0 mhz 2 mhz 1 10 0 2 40 16 mhz 16 mhz 4.0 mhz 2 mhz 1 8 0 1 40 32 mhz 32 mhz 8.0 mhz 4 mhz 1 8 0 2 40 16 mhz 16 mhz 4.0 mhz 4 mhz 1 4 0 1 40 32 mhz 32 mhz 8.0 mhz 8 mhz 1 4 0 2 40 16 mhz 16 mhz 4.0 mhz 8 mhz 1 2 0 1 40 29.4912 mhz 29.4912 mhz 7.3728 mhz 4.9152 mhz 1 6 0 2 3c 19.6608 mhz 19.6608 mhz 4.9152 mhz 4.9152 mhz 1 4 0 2 27 i/o signals mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 87 care should be taken with pcb routing in order to minimize signal cross talk and noise. (see 6.8 acquisition/lock time specifications for routing information, filter network and its effects on pll performance.) figure 6-3. cgm external connections 6.4 i/o signals the following paragraphs describe the cgm i/o signals. 6.4.1 external filter capacitor pin (cgmxfc) the cgmxfc pin is required by the loop filter to filter out phase corrections. an external filter network is connected to this pin. (see figure 6-3 .) note to prevent noise problems, the filter network should be placed as close to the cgmxfc pin as possible, with minimum routing distances and no routing of other signals across the network. 6.4.2 pll analog power pin (v dda ) v dda is a power pin used by the analog portions of the pll. connect the v dda pin to the same voltage potential as the v dd pin. note route v dda carefully for maximum noise immunity and place bypass capacitors as close as possible to the package. 6.4.3 pll analog ground pin (v ssa ) v ssa is a ground pin used by the analog portions of the pll. connect the v ssa pin to the same voltage potential as the v ss pin. c byp note: filter network in box can be replaced with a 0.47 f capacitor, but will degrade stability. 1 k ? 10 nf 0.22 f 0.1 f v ssa v dda cgmxfc v dd mcu clock generator module (cgm) mc68hc908ap a-family data sheet, rev. 2 88 freescale semiconductor note route v ssa carefully for maximum noise immunity and place bypass capacitors as close as possible to the package. 6.4.4 oscillator output frequency signal (cgmxclk) cgmxclk is the oscillator output signal. it runs at the full speed of the oscillator, and is generated directly from the crystal oscillator circuit, the rc oscillator circuit, or the internal oscillator circuit. 6.4.5 cgm reference clock (cgmrclk) cgmrclk is a buffered version of cgmxclk, this clock is the reference clock for the phase-locked-loop circuit. 6.4.6 cgm vco clock output (cgmvclk) cgmvclk is the clock output from the vco. 6.4.7 cgm base clock output (cgmout) cgmout is the clock output of the cgm. this signal goes to the sim, which generates the mcu clocks. cgmout is a 50 percent duty cycle clock running at twice the bus frequency. cgmout is software programmable to be either the oscillator output, cgmxclk, divided by two or the divided vco clock, cgmpclk, divided by two. 6.4.8 cgm cpu interrupt (cgmint) cgmint is the interrupt signal generated by the pll lock detector. 6.5 cgm registers the following registers control and monitor operation of the cgm: pll control register (pctl) (see 6.5.1 pll control register .) pll bandwidth control register (pbwc) (see 6.5.2 pll bandwidth control register .) pll multiplier select registers (pmsh and pmsl) (see 6.5.3 pll multiplier select registers .) pll vco range select register (pmrs) (see 6.5.4 pll vco range select register .) pll reference divider select register (pmds) (see 6.5.5 pll reference divider select register .) cgm registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 89 6.5.1 pll control register the pll control register (pctl) contains the interrupt enable and flag bits, the on/off switch, the base clock selector bit, the prescaler bits, and the vco power-of-two range selector bits. pllie ?pll interrupt enable bit this read/write bit enables the pll to generate an interrupt request when the lock bit toggles, setting the pll flag, pllf. when the auto bit in the pll bandwidth control register (pbwc) is clear, pllie cannot be written and reads as logic 0. reset clears the pllie bit. 1 = pll interrupts enabled 0 = pll interrupts disabled pllf ?pll interrupt flag bit this read-only bit is set whenever the lock bit toggles. pllf generates an interrupt request if the pllie bit also is set. pllf always reads as logic 0 when the auto bit in the pll bandwidth control register (pbwc) is clear. clear the pllf bit by reading the pll control register. reset clears the pllf bit. 1 = change in lock condition 0 = no change in lock condition note do not inadvertently clear the pllf bit. any read or read-modify-write operation on the pll control register clears the pllf bit. pllon ?pll on bit this read/write bit activates the pll and enables the vco clock, cgmvclk. pllon cannot be cleared if the vco clock is driving the base clock, cgmout (bcs = 1). (see 6.3.8 base clock selector circuit .) reset sets this bit so that the loop can stabilize as the mcu is powering up. 1 = pll on 0 = pll off bcs ?base clock select bit this read/write bit selects either the oscillator output, cgmxclk, or the divided vco clock, cgmpclk, as the source of the cgm output, cgmout. cgmout frequency is one-half the frequency of the selected clock. bcs cannot be set while the pllon bit is clear. after toggling bcs, it may take up to three cgmxclk and three cgmpclk cycles to complete the transition from one source clock to the other. during the transition, cgmout is held in stasis. (see 6.3.8 base clock selector circuit .) reset clears the bcs bit. 1 = cgmpclk divided by two drives cgmout 0 = cgmxclk divided by two drives cgmout address: $0036 bit 7654321bit 0 read: pllie pllf pllon bcs pre1 pre0 vpr1 vpr0 write: reset:00100000 = unimplemented figure 6-4. pll control register (pctl) clock generator module (cgm) mc68hc908ap a-family data sheet, rev. 2 90 freescale semiconductor note pllon and bcs have built-in protection that prevents the base clock selector circuit from selecting the vco clock as the source of the base clock if the pll is off. therefore, pllon cannot be cleared when bcs is set, and bcs cannot be set when pllon is clear. if the pll is off (pllon = 0), selecting cgmpclk requires two writes to the pll control register. (see 6.3.8 base clock selector circuit .) pre1 and pre0 ?prescaler program bits these read/write bits control a prescaler that selects the prescaler power-of-two multiplier, p. (see 6.3.3 pll circuits and 6.3.6 programming the pll .) pre1 and pre0 cannot be written when the pllon bit is set. reset clears these bits. these prescaler bits affects the relationship between the vco clock and the final system bus clock. vpr1 and vpr0 ?vco power-of-two range select bits these read/write bits control the vco? hardware power-of-two range multiplier e that, in conjunction with l (see 6.3.3 pll circuits , 6.3.6 programming the pll , and 6.5.4 pll vco range select register .) controls the hardware center-of-range frequency, f vrs . vpr1:vpr0 cannot be written when the pllon bit is set. reset clears these bits. table 6-2. pre1 and pre0 programming pre1 and pre0 p prescaler multiplier 00 0 1 01 1 2 10 2 4 11 3 8 table 6-3. vpr1 and vpr0 programming vpr1 and vpr0 e vco power-of-two range multiplier 00 0 1 01 1 2 10 2 4 note: do not program e to a value of 3. cgm registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 91 6.5.2 pll bandwidth control register the pll bandwidth control register (pbwc): selects automatic or manual (software-controlled) bandwidth control mode indicates when the pll is locked in automatic bandwidth control mode, indicates when the pll is in acquisition or tracking mode in manual operation, forces the pll into acquisition or tracking mode auto ?automatic bandwidth control bit this read/write bit selects automatic or manual bandwidth control. when initializing the pll for manual operation (auto = 0), clear the acq bit before turning on the pll. reset clears the auto bit. 1 = automatic bandwidth control 0 = manual bandwidth control lock ?lock indicator bit when the auto bit is set, lock is a read-only bit that becomes set when the vco clock, cgmvclk, is locked (running at the programmed frequency). when the auto bit is clear, lock reads as logic 0 and has no meaning. the write one function of this bit is reserved for test, so this bit must always be written a 0. reset clears the lock bit. 1 = vco frequency correct or locked 0 = vco frequency incorrect or unlocked acq ?acquisition mode bit when the auto bit is set, acq is a read-only bit that indicates whether the pll is in acquisition mode or tracking mode. when the auto bit is clear, acq is a read/write bit that controls whether the pll is in acquisition or tracking mode. in automatic bandwidth control mode (auto = 1), the last-written value from manual operation is stored in a temporary location and is recovered when manual operation resumes. reset clears this bit, enabling acquisition mode. 1 = tracking mode 0 = acquisition mode address: $0037 bit 7654321bit 0 read: auto lock acq 0000 r write: reset:0000000 = unimplemented r = reserved figure 6-5. pll bandwidth control register (pbwcr) clock generator module (cgm) mc68hc908ap a-family data sheet, rev. 2 92 freescale semiconductor 6.5.3 pll multiplier select registers the pll multiplier select registers (pmsh and pmsl) contain the programming information for the modulo feedback divider. mul[11:0] ?multiplier select bits these read/write bits control the modulo feedback divider that selects the vco frequency multiplier n. (see 6.3.3 pll circuits and 6.3.6 programming the pll .) a value of $0000 in the multiplier select registers configure the modulo feedback divider the same as a value of $0001. reset initializes the registers to $0040 for a default multiply value of 64. note the multiplier select bits have built-in protection such that they cannot be written when the pll is on (pllon = 1). 6.5.4 pll vco range select register the pll vco range select register (pmrs) contains the programming information required for the hardware configuration of the vco. vrs[7:0] ?vco range select bits these read/write bits control the hardware center-of-range linear multiplier l which, in conjunction with e(see 6.3.3 pll circuits , 6.3.6 programming the pll , and 6.5.1 pll control register .), controls the hardware center-of-range frequency, f vrs . vrs[7:0] cannot be written when the pllon bit in the pctl is set. (see 6.3.7 special programming exceptions .) a value of $00 in the vco range select address: $0038 bit 7654321bit 0 read: 0 0 0 0 mul11 mul10 mul9 mul8 write: reset:00000000 = unimplemented figure 6-6. pll multiplier select register high (pmsh) address: $0039 bit 7654321bit 0 read: mul7 mul6 mul5 mul4 mul3 mul2 mul1 mul0 write: reset:01000000 figure 6-7. pll multiplier select register low (pmsl) address: $003a bit 7654321bit 0 read: vrs7 vrs6 vrs5 vrs4 vrs3 vrs2 vrs1 vrs0 write: reset:01000000 figure 6-8. pll vco range select register (pmrs) interrupts mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 93 register disables the pll and clears the bcs bit in the pll control register (pctl). (see 6.3.8 base clock selector circuit and 6.3.7 special programming exceptions .). reset initializes the register to $40 for a default range multiply value of 64. note the vco range select bits have built-in protection such that they cannot be written when the pll is on (pllon = 1) and such that the vco clock cannot be selected as the source of the base clock (bcs = 1) if the vco range select bits are all clear. the pll vco range select register must be programmed correctly. incorrect programming can result in failure of the pll to achieve lock. 6.5.5 pll reference divider select register the pll reference divider select register (pmds) contains the programming information for the modulo reference divider. rds[3:0] ?reference divider select bits these read/write bits control the modulo reference divider that selects the reference division factor, r. (see 6.3.3 pll circuits and 6.3.6 programming the pll .) rds[3:0] cannot be written when the pllon bit in the pctl is set. a value of $00 in the reference divider select register configures the reference divider the same as a value of $01. (see 6.3.7 special programming exceptions .) reset initializes the register to $01 for a default divide value of 1. note the reference divider select bits have built-in protection such that they cannot be written when the pll is on (pllon = 1). note the default divide value of 1 is recommended for all applications. 6.6 interrupts when the auto bit is set in the pll bandwidth control register (pbwc), the pll can generate a cpu interrupt request every time the lock bit changes state. the pllie bit in the pll control register (pctl) enables cpu interrupts from the pll. pllf, the interrupt flag in the pctl, becomes set whether interrupts are enabled or not. when the auto bit is clear, cpu interrupts from the pll are disabled and pllf reads as logic 0. software should read the lock bit after a pll interrupt request to see if the request was due to an entry into lock or an exit from lock. when the pll enters lock, the divided vco clock, cgmpclk, divided by two can be selected as the cgmout source by setting bcs in the pctl. when the pll exits lock, the address: $003b bit 7654321bit 0 read: 0 0 0 0 rds3 rds2 rds1 rds0 write: reset:00000001 = unimplemented figure 6-9. pll reference divider select register (pmds) clock generator module (cgm) mc68hc908ap a-family data sheet, rev. 2 94 freescale semiconductor vco clock frequency is corrupt, and appropriate precautions should be taken. if the application is not frequency sensitive, interrupts should be disabled to prevent pll interrupt service routines from impeding software performance or from exceeding stack limitations. note software can select the cgmpclk divided by two as the cgmout source even if the pll is not locked (lock = 0). therefore, software should make sure the pll is locked before setting the bcs bit. 6.7 special modes the wait instruction puts the mcu in low power-consumption standby modes. 6.7.1 wait mode the wait instruction does not affect the cgm. before entering wait mode, software can disengage and turn off the pll by clearing the bcs and pllon bits in the pll control register (pctl) to save power. less power-sensitive applications can disengage the pll without turning it off, so that the pll clock is immediately available at wait exit. this would be the case also when the pll is to wake the mcu from wait mode, such as when the pll is first enabled and waiting for lock or lock is lost. 6.7.2 stop mode the stop instruction disables the pll analog circuits and no clock will be driven out of the vco. when entering stop mode with the vco clock (cgmpclk) selected, before executing the stop instruction: 1. set the oscillator stop mode enable bit (stop_xclken in config2) if continuos clock is required in stop mode. 2. clear the bcs bit to select cgmxclk as cgmout. on exit from stop mode: 1. set the pllon bit if cleared before entering stop mode. 2. wait for pll to lock by checking the lock bit. 3. set bcs bit to select cgmpclk as cgmout. 6.7.3 cgm during break interrupts the system integration module (sim) controls whether status bits in other modules can be cleared during the break state. the bcfe bit in the sim break flag control register (sbfcr) enables software to clear status bits during the break state. (see 7.7.3 sim break flag control register .) to allow software to clear status bits during a break interrupt, write a logic 1 to the bcfe bit. if a status bit is cleared during the break state, it remains cleared when the mcu exits the break state. to protect the pllf bit during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), software can read and write the pll control register during the break state without affecting the pllf bit. acquisition/lock time specifications mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 95 6.8 acquisition/lock time specifications the acquisition and lock times of the pll are, in many applications, the most critical pll design parameters. proper design and use of the pll ensures the highest stability and lowest acquisition/lock times. 6.8.1 acquisition/lock time definitions typical control systems refer to the acquisition time or lock time as the reaction time, within specified tolerances, of the system to a step input. in a pll, the step input occurs when the pll is turned on or when it suffers a noise hit. the tolerance is usually specified as a percent of the step input or when the output settles to the desired value plus or minus a percent of the frequency change. therefore, the reaction time is constant in this definition, regardless of the size of the step input. for example, consider a system with a 5 percent acquisition time tolerance. if a command instructs the system to change from 0hz to 1mhz, the acquisition time is the time taken for the frequency to reach 1mhz 50khz. 50khz = 5% of the 1mhz step input. if the system is operating at 1mhz and suffers a ?00khz noise hit, the acquisition time is the time taken to return from 900khz to 1mhz 5khz. 5khz = 5% of the 100khz step input. other systems refer to acquisition and lock times as the time the system takes to reduce the error between the actual output and the desired output to within specified tolerances. therefore, the acquisition or lock time varies according to the original error in the output. minor errors may not even be registered. typical pll applications prefer to use this definition because the system requires the output frequency to be within a certain tolerance of the desired frequency regardless of the size of the initial error. 6.8.2 parametric influences on reaction time acquisition and lock times are designed to be as short as possible while still providing the highest possible stability. these reaction times are not constant, however. many factors directly and indirectly affect the acquisition time. the most critical parameter which affects the reaction times of the pll is the reference frequency, f rdv . this frequency is the input to the phase detector and controls how often the pll makes corrections. for stability, the corrections must be small compared to the desired frequency, so several corrections are required to reduce the frequency error. therefore, the slower the reference the longer it takes to make these corrections. this parameter is under user control via the choice of crystal frequency f xclk and the r value programmed in the reference divider. (see 6.3.3 pll circuits , 6.3.6 programming the pll , and 6.5.5 pll reference divider select register .) another critical parameter is the external filter network. the pll modifies the voltage on the vco by adding or subtracting charge from capacitors in this network. therefore, the rate at which the voltage changes for a given frequency error (thus change in charge) is proportional to the capacitance. the size of the capacitor also is related to the stability of the pll. if the capacitor is too small, the pll cannot make small enough adjustments to the voltage and the system cannot lock. if the capacitor is too large, the pll may not be able to adjust the voltage in a reasonable time. (see 6.8.3 choosing a filter .) also important is the operating voltage potential applied to v dda . the power supply potential alters the characteristics of the pll. a fixed value is best. variable supplies, such as batteries, are acceptable if they vary within a known range at very slow speeds. noise on the power supply is not acceptable, because it causes small frequency errors which continually change the acquisition time of the pll. clock generator module (cgm) mc68hc908ap a-family data sheet, rev. 2 96 freescale semiconductor temperature and processing also can affect acquisition time because the electrical characteristics of the pll change. the part operates as specified as long as these influences stay within the specified limits. external factors, however, can cause drastic changes in the operation of the pll. these factors include noise injected into the pll through the filter capacitor, filter capacitor leakage, stray impedances on the circuit board, and even humidity or circuit board contamination. 6.8.3 choosing a filter as described in 6.8.2 parametric influences on reaction time , the external filter network is critical to the stability and reaction time of the pll. the pll is also dependent on reference frequency and supply voltage. either of the filter networks in figure 6-10 is recommended when using a 4mhz reference clock (cgmrclk). figure 6-10 (a) is used for applications requiring better stability. figure 6-10 (b) is used in low-cost applications where stability is not critical. figure 6-10. pll filter 1 k ? 10 nf 0.22 f v ssa 0.22 f v ssa (a) (b) cgmxfc cgmxfc mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 97 chapter 7 system integration module (sim) 7.1 introduction this section describes the system integration module (sim). together with the cpu, the sim controls all mcu activities. a block diagram of the sim is shown in figure 7-1 . figure 7-2 is a summary of the sim input/output (i/o) registers. the sim is a system state controller that coordinates cpu and exception timing. the sim is responsible for: bus clock generation and control for cpu and peripherals: stop/wait/reset/break entry and recovery internal clock control master reset control, including power-on reset (por) and cop timeout interrupt control: acknowledge timing arbitration control timing vector address generation cpu enable/disable timing modular architecture expandable to 128 interrupt sources table 7-1 shows the internal signal names used in this section. table 7-1. signal name conventions signal name description iclk internal oscillator clock cgmxclk selected oscillator clock from oscillator module cgmvclk, cgmpclk pll output and the divided pll output cgmout cgmpclk-based or oscillator-based clock output from cgm module (bus clock = cgmout 2) iab internal address bus idb internal data bus porrst signal from the power-on reset module to the sim irst internal reset signal r/ w read/write signal system integration module (sim) mc68hc908ap a-family data sheet, rev. 2 98 freescale semiconductor figure 7-1. sim block diagram addr. register name bit 7 654321 bit 0 $fe00 sim break status register (sbsr) read: rrrrrr sbsw r write: note reset: 00000000 note: writing a logic 0 clears sbsw. $fe01 sim reset status register (srsr) read: por pin cop ilop ilad modrst lvi 0 write: por: 10000000 $fe03 sim break flag control register (sbfcr) read: bcfe rrrrrrr write: reset: 0 $fe04 interrupt status register 1 (int1) read: if6 if5 if4 if3 if2 if1 0 0 write: rrrrrrrr reset: 00000000 figure 7-2. sim i/o register summary stop/wait clock control clock generators por control reset pin control sim reset status register interrupt control and priority decode module stop module wait cpu stop (from cpu) cpu wait (from cpu) simoscen (to cgm, osc) cgmout (from cgm) internal clocks master reset control reset pin logic lvi (from lvi module) illegal opcode (from cpu) illegal address (from address map decoders) cop (from cop module) interrupt sources cpu interface reset control sim counter cop clock iclk (from osc) 2 v dd internal pullup device sim bus clock control and generation mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 99 7.2 sim bus clock control and generation the bus clock generator provides system clock signals for the cpu and peripherals on the mcu. the system clocks are generated from an incoming clock, cgmout, as shown in figure 7-3 . this clock can come from either an external oscillator or from the on-chip pll. (see chapter 6 clock generator module (cgm) .) figure 7-3. cgm clock signals 7.2.1 bus timing in user mode, the internal bus frequency is either the oscillator output (cgmxclk) divided by four or the divided pll output (cgmpclk) divided by four. $fe05 interrupt status register 2 (int2) read: if14 if13 if12 if11 if10 if9 if8 if7 write: rrrrrrrr reset: 00000000 $fe06 interrupt status register 3 (int3) read: 0 if21 if20 if19 if18 if17 if16 if15 write: rrrrrrrr reset: 00000000 = unimplemented figure 7-2. sim i/o register summary 2 bus clock generators system integration module monitor mode user mode simoscen oscillator (osc) module osc2 osc1 phase-locked loop (pll) cgmxclk cgmrclk it12 cgmout simdiv2 ptb0 to tim, adc stop mode clock to rest of mcu it23 to rest of mcu enable signals from config2 iclk to tbm oscclk cgmvclk to pwm sim counter system integration module (sim) mc68hc908ap a-family data sheet, rev. 2 100 freescale semiconductor 7.2.2 clock start-up from por or lvi reset when the power-on reset module or the low-voltage inhibit module generates a reset, the clocks to the cpu and peripherals are inactive and held in an inactive phase until after the 4096 iclk cycle por timeout has completed. the rst pin is driven low by the sim during this entire period. the ibus clocks start upon completion of the timeout. 7.2.3 clocks in stop mode and wait mode upon exit from stop mode by an interrupt, break, or reset, the sim allows iclk to clock the sim counter. the cpu and peripheral clocks do not become active until after the stop delay timeout. this timeout is selectable as 4096 or 32 iclk cycles. (see 7.6.2 stop mode .) in wait mode, the cpu clocks are inactive. the sim also produces two sets of clocks for other modules. refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode. some modules can be programmed to be active in wait mode. 7.3 reset and system initialization the mcu has these reset sources: power-on reset module (por) external reset pin ( rst) computer operating properly module (cop) low-voltage inhibit module (lvi) illegal opcode illegal address all of these resets produce the vector $fffe:$ffff ($fefe:$feff in monitor mode) and assert the internal reset signal (irst). irst causes all registers to be returned to their default values and all modules to be returned to their reset states. an internal reset clears the sim counter (see 7.4 sim counter ), but an external reset does not. each of the resets sets a corresponding bit in the sim reset status register (srsr). (see 7.7 sim registers .) 7.3.1 external pin reset the rst pin circuit includes an internal pull-up device. pulling the asynchronous rst pin low halts all processing. the pin bit of the sim reset status register (srsr) is set as long as rst is held low for a minimum of 67 iclk cycles, assuming that neither the por nor the lvi was the source of the reset. see table 7-2 for details. figure 7-4 shows the relative timing. table 7-2. pin bit set timing reset type number of cycles required to set pin por/lvi 4163 (4096 + 64 + 3) all others 67 (64 + 3) reset and system initialization mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 101 figure 7-4. external reset timing 7.3.2 active resets from internal sources all internal reset sources actively pull the rst pin low for 32 iclk cycles to allow resetting of external peripherals. the internal reset signal irst continues to be asserted for an additional 32 cycles (see figure 7-5 ). an internal reset can be caused by an illegal address, illegal opcode, cop timeout, lvi, or por (see figure 7-6 ). note for lvi or por resets, the sim cycles through 4096 + 32 iclk cycles during which the sim forces the rst pin low. the internal reset signal then follows the sequence from the falling edge of rst shown in figure 7-5 . figure 7-5. internal reset timing the cop reset is asynchronous to the bus clock. figure 7-6. sources of internal reset the active reset feature allows the part to issue a reset to peripherals and other chips within a system built around the mcu. 7.3.2.1 power-on reset when power is first applied to the mcu, the power-on reset module (por) generates a pulse to indicate that power-on has occurred. the external reset pin ( rst) is held low while the sim counter counts out 4096 + 32 iclk cycles. thirty-two iclk cycles later, the cpu and memories are released from reset to allow the reset vector sequence to occur. rst iab pc vect h vect l iclk irst rst rst pulled low by mcu iab 32 cycles 32 cycles vector high iclk illegal address rst illegal opcode rst coprst lvi por internal reset system integration module (sim) mc68hc908ap a-family data sheet, rev. 2 102 freescale semiconductor at power-on, these events occur: a por pulse is generated. the internal reset signal is asserted. the sim enables cgmout. internal clocks to the cpu and modules are held inactive for 4096 iclk cycles to allow stabilization of the oscillator. the pin is driven low during the oscillator stabilization time. the por bit of the sim reset status register (srsr) is set and all other bits in the register are cleared. figure 7-7. por recovery 7.3.2.2 computer operating properly (cop) reset an input to the sim is reserved for the cop reset signal. the overflow of the cop counter causes an internal reset and sets the cop bit in the sim reset status register (srsr). the sim actively pulls down the rst pin for all internal reset sources. to prevent a cop module timeout, write any value to location $ffff. writing to location $ffff clears the cop counter and bits 12 through 5 of the sim counter. the sim counter output, which occurs at least every 2 13 ?2 4 iclk cycles, drives the cop counter. the cop should be serviced as soon as possible out of reset to guarantee the maximum amount of time before the first timeout. the cop module is disabled if the rst pin or the irq1 pin is held at v tst while the mcu is in monitor mode. the cop module can be disabled only through combinational logic conditioned with the high voltage signal on the rst or the irq1 pin. this prevents the cop from becoming disabled as a result of external noise. during a break state, v tst on the rst pin disables the cop module. 7.3.2.3 illegal opcode reset the sim decodes signals from the cpu to detect illegal instructions. an illegal instruction sets the ilop bit in the sim reset status register (srsr) and causes a reset. porrst osc1 iclk cgmout rst iab 4096 cycles 32 cycles 32 cycles $fffe $ffff irst sim counter mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 103 if the stop enable bit, stop, in the mask option register is logic 0, the sim treats the stop instruction as an illegal opcode and causes an illegal opcode reset. the sim actively pulls down the rst pin for all internal reset sources. 7.3.2.4 illegal address reset an opcode fetch from an unmapped address generates an illegal address reset. the sim verifies that the cpu is fetching an opcode prior to asserting the ilad bit in the sim reset status register (srsr) and resetting the mcu. a data fetch from an unmapped address does not generate a reset. the sim actively pulls down the rst pin for all internal reset sources. 7.3.2.5 low-voltage inhibit (lvi) reset the low-voltage inhibit module (lvi) asserts its output to the sim when the v dd voltage falls to the lvi tripf voltage. the lvi bit in the sim reset status register (srsr) is set, and the external reset pin ( rst) is held low while the sim counter counts out 4096 + 32 iclk cycles. thirty-two iclk cycles later, the cpu is released from reset to allow the reset vector sequence to occur. the sim actively pulls down the rst pin for all internal reset sources. 7.3.2.6 monitor mode entry module reset the monitor mode entry module reset asserts its output to the sim when monitor mode is entered in the condition where the reset vectors are blank ($ff). (see chapter 8 monitor rom (mon) .) when modrst gets asserted, an internal reset occurs. the sim actively pulls down the rst pin for all internal reset sources. 7.4 sim counter the sim counter is used by the power-on reset module (por) and in stop mode recovery to allow the oscillator time to stabilize before enabling the internal bus (ibus) clocks. the sim counter also serves as a prescaler for the computer operating properly module (cop). the sim counter overflow supplies the clock for the cop module. the sim counter is 13 bits long and is clocked by the falling edge of cgmxclk. 7.4.1 sim counter during power-on reset the power-on reset module (por) detects power applied to the mcu. at power-on, the por circuit asserts the signal porrst. once the sim is initialized, it enables the clock generation module (cgm) to drive the bus clock state machine. 7.4.2 sim counter during stop mode recovery the sim counter also is used for stop mode recovery. the stop instruction clears the sim counter. after an interrupt, break, or reset, the sim senses the state of the short stop recovery bit, ssrec, in the mask option register. if the ssrec bit is a logic 1, then the stop recovery is reduced from the normal delay of 4096 cgmxclk cycles down to 32 cgmxclk cycles. this is ideal for applications using canned oscillators that do not require long start-up times from stop mode. external crystal applications should use the full stop recovery time, that is, with ssrec cleared. system integration module (sim) mc68hc908ap a-family data sheet, rev. 2 104 freescale semiconductor 7.4.3 sim counter and reset states external reset has no effect on the sim counter. ( see 7.6.2 stop mode for details.) the sim counter is free-running after all reset states. ( see 7.3.2 active resets from internal sources for counter control and internal reset recovery sequences.) 7.5 exception control normal, sequential program execution can be changed in three different ways: interrupts: maskable hardware cpu interrupts non-maskable software interrupt instruction (swi) reset break interrupts 7.5.1 interrupts at the beginning of an interrupt, the cpu saves the cpu register contents on the stack and sets the interrupt mask (i bit) to prevent additional interrupts. at the end of an interrupt, the rti instruction recovers the cpu register contents from the stack so that normal processing can resume. figure 7-8 shows interrupt entry timing, and figure 7-9 shows interrupt recovery timing. figure 7-8. interrupt entry timing figure 7-9. interrupt recovery timing interrupts are latched, and arbitration is performed in the sim at the start of interrupt processing. the arbitration result is a constant that the cpu uses to determine which vector to fetch. once an interrupt is latched by the sim, no other interrupt can take precedence, regardless of priority, until the latched interrupt is serviced (or the i bit is cleared). (see figure 7-10 .) module idb r/ w interrupt dummy sp sp ?1 sp ?2 sp ?3 sp ?4 vect h vect l start addr iab dummy pc ?1[7:0] pc ?1[15:8] x a ccr v data h v data l opcode i-bit module idb r/ w interrupt sp ?4 sp ?3 sp ?2 sp ?1 sp pc pc + 1 iab ccr a x pc ?1[15:8] pc ?1[7:0] opcode operand i-bit exception control mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 105 figure 7-10. interrupt processing 7.5.1.1 hardware interrupts a hardware interrupt does not stop the current instruction. processing of a hardware interrupt begins after completion of the current instruction. when the current instruction is complete, the sim checks all pending hardware interrupts. if interrupts are not masked (i bit clear in the condition code register) and if the corresponding interrupt enable bit is set, the sim proceeds with interrupt processing; otherwise, the next instruction is fetched and executed. if more than one interrupt is pending at the end of an instruction execution, the highest priority interrupt is serviced first. figure 7-11 demonstrates what happens when two interrupts are pending. if an interrupt is pending upon exit from the original interrupt service routine, the pending interrupt is serviced before the lda instruction is executed. no no no yes no no yes yes as many interrupts i bit set? from reset break i-bit set? irq1 interrupt? swi instruction? rti instruction? fetch next instruction unstack cpu registers stack cpu registers set i-bit load pc with interrupt vector execute instruction yes yes as exist on chip interrupt? system integration module (sim) mc68hc908ap a-family data sheet, rev. 2 106 freescale semiconductor figure 7-11 . interrupt recognition example the lda opcode is prefetched by both the int1 and int2 rti instructions. however, in the case of the int1 rti prefetch, this is a redundant operation. note to maintain compatibility with the m6805 family, the h register is not pushed on the stack during interrupt entry. if the interrupt service routine modifies the h register or uses the indexed addressing mode, software should save the h register and then restore it prior to exiting the routine. 7.5.1.2 swi instruction the swi instruction is a non-maskable instruction that causes an interrupt regardless of the state of the interrupt mask (i bit) in the condition code register. note a software interrupt pushes pc onto the stack. a software interrupt does not push pc ?1, as a hardware interrupt does. 7.5.2 interrupt status registers the flags in the interrupt status registers identify maskable interrupt sources. table 7-3 summarizes the interrupt sources and the interrupt status register flags that they set. the interrupt status registers can be useful for debugging. cli lda int1 pulh rti int2 background #$ff pshh int1 interrupt service routine pulh rti pshh int2 interrupt service routine routine exception control mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 107 7.5.2.1 interrupt status register 1 if6?f1 ?interrupt flags 6? these flags indicate the presence of interrupt requests from the sources shown in table 7-3 . 1 = interrupt request present 0 = no interrupt request present bit 0 and bit 1 ?always read 0 7.5.2.2 interrupt status register 2 if14?f7 ?interrupt flags 14? these flags indicate the presence of interrupt requests from the sources shown in table 7-3 . 1 = interrupt request present 0 = no interrupt request present 7.5.2.3 interrupt status register 3 if21?f15 ?interrupt flags 21?5 these flags indicate the presence of an interrupt request from the source shown in table 7-3 . 1 = interrupt request present 0 = no interrupt request present address: $fe04 bit 7654321bit 0 read: if6 if5 if4 if3 if2 if1 0 0 write: rrrrrrrr reset:00000000 r = reserved figure 7-12. interrupt status register 1 (int1) address: $fe05 bit 7654321bit 0 read: if14 if13 if12 if11 if10 if9 if8 if7 write: rrrrrrrr reset:00000000 r = reserved figure 7-13. interrupt status register 2 (int2) address: $fe06 bit 7654321bit 0 read: 0 if21 if20 if19 if18 if17 if16 if15 write: rrrrrrrr reset:00000000 r = reserved figure 7-14. interrupt status register 3 (int3) system integration module (sim) mc68hc908ap a-family data sheet, rev. 2 108 freescale semiconductor table 7-3. interrupt sources priority int flag vector address interrupt source lowest $ffd0 reserved $ffd1 if21 $ffd2 timebase $ffd3 if20 $ffd4 infrared sci transmit $ffd5 if19 $ffd6 infrared sci receive $ffd7 if18 $ffd8 infrared sci error $ffd9 if17 $ffda spi transmit $ffdb if16 $ffdc spi receive $ffdd if15 $ffde adc conversion complete $ffdf if14 $ffe0 keyboard $ffe1 if13 $ffe2 sci transmit $ffe3 if12 $ffe4 sci receive $ffe5 if11 $ffe6 sci error $ffe7 if10 $ffe8 mmiic $ffe9 if9 $ffea tim2 over?w $ffeb if8 $ffec tim2 channel 1 $ffed if7 $ffee tim2 channel 0 $ffef if6 $fff0 tim1 over?w $fff1 if5 $fff2 tim1 channel 1 $fff3 if4 $fff4 tim1 channel 0 $fff5 if3 $fff6 pll $fff7 if2 $fff8 irq2 $fff9 if1 $fffa irq1 $fffb $fffc swi $fffd $fffe reset highest $ffff low-power modes mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 109 7.5.3 reset all reset sources always have equal and highest priority and cannot be arbitrated. 7.5.4 break interrupts the break module can stop normal program flow at a software-programmable break point by asserting its break interrupt output. (see chapter 21 break module (brk) .) the sim puts the cpu into the break state by forcing it to the swi vector location. refer to the break interrupt subsection of each module to see how each module is affected by the break state. 7.5.5 status flag protection in break mode the sim controls whether status flags contained in other modules can be cleared during break mode. the user can select whether flags are protected from being cleared by properly initializing the break clear flag enable bit (bcfe) in the sim break flag control register (sbfcr). protecting flags in break mode ensures that set flags will not be cleared while in break mode. this protection allows registers to be freely read and written during break mode without losing status flag information. setting the bcfe bit enables the clearing mechanisms. once cleared in break mode, a flag remains cleared even when break mode is exited. status flags with a 2-step clearing mechanism for example, a read of one register followed by the read or write of another are protected, even when the first step is accomplished prior to entering break mode. upon leaving break mode, execution of the second step will clear the flag as normal. 7.6 low-power modes executing the wait or stop instruction puts the mcu in a low power-consumption mode for standby situations. the sim holds the cpu in a non-clocked state. the operation of each of these modes is described in the following subsections. both stop and wait clear the interrupt mask (i) in the condition code register, allowing interrupts to occur. 7.6.1 wait mode in wait mode, the cpu clocks are inactive while the peripheral clocks continue to run. figure 7-15 shows the timing for wait mode entry. a module that is active during wait mode can wake up the cpu with an interrupt if the interrupt is enabled. stacking for the interrupt begins one cycle after the wait instruction during which the interrupt occurred. in wait mode, the cpu clocks are inactive. refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode. some modules can be programmed to be active in wait mode. wait mode also can be exited by a reset or break. a break interrupt during wait mode sets the sim break stop/wait bit, sbsw, in the sim break status register (sbsr). if the cop disable bit, copd, in the mask option register is logic 0, then the computer operating properly module (cop) is enabled and remains active in wait mode. system integration module (sim) mc68hc908ap a-family data sheet, rev. 2 110 freescale semiconductor figure 7-15. wait mode entry timing figure 7-16 and figure 7-17 show the timing for wait recovery. figure 7-16. wait recovery from interrupt or break figure 7-17. wait recovery from internal reset 7.6.2 stop mode in stop mode, the sim counter is reset and the system clocks are disabled. an interrupt request from a module can cause an exit from stop mode. stacking for interrupts begins after the selected stop recovery time has elapsed. reset or break also causes an exit from stop mode. the sim disables the clock generator module output (cgmout) in stop mode, stopping the cpu and peripherals. stop recovery time is selectable using the ssrec bit in the configuration register 1 (config1). if ssrec is set, stop recovery is reduced from the normal delay of 4096 iclk cycles down to 32. this is ideal for applications using canned oscillators that do not require long start-up times from stop mode. note external crystal applications should use the full stop recovery time by clearing the ssrec bit. wait addr + 1 same same iab idb previous data next opcode same wait addr same r/ w note: previous data can be operand data or the wait opcode, depending on the last instruction. $6e0c $6e0b $00ff $00fe $00fd $00fc $a6 $a6 $01 $0b $6e $a6 iab idb exitstopwait note: exitstopwait = rst pin or cpu interrupt or break interrupt iab idb rst $a6 $a6 $6e0b rst vct h rst vct l $a6 iclk 32 cycles 32 cycles sim registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 111 a break interrupt during stop mode sets the sim break stop/wait bit (sbsw) in the sim break status register (sbsr). the sim counter is held in reset from the execution of the stop instruction until the beginning of stop recovery. it is then used to time the recovery period. figure 7-18 shows stop mode entry timing. note to minimize stop current, all pins configured as inputs should be driven to a logic 1 or logic 0. figure 7-18. stop mode entry timing figure 7-19. stop mode recovery from interrupt or break 7.7 sim registers the sim has three memory-mapped registers: sim break status register (sbsr) ?$fe00 sim reset status register (srsr) ?$fe01 sim break flag control register (sbfcr) ?$fe03 stop addr + 1 same same iab idb previous data next opcode same stop addr same r/ w cpustop note: previous data can be operand data or the stop opcode, depending on the last instruction. iclk int/break iab stop + 2 stop + 2 sp sp ?1 sp ?2 sp ?3 stop +1 stop recovery period system integration module (sim) mc68hc908ap a-family data sheet, rev. 2 112 freescale semiconductor 7.7.1 sim break status register the sim break status register (sbsr) contains a flag to indicate that a break caused an exit from stop mode or wait mode. sbsw ?break wait bit this status bit is set when a break interrupt causes an exit from wait mode or stop mode. clear sbsw by writing a logic 0 to it. reset clears sbsw. 1 = stop mode or wait mode was exited by break interrupt 0 = stop mode or wait mode was not exited by break interrupt sbsw can be read within the break interrupt routine. the user can modify the return address on the stack by subtracting 1 from it. the following code is an example. address: $fe00 bit 7654321bit 0 read: rrrrrr sbsw r write: note reset: 0 note: writing a logic 0 clears sbsw. r = reserved figure 7-20. sim break status register (sbsr) this code works if the h register has been pushed onto the stack in the break service routine software. this code should be executed at the end of the break service routine software. hibyte equ 5 lobyte equ 6 if not sbsw, do rti brclr sbsw,sbsr, return ; ; see if wait mode or stop mode was exited by break. tst lobyte,sp ;if returnlo is not zero, bne dolo ;then just decrement low byte. dec hibyte,sp ;else deal with high byte, too. dolo dec lobyte,sp ;point to wait/stop opcode. return pulh rti ;restore h register. sim registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 113 7.7.2 sim reset status register this register contains six flags that show the source of the last reset provided all previous reset status bits have been cleared. clear the sim reset status register by reading it. a power-on reset sets the por bit and clears all other bits in the register. por ?power-on reset bit 1 = last reset caused by por circuit 0 = read of srsr pin ?external reset bit 1 = last reset caused by external reset pin ( rst) 0 = por or read of srsr cop ?computer operating properly reset bit 1 = last reset caused by cop counter 0 = por or read of srsr ilop ?illegal opcode reset bit 1 = last reset caused by an illegal opcode 0 = por or read of srsr ilad ?illegal address reset bit (opcode fetches only) 1 = last reset caused by an opcode fetch from an illegal address 0 = por or read of srsr modrst ?monitor mode entry module reset bit 1 = last reset caused by monitor mode entry when vector locations $fffe and $ffff are $ff after por while irq1 = v dd 0 = por or read of srsr lvi ?low-voltage inhibit reset bit 1 = last reset caused by the lvi circuit 0 = por or read of srsr address: $fe01 bit 7654321bit 0 read: por pin cop ilop ilad modrst lvi 0 write: reset:10000000 = unimplemented figure 7-21. sim reset status register (srsr) system integration module (sim) mc68hc908ap a-family data sheet, rev. 2 114 freescale semiconductor 7.7.3 sim break flag control register the sim break control register contains a bit that enables software to clear status bits while the mcu is in a break state. bcfe ?break clear flag enable bit this read/write bit enables software to clear status bits by accessing status registers while the mcu is in a break state. to clear status bits during the break state, the bcfe bit must be set. 1 = status bits clearable during break 0 = status bits not clearable during break address: $fe03 bit 7654321bit 0 read: bcfe rrrrrrr write: reset: 0 r = reserved figure 7-22. sim break flag control register (sbfcr) mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 115 chapter 8 monitor rom (mon) 8.1 introduction this section describes the monitor rom (mon) and the monitor mode entry methods. the monitor rom allows complete testing of the mcu through a single-wire interface with a host computer. monitor mode entry can be achieved without use of the higher test voltage, v tst , as long as vector addresses $fffe and $ffff are blank, thus reducing the hardware requirements for in-circuit programming. in addition, to simplify user coding, routines are also stored in the monitor rom area for flash memory program /erase. 8.2 features features of the monitor rom include: normal user-mode pin functionality one pin dedicated to serial communication between monitor rom and host computer standard mark/space non-return-to-zero (nrz) communication with host computer execution of code in ram or flash flash memory security feature (1) 959 bytes monitor rom code size ($fc00?fdff and $fe10?ffce) monitor mode entry without high voltage, v tst , if reset vector is blank ($fffe and $ffff contain $ff) standard monitor mode entry if high voltage, v tst , is applied to irq1 resident routines for in-circuit programming 8.3 functional description the monitor rom receives and executes commands from a host computer. figure 8-1 shows an example circuit used to enter monitor mode and communicate with a host computer via a standard rs-232 interface. simple monitor commands can access any memory address. in monitor mode, the mcu can execute code downloaded into ram by a host computer while most mcu pins retain normal operating mode functions. all communication between the host computer and the mcu is through the pta0 pin. a level-shifting and multiplexing interface is required between pta0 and the host computer. pta0 is used in a wired-or configuration and requires a pullup resistor. 1. no security feature is absolutely secure. however, freescale? strategy is to make reading or copying the flash difficult for unauthorized users. monitor rom (mon) mc68hc908ap a-family data sheet, rev. 2 116 freescale semiconductor figure 8-1. monitor mode circuit notes: 1. monitor mode entry method: sw2: position c ?high voltage entry (v tst ); must use external osc bus clock depends on sw1 (note 2). sw2: position d ?reset vector must be blank ($fffe:$ffff = $ff) bus clock = 1.2288mhz. 2. affects high voltage entry to monitor mode only (sw2 at position c): sw1: position a ?bus clock = osc1 4 sw1: position b ?bus clock = osc1 2 5. see table 22-4 for v tst voltage level requirements. 1m hc908ap rst irq1 osc1 osc2 v ss pta0 6?0 pf 6?0 pf 0.1 f 4.9152mhz pta1 v dd 0.1 f v dd pta2 10k ptb0 v dd 10k 10 k sw1 a b v reg (see note 2) c d xtal circuit 16 15 2 6 v dd max232 v+ v v dd 10 k c1+ c1 5 4 c2+ c2 + 3 1 1 f + + + 8 7 db9 2 3 5 10 9 + 1 2 3 4 5 6 74hc125 74hc125 1k v tst v cc gnd 1 f 1 f 1 f 1 f 8.5 v 10 k connect to osc1, with osc2 unconnected. must be used if sw2 is at position c. osc1 (see note 1) sw2 10k 0.033 f 0.01 f cgmxfc v dda v refl v ssa ext osc 4.9152mhz/9.8304mhz (50% duty) v refh v reg 10k v dd v dd functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 117 8.3.1 entering monitor mode table 8-1 shows the pin conditions for entering monitor mode. as specified in the table, monitor mode may be entered after a por and will allow communication at 9600 baud provided one of the following sets of conditions is met: 1. if $fffe and $ffff do not contain $ff (programmed state): the external clock is 4.9152 mhz with ptb0 low or 9.8304 mhz with ptb0 high irq1 = v tst 2. if $fffe and $ffff both contain $ff (erased state): the external clock is 9.8304 mhz irq1 = v dd (this can be implemented through the internal irq1 pullup if v tst is applied to irq1 and ptb0 is low upon monitor mode entry (above condition set 1), the bus frequency is a divide-by-two of the input clock. if ptb0 is high with v tst applied to irq1 upon monitor mode entry, the bus frequency will be a divide-by-four of the input clock. holding the ptb0 pin low when entering monitor mode causes a bypass of a divide-by-two stage at the oscillator only if v tst is applied to irq1. in this event, the cgmout frequency is equal to the cgmxclk frequency, and the osc1 input directly generates internal bus clocks. in this case, the osc1 signal must have a 50% duty cycle at maximum bus frequency. if entering monitor mode without high voltage on irq1 (above condition set 2, where applied voltage is either v dd ), then all port a pin requirements and conditions, including the ptb0 frequency divisor selection, are not in effect. this is to reduce circuit requirements when performing in-circuit programming. note if the reset vector is blank and monitor mode is entered, the chip will see an additional reset cycle after the initial por reset. once the part has been programmed, the traditional method of applying a voltage, v tst , to irq1 must be used to enter monitor mode. the cop module is disabled in monitor mode based on these conditions: if monitor mode was entered as a result of the reset vector being blank (above condition set 2), the cop is always disabled regardless of the state of irq1 or rst. if monitor mode was entered with v tst on irq1 (condition set 1), then the cop is disabled as long as v tst is applied to either irq1 or rst. the second condition states that as long as v tst is maintained on the irq1 pin after entering monitor mode, or if v tst is applied to rst after the initial reset to get into monitor mode (when v tst was applied to irq1), then the cop will be disabled. in the latter situation, after v tst is applied to the rst pin, v tst can be removed from the irq1 pin in the interest of freeing the irq1 for normal functionality in monitor mode. figure 8-2 shows a simplified diagram of the monitor mode entry when the reset vector is blank and just v dd voltage is applied to the irq1 pin. an external oscillator of 9.8304 mhz is required for a baud rate of 9600, as the internal bus frequency is automatically set to the external frequency divided by four. enter monitor mode with pin configuration shown in figure 8-1 by pulling rst low and then high. the rising edge of rst latches monitor mode. once monitor mode is latched, the values on the specified pins can change. once out of reset, the mcu waits for the host to send eight security bytes. (see 8.4 security .) after the security bytes, the mcu sends a break signal (10 consecutive logic 0?) to the host, indicating that it is ready to receive a command. mc68hc908ap a-family data sheet, rev. 2 118 freescale semiconductor monitor rom (mon) table 8-1. monitor mode signal requirements and options irq1 rst address $fffe/ $ffff pta2 pta1 pta0 (1) 1. pta0 = 1 if serial communication; pta0 = 0 if parallel communication ptb0 external clock (2) 2. external clock is derived by a 4.9152mhz crystal/off-chip oscillator or a 9.8304mhz off-chip oscillator. bus frequency pll cop baud rate comment xgndx xxxx x 0 x disabled 0 no operation until reset goes high v tst (3) 3. monitor mode entry by irq1= v tst , a 4.9152/9.8304 mhz off-chip oscillator must be used. the mcu internal crystal oscillator circuit is by- passed. v dd or v tst x 0110 4.9152 mhz 2.4576 mhz off disabled 9600 pta1 and pta2 voltages only required if irq1 = v tst ; ptb0 determines frequency divider v tst (3) v dd or v tst x 0111 9.8304 mhz 2.4576 mhz off disabled 9600 pta1 and pta2 voltages only required if irq1 = v tst ; ptb0 determines frequency divider v dd v dd blank "$ffff" xx1x 4.9152 mhz 1.2288 mhz off disabled 4800 external frequency always divided by 4 v dd v dd blank "$ffff" xx1x 9.8304 mhz 2.4576 mhz off disabled 9600 external frequency always divided by 4 v dd or gnd v tst blank "$ffff" xxxx x off enabled enters user mode ?will encounter an illegal address reset v dd or gnd v dd or v tst not blank xxxx x off enabled enters user mode functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 119 figure 8-2. low-voltage monitor mode entry flowchart in monitor mode, the mcu uses different vectors for reset, swi (software interrupt), and break interrupt than those for user mode. the alternate vectors are in the $fe page instead of the $ff page and allow code execution from the internal monitor firmware instead of user code. note exiting monitor mode after it has been initiated by having a blank reset vector requires a power-on reset (por). pulling rst low will not exit monitor mode in this situation. table 8-2 summarizes the differences between user mode and monitor mode vectors. 8.3.2 data format communication with the monitor rom is in standard non-return-to-zero (nrz) mark/space data format. transmit and receive baud rates must be identical. figure 8-3. monitor data format table 8-2. mode differences (vectors) modes functions reset vector high reset vector low break vector high break vector low swi vector high swi vector low user $fffe $ffff $fffc $fffd $fffc $fffd monitor $fefe $feff $fefc $fefd $fefc $fefd is vector blank? por triggered? normal user mode monitor mode execute monitor code no no yes yes por reset bit 5 start bit bit 0 bit 1 next stop bit start bit bit 2 bit 3 bit 4 bit 6 bit 7 monitor rom (mon) mc68hc908ap a-family data sheet, rev. 2 120 freescale semiconductor 8.3.3 break signal a start bit (logic 0) followed by nine logic 0 bits is a break signal. when the monitor receives a break signal, it drives the pta0 pin high for the duration of two bits and then echoes back the break signal. figure 8-4. break transaction 8.3.4 baud rate the communication baud rate is controlled by the crystal frequency and the state of the ptb0 pin (when irq1 is set to v tst ) upon entry into monitor mode. when ptb0 is high, the divide by ratio is 1024. if the ptb0 pin is at logic 0 upon entry into monitor mode, the divide by ratio is 512. if monitor mode was entered with v dd on irq1, then the divide by ratio is set at 1024, regardless of ptb0. this condition for monitor mode entry requires that the reset vector is blank. table 8-3 lists external frequencies required to achieve a standard baud rate of 9600 bps. other standard baud rates can be accomplished using proportionally higher or lower frequency generators. if using a crystal as the clock source, be aware of the upper frequency limit that the internal clock module can handle. 8.3.5 commands the monitor rom firmware uses these commands: read (read memory) write (write memory) iread (indexed read) iwrite (indexed write) readsp (read stack pointer) run (run user program) the monitor rom firmware echoes each received byte back to the pta0 pin for error checking. an 11-bit delay at the end of each command allows the host to send a break character to cancel the command. a delay of two bit times occurs before each echo and before read, iread, or readsp data is returned. the data returned by a read command appears after the echo of the last byte of the command. table 8-3. monitor baud rate selection external frequency irq1 ptb0 internal frequency baud rate (bps) 4.9152 mhz v tst 0 2.4576 mhz 9600 9.8304 mhz v tst 1 2.4576 mhz 9600 9.8304 mhz v dd x 2.4576 mhz 9600 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 missing stop bit 2-stop bit delay before zero echo functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 121 note wait one bit time after each echo before sending the next byte. figure 8-5. read transaction figure 8-6. write transaction a brief description of each monitor mode command is given in table 8-4 through table 8-9 . table 8-4. read (read memory) command description read byte from memory operand 2-byte address in high-byte:low-byte order data returned returns contents of speci?d address opcode $4a command sequence read read echo from host address high address high address low address low data return 1 3, 2 11 4 4 notes: 2 = data return delay, 2 bit times 3 = cancel command delay, 11 bit times 4 = wait 1 bit time before sending next byte. 44 1 = echo delay, 2 bit times write write echo from host address high address high address low address low data data notes: 2 = cancel command delay, 11 bit times 3 = wait 1 bit time before sending next byte. 11 3 11 3 3 3 2, 3 1 = echo delay, 2 bit times read read echo sent to monitor address high address high address low data return address low monitor rom (mon) mc68hc908ap a-family data sheet, rev. 2 122 freescale semiconductor table 8-5. write (write memory) command description write byte to memory operand 2-byte address in high-byte:low-byte order; low byte followed by data byte data returned none opcode $49 command sequence table 8-6. iread (indexed read) command description read next 2 bytes in memory from last address accessed operand 2-byte address in high byte:low byte order data returned returns contents of next two addresses opcode $1a command sequence write write echo from host address high address high address low address low data data iread iread echo from host data return data functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 123 a sequence of iread or iwrite commands can access a block of memory sequentially over the full 64-kbyte memory map. table 8-7. iwrite (indexed write) command description write to last address accessed + 1 operand single data byte data returned none opcode $19 command sequence table 8-8. readsp (read stack pointer) command description reads stack pointer operand none data returned returns incremented stack pointer value (sp + 1) in high-byte:low-byte order opcode $0c command sequence iwrite iwrite echo from host data data readsp readsp echo from host sp return sp high low monitor rom (mon) mc68hc908ap a-family data sheet, rev. 2 124 freescale semiconductor the mcu executes the swi and pshh instructions when it enters monitor mode. the run command tells the mcu to execute the pulh and rti instructions. before sending the run command, the host can modify the stacked cpu registers to prepare to run the host program. the readsp command returns the incremented stack pointer value, sp + 1. the high and low bytes of the program counter are at addresses sp + 5 and sp + 6. figure 8-7. stack pointer at monitor mode entry 8.4 security a security feature discourages unauthorized reading of flash locations while in monitor mode. the host can bypass the security feature at monitor mode entry by sending eight security bytes that match the bytes at locations $fff6?fffd. locations $fff6?fffd contain user-defined data. note do not leave locations $fff6?fffd blank. for security reasons, program locations $fff6?fffd even if they are not used for vectors. table 8-9. run (run user program) command description executes pulh and rti instructions operand none data returned none opcode $28 command sequence run run echo from host condition code register accumulator low byte of index register high byte of program counter low byte of program counter sp + 1 sp + 2 sp + 3 sp + 4 sp + 5 sp sp + 6 high byte of index register sp + 7 security mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 125 during monitor mode entry, the mcu waits after the power-on reset for the host to send the eight security bytes on pin pta0. if the received bytes match those at locations $fff6?fffd, the host bypasses the security feature and can read all flash locations and execute code from flash. security remains bypassed until a power-on reset occurs. if the reset was not a power-on reset, security remains bypassed and security code entry is not required. (see figure 8-8 .) figure 8-8. monitor mode entry timing upon power-on reset, if the received bytes of the security code do not match the data at locations $fff6?fffd, the host fails to bypass the security feature. the mcu remains in monitor mode, but reading a flash location returns an invalid value and trying to execute code from flash causes an illegal address reset. after receiving the eight security bytes from the host, the mcu transmits a break character, signifying that it is ready to receive a command. note the mcu does not transmit a break character until after the host sends the eight security bits. to determine whether the security code entered is correct, check to see if bit 6 of ram address $60 is set. if it is, then the correct security code has been entered and flash can be accessed. if the security sequence fails, the device should be reset by a power-on reset and brought up in monitor mode to attempt another entry. after failing the security sequence, the flash module can also be mass erased by executing an erase routine that was downloaded into internal ram. the mass erase operation clears the security code locations so that all eight security bytes become $ff (blank). byte 1 byte 1 echo byte 2 byte 2 echo byte 8 byte 8 echo command command echo pta0 rst v dd 4096 + 32 iclk cycles 256 bus cycles (minimum) 1 4 1 1 2 1 break notes: 2 = data return delay, 2 bit times. 4 = wait 1 bit time before sending next byte. 4 from host from mcu 1 = echo delay, 2 bit times. monitor rom (mon) mc68hc908ap a-family data sheet, rev. 2 126 freescale semiconductor 8.5 rom-resident routines seven routines stored in the monitor rom area (thus rom-resident) are provided for flash memory manipulation. five of the seven routines are intended to simplify flash program, erase, and load operations. the other two routines are intended to simplify the use of the flash memory as eeprom. table 8-10 shows a summary of the rom-resident routines. the routines are designed to be called as stand-alone subroutines in the user program or monitor mode. the parameters that are passed to a routine are in the form of a contiguous data block, stored in ram. the index register (h:x) is loaded with the address of the first byte of the data block (acting as a pointer), and the subroutine is called (jsr). using the start address as a pointer, multiple data blocks can be used, any area of ram be used. a data block has the control and data bytes in a defined order, as shown in figure 8-9 . during the software execution, it does not consume any dedicated ram location, the run-time heap will extend the system stack, all other ram location will not be affected. figure 8-9. data block format for rom-resident routines the control and data bytes are described below. table 8-10. summary of rom-resident routines routine name routine description call address stack used (bytes) prgrnge program a range of locations $fc34 15 erarnge erase a page or the entire array $fce4 9 ldrnge loads data from a range of locations $fc00 7 mon_prgrnge program a range of locations in monitor mode $ff24 17 mon_erarnge erase a page or the entire array in monitor mode $ff28 11 data size (datasize) start address high (addrh) start address low (addrl) data 0 data 1 bus speed (bus_spd) file_ptr data n data array $xxxx data block address as pointer ram rom-resident routines mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 127 bus speed this one byte indicates the operating bus speed of the mcu. the value of this byte should be equal to 4 times the bus speed. e.g., for a 4mhz bus, the value is 16 ($10). this control byte is useful where the mcu clock source is switched between the pll clock and the crystal clock. data size ?this one byte indicates the number of bytes in the data array that are to be manipulated. the maximum data array size is 255. erarnge and mon_erarnge routines do not manipulate a data array, thus, this data size byte has no meaning. start address these two bytes, high byte followed by low byte, indicate the start address of the flash memory to be manipulated. data array ?this data array contains data that are to be manipulated. data in this array are programmed to flash memory by the programming routines, prgrnge and mon_prgrnge. for the read routine, ldrnge, data is read from flash and stored in this array. 8.5.1 prgrnge prgrnge is used to program a range of flash locations with data loaded into the data array. the start location of the flash to be programmed is specified by the address addrh:addrl and the number of bytes from this location is specified by datasize. the maximum number of bytes that can be programmed in one routine call is 255 bytes (max. datasize is 255). addrh:addrl do not need to be at a page boundary, the routine handles any boundary misalignment during programming. a check to see that all bytes in the specified range are erased is not performed by this routine prior programming. nor does this routine do a verification after programming, so there is no return confirmation that programming was successful. user must assure that the range specified is first erased. the coding example below is to program 64 bytes of data starting at flash location $ee00, with a bus speed of 4.9152 mhz. the coding assumes the data block is already loaded in ram, with the address pointer, file_ptr, pointing to the first byte of the data block. table 8-11. prgrnge routine routine name prgrnge routine description program a range of locations calling address $fc34 stack used 15 bytes data block format bus speed (bus_spd) data size (datasize) start address high (addrh) start address (addrl) data 1 (data1) : data n (datan) monitor rom (mon) mc68hc908ap a-family data sheet, rev. 2 128 freescale semiconductor org ram : file_ptr: bus_spd ds.b 1 ; indicates 4x bus frequency datasize ds.b 1 ; data size to be programmed start_addr ds.w 1 ; flash start address dataarray ds.b 64 ; reserved data array prgrnge equ $fc34 flash_start equ $ee00 org flash initialisation: mov #20, bus_spd mov #64, datasize ldhx #flash_start sthx start_addr rts main: bsr initialisation : : ldhx #file_ptr jsr prgrnge 8.5.2 erarnge erarnge is used to erase a range of locations in flash. there are two sizes of erase ranges: a page or the entire array. the erarnge will erase the page (512 consecutive bytes) in flash specified by the address addrh:addrl. this address can be any address within the page. calling erarnge with addrh:addrl equal to $ffff will erase the entire flash array (mass erase). therefore, care must be taken when calling this routine to prevent an accidental mass erase. the erarnge routine do not use a data array. the datasize byte is a dummy byte that is also not used. table 8-12. erarnge routine routine name erarnge routine description erase a page or the entire array calling address $fce4 stack used 9 bytes data block format bus speed (bus_spd) data size (datasize) starting address (addrh) starting address (addrl) rom-resident routines mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 129 the coding example below is to perform a page erase, from $ee00?efff. the initialization subroutine is the same as the coding example for prgrnge (see 8.5.1 prgrnge ). erarnge equ $fce4 main: bsr initialisation : : ldhx #file_ptr jsr erarnge : 8.5.3 ldrnge ldrnge is used to load the data array in ram with data from a range of flash locations. the start location of flash from where data is retrieved is specified by the address addrh:addrl and the number of bytes from this location is specified by datasize. the maximum number of bytes that can be retrieved in one routine call is 255 bytes. the data retrieved from flash is loaded into the data array in ram. previous data in the data array will be overwritten. user can use this routine to retrieve data from flash that was previously programmed. the coding example below is to retrieve 64 bytes of data starting from $ee00 in flash. the initialization subroutine is the same as the coding example for prgrnge (see 8.5.1 prgrnge ). ldrnge equ $fc00 main: bsr initialization : : ldhx #file_ptr jsr ldrnge : table 8-13. ldrnge routine routine name ldrnge routine description loads data from a range of locations calling address $fc00 stack used 7 bytes data block format bus speed (bus_spd) data size (datasize) starting address (addrh) starting address (addrl) data 1 : data n monitor rom (mon) mc68hc908ap a-family data sheet, rev. 2 130 freescale semiconductor 8.5.4 mon_prgrnge in monitor mode, mon_prgrnge is used to program a range of flash locations with data loaded into the data array. the mon_prgrnge routine is designed to be used in monitor mode. it performs the same function as the prgrnge routine (see 8.5.1 prgrnge ), except that mon_prgrnge returns to the main program via an swi instruction. after a mon_prgrnge call, the swi instruction will return the control back to the monitor code. 8.5.5 mon_erarnge in monitor mode, erarnge is used to erase a range of locations in flash. the mon_erarnge routine is designed to be used in monitor mode. it performs the same function as the erarnge routine (see 8.5.2 erarnge ), except that mon_erarnge returns to the main program via an swi instruction. after a mon_erarnge call, the swi instruction will return the control back to the monitor code. table 8-14. mon_prgrnge routine routine name mon_prgrnge routine description program a range of locations, in monitor mode calling address $ff24 stack used 17 bytes data block format bus speed data size starting address (high byte) starting address (low byte) data 1 : data n table 8-15. mon_erarnge routine routine name mon_erarnge routine description erase a page or the entire array, in monitor mode calling address $ff28 stack used 11 bytes data block format bus speed data size starting address (high byte) starting address (low byte) mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 131 chapter 9 timer interface module (tim) 9.1 introduction this section describes the timer interface (tim) module. the tim is a two-channel timer that provides a timing reference with input capture, output compare, and pulse-width-modulation functions. figure 9-1 is a block diagram of the tim. this particular mcu has two timer interface modules which are denoted as tim1 and tim2. 9.2 features features of the tim include: two input capture/output compare channels: rising-edge, falling-edge, or any-edge input capture trigger set, clear, or toggle output compare action buffered and unbuffered pulse-width-modulation (pwm) signal generation programmable tim clock input with 7-frequency internal bus clock prescaler selection free-running or modulo up-count operation toggle any channel pin on overflow tim counter stop and reset bits 9.3 pin name conventions the text that follows describes both timers, tim1 and tim2. the tim input/output (i/o) pin names are t[1,2]ch0 (timer channel 0) and t[1,2]ch1 (timer channel 1), where ? is used to indicate tim1 and ? is used to indicate tim2. the two tims share four i/o pins with four i/o port pins. the external clock input for tim2 is shared with the an adc channel pin. the full names of the tim i/o pins are listed in table 9-1 . the generic pin names appear in the text that follows. note references to either timer 1 or timer 2 may be made in the following text by omitting the timer number. for example, tch0 may refer generically to t1ch0 and t2ch0, and tch1 may refer to t1ch1 and t2ch1. table 9-1. pin name conventions tim generic pin names: t[1,2]ch0 t[1,2]ch1 full tim pin names: tim1 ptb4/t1ch0 ptb5/t1ch1 tim2 ptb6/t2ch0 ptb7/t2ch1 timer interface module (tim) mc68hc908ap a-family data sheet, rev. 2 132 freescale semiconductor 9.4 functional description figure 9-1 shows the structure of the tim. the central component of the tim is the 16-bit tim counter that can operate as a free-running counter or a modulo up-counter. the tim counter provides the timing reference for the input capture and output compare functions. the tim counter modulo registers, tmodh:tmodl, control the modulo value of the tim counter. software can read the tim counter value at any time without affecting the counting sequence. the two tim channels (per timer) are programmable independently as input capture or output compare channels. figure 9-1. tim block diagram figure 9-2 summarizes the timer registers. note references to either timer 1 or timer 2 may be made in the following text by omitting the timer number. for example, tsc may generically refer to both t1sc and t2sc. prescaler prescaler select internal 16-bit comparator ps2 ps1 ps0 16-bit comparator 16-bit latch tch0h:tch0l tof toie 16-bit comparator 16-bit latch tch1h:tch1l channel 0 channel 1 tmodh:tmodl trst tstop tov0 ch0ie ch0f tov1 ch1ie ch1max ch1f ch0max ms0b 16-bit counter internal bus bus clock t[1,2]ch0 interrupt logic port logic interrupt logic interrupt logic port logic ch01ie els0b els0a ms0a els0b els0a ms0a t[1,2]ch1 functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 133 addr. register name bit 7 654321bit 0 $0020 tim1 status and control register (t1sc) read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst reset:00100000 $0021 tim1 counter register high (t1cnth) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 $0022 tim1 counter register low (t1cntl) read: bit 7 654321bit 0 write: reset:00000000 $0023 tim counter modulo register high (tmodh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:11111111 $0024 tim1 counter modulo register low (t1modl) read: bit 7654321bit 0 write: reset:11111111 $0025 tim1 channel 0 status and control register (t1sc0) read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 $0026 tim1 channel 0 register high (t1ch0h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $0027 tim1 channel 0 register low (t1ch0l) read: bit 7654321bit 0 write: reset: indeterminate after reset $0028 tim1 channel 1 status and control register (t1sc1) read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 reset:00000000 $0029 tim1 channel 1 register high (t1ch1h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $002a tim1 channel 1 register low (t1ch1l) read: bit 7654321bit 0 write: reset: indeterminate after reset $002b tim2 status and control register (t2sc) read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst reset:00100000 $002c tim2 counter register high (t2cnth) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 $002d tim2 counter register low (t2cntl) read: bit 7 654321bit 0 write: reset:00000000 $002e tim2 counter modulo register high (t2modh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset:11111111 = unimplemented figure 9-2. tim i/o register summary (sheet 1 of 2) timer interface module (tim) mc68hc908ap a-family data sheet, rev. 2 134 freescale semiconductor 9.4.1 tim counter prescaler the tim clock source can be one of the seven prescaler outputs. the prescaler generates seven clock rates from the internal bus clock. the prescaler select bits, ps[2:0], in the tim status and control register select the tim clock source. 9.4.2 input capture with the input capture function, the tim can capture the time at which an external event occurs. when an active edge occurs on the pin of an input capture channel, the tim latches the contents of the tim counter into the tim channel registers, tchxh:tchxl. the polarity of the active edge is programmable. input captures can generate tim cpu interrupt requests. 9.4.3 output compare with the output compare function, the tim can generate a periodic pulse with a programmable polarity, duration, and frequency. when the counter reaches the value in the registers of an output compare channel, the tim can set, clear, or toggle the channel pin. output compares can generate tim cpu interrupt requests. 9.4.3.1 unbuffered output compare any output compare channel can generate unbuffered output compare pulses as described in 9.4.3 output compare . the pulses are unbuffered because changing the output compare value requires writing the new value over the old value currently in the tim channel registers. $002f tim2 counter modulo register low (t2modl) read: bit 7654321bit 0 write: reset:11111111 $0030 tim2 channel 0 status and control register (t2sc0) read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 $0031 tim2 channel 0 register high (t2ch0h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $0032 tim2 channel 0 register low (t2ch0l) read: bit 7654321bit 0 write: reset: indeterminate after reset $0033 tim2 channel 1 status and control register (t2sc1) read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 reset:00000000 $0034 tim2 channel 1 register high (t2ch1h) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $0035 tim2 channel 1 register low (t2ch1l) read: bit 7654321bit 0 write: reset: indeterminate after reset addr. register name bit 7 654321bit 0 = unimplemented figure 9-2. tim i/o register summary (sheet 2 of 2) functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 135 an unsynchronized write to the tim channel registers to change an output compare value could cause incorrect operation for up to two counter overflow periods. for example, writing a new value before the counter reaches the old value but after the counter reaches the new value prevents any compare during that counter overflow period. also, using a tim overflow interrupt routine to write a new, smaller output compare value may cause the compare to be missed. the tim may pass the new value before it is written. use the following methods to synchronize unbuffered changes in the output compare value on channel x: when changing to a smaller value, enable channel x output compare interrupts and write the new value in the output compare interrupt routine. the output compare interrupt occurs at the end of the current output compare pulse. the interrupt routine has until the end of the counter overflow period to write the new value. when changing to a larger output compare value, enable tim overflow interrupts and write the new value in the tim overflow interrupt routine. the tim overflow interrupt occurs at the end of the current counter overflow period. writing a larger value in an output compare interrupt routine (at the end of the current pulse) could cause two output compares to occur in the same counter overflow period. 9.4.3.2 buffered output compare channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the tch0 pin. the tim channel registers of the linked pair alternately control the output. setting the ms0b bit in tim channel 0 status and control register (tsc0) links channel 0 and channel 1. the output compare value in the tim channel 0 registers initially controls the output on the tch0 pin. writing to the tim channel 1 registers enables the tim channel 1 registers to synchronously control the output after the tim overflows. at each subsequent overflow, the tim channel registers (0 or 1) that control the output are the ones written to last. tsc0 controls and monitors the buffered output compare function, and tim channel 1 status and control register (tsc1) is unused. while the ms0b bit is set, the channel 1 pin, tch1, is available as a general-purpose i/o pin. note in buffered output compare operation, do not write new output compare values to the currently active channel registers. user software should track the currently active channel to prevent writing a new value to the active channel. writing to the active channel registers is the same as generating unbuffered output compares. 9.4.4 pulse width modulation (pwm) by using the toggle-on-overflow feature with an output compare channel, the tim can generate a pwm signal. the value in the tim counter modulo registers determines the period of the pwm signal. the channel pin toggles when the counter reaches the value in the tim counter modulo registers. the time between overflows is the period of the pwm signal. as figure 9-3 shows, the output compare value in the tim channel registers determines the pulse width of the pwm signal. the time between overflow and output compare is the pulse width. program the tim to clear the channel pin on output compare if the state of the pwm pulse is logic 1. program the tim to set the pin if the state of the pwm pulse is logic 0. the value in the tim counter modulo registers and the selected prescaler output determines the frequency of the pwm output. the frequency of an 8-bit pwm signal is variable in 256 increments. writing timer interface module (tim) mc68hc908ap a-family data sheet, rev. 2 136 freescale semiconductor $00ff (255) to the tim counter modulo registers produces a pwm period of 256 times the internal bus clock period if the prescaler select value is $000. see 9.9.1 tim status and control register . figure 9-3. pwm period and pulse width the value in the tim channel registers determines the pulse width of the pwm output. the pulse width of an 8-bit pwm signal is variable in 256 increments. writing $0080 (128) to the tim channel registers produces a duty cycle of 128/256 or 50%. 9.4.4.1 unbuffered pwm signal generation any output compare channel can generate unbuffered pwm pulses as described in 9.4.4 pulse width modulation (pwm) . the pulses are unbuffered because changing the pulse width requires writing the new pulse width value over the old value currently in the tim channel registers. an unsynchronized write to the tim channel registers to change a pulse width value could cause incorrect operation for up to two pwm periods. for example, writing a new value before the counter reaches the old value but after the counter reaches the new value prevents any compare during that pwm period. also, using a tim overflow interrupt routine to write a new, smaller pulse width value may cause the compare to be missed. the tim may pass the new value before it is written. use the following methods to synchronize unbuffered changes in the pwm pulse width on channel x: when changing to a shorter pulse width, enable channel x output compare interrupts and write the new value in the output compare interrupt routine. the output compare interrupt occurs at the end of the current pulse. the interrupt routine has until the end of the pwm period to write the new value. when changing to a longer pulse width, enable tim overflow interrupts and write the new value in the tim overflow interrupt routine. the tim overflow interrupt occurs at the end of the current pwm period. writing a larger value in an output compare interrupt routine (at the end of the current pulse) could cause two output compares to occur in the same pwm period. note in pwm signal generation, do not program the pwm channel to toggle on output compare. toggling on output compare prevents reliable 0% duty cycle generation and removes the ability of the channel to self-correct in the event of software error or noise. toggling on output compare also can cause incorrect pwm signal generation when changing the pwm pulse width to a new, much larger value. tchx period pulse width overflow overflow overflow output compare output compare output compare functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 137 9.4.4.2 buffered pwm signal generation channels 0 and 1 can be linked to form a buffered pwm channel whose output appears on the tch0 pin. the tim channel registers of the linked pair alternately control the pulse width of the output. setting the ms0b bit in tim channel 0 status and control register (tsc0) links channel 0 and channel 1. the tim channel 0 registers initially control the pulse width on the tch0 pin. writing to the tim channel 1 registers enables the tim channel 1 registers to synchronously control the pulse width at the beginning of the next pwm period. at each subsequent overflow, the tim channel registers (0 or 1) that control the pulse width are the ones written to last. tsc0 controls and monitors the buffered pwm function, and tim channel 1 status and control register (tsc1) is unused. while the ms0b bit is set, the channel 1 pin, tch1, is available as a general-purpose i/o pin. note in buffered pwm signal generation, do not write new pulse width values to the currently active channel registers. user software should track the currently active channel to prevent writing a new value to the active channel. writing to the active channel registers is the same as generating unbuffered pwm signals. 9.4.4.3 pwm initialization to ensure correct operation when generating unbuffered or buffered pwm signals, use the following initialization procedure: 1. in the tim status and control register (tsc): a. stop the tim counter by setting the tim stop bit, tstop. b. reset the tim counter and prescaler by setting the tim reset bit, trst. 2. in the tim counter modulo registers (tmodh:tmodl), write the value for the required pwm period. 3. in the tim channel x registers (tchxh:tchxl), write the value for the required pulse width. 4. in tim channel x status and control register (tscx): a. write 0:1 (for unbuffered output compare or pwm signals) or 1:0 (for buffered output compare or pwm signals) to the mode select bits, msxb:msxa. (see table 9-3 .) b. write 1 to the toggle-on-overflow bit, tovx. c. write 1:0 (to clear output on compare) or 1:1 (to set output on compare) to the edge/level select bits, elsxb:elsxa. the output action on compare must force the output to the complement of the pulse width level. (see table 9-3 .) note in pwm signal generation, do not program the pwm channel to toggle on output compare. toggling on output compare prevents reliable 0% duty cycle generation and removes the ability of the channel to self-correct in the event of software error or noise. toggling on output compare can also cause incorrect pwm signal generation when changing the pwm pulse width to a new, much larger value. 5. in the tim status control register (tsc), clear the tim stop bit, tstop. timer interface module (tim) mc68hc908ap a-family data sheet, rev. 2 138 freescale semiconductor setting ms0b links channels 0 and 1 and configures them for buffered pwm operation. the tim channel 0 registers (tch0h:tch0l) initially control the buffered pwm output. tim status control register 0 (tscr0) controls and monitors the pwm signal from the linked channels. clearing the toggle-on-overflow bit, tovx, inhibits output toggles on tim overflows. subsequent output compares try to force the output to a state it is already in and have no effect. the result is a 0% duty cycle output. setting the channel x maximum duty cycle bit (chxmax) and setting the tovx bit generates a 100% duty cycle output. (see 9.9.4 tim channel status and control registers .) 9.5 interrupts the following tim sources can generate interrupt requests: tim overflow flag (tof) ?the tof bit is set when the tim counter reaches the modulo value programmed in the tim counter modulo registers. the tim overflow interrupt enable bit, toie, enables tim overflow cpu interrupt requests. tof and toie are in the tim status and control register. tim channel flags (ch1f:ch0f) the chxf bit is set when an input capture or output compare occurs on channel x. channel x tim cpu interrupt requests are controlled by the channel x interrupt enable bit, chxie. channel x tim cpu interrupt requests are enabled when chxie = 1. chxf and chxie are in the tim channel x status and control register. 9.6 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 9.6.1 wait mode the tim remains active after the execution of a wait instruction. in wait mode, the tim registers are not accessible by the cpu. any enabled cpu interrupt request from the tim can bring the mcu out of wait mode. if tim functions are not required during wait mode, reduce power consumption by stopping the tim before executing the wait instruction. 9.6.2 stop mode the tim is inactive after the execution of a stop instruction. the stop instruction does not affect register conditions or the state of the tim counter. tim operation resumes when the mcu exits stop mode after an external interrupt. 9.7 tim during break interrupts a break interrupt stops the tim counter. the system integration module (sim) controls whether status bits in other modules can be cleared during the break state. the bcfe bit in the break flag control register (bfcr) enables software to clear status bits during the break state. (see 21.5.4 sim break flag control register .) i/o signals mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 139 to allow software to clear status bits during a break interrupt, write a logic 1 to the bcfe bit. if a status bit is cleared during the break state, it remains cleared when the mcu exits the break state. to protect status bits during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), software can read and write i/o registers during the break state without affecting status bits. some status bits have a 2-step read/write clearing procedure. if software does the first step on such a bit before the break, the bit cannot change during the break state as long as bcfe is at logic 0. after the break, doing the second step clears the status bit. 9.8 i/o signals port b shares four of its pins with the tim. the four tim channel i/o pins are t1ch0, t1ch1, t2ch0, and t2ch1 as described in 9.3 pin name conventions . each channel i/o pin is programmable independently as an input capture pin or an output compare pin. t1ch0 and t2ch0 can be configured as buffered output compare or buffered pwm pins. 9.9 i/o registers note references to either timer 1 or timer 2 may be made in the following text by omitting the timer number. for example, tsc may generically refer to both t1sc and t2sc. these i/o registers control and monitor operation of the tim: tim status and control register (tsc) tim counter registers (tcnth:tcntl) tim counter modulo registers (tmodh:tmodl) tim channel status and control registers (tsc0, tsc1) tim channel registers (tch0h:tch0l, tch1h:tch1l) 9.9.1 tim status and control register the tim status and control register (tsc): enables tim overflow interrupts flags tim overflows stops the tim counter resets the tim counter prescales the tim counter clock address: t1sc, $0020 and t2sc, $002b bit 7654321bit 0 read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst reset:00100000 = unimplemented figure 9-4. tim status and control register (tsc) timer interface module (tim) mc68hc908ap a-family data sheet, rev. 2 140 freescale semiconductor tof ?tim over?w flag bit this read/write flag is set when the tim counter reaches the modulo value programmed in the tim counter modulo registers. clear tof by reading the tim status and control register when tof is set and then writing a logic 0 to tof. if another tim overflow occurs before the clearing sequence is complete, then writing logic 0 to tof has no effect. therefore, a tof interrupt request cannot be lost due to inadvertent clearing of tof. reset clears the tof bit. writing a logic 1 to tof has no effect. 1 = tim counter has reached modulo value 0 = tim counter has not reached modulo value toie ?tim overflow interrupt enable bit this read/write bit enables tim overflow interrupts when the tof bit becomes set. reset clears the toie bit. 1 = tim overflow interrupts enabled 0 = tim overflow interrupts disabled tstop ?tim stop bit this read/write bit stops the tim counter. counting resumes when tstop is cleared. reset sets the tstop bit, stopping the tim counter until software clears the tstop bit. 1 = tim counter stopped 0 = tim counter active note do not set the tstop bit before entering wait mode if the tim is required to exit wait mode. trst ?tim reset bit setting this write-only bit resets the tim counter and the tim prescaler. setting trst has no effect on any other registers. counting resumes from $0000. trst is cleared automatically after the tim counter is reset and always reads as logic 0. reset clears the trst bit. 1 = prescaler and tim counter cleared 0 = no effect note setting the tstop and trst bits simultaneously stops the tim counter at a value of $0000. ps[2:0] ?prescaler select bits these read/write bits select one of the seven prescaler outputs as the input to the tim counter as table 9-2 shows. reset clears the ps[2:0] bits. table 9-2. prescaler selection ps2 ps1 ps0 tim clock source 0 0 0 internal bus clock 1 0 0 1 internal bus clock 2 0 1 0 internal bus clock 4 0 1 1 internal bus clock 8 1 0 0 internal bus clock 16 1 0 1 internal bus clock 32 1 1 0 internal bus clock 64 1 1 1 not available i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 141 9.9.2 tim counter registers the two read-only tim counter registers contain the high and low bytes of the value in the tim counter. reading the high byte (tcnth) latches the contents of the low byte (tcntl) into a buffer. subsequent reads of tcnth do not affect the latched tcntl value until tcntl is read. reset clears the tim counter registers. setting the tim reset bit (trst) also clears the tim counter registers. note if you read tcnth during a break interrupt, be sure to unlatch tcntl by reading tcntl before exiting the break interrupt. otherwise, tcntl retains the value latched during the break. 9.9.3 tim counter modulo registers the read/write tim modulo registers contain the modulo value for the tim counter. when the tim counter reaches the modulo value, the overflow flag (tof) becomes set, and the tim counter resumes counting from $0000 at the next timer clock. writing to the high byte (tmodh) inhibits the tof bit and overflow interrupts until the low byte (tmodl) is written. reset sets the tim counter modulo registers. note reset the tim counter before writing to the tim counter modulo registers. address: t1cnth, $0021 and t2cnth, $002c bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 figure 9-5. tim counter registers high (tcnth) address: t1cntl, $0022 and t2cntl, $002d bit 7654321bit 0 read: bit 7 654321bit 0 write: reset:00000000 figure 9-6. tim counter registers low (tcntl) address: t1modh, $0023 and t2modh, $002e bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:11111111 figure 9-7. tim counter modulo register high (tmodh) address: t1modl, $0024 and t2modl, $002f bit 7654321bit 0 read: bit 7654321bit 0 write: reset:11111111 figure 9-8. tim counter modulo register low (tmodl) timer interface module (tim) mc68hc908ap a-family data sheet, rev. 2 142 freescale semiconductor 9.9.4 tim channel status and control registers each of the tim channel status and control registers: flags input captures and output compares enables input capture and output compare interrupts selects input capture, output compare, or pwm operation selects high, low, or toggling output on output compare selects rising edge, falling edge, or any edge as the active input capture trigger selects output toggling on tim overflow selects 0% and 100% pwm duty cycle selects buffered or unbuffered output compare/pwm operation chxf ?channel x flag bit when channel x is an input capture channel, this read/write bit is set when an active edge occurs on the channel x pin. when channel x is an output compare channel, chxf is set when the value in the tim counter registers matches the value in the tim channel x registers. when tim cpu interrupt requests are enabled (chxie = 1), clear chxf by reading tim channel x status and control register with chxf set and then writing a logic 0 to chxf. if another interrupt request occurs before the clearing sequence is complete, then writing logic 0 to chxf has no effect. therefore, an interrupt request cannot be lost due to inadvertent clearing of chxf. reset clears the chxf bit. writing a logic 1 to chxf has no effect. 1 = input capture or output compare on channel x 0 = no input capture or output compare on channel x chxie ?channel x interrupt enable bit this read/write bit enables tim cpu interrupt service requests on channel x. reset clears the chxie bit. 1 = channel x cpu interrupt requests enabled 0 = channel x cpu interrupt requests disabled msxb ?mode select bit b this read/write bit selects buffered output compare/pwm operation. msxb exists only in the tim1 channel 0 and tim2 channel 0 status and control registers. address: t1sc0, $0025 and t2sc0, $0030 bit 7654321bit 0 read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 figure 9-9. tim channel 0 status and control register (tsc0) address: t1sc1, $0028 and t2sc1, $0033 bit 7654321bit 0 read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 reset:00000000 figure 9-10. tim channel 1 status and control register (tsc1) i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 143 setting ms0b disables the channel 1 status and control register and reverts tch1 to general-purpose i/o. reset clears the msxb bit. 1 = buffered output compare/pwm operation enabled 0 = buffered output compare/pwm operation disabled msxa ?mode select bit a when elsxb:elsxa 0:0, this read/write bit selects either input capture operation or unbuffered output compare/pwm operation. see table 9-3 . 1 = unbuffered output compare/pwm operation 0 = input capture operation when elsxb:elsxa = 0:0, this read/write bit selects the initial output level of the tchx pin. see table 9-3 . reset clears the msxa bit. 1 = initial output level low 0 = initial output level high note before changing a channel function by writing to the msxb or msxa bit, set the tstop and trst bits in the tim status and control register (tsc). elsxb and elsxa ?edge/level select bits when channel x is an input capture channel, these read/write bits control the active edge-sensing logic on channel x. when channel x is an output compare channel, elsxb and elsxa control the channel x output behavior when an output compare occurs. when elsxb and elsxa are both clear, channel x is not connected to an i/o port, and pin tchx is available as a general-purpose i/o pin. table 9-3 shows how elsxb and elsxa work. reset clears the elsxb and elsxa bits. table 9-3. mode, edge, and level selection msxb:msxa elsxb:elsxa mode configuration x0 00 output preset pin under port control; initial output level high x1 00 pin under port control; initial output level low 00 01 input capture capture on rising edge only 00 10 capture on falling edge only 00 11 capture on rising or falling edge 01 01 output compare or pwm toggle output on compare 01 10 clear output on compare 01 11 set output on compare 1x 01 buffered output compare or buffered pwm toggle output on compare 1x 10 clear output on compare 1x 11 set output on compare timer interface module (tim) mc68hc908ap a-family data sheet, rev. 2 144 freescale semiconductor note before enabling a tim channel register for input capture operation, make sure that the tchx pin is stable for at least two bus clocks. tovx ?toggle on over?w bit when channel x is an output compare channel, this read/write bit controls the behavior of the channel x output when the tim counter overflows. when channel x is an input capture channel, tovx has no effect. reset clears the tovx bit. 1 = channel x pin toggles on tim counter overflow 0 = channel x pin does not toggle on tim counter overflow note when tovx is set, a tim counter overflow takes precedence over a channel x output compare if both occur at the same time. chxmax ?channel x maximum duty cycle bit when the tovx bit is at logic 1, setting the chxmax bit forces the duty cycle of buffered and unbuffered pwm signals to 100%. as figure 9-11 shows, the chxmax bit takes effect in the cycle after it is set or cleared. the output stays at the 100% duty cycle level until the cycle after chxmax is cleared. figure 9-11. chxmax latency 9.9.5 tim channel registers these read/write registers contain the captured tim counter value of the input capture function or the output compare value of the output compare function. the state of the tim channel registers after reset is unknown. in input capture mode (msxb:msxa = 0:0), reading the high byte of the tim channel x registers (tchxh) inhibits input captures until the low byte (tchxl) is read. in output compare mode (msxb:msxa 0:0), writing to the high byte of the tim channel x registers (tchxh) inhibits output compares until the low byte (tchxl) is written. output overflow tchx period chxmax overflow overflow overflow overflow compare output compare output compare output compare i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 145 address: t1ch0h, $0026 and t2ch0h, $0031 bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset figure 9-12. tim channel 0 register high (tch0h) address: t1ch0l, $0027 and t2ch0l $0032 bit 7654321bit 0 read: bit 7654321bit 0 write: reset: indeterminate after reset figure 9-13. tim channel 0 register low (tch0l) address: t1ch1h, $0029 and t2ch1h, $0034 bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset figure 9-14. tim channel 1 register high (tch1h) address: t1ch1l, $002a and t2ch1l, $0035 bit 7654321bit 0 read: bit 7654321bit 0 write: reset: indeterminate after reset figure 9-15. tim channel 1 register low (tch1l) timer interface module (tim) mc68hc908ap a-family data sheet, rev. 2 146 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 147 chapter 10 timebase module (tbm) 10.1 introduction this section describes the timebase module (tbm). the tbm will generate periodic interrupts at user selectable rates using a counter clocked by the selected oscclk clock from the oscillator module. this tbm version uses 18 divider stages, eight of which are user selectable. 10.2 features features of the tbm module include: eight user selectable periodic interrupts user selectable oscillator clock source enable during stop mode to allow periodic wake-up from stop 10.3 functional description this module can generate a periodic interrupt by dividing the oscillator clock frequency, oscclk. the counter is initialized to all 0s when tbon bit is cleared. the counter, shown in figure 10-1 , starts counting when the tbon bit is set. when the counter overflows at the tap selected by tbr[2:0], the tbif bit gets set. if the tbie bit is set, an interrupt request is sent to the cpu. the tbif flag is cleared by writing a 1 to the tack bit. the first time the tbif flag is set after enabling the timebase module, the interrupt is generated at approximately half of the overflow period. subsequent events occur at the exact period. the reference clock oscclk is derived from the oscillator module, see 5.2.2 tbm reference clock selection . timebase module (tbm) mc68hc908ap a-family data sheet, rev. 2 148 freescale semiconductor figure 10-1. timebase block diagram 10.4 timebase register description the timebase has one register, the tbcr, which is used to enable the timebase interrupts and set the rate. tbif ?timebase interrupt flag this read-only flag bit is set when the timebase counter has rolled over. 1 = timebase interrupt pending 0 = timebase interrupt not pending address: $0051 bit 7654321bit 0 read: tbif tbr2 tbr1 tbr0 0 tbie tbon r write: tack reset:00000000 = unimplemented r = reserved figure 10-2. timebase control register (tbcr) (see chapter 5 oscillator (osc) .) 2 sel 0 0 0 0 0 1 0 1 0 0 1 1 tbif tbr1 tbr0 tbie tbon r tack tbr2 1 0 0 1 0 1 1 1 0 1 1 1 oscclk 2 2 2 2 2 2 2 2 2 2 2 2 2 8 16 32 64 2048 32768 65536 131072 tbmint 2 2 2 2 262144 from osc module timebase register description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 149 tbr[2:0] ?timebase rate selection these read/write bits are used to select the rate of timebase interrupts as shown in table 10-1 . note do not change tbr[2:0] bits while the timebase is enabled (tbon = 1). tack ?timebase acknowledge the tack bit is a write-only bit and always reads as 0. writing a logic 1 to this bit clears tbif, the timebase interrupt flag bit. writing a logic 0 to this bit has no effect. 1 = clear timebase interrupt flag 0 = no effect tbie ?timebase interrupt enabled this read/write bit enables the timebase interrupt when the tbif bit becomes set. reset clears the tbie bit. 1 = timebase interrupt enabled 0 = timebase interrupt disabled tbon ?timebase enabled this read/write bit enables the timebase. timebase may be turned off to reduce power consumption when its function is not necessary. the counter can be initialized by clearing and then setting this bit. reset clears the tbon bit. 1 = timebase enabled 0 = timebase disabled and the counter initialized to 0? table 10-1. timebase rate selection for oscclk = 4 mhz tbr2 tbr1 tbr0 divider timebase interrupt rate (1) 1. if user selects one of the shaded timebase settings, ensure that the operating bus frequency is fast enough to service the periodic interrupts. hz ms 0 0 0 262144 15.259 65.536 0 0 1 131072 30.518 32.768 0 1 0 65536 61.035 16.384 0 1 1 32768 122.07 8.192 1 0 0 64 62,500 0.016 1 0 1 32 125,000 0.008 1 1 0 16 250,000 0.004 1 1 1 8 500,000 0.002 timebase module (tbm) mc68hc908ap a-family data sheet, rev. 2 150 freescale semiconductor 10.5 interrupts the timebase module can interrupt the cpu on a regular basis with a rate defined by tbr[2:0]. when the timebase counter chain rolls over, the tbif flag is set. if the tbie bit is set, enabling the timebase interrupt, the counter chain overflow will generate a cpu interrupt request. the interrupt vector is defined in table 2-1 . vector addresses . interrupts must be acknowledged by writing a logic 1 to the tack bit. 10.6 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 10.6.1 wait mode the timebase module remains active after execution of the wait instruction. in wait mode, the timebase register is not accessible by the cpu. if the timebase functions are not required during wait mode, reduce the power consumption by stopping the timebase before enabling the wait instruction. 10.6.2 stop mode the timebase module may remain active after execution of the stop instruction if the oscillator has been enabled to operate during stop mode through the stop mode oscillator enable bit (stop_iclkdis, stop_rclken, or stop_xclken) for the selected oscillator in the config2 register. the timebase module can be used in this mode to generate a periodic walk-up from stop mode. if the oscillator has not been enabled to operate in stop mode, the timebase module will not be active during stop mode. in stop mode the timebase register is not accessible by the cpu. if the timebase functions are not required during stop mode, reduce the power consumption by stopping the timebase before enabling the stop instruction. mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 151 chapter 11 serial communications interface module (sci) 11.1 introduction the mc68hc908ap64a has two sci modules: sci1 is a standard sci module, and sci2 is an infrared sci module. this section describes sci1, the serial communications interface (sci) module, which allows high-speed asynchronous communications with peripheral devices and other mcus. note when the sci is enabled, the txd pin is an open-drain output and requires a pullup resistor to be connected for proper sci operation. 11.2 features features of the sci module include the following: full-duplex operation standard mark/space non-return-to-zero (nrz) format 32 programmable baud rates programmable 8-bit or 9-bit character length separately enabled transmitter and receiver separate receiver and transmitter cpu interrupt requests programmable transmitter output polarity two receiver wakeup methods: idle line wakeup address mark wakeup interrupt-driven operation with eight interrupt flags: transmitter empty transmission complete receiver full idle receiver input receiver overrun noise error framing error parity error receiver framing error detection hardware parity checking 1/16 bit-time noise detection configuration register bit, scibdsrc, to allow selection of baud rate clock source serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 152 freescale semiconductor 11.3 pin name conventions the generic names of the sci i/o pins are: rxd (receive data) txd (transmit data) sci i/o (input/output) lines are implemented by sharing parallel i/o port pins. the full name of an sci input or output reflects the name of the shared port pin. table 11-1 shows the full names and the generic names of the sci i/o pins. the generic pin names appear in the text of this section. note when the sci is enabled, the txd pin is an open-drain output and requires a pullup resistor to be connected for proper sci operation. table 11-1. pin name conventions generic pin names: rxd txd full pin names: ptb3/rxd ptb2/txd addr. register name bit 7 654321bit 0 $0013 sci control register 1 (scc1) read: loops ensci txinv m wake ilty pen pty write: reset:00000000 $0014 sci control register 2 (scc2) read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 $0015 sci control register 3 (scc3) read: r8 t8 dmare dmate orie neie feie peie write: reset:uu000000 $0016 sci status register 1 (scs1) read: scte tc scrf idle or nf fe pe write: reset:11000000 $0017 sci status register 2 (scs2) read: bkf rpf write: reset:00000000 $0018 sci data register (scdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset $0019 sci baud rate register (scbr) read: 0 0 scp1 scp0 r scr2 scr1 scr0 write: reset:00000000 = unimplemented r = reserved u = unaffected figure 11-1. sci i/o register summary functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 153 11.4 functional description figure 11-2 shows the structure of the sci module. the sci allows full-duplex, asynchronous, nrz serial communication among the mcu and remote devices, including other mcus. the transmitter and receiver of the sci operate independently, although they use the same baud rate generator. during normal operation, the cpu monitors the status of the sci, writes the data to be transmitted, and processes received data. the baud rate clock source for the sci can be selected via the configuration bit, scibdsrc, of the config2 register ($001d). figure 11-2. sci module block diagram scte tc scrf idle or nf fe pe sctie tcie scrie ilie te re rwu sbk r8 t8 dmate orie feie peie bkf rpf sci data receive shift register sci data register transmit shift register neie m wake ilty flag control transmit control receive control data selection control wakeup pty pen register dma interrupt control transmitter interrupt control receiver interrupt control error interrupt control control dmare ensci loops ensci internal bus txinv loops 4 16 pre- scaler baud divider cgmxclk it12 a b sl x scibdsrc from sl = 0 => x = a sl = 1 => x = b config rxd txd cgmxclk is from cgm module it12 = f bus serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 154 freescale semiconductor 11.4.1 data format the sci uses the standard non-return-to-zero mark/space data format illustrated in figure 11-3 . figure 11-3. sci data formats 11.4.2 transmitter figure 11-4 shows the structure of the sci transmitter. the baud rate clock source for the sci can be selected via the configuration bit, scibdsrc. source selection values are shown in figure 11-4 . figure 11-4. sci transmitter bit 5 start bit bit 0 bit 1 next stop bit start bit 8-bit data format bit m in scc1 clear start bit bit 0 next stop bit start bit 9-bit data format bit m in scc1 set bit 1 bit 2 bit 3 bit 4 bit 5 bit 6 bit 7 bit 8 bit 2 bit 3 bit 4 bit 6 bit 7 parity bit parity bit dmate scte pen pty h876543210l 11-bit transmit stop start t8 dmate scte sctie tcie sbk tc parity generation msb sci data register load from scdr shift enable preamble all 1s break all 0s transmitter control logic shift register dmate tc sctie tcie scte transmitter cpu i nterrupt request transmitter dma service request m ensci loops te txinv internal bus 4 pre- scaler scp1 scp0 scr2 scr1 scr0 baud divider 16 sctie cgmxclk it12 a b sl x sl = 0 => x = a sl = 1 => x = b scibdsrc from config2 txd functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 155 11.4.2.1 character length the transmitter can accommodate either 8-bit or 9-bit data. the state of the m bit in sci control register 1 (scc1) determines character length. when transmitting 9-bit data, bit t8 in sci control register 3 (scc3) is the ninth bit (bit 8). 11.4.2.2 character transmission during an sci transmission, the transmit shift register shifts a character out to the txd pin. the sci data register (scdr) is the write-only buffer between the internal data bus and the transmit shift register. to initiate an sci transmission: 1. enable the sci by writing a logic 1 to the enable sci bit (ensci) in sci control register 1 (scc1). 2. enable the transmitter by writing a logic 1 to the transmitter enable bit (te) in sci control register 2 (scc2). 3. clear the sci transmitter empty bit by first reading sci status register 1 (scs1) and then writing to the scdr. 4. repeat step 3 for each subsequent transmission. at the start of a transmission, transmitter control logic automatically loads the transmit shift register with a preamble of logic 1s. after the preamble shifts out, control logic transfers the scdr data into the transmit shift register. a logic 0 start bit automatically goes into the least significant bit position of the transmit shift register. a logic 1 stop bit goes into the most significant bit position. the sci transmitter empty bit, scte, in scs1 becomes set when the scdr transfers a byte to the transmit shift register. the scte bit indicates that the scdr can accept new data from the internal data bus. if the sci transmit interrupt enable bit, sctie, in scc2 is also set, the scte bit generates a transmitter cpu interrupt request. when the transmit shift register is not transmitting a character, the txd pin goes to the idle condition, logic 1. if at any time software clears the ensci bit in sci control register 1 (scc1), the transmitter and receiver relinquish control of the port pin. 11.4.2.3 break characters writing a logic 1 to the send break bit, sbk, in scc2 loads the transmit shift register with a break character. a break character contains all logic 0s and has no start, stop, or parity bit. break character length depends on the m bit in scc1. as long as sbk is at logic 1, transmitter logic continuously loads break characters into the transmit shift register. after software clears the sbk bit, the shift register finishes transmitting the last break character and then transmits at least one logic 1. the automatic logic 1 at the end of a break character guarantees the recognition of the start bit of the next character. the sci recognizes a break character when a start bit is followed by eight or nine logic 0 data bits and a logic 0 where the stop bit should be. receiving a break character has these effects on sci registers: sets the framing error bit (fe) in scs1 sets the sci receiver full bit (scrf) in scs1 clears the sci data register (scdr) clears the r8 bit in scc3 sets the break flag bit (bkf) in scs2 may set the overrun (or), noise flag (nf), parity error (pe), or reception in progress flag (rpf) bits serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 156 freescale semiconductor 11.4.2.4 idle characters an idle character contains all logic 1s and has no start, stop, or parity bit. idle character length depends on the m bit in scc1. the preamble is a synchronizing idle character that begins every transmission. if the te bit is cleared during a transmission, the txd pin becomes idle after completion of the transmission in progress. clearing and then setting the te bit during a transmission queues an idle character to be sent after the character currently being transmitted. note when queueing an idle character, return the te bit to logic 1 before the stop bit of the current character shifts out to the txd pin. setting te after the stop bit appears on txd causes data previously written to the scdr to be lost. toggle the te bit for a queued idle character when the scte bit becomes set and just before writing the next byte to the scdr. 11.4.2.5 inversion of transmitted output the transmit inversion bit (txinv) in sci control register 1 (scc1) reverses the polarity of transmitted data. all transmitted values, including idle, break, start, and stop bits, are inverted when txinv is at logic 1. (see 11.8.1 sci control register 1 .) 11.4.2.6 transmitter interrupts these conditions can generate cpu interrupt requests from the sci transmitter: sci transmitter empty (scte) the scte bit in scs1 indicates that the scdr has transferred a character to the transmit shift register. scte can generate a transmitter cpu interrupt request. setting the sci transmit interrupt enable bit, sctie, in scc2 enables the scte bit to generate transmitter cpu interrupt requests. transmission complete (tc) ?the tc bit in scs1 indicates that the transmit shift register and the scdr are empty and that no break or idle character has been generated. the transmission complete interrupt enable bit, tcie, in scc2 enables the tc bit to generate transmitter cpu interrupt requests. 11.4.3 receiver figure 11-5 shows the structure of the sci receiver. 11.4.3.1 character length the receiver can accommodate either 8-bit or 9-bit data. the state of the m bit in sci control register 1 (scc1) determines character length. when receiving 9-bit data, bit r8 in sci control register 2 (scc2) is the ninth bit (bit 8). when receiving 8-bit data, bit r8 is a copy of the eighth bit (bit 7). 11.4.3.2 character reception during an sci reception, the receive shift register shifts characters in from the rxd pin. the sci data register (scdr) is the read-only buffer between the internal data bus and the receive shift register. after a complete character shifts into the receive shift register, the data portion of the character transfers to the scdr. the sci receiver full bit, scrf, in sci status register 1 (scs1) becomes set, indicating that functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 157 the received byte can be read. if the sci receive interrupt enable bit, scrie, in scc2 is also set, the scrf bit generates a receiver cpu interrupt request. figure 11-5. sci receiver block diagram all 1s all 0s m wake ilty pen pty bkf rpf h876543210l 11-bit receive shift register stop start data recovery dmare scrf or orie nf neie fe feie pe peie dmare scrie scrf ilie idle wakeup logic parity checking msb error cpu i nterrupt request dma service request cpu interrupt request sci data register r8 dmare orie neie feie peie scrie ilie rwu scrf idle or nf fe pe internal bus pre- scaler baud divider 4 16 scp1 scp0 scr2 scr1 scr0 scrie dmare cgmxclk it12 a b sl x scibdsrc from sl = 0 => x = a sl = 1 => x = b config2 rxd serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 158 freescale semiconductor 11.4.3.3 data sampling the receiver samples the rxd pin at the rt clock rate. the rt clock is an internal signal with a frequency 16 times the baud rate. to adjust for baud rate mismatch, the rt clock is resynchronized at the following times (see figure 11-6 ): after every start bit after the receiver detects a data bit change from logic 1 to logic 0 (after the majority of data bit samples at rt8, rt9, and rt10 returns a valid logic 1 and the majority of the next rt8, rt9, and rt10 samples returns a valid logic 0) to locate the start bit, data recovery logic does an asynchronous search for a logic 0 preceded by three logic 1s. when the falling edge of a possible start bit occurs, the rt clock begins to count to 16. figure 11-6. receiver data sampling to verify the start bit and to detect noise, data recovery logic takes samples at rt3, rt5, and rt7. table 11-2 summarizes the results of the start bit verification samples. table 11-2. start bit veri?ation rt3, rt5, and rt7 samples start bit verification noise flag 000 yes 0 001 yes 1 010 yes 1 011 no 0 100 yes 1 101 no 0 110 no 0 111 no 0 rt clock reset rt1 rt1 rt1 rt1 rt1 rt1 rt1 rt1 rt1 rt2 rt3 rt4 rt5 rt8 rt7 rt6 rt11 rt10 rt9 rt15 rt14 rt13 rt12 rt16 rt1 rt2 rt3 rt4 start bit qualification start bit verification data sampling samples rt clock rt clock state start bit lsb rxd functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 159 start bit verification is not successful if any two of the three verification samples are logic 1s. if start bit verification is not successful, the rt clock is reset and a new search for a start bit begins. to determine the value of a data bit and to detect noise, recovery logic takes samples at rt8, rt9, and rt10. table 11-3 summarizes the results of the data bit samples. note the rt8, rt9, and rt10 samples do not affect start bit verification. if any or all of the rt8, rt9, and rt10 start bit samples are logic 1s following a successful start bit verification, the noise flag (nf) is set and the receiver assumes that the bit is a start bit. to verify a stop bit and to detect noise, recovery logic takes samples at rt8, rt9, and rt10. table 11-4 summarizes the results of the stop bit samples. table 11-3. data bit recovery rt8, rt9, and rt10 samples data bit determination noise flag 000 0 0 001 0 1 010 0 1 011 1 1 100 0 1 101 1 1 110 1 1 111 1 0 table 11-4. stop bit recovery rt8, rt9, and rt10 samples framing error flag noise flag 000 1 0 001 1 1 010 1 1 011 0 1 100 1 1 101 0 1 110 0 1 111 0 0 serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 160 freescale semiconductor 11.4.3.4 framing errors if the data recovery logic does not detect a logic 1 where the stop bit should be in an incoming character, it sets the framing error bit, fe, in scs1. a break character also sets the fe bit because a break character has no stop bit. the fe bit is set at the same time that the scrf bit is set. 11.4.3.5 baud rate tolerance a transmitting device may be operating at a baud rate below or above the receiver baud rate. accumulated bit time misalignment can cause one of the three stop bit data samples to fall outside the actual stop bit. then a noise error occurs. if more than one of the samples is outside the stop bit, a framing error occurs. in most applications, the baud rate tolerance is much more than the degree of misalignment that is likely to occur. as the receiver samples an incoming character, it resynchronizes the rt clock on any valid falling edge within the character. resynchronization within characters corrects misalignments between transmitter bit times and receiver bit times. slow data tolerance figure 11-7 shows how much a slow received character can be misaligned without causing a noise error or a framing error. the slow stop bit begins at rt8 instead of rt1 but arrives in time for the stop bit data samples at rt8, rt9, and rt10. figure 11-7. slow data for an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times 16 rt cycles + 10 rt cycles = 154 rt cycles. with the misaligned character shown in figure 11-7 , the receiver counts 154 rt cycles at the point when the count of the transmitting device is 9 bit times 16 rt cycles + 3 rt cycles = 147 rt cycles. the maximum percent difference between the receiver count and the transmitter count of a slow 8-bit character with no errors is for a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times 16 rt cycles + 10 rt cycles = 170 rt cycles. with the misaligned character shown in figure 11-7 , the receiver counts 170 rt cycles at the point when the count of the transmitting device is 10 bit times 16 rt cycles + 3 rt cycles = 163 rt cycles. msb stop rt1 rt2 rt3 rt4 rt5 rt6 rt7 rt8 rt9 rt10 rt11 rt12 rt13 rt14 rt15 rt16 data samples receiver rt clock 154 147 154 ------------------------- - 100 4.54% = functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 161 the maximum percent difference between the receiver count and the transmitter count of a slow 9-bit character with no errors is fast data tolerance figure 11-8 shows how much a fast received character can be misaligned without causing a noise error or a framing error. the fast stop bit ends at rt10 instead of rt16 but is still there for the stop bit data samples at rt8, rt9, and rt10. figure 11-8. fast data for an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times 16 rt cycles + 10 rt cycles = 154 rt cycles. with the misaligned character shown in figure 11-8 , the receiver counts 154 rt cycles at the point when the count of the transmitting device is 10 bit times 16 rt cycles = 160 rt cycles. the maximum percent difference between the receiver count and the transmitter count of a fast 8-bit character with no errors is for a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times 16 rt cycles + 10 rt cycles = 170 rt cycles. with the misaligned character shown in figure 11-8 , the receiver counts 170 rt cycles at the point when the count of the transmitting device is 11 bit times 16 rt cycles = 176 rt cycles. the maximum percent difference between the receiver count and the transmitter count of a fast 9-bit character with no errors is 11.4.3.6 receiver wakeup so that the mcu can ignore transmissions intended only for other receivers in multiple-receiver systems, the receiver can be put into a standby state. setting the receiver wakeup bit, rwu, in scc2 puts the receiver into a standby state during which receiver interrupts are disabled. 170 163 170 ------------------------- - 100 4.12% = idle or next character stop rt1 rt2 rt3 rt4 rt5 rt6 rt7 rt8 rt9 rt10 rt11 rt12 rt13 rt14 rt15 rt16 data samples receiver rt clock 154 160 154 ------------------------- - 100 3.90% ? = 170 176 170 ------------------------- - 100 3.53% = serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 162 freescale semiconductor depending on the state of the wake bit in scc1, either of two conditions on the rxd pin can bring the receiver out of the standby state: address mark ?an address mark is a logic 1 in the most significant bit position of a received character. when the wake bit is set, an address mark wakes the receiver from the standby state by clearing the rwu bit. the address mark also sets the sci receiver full bit, scrf. software can then compare the character containing the address mark to the user-defined address of the receiver. if they are the same, the receiver remains awake and processes the characters that follow. if they are not the same, software can set the rwu bit and put the receiver back into the standby state. idle input line condition when the wake bit is clear, an idle character on the rxd pin wakes the receiver from the standby state by clearing the rwu bit. the idle character that wakes the receiver does not set the receiver idle bit, idle, or the sci receiver full bit, scrf. the idle line type bit, ilty, determines whether the receiver begins counting logic 1s as idle character bits after the start bit or after the stop bit. note with the wake bit clear, setting the rwu bit after the rxd pin has been idle may cause the receiver to wake up immediately. 11.4.3.7 receiver interrupts the following sources can generate cpu interrupt requests from the sci receiver: sci receiver full (scrf) ?the scrf bit in scs1 indicates that the receive shift register has transferred a character to the scdr. scrf can generate a receiver cpu interrupt request. setting the sci receive interrupt enable bit, scrie, in scc2 enables the scrf bit to generate receiver cpu interrupts. idle input (idle) ?the idle bit in scs1 indicates that 10 or 11 consecutive logic 1s shifted in from the rxd pin. the idle line interrupt enable bit, ilie, in scc2 enables the idle bit to generate cpu interrupt requests. 11.4.3.8 error interrupts the following receiver error flags in scs1 can generate cpu interrupt requests: receiver overrun (or) ?the or bit indicates that the receive shift register shifted in a new character before the previous character was read from the scdr. the previous character remains in the scdr, and the new character is lost. the overrun interrupt enable bit, orie, in scc3 enables or to generate sci error cpu interrupt requests. noise flag (nf) ?the nf bit is set when the sci detects noise on incoming data or break characters, including start, data, and stop bits. the noise error interrupt enable bit, neie, in scc3 enables nf to generate sci error cpu interrupt requests. framing error (fe) the fe bit in scs1 is set when a logic 0 occurs where the receiver expects a stop bit. the framing error interrupt enable bit, feie, in scc3 enables fe to generate sci error cpu interrupt requests. parity error (pe) the pe bit in scs1 is set when the sci detects a parity error in incoming data. the parity error interrupt enable bit, peie, in scc3 enables pe to generate sci error cpu interrupt requests. low-power modes mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 163 11.5 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 11.5.1 wait mode the sci module remains active after the execution of a wait instruction. in wait mode, the sci module registers are not accessible by the cpu. any enabled cpu interrupt request from the sci module can bring the mcu out of wait mode. if sci module functions are not required during wait mode, reduce power consumption by disabling the module before executing the wait instruction. refer to 7.6 low-power modes for information on exiting wait mode. 11.5.2 stop mode the sci module is inactive after the execution of a stop instruction. the stop instruction does not affect sci register states. sci module operation resumes after an external interrupt. because the internal clock is inactive during stop mode, entering stop mode during an sci transmission or reception results in invalid data. refer to 7.6 low-power modes for information on exiting stop mode. 11.6 sci during break module interrupts the system integration module (sim) controls whether status bits in other modules can be cleared during the break state. the bcfe bit in the sim break flag control register (sbfcr) enables software to clear status bits during the break state. to allow software to clear status bits during a break interrupt, write a logic 1 to the bcfe bit. if a status bit is cleared during the break state, it remains cleared when the mcu exits the break state. to protect status bits during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), software can read and write i/o registers during the break state without affecting status bits. some status bits have a 2-step read/write clearing procedure. if software does the first step on such a bit before the break, the bit cannot change during the break state as long as bcfe is at logic 0. after the break, doing the second step clears the status bit. 11.7 i/o signals port b shares two of its pins with the sci module. the two sci i/o pins are: ptb2/txd ?transmit data ptb3/rxd ?receive data 11.7.1 txd (transmit data) when the sci is enabled (ensci=1), the ptb2/txd pin becomes the serial data output, txd, from the sci transmitter regardless of the state of the ddrb2 bit in data direction register b (ddrb). the txd pin is an open-drain output and requires a pullup resistor to be connected for proper sci operation. serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 164 freescale semiconductor note the ptb2/txd pin is an open-drain pin when configured as an output. therefore, when configured as a general purpose output pin (ptb2), a pullup resistor must be connected to this pin. 11.7.2 rxd (receive data) when the sci is enabled (ensci=1), the ptb3/rxd pin becomes the serial data input, rxd, to the sci receiver regardless of the state of the ddrb3 bit in data direction register b (ddrb). note the ptb3/rxd pin is an open-drain pin when configured as an output. therefore, when configured as a general purpose output pin (ptb3), a pullup resistor must be connected to this pin. 11.8 i/o registers these i/o registers control and monitor sci operation: sci control register 1 (scc1) sci control register 2 (scc2) sci control register 3 (scc3) sci status register 1 (scs1) sci status register 2 (scs2) sci data register (scdr) sci baud rate register (scbr) i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 165 11.8.1 sci control register 1 sci control register 1: enables loop mode operation enables the sci controls output polarity controls character length controls sci wakeup method controls idle character detection enables parity function controls parity type loops ?loop mode select bit this read/write bit enables loop mode operation. in loop mode the rxd pin is disconnected from the sci, and the transmitter output goes into the receiver input. both the transmitter and the receiver must be enabled to use loop mode. reset clears the loops bit. 1 = loop mode enabled 0 = normal operation enabled ensci ?enable sci bit this read/write bit enables the sci and the sci baud rate generator. clearing ensci sets the scte and tc bits in sci status register 1 and disables transmitter interrupts. reset clears the ensci bit. 1 = sci enabled 0 = sci disabled txinv ?transmit inversion bit this read/write bit reverses the polarity of transmitted data. reset clears the txinv bit. 1 = transmitter output inverted 0 = transmitter output not inverted note setting the txinv bit inverts all transmitted values, including idle, break, start, and stop bits. m ?mode (character length) bit this read/write bit determines whether sci characters are eight or nine bits long. (see table 11-5 .) the ninth bit can serve as an extra stop bit, as a receiver wakeup signal, or as a parity bit. reset clears the m bit. 1 = 9-bit sci characters 0 = 8-bit sci characters address: $0013 bit 7654321bit 0 read: loops ensci txinv m wake ilty pen pty write: reset:00000000 figure 11-9. sci control register 1 (scc1) serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 166 freescale semiconductor wake ?wakeup condition bit this read/write bit determines which condition wakes up the sci: a logic 1 (address mark) in the most significant bit position of a received character or an idle condition on the rxd pin. reset clears the wake bit. 1 = address mark wakeup 0 = idle line wakeup ilty ?idle line type bit this read/write bit determines when the sci starts counting logic 1s as idle character bits. the counting begins either after the start bit or after the stop bit. if the count begins after the start bit, then a string of logic 1s preceding the stop bit may cause false recognition of an idle character. beginning the count after the stop bit avoids false idle character recognition, but requires properly synchronized transmissions. reset clears the ilty bit. 1 = idle character bit count begins after stop bit 0 = idle character bit count begins after start bit pen ?parity enable bit this read/write bit enables the sci parity function. (see table 11-5 .) when enabled, the parity function inserts a parity bit in the most significant bit position. (see figure 11-3 .) reset clears the pen bit. 1 = parity function enabled 0 = parity function disabled pty ?parity bit this read/write bit determines whether the sci generates and checks for odd parity or even parity. (see table 11-5 .) reset clears the pty bit. 1 = odd parity 0 = even parity note changing the pty bit in the middle of a transmission or reception can generate a parity error. table 11-5. character format selection control bits character format m pen:pty start bits data bits parity stop bits character length 0 0x 1 8 none 1 10 bits 1 0x 1 9 none 1 11 bits 0 10 1 7 even 1 10 bits 0 11 1 7 odd 1 10 bits 1 10 1 8 even 1 11 bits 1 11 1 8 odd 1 11 bits i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 167 11.8.2 sci control register 2 sci control register 2: enables the following cpu interrupt requests: enables the scte bit to generate transmitter cpu interrupt requests enables the tc bit to generate transmitter cpu interrupt requests enables the scrf bit to generate receiver cpu interrupt requests enables the idle bit to generate receiver cpu interrupt requests enables the transmitter enables the receiver enables sci wakeup transmits sci break characters sctie ?sci transmit interrupt enable bit this read/write bit enables the scte bit to generate sci transmitter cpu interrupt requests. reset clears the sctie bit. 1 = scte enabled to generate cpu interrupt 0 = scte not enabled to generate cpu interrupt tcie ?transmission complete interrupt enable bit this read/write bit enables the tc bit to generate sci transmitter cpu interrupt requests. reset clears the tcie bit. 1 = tc enabled to generate cpu interrupt requests 0 = tc not enabled to generate cpu interrupt requests scrie ?sci receive interrupt enable bit this read/write bit enables the scrf bit to generate sci receiver cpu interrupt requests. reset clears the scrie bit. 1 = scrf enabled to generate cpu interrupt 0 = scrf not enabled to generate cpu interrupt ilie ?idle line interrupt enable bit this read/write bit enables the idle bit to generate sci receiver cpu interrupt requests. reset clears the ilie bit. 1 = idle enabled to generate cpu interrupt requests 0 = idle not enabled to generate cpu interrupt requests address: $0014 bit 7654321bit 0 read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 figure 11-10. sci control register 2 (scc2) serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 168 freescale semiconductor te ?transmitter enable bit setting this read/write bit begins the transmission by sending a preamble of 10 or 11 logic 1s from the transmit shift register to the txd pin. if software clears the te bit, the transmitter completes any transmission in progress before the txd returns to the idle condition (logic 1). clearing and then setting te during a transmission queues an idle character to be sent after the character currently being transmitted. reset clears the te bit. 1 = transmitter enabled 0 = transmitter disabled note writing to the te bit is not allowed when the enable sci bit (ensci) is clear. ensci is in sci control register 1. re ?receiver enable bit setting this read/write bit enables the receiver. clearing the re bit disables the receiver but does not affect receiver interrupt flag bits. reset clears the re bit. 1 = receiver enabled 0 = receiver disabled note writing to the re bit is not allowed when the enable sci bit (ensci) is clear. ensci is in sci control register 1. rwu ?receiver wakeup bit this read/write bit puts the receiver in a standby state during which receiver interrupts are disabled. the wake bit in scc1 determines whether an idle input or an address mark brings the receiver out of the standby state and clears the rwu bit. reset clears the rwu bit. 1 = standby state 0 = normal operation sbk ?send break bit setting and then clearing this read/write bit transmits a break character followed by a logic 1. the logic 1 after the break character guarantees recognition of a valid start bit. if sbk remains set, the transmitter continuously transmits break characters with no logic 1s between them. reset clears the sbk bit. 1 = transmit break characters 0 = no break characters being transmitted note do not toggle the sbk bit immediately after setting the scte bit. toggling sbk before the preamble begins causes the sci to send a break character instead of a preamble. i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 169 11.8.3 sci control register 3 sci control register 3: stores the ninth sci data bit received and the ninth sci data bit to be transmitted enables these interrupts: receiver overrun interrupts noise error interrupts framing error interrupts parity error interrupts r8 ?received bit 8 when the sci is receiving 9-bit characters, r8 is the read-only ninth bit (bit 8) of the received character. r8 is received at the same time that the scdr receives the other 8 bits. when the sci is receiving 8-bit characters, r8 is a copy of the eighth bit (bit 7). reset has no effect on the r8 bit. t8 ?transmitted bit 8 when the sci is transmitting 9-bit characters, t8 is the read/write ninth bit (bit 8) of the transmitted character. t8 is loaded into the transmit shift register at the same time that the scdr is loaded into the transmit shift register. reset has no effect on the t8 bit. dmare ?dma receive enable bit caution the dma module is not included on this mcu. writing a logic 1 to dmare or dmate may adversely affect mcu performance. 1 = dma not enabled to service sci receiver dma service requests generated by the scrf bit (sci receiver cpu interrupt requests enabled) 0 = dma not enabled to service sci receiver dma service requests generated by the scrf bit (sci receiver cpu interrupt requests enabled) dmate ?dma transfer enable bit caution the dma module is not included on this mcu. writing a logic 1 to dmare or dmate may adversely affect mcu performance. 1 = scte dma service requests enabled; scte cpu interrupt requests disabled 0 = scte dma service requests disabled; scte cpu interrupt requests enabled orie ?receiver overrun interrupt enable bit this read/write bit enables sci error cpu interrupt requests generated by the receiver overrun bit, or. 1 = sci error cpu interrupt requests from or bit enabled 0 = sci error cpu interrupt requests from or bit disabled address: $0015 bit 7654321bit 0 read: r8 t8 dmare dmate orie neie feie peie write: reset:uu000000 = unimplemented u = unaffected figure 11-11. sci control register 3 (scc3) serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 170 freescale semiconductor neie ?receiver noise error interrupt enable bit this read/write bit enables sci error cpu interrupt requests generated by the noise error bit, ne. reset clears neie. 1 = sci error cpu interrupt requests from ne bit enabled 0 = sci error cpu interrupt requests from ne bit disabled feie ?receiver framing error interrupt enable bit this read/write bit enables sci error cpu interrupt requests generated by the framing error bit, fe. reset clears feie. 1 = sci error cpu interrupt requests from fe bit enabled 0 = sci error cpu interrupt requests from fe bit disabled peie ?receiver parity error interrupt enable bit this read/write bit enables sci error cpu interrupt requests generated by the parity error bit, pe. (see 11.8.4 sci status register 1 .) reset clears peie. 1 = sci error cpu interrupt requests from pe bit enabled 0 = sci error cpu interrupt requests from pe bit disabled 11.8.4 sci status register 1 sci status register 1 (scs1) contains flags to signal these conditions: transfer of scdr data to transmit shift register complete transmission complete transfer of receive shift register data to scdr complete receiver input idle receiver overrun noisy data framing error parity error scte ?sci transmitter empty bit this clearable, read-only bit is set when the scdr transfers a character to the transmit shift register. scte can generate an sci transmitter cpu interrupt request. when the sctie bit in scc2 is set, scte generates an sci transmitter cpu interrupt request. in normal operation, clear the scte bit by reading scs1 with scte set and then writing to scdr. reset sets the scte bit. 1 = scdr data transferred to transmit shift register 0 = scdr data not transferred to transmit shift register address: $0016 bit 7654321bit 0 read: scte tc scrf idle or nf fe pe write: reset:11000000 = unimplemented figure 11-12. sci status register 1 (scs1) i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 171 tc ?transmission complete bit this read-only bit is set when the scte bit is set, and no data, preamble, or break character is being transmitted. tc generates an sci transmitter cpu interrupt request if the tcie bit in scc2 is also set. tc is automatically cleared when data, preamble or break is queued and ready to be sent. there may be up to 1.5 transmitter clocks of latency between queueing data, preamble, and break and the transmission actually starting. reset sets the tc bit. 1 = no transmission in progress 0 = transmission in progress scrf ?sci receiver full bit this clearable, read-only bit is set when the data in the receive shift register transfers to the sci data register. scrf can generate an sci receiver cpu interrupt request. when the scrie bit in scc2 is set, scrf generates a cpu interrupt request. in normal operation, clear the scrf bit by reading scs1 with scrf set and then reading the scdr. reset clears scrf. 1 = received data available in scdr 0 = data not available in scdr idle ?receiver idle bit this clearable, read-only bit is set when 10 or 11 consecutive logic 1s appear on the receiver input. idle generates an sci receiver cpu interrupt request if the ilie bit in scc2 is also set. clear the idle bit by reading scs1 with idle set and then reading the scdr. after the receiver is enabled, it must receive a valid character that sets the scrf bit before an idle condition can set the idle bit. also, after the idle bit has been cleared, a valid character must again set the scrf bit before an idle condition can set the idle bit. reset clears the idle bit. 1 = receiver input idle 0 = receiver input active (or idle since the idle bit was cleared) or ?receiver overrun bit this clearable, read-only bit is set when software fails to read the scdr before the receive shift register receives the next character. the or bit generates an sci error cpu interrupt request if the orie bit in scc3 is also set. the data in the shift register is lost, but the data already in the scdr is not affected. clear the or bit by reading scs1 with or set and then reading the scdr. reset clears the or bit. 1 = receive shift register full and scrf = 1 0 = no receiver overrun software latency may allow an overrun to occur between reads of scs1 and scdr in the flag-clearing sequence. figure 11-13 shows the normal flag-clearing sequence and an example of an overrun caused by a delayed flag-clearing sequence. the delayed read of scdr does not clear the or bit because or was not set when scs1 was read. byte 2 caused the overrun and is lost. the next flag-clearing sequence reads byte 3 in the scdr instead of byte 2. in applications that are subject to software latency or in which it is important to know which byte is lost due to an overrun, the flag-clearing routine can check the or bit in a second read of scs1 after reading the data register. nf ?receiver noise flag bit this clearable, read-only bit is set when the sci detects noise on the rxd pin. nf generates an sci error cpu interrupt request if the neie bit in scc3 is also set. clear the nf bit by reading scs1 and then reading the scdr. reset clears the nf bit. 1 = noise detected 0 = no noise detected serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 172 freescale semiconductor fe ?receiver framing error bit this clearable, read-only bit is set when a logic 0 is accepted as the stop bit. fe generates an sci error cpu interrupt request if the feie bit in scc3 also is set. clear the fe bit by reading scs1 with fe set and then reading the scdr. reset clears the fe bit. 1 = framing error detected 0 = no framing error detected figure 11-13. flag clearing sequence pe ?receiver parity error bit this clearable, read-only bit is set when the sci detects a parity error in incoming data. pe generates an sci error cpu interrupt request if the peie bit in scc3 is also set. clear the pe bit by reading scs1 with pe set and then reading the scdr. reset clears the pe bit. 1 = parity error detected 0 = no parity error detected byte 1 normal flag clearing sequence read scs1 scrf = 1 read scdr byte 1 scrf = 1 scrf = 1 byte 2 byte 3 byte 4 or = 0 read scs1 scrf = 1 or = 0 read scdr byte 2 scrf = 0 read scs1 scrf = 1 or = 0 scrf = 1 scrf = 0 read scdr byte 3 scrf = 0 byte 1 read scs1 scrf = 1 read scdr byte 1 scrf = 1 scrf = 1 byte 2 byte 3 byte 4 or = 0 read scs1 scrf = 1 or = 1 read scdr byte 3 delayed flag clearing sequence or = 1 scrf = 1 or = 1 scrf = 0 or = 1 scrf = 0 or = 0 i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 173 11.8.5 sci status register 2 sci status register 2 contains flags to signal the following conditions: break character detected incoming data bkf ?break flag bit this clearable, read-only bit is set when the sci detects a break character on the rxd pin. in scs1, the fe and scrf bits are also set. in 9-bit character transmissions, the r8 bit in scc3 is cleared. bkf does not generate a cpu interrupt request. clear bkf by reading scs2 with bkf set and then reading the scdr. once cleared, bkf can become set again only after logic 1s again appear on the rxd pin followed by another break character. reset clears the bkf bit. 1 = break character detected 0 = no break character detected rpf ?reception in progress flag bit this read-only bit is set when the receiver detects a logic 0 during the rt1 time period of the start bit search. rpf does not generate an interrupt request. rpf is reset after the receiver detects false start bits (usually from noise or a baud rate mismatch) or when the receiver detects an idle character. polling rpf before disabling the sci module or entering stop mode can show whether a reception is in progress. 1 = reception in progress 0 = no reception in progress 11.8.6 sci data register the sci data register (scdr) is the buffer between the internal data bus and the receive and transmit shift registers. reset has no effect on data in the sci data register. r7/t7?0/t0 ?receive/transmit data bits reading the scdr accesses the read-only received data bits, r7?0. writing to the scdr writes the data to be transmitted, t7?0. reset has no effect on the scdr. note do not use read/modify/write instructions on the sci data register. address: $0017 bit 7654321bit 0 read: bkf rpf write: reset:00000000 = unimplemented figure 11-14. sci status register 2 (scs2) address: $0018 bit 7654321bit 0 read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset figure 11-15. sci data register (scdr) serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 174 freescale semiconductor 11.8.7 sci baud rate register the baud rate register (scbr) selects the baud rate for both the receiver and the transmitter. scp1 and scp0 ?sci baud rate prescaler bits these read/write bits select the baud rate prescaler divisor as shown in table 11-6 . reset clears scp1 and scp0. scr2?cr0 ?sci baud rate select bits these read/write bits select the sci baud rate divisor as shown in table 11-7 . reset clears scr2?cr0. use this formula to calculate the sci baud rate: where: sci clock source = f bus or cgmxclk (selected by scibdsrc bit in config2 register) pd = prescaler divisor bd = baud rate divisor address: $0019 654321bit 0 read: 0 0 scp1 scp0 r scr2 scr1 scr0 write: reset:00000000 = unimplemented r = reserved figure 11-16. sci baud rate register (scbr) table 11-6. sci baud rate prescaling scp1 and scp0 prescaler divisor (pd) 00 1 01 3 10 4 11 13 table 11-7. sci baud rate selection scr2, scr1, and scr0 baud rate divisor (bd) 000 1 001 2 010 4 011 8 100 16 101 32 110 64 111 128 baud rate sci clock source 64 pd bd -------------------------------------------- - = i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 175 table 11-8 shows the sci baud rates that can be generated with a 4.9152-mhz bus clock when f bus is selected as sci clock source. table 11-8. sci baud rate selection examples scp1 and scp0 prescaler divisor (pd) scr2, scr1, and scr0 baud rate divisor (bd) baud rate (f bus = 4.9152 mhz) 00 1 000 1 76,800 00 1 001 2 38,400 00 1 010 4 19,200 00 1 011 8 9600 00 1 100 16 4800 00 1 101 32 2400 00 1 110 64 1200 00 1 111 128 600 01 3 000 1 25,600 01 3 001 2 12,800 01 3 010 4 6400 01 3 011 8 3200 01 3 100 16 1600 01 3 101 32 800 01 3 110 64 400 01 3 111 128 200 10 4 000 1 19,200 10 4 001 2 9600 10 4 010 4 4800 10 4 011 8 2400 10 4 100 16 1200 10 4 101 32 600 10 4 110 64 300 10 4 111 128 150 11 13 000 1 5908 11 13 001 2 2954 11 13 010 4 1477 11 13 011 8 739 11 13 100 16 369 11 13 101 32 185 11 13 110 64 92 11 13 111 128 46 serial communications interface module (sci) mc68hc908ap a-family data sheet, rev. 2 176 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 177 chapter 12 infrared serial communications interface module (irsci) 12.1 introduction the mc68hc908ap64a has two sci modules: sci1 is a standard sci module, and sci2 is an infrared sci module. this section describes sci2, the infrared serial communications interface (irsci) module which allows high-speed asynchronous communications with peripheral devices and other mcus. this irsci consists of an sci module for conventional sci functions and a software programmable infrared encoder/decoder sub-module for encoding/decoding the serial data for connection to infrared leds in remote control applications. note when the irsci is enabled, the sctxd pin is an open-drain output and requires a pullup resistor to be connected for proper sci operation. features of the sci module include the following: full duplex operation standard mark/space non-return-to-zero (nrz) format programmable 8-bit or 9-bit character length separately enabled transmitter and receiver separate receiver and transmitter cpu interrupt requests two receiver wakeup methods: idle line wakeup address mark wakeup interrupt-driven operation with eight interrupt flags: transmitter empty transmission complete receiver full idle receiver input receiver overrun noise error framing error parity error receiver framing error detection hardware parity checking 1/16 bit-time noise detection features of the infrared (ir) sub-module include the following: ir sub-module enable/disable for infrared sci or conventional sci on sctxd and scrxd pins software selectable infrared modulation/demodulation (3/16, 1/16 or 1/32 width pulses) infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 178 freescale semiconductor 12.2 pin name conventions the generic names of the irsci i/o pins are: rxd (receive data) txd (transmit data) irsci i/o (input/output) lines are implemented by sharing parallel i/o port pins. the full name of an irsci input or output reflects the name of the shared port pin. table 12-1 shows the full names and the generic names of the irsci i/o pins. the generic pin names appear in the text of this section. note when the irsci is enabled, the sctxd pin is an open-drain output and requires a pullup resistor to be connected for proper sci operation. table 12-1. pin name conventions generic pin names: rxd txd full pin names: ptc7/scrxd ptc6/sctxd addr. register name bit 7 654321bit 0 $0040 irsci control register 1 (irscc1) read: loops ensci 0 m wake ilty pen pty write: reset:00000000 $0041 irsci control register 2 (irscc2) read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 $0042 irsci control register 3 (irscc3) read: r8 t8 dmare dmate orie neie feie peie write: reset:uu000000 $0043 irsci status register 1 (irscs1) read: scte tc scrf idle or nf fe pe write: reset:11000000 $0044 irsci status register 2 (irscs2) read: bkf rpf write: reset:00000000 $0045 irsci data register (irscdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset $0046 irsci baud rate register (irscbr) read: cks 0 scp1 scp0 r scr2 scr1 scr0 write: reset:00000000 $0047 irsci infrared control register (irscircr) read: r 000 r tnp1 tnp0 iren write: reset:00000000 = unimplemented r = reserved u = unaffected figure 12-1. irsci i/o registers summary irsci module overview mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 179 12.3 irsci module overview the irsci consists of a serial communications interface (sci) and a infrared interface sub-module as shown in figure 12-2 . figure 12-2. irsci block diagram the sci module provides serial data transmission and reception, with a programmable baud rate clock based on the bus clock or the cgmxclk. the infrared sub-module receives two clock sources from the sci module: sci_r16xclk and sci_r32xclk. both reference clocks are used to generate the narrow pulses during data transmission. the sci_r16xclk and sci_r32xclk are internal clocks with frequencies that are 16 and 32 times the baud rate respectively. both sci_r16xclk and sci_r32xclk clocks are used for transmitting data. the sci_r16xclk clock is used only for receiving data. note for proper sci function (transmit or receive), the bus clock must be programmed to at least 32 times that of the selected baud rate. when the infrared sub-module is disabled, signals on the txd and rxd pins pass through unchanged to the sci module. 12.4 infrared functional description figure 12-3 shows the structure of the infrared sub-module. the infrared sub-module provides the capability of transmitting narrow pulses to an infrared led and receiving narrow pulses and transforming them to serial bits, which are sent to the sci module. the infrared sub-module receives two clocks from the sci. one of these two clocks is selected as the base clock to generate the 3/16, 1/16, or 1/32 bit width narrow pulses during transmission. the sub-module consists of two main blocks: the transmit encoder and the receive decoder. when transmitting data, the sci data stream is encoded by the infrared sub-module. for every "0" bit, a narrow "low" pulse is transmitted; no pulse is transmitted for "1" bits. when receiving data, the infrared pulses should be detected using an infrared photo diode for conversion to cmos voltage levels before connecting to the rxd pin for the infrared decoder. the sci data stream is reconstructed by stretching the "0" pulses. sctxd infrared sub-module sci_txd sci_r32xclk sci_r16xclk serial cgmxclk bus clock internal bus communications interface module (sci) scrxd sci_rxd infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 180 freescale semiconductor figure 12-3. infrared sub-module diagram 12.4.1 infrared transmit encoder the infrared transmit encoder converts the "0" bits in the serial data stream from the sci module to narrow "low" pulses, to the txd pin. the narrow pulse is sent with a duration of 1/32, 1/16, or 3/16 of a data bit width . when two consecutive zeros are sent, the two consecutive narrow pulses will be separated by a time equal to a data bit width. figure 12-4. infrared sci data example 12.4.2 infrared receive decoder the infrared receive decoder converts low narrow pulses from the rxd pin to standard sci data bits. the reference clock, sci_r16xclk, clocks a four bit internal counter which counts from 0 to 15. an incoming pulse starts the internal counter and a "0" is sent out to the ir_rxd output. subsequent incoming pulses are ignored when the counter count is between 0 and 7; ir_rxd remains "0". once the counter passes 7, an incoming pulse will reset the counter; ir_rxd remains "0". when the counter reaches 15, the ir_rxd output returns to "1", the counter stops and waits for further pulses. a pulse is interpreted as jitter if it arrives shortly after the counter reaches 15; ir_rxd remains "1". sci_r16xclk transmit encoder receive decoder mux mux sctxd scrxd ir_txd tnp[1:0] sci_txd ir_rxd sci_rxd iren sci_r32xclk sci data infrared sci data data bit width determined by baud rate pulse width = 1/32, 1/16, or 3/16 data bit width sci functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 181 12.5 sci functional description figure 12-5 shows the structure of the sci. figure 12-5. sci module block diagram scte tc scrf idle or nf fe pe sctie tcie scrie ilie te re rwu sbk r8 t8 dmate orie feie peie bkf rpf sci data receive shift register sci data register transmit shift register neie m wake ilty flag control transmit control receive control data selection control wakeup pty pen register dma interrupt control transmitter interrupt control receiver interrupt control error interrupt control control dmare ensci loops ensci internal bus loops 16 baud rate generator cgmxclk bus clock a b sl x sl = 0 => x = a sl = 1 => x = b cks sci_txd sci_rxd sci_r32xclk sci_r16xclk infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 182 freescale semiconductor the sci allows full-duplex, asynchronous, nrz serial communication between the mcu and remote devices, including other mcus. the transmitter and receiver of the sci operate independently, although they use the same baud rate generator. during normal operation, the cpu monitors the status of the sci, writes the data to be transmitted, and processes received data. note for sci operations, the ir sub-module is transparent to the sci module. data at going out of the sci transmitter and data going into the sci receiver is always in sci format. it makes no difference to the sci module whether the ir sub-module is enabled or disabled. note this sci module is a standard hc08 sci module with the following modifications: a control bit, cks, is added to the sci baud rate control register to select between two input clocks for baud rate clock generation the txinv bit is removed from the sci control register 1 12.5.1 data format the sci uses the standard non-return-to-zero mark/space data format illustrated in figure 12-6 . figure 12-6. sci data formats 12.5.2 transmitter figure 12-7 shows the structure of the sci transmitter. the baud rate clock source for the sci can be selected by the cks bit, in the sci baud rate register (see 12.9.7 irsci baud rate register ). 12.5.2.1 character length the transmitter can accommodate either 8-bit or 9-bit data. the state of the m bit in irsci control register 1 (irscc1) determines character length. when transmitting 9-bit data, bit t8 in irsci control register 3 (irscc3) is the ninth bit (bit 8). bit 5 start bit bit 0 bit 1 next stop bit start bit 8-bit data format bit m in irscc1 clear start bit bit 0 next stop bit start bit 9-bit data format bit m in irscc1 set bit 1 bit 2 bit 3 bit 4 bit 5 bit 6 bit 7 bit 8 bit 2 bit 3 bit 4 bit 6 bit 7 parity bit parity bit sci functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 183 figure 12-7. sci transmitter 12.5.2.2 character transmission during an sci transmission, the transmit shift register shifts a character out to the txd pin. the irsci data register (irscdr) is the write-only buffer between the internal data bus and the transmit shift register. to initiate an sci transmission: 1. enable the sci by writing a logic 1 to the enable sci bit (ensci) in irsci control register 1 (irscc1). 2. enable the transmitter by writing a logic 1 to the transmitter enable bit (te) in irsci control register 2 (irscc2). 3. clear the sci transmitter empty bit by first reading irsci status register 1 (irscs1) and then writing to the irscdr. 4. repeat step 3 for each subsequent transmission. at the start of a transmission, transmitter control logic automatically loads the transmit shift register with a preamble of logic 1s. after the preamble shifts out, control logic transfers the irscdr data into the transmit shift register. a logic 0 start bit automatically goes into the least significant bit position of the transmit shift register. a logic 1 stop bit goes into the most significant bit position. dmate scte pen pty h876543210l 11-bit transmit stop start t8 dmate scte sctie tcie sbk tc parity generation msb sci data register load from irscdr shift enable preamble all 1s break all 0s transmitter control logic shift register dmate tc sctie tcie scte transmitter cpu interrupt request transmitter dma service request m ensci loops te internal bus pre- scaler scp1 scp0 scr2 scr1 scr0 baud divider 16 sctie sci_txd cgmxclk bus clock a b sl x sl = 0 => x = a sl = 1 => x = b cks infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 184 freescale semiconductor the sci transmitter empty bit, scte, in irscs1 becomes set when the irscdr transfers a byte to the transmit shift register. the scte bit indicates that the irscdr can accept new data from the internal data bus. if the sci transmit interrupt enable bit, sctie, in irscc2 is also set, the scte bit generates a transmitter interrupt request. when the transmit shift register is not transmitting a character, the txd pin goes to the idle condition, logic 1. if at any time software clears the ensci bit in irsci control register 1 (irscc1), the transmitter and receiver relinquish control of the port pins. 12.5.2.3 break characters writing a logic 1 to the send break bit, sbk, in irscc2 loads the transmit shift register with a break character. a break character contains all logic 0s and has no start, stop, or parity bit. break character length depends on the m bit in irscc1. as long as sbk is at logic 1, transmitter logic continuously loads break characters into the transmit shift register. after software clears the sbk bit, the shift register finishes transmitting the last break character and then transmits at least one logic 1. the automatic logic 1 at the end of a break character guarantees the recognition of the start bit of the next character. the sci recognizes a break character when a start bit is followed by eight or nine logic 0 data bits and a logic 0 where the stop bit should be. receiving a break character has the following effects on sci registers: sets the framing error bit (fe) in irscs1 sets the sci receiver full bit (scrf) in irscs1 clears the sci data register (irscdr) clears the r8 bit in irscc3 sets the break flag bit (bkf) in irscs2 may set the overrun (or), noise flag (nf), parity error (pe), or reception in progress flag (rpf) bits 12.5.2.4 idle characters an idle character contains all logic 1s and has no start, stop, or parity bit. idle character length depends on the m bit in irscc1. the preamble is a synchronizing idle character that begins every transmission. if the te bit is cleared during a transmission, the txd pin becomes idle after completion of the transmission in progress. clearing and then setting the te bit during a transmission queues an idle character to be sent after the character currently being transmitted. note when queueing an idle character, return the te bit to logic 1 before the stop bit of the current character shifts out to the txd pin. setting te after the stop bit appears on txd causes data previously written to the irscdr to be lost. toggle the te bit for a queued idle character when the scte bit becomes set and just before writing the next byte to the irscdr. 12.5.2.5 transmitter interrupts the following conditions can generate cpu interrupt requests from the sci transmitter: sci functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 185 sci transmitter empty (scte) ?the scte bit in irscs1 indicates that the irscdr has transferred a character to the transmit shift register. scte can generate a transmitter cpu interrupt request. setting the sci transmit interrupt enable bit, sctie, in irscc2 enables the scte bit to generate transmitter cpu interrupt requests. transmission complete (tc) the tc bit in irscs1 indicates that the transmit shift register and the irscdr are empty and that no break or idle character has been generated. the transmission complete interrupt enable bit, tcie, in irscc2 enables the tc bit to generate transmitter cpu interrupt requests. 12.5.3 receiver figure 12-8 shows the structure of the sci receiver. infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 186 freescale semiconductor figure 12-8. sci receiver block diagram 12.5.3.1 character length the receiver can accommodate either 8-bit or 9-bit data. the state of the m bit in irsci control register 1 (irscc1) determines character length. when receiving 9-bit data, bit r8 in irsci control register 2 (irscc2) is the ninth bit (bit 8). when receiving 8-bit data, bit r8 is a copy of the eighth bit (bit 7). all 1s all 0s m wake ilty pen pty bkf rpf h876543210l 11-bit receive shift register stop start data recovery dmare scrf or orie nf neie fe feie pe peie dmare scrie scrf ilie idle wakeup logic parity checking msb error cpu i nterrupt request dma service request cpu interrupt request sci data register r8 dmare orie neie feie peie scrie ilie rwu scrf idle or nf fe pe internal bus pre- scaler baud divider 16 scp1 scp0 scr2 scr1 scr0 scrie dmare sci_rxd cgmxclk bus clock a b sl x sl = 0 => x = a sl = 1 => x = b cks sci functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 187 12.5.3.2 character reception during an sci reception, the receive shift register shifts characters in from the rxd pin. the sci data register (irscdr) is the read-only buffer between the internal data bus and the receive shift register. after a complete character shifts into the receive shift register, the data portion of the character transfers to the irscdr. the sci receiver full bit, scrf, in irsci status register 1 (irscs1) becomes set, indicating that the received byte can be read. if the sci receive interrupt enable bit, scrie, in irscc2 is also set, the scrf bit generates a receiver cpu interrupt request. 12.5.3.3 data sampling the receiver samples the rxd pin at the rt clock rate. the rt clock is an internal signal with a frequency 16 times the baud rate. to adjust for baud rate mismatch, the rt clock is resynchronized at the following times (see figure 12-9 ): after every start bit after the receiver detects a data bit change from logic 1 to logic 0 (after the majority of data bit samples at rt8, rt9, and rt10 returns a valid logic 1 and the majority of the next rt8, rt9, and rt10 samples returns a valid logic 0) figure 12-9. receiver data sampling to locate the start bit, data recovery logic does an asynchronous search for a logic 0 preceded by three logic 1s. when the falling edge of a possible start bit occurs, the rt clock begins to count to 16. to verify the start bit and to detect noise, data recovery logic takes samples at rt3, rt5, and rt7. table 12-2 summarizes the results of the start bit verification samples. table 12-2. start bit veri?ation rt3, rt5, and rt7 samples start bit verification noise flag 000 yes 0 001 yes 1 010 yes 1 rt clock reset rt1 rt1 rt1 rt1 rt1 rt1 rt1 rt1 rt1 rt2 rt3 rt4 rt5 rt8 rt7 rt6 rt11 rt10 rt9 rt15 rt14 rt13 rt12 rt16 rt1 rt2 rt3 rt4 start bit qualification start bit verification data sampling samples rt clock rt clock state start bit lsb sci_rxd infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 188 freescale semiconductor if start bit verification is not successful, the rt clock is reset and a new search for a start bit begins. to determine the value of a data bit and to detect noise, recovery logic takes samples at rt8, rt9, and rt10. table 12-3 summarizes the results of the data bit samples. note the rt8, rt9, and rt10 samples do not affect start bit verification. if any or all of the rt8, rt9, and rt10 start bit samples are logic 1s following a successful start bit verification, the noise flag (nf) is set and the receiver assumes that the bit is a start bit. to verify a stop bit and to detect noise, recovery logic takes samples at rt8, rt9, and rt10. table 12-4 summarizes the results of the stop bit samples. 011 no 0 100 yes 1 101 no 0 110 no 0 111 no 0 table 12-3. data bit recovery rt8, rt9, and rt10 samples data bit determination noise flag 000 0 0 001 0 1 010 0 1 011 1 1 100 0 1 101 1 1 110 1 1 111 1 0 table 12-4. stop bit recovery rt8, rt9, and rt10 samples framing error flag noise flag 000 1 0 001 1 1 table 12-2. start bit veri?ation rt3, rt5, and rt7 samples start bit verification noise flag sci functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 189 12.5.3.4 framing errors if the data recovery logic does not detect a logic 1 where the stop bit should be in an incoming character, it sets the framing error bit, fe, in irscs1. the fe flag is set at the same time that the scrf bit is set. a break character that has no stop bit also sets the fe bit. 12.5.3.5 baud rate tolerance a transmitting device may be operating at a baud rate below or above the receiver baud rate. accumulated bit time misalignment can cause one of the three stop bit data samples to fall outside the actual stop bit. then a noise error occurs. if more than one of the samples is outside the stop bit, a framing error occurs. in most applications, the baud rate tolerance is much more than the degree of misalignment that is likely to occur. as the receiver samples an incoming character, it resynchronizes the rt clock on any valid falling edge within the character. resynchronization within characters corrects misalignments between transmitter bit times and receiver bit times. slow data tolerance figure 12-10 shows how much a slow received character can be misaligned without causing a noise error or a framing error. the slow stop bit begins at rt8 instead of rt1 but arrives in time for the stop bit data samples at rt8, rt9, and rt10. figure 12-10. slow data for an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times 16 rt cycles + 10 rt cycles = 154 rt cycles. with the misaligned character shown in figure 12-10 , the receiver counts 154 rt cycles at the point when the count of the transmitting device is 9 bit times 16 rt cycles + 3 rt cycles = 147 rt cycles. 010 1 1 011 0 1 100 1 1 101 0 1 110 0 1 111 0 0 table 12-4. stop bit recovery rt8, rt9, and rt10 samples framing error flag noise flag msb stop rt1 rt2 rt3 rt4 rt5 rt6 rt7 rt8 rt9 rt10 rt11 rt12 rt13 rt14 rt15 rt16 data samples receiver rt clock infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 190 freescale semiconductor the maximum percent difference between the receiver count and the transmitter count of a slow 8-bit character with no errors is for a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times 16 rt cycles + 10 rt cycles = 170 rt cycles. with the misaligned character shown in figure 12-10 , the receiver counts 170 rt cycles at the point when the count of the transmitting device is 10 bit times 16 rt cycles + 3 rt cycles = 163 rt cycles. the maximum percent difference between the receiver count and the transmitter count of a slow 9-bit character with no errors is fast data tolerance figure 12-11 shows how much a fast received character can be misaligned without causing a noise error or a framing error. the fast stop bit ends at rt10 instead of rt16 but is still there for the stop bit data samples at rt8, rt9, and rt10. figure 12-11. fast data for an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times 16 rt cycles + 10 rt cycles = 154 rt cycles. with the misaligned character shown in figure 12-11 , the receiver counts 154 rt cycles at the point when the count of the transmitting device is 10 bit times 16 rt cycles = 160 rt cycles. the maximum percent difference between the receiver count and the transmitter count of a fast 8-bit character with no errors is for a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times 16 rt cycles + 10 rt cycles = 170 rt cycles. with the misaligned character shown in figure 12-11 , the receiver counts 170 rt cycles at the point when the count of the transmitting device is 11 bit times 16 rt cycles = 176 rt cycles. the maximum percent difference between the receiver count and the transmitter count of a fast 9-bit character with no errors is 154 147 154 ------------------------- - 100 4.54% = 170 163 170 ------------------------- - 100 4.12% = idle or next character stop rt1 rt2 rt3 rt4 rt5 rt6 rt7 rt8 rt9 rt10 rt11 rt12 rt13 rt14 rt15 rt16 data samples receiver rt clock 154 160 154 ------------------------- - 100 3.90% ? = sci functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 191 12.5.3.6 receiver wakeup so that the mcu can ignore transmissions intended only for other receivers in multiple-receiver systems, the receiver can be put into a standby state. setting the receiver wakeup bit, rwu, in irscc2 puts the receiver into a standby state during which receiver interrupts are disabled. depending on the state of the wake bit in irscc1, either of two conditions on the rxd pin can bring the receiver out of the standby state: address mark ?an address mark is a logic 1 in the most significant bit position of a received character. when the wake bit is set, an address mark wakes the receiver from the standby state by clearing the rwu bit. the address mark also sets the sci receiver full bit, scrf. software can then compare the character containing the address mark to the user-defined address of the receiver. if they are the same, the receiver remains awake and processes the characters that follow. if they are not the same, software can set the rwu bit and put the receiver back into the standby state. idle input line condition when the wake bit is clear, an idle character on the rxd pin wakes the receiver from the standby state by clearing the rwu bit. the idle character that wakes the receiver does not set the receiver idle bit, idle, or the sci receiver full bit, scrf. the idle line type bit, ilty, determines whether the receiver begins counting logic 1s as idle character bits after the start bit or after the stop bit. note clearing the wake bit after the rxd pin has been idle may cause the receiver to wake up immediately. 12.5.3.7 receiver interrupts the following sources can generate cpu interrupt requests from the sci receiver: sci receiver full (scrf) ?the scrf bit in irscs1 indicates that the receive shift register has transferred a character to the irscdr. scrf can generate a receiver interrupt request. setting the sci receive interrupt enable bit, scrie, in irscc2 enables the scrf bit to generate receiver cpu interrupts. idle input (idle) the idle bit in irscs1 indicates that 10 or 11 consecutive logic 1s shifted in from the rxd pin. the idle line interrupt enable bit, ilie, in irscc2 enables the idle bit to generate cpu interrupt requests. 12.5.3.8 error interrupts the following receiver error flags in irscs1 can generate cpu interrupt requests: receiver overrun (or) ?the or bit indicates that the receive shift register shifted in a new character before the previous character was read from the irscdr. the previous character remains in the irscdr, and the new character is lost. the overrun interrupt enable bit, orie, in irscc3 enables or to generate sci error cpu interrupt requests. noise flag (nf) ?the nf bit is set when the sci detects noise on incoming data or break characters, including start, data, and stop bits. the noise error interrupt enable bit, neie, in irscc3 enables nf to generate sci error cpu interrupt requests. 170 176 170 ------------------------- - 100 3.53% = infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 192 freescale semiconductor framing error (fe) the fe bit in irscs1 is set when a logic 0 occurs where the receiver expects a stop bit. the framing error interrupt enable bit, feie, in irscc3 enables fe to generate sci error cpu interrupt requests. parity error (pe) ?the pe bit in irscs1 is set when the sci detects a parity error in incoming data. the parity error interrupt enable bit, peie, in irscc3 enables pe to generate sci error cpu interrupt requests. 12.6 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 12.6.1 wait mode the sci module remains active after the execution of a wait instruction. in wait mode, the sci module registers are not accessible by the cpu. any enabled cpu interrupt request from the sci module can bring the mcu out of wait mode. if sci module functions are not required during wait mode, reduce power consumption by disabling the module before executing the wait instruction. refer to 7.6 low-power modes for information on exiting wait mode. 12.6.2 stop mode the sci module is inactive after the execution of a stop instruction. the stop instruction does not affect sci register states. sci module operation resumes after an external interrupt. because the internal clock is inactive during stop mode, entering stop mode during an sci transmission or reception results in invalid data. refer to 7.6 low-power modes for information on exiting stop mode. 12.7 sci during break module interrupts the system integration module (sim) controls whether status bits in other modules can be cleared during interrupts generated by the break module. the bcfe bit in the sim break flag control register (sbfcr) enables software to clear status bits during the break state. to allow software to clear status bits during a break interrupt, write a logic 1 to the bcfe bit. if a status bit is cleared during the break state, it remains cleared when the mcu exits the break state. to protect status bits during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), software can read and write i/o registers during the break state without affecting status bits. some status bits have a two-step read/write clearing procedure. if software does the first step on such a bit before the break, the bit cannot change during the break state as long as bcfe is at logic 0. after the break, doing the second step clears the status bit. 12.8 i/o signals the two irsci i/o pins are: ptc6/sctxd ?transmit data ptc7/scrxd ?receive data i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 193 12.8.1 ptc6/sctxd (transmit data) the ptc6/sctxd pin is the serial data (standard or infrared) output from the sci transmitter. the irsci shares the ptc6/sctxd pin with port c. when the irsci is enabled, the ptc6/sctxd pin is an output regardless of the state of the ddrc6 bit in data direction register c (ddrc). note the ptc6/sctxd pin is an open-drain pin when configured as an output. therefore, when configured as sctxd or a general purpose output pin (ptc6), a pullup resistor must be connected to this pin. 12.8.2 ptc7/scrxd (receive data) the ptc7/scrxd pin is the serial data input to the irsci receiver. the irsci shares the ptc7/scrxd pin with port c. when the irsci is enabled, the ptc7/scrxd pin is an input regardless of the state of the ddrc7 bit in data direction register c (ddrc). note the ptc7/scrxd pin is an open-drain pin when configured as an output. therefore, when configured as a general purpose output pin (ptc7), a pullup resistor must be connected to this pin. table 12-5 shows a summary of i/o pin functions when the sci is enabled. 12.9 i/o registers the following i/o registers control and monitor sci operation: irsci control register 1 (irscc1) irsci control register 2 (irscc2) irsci control register 3 (irscc3) table 12-5. sci pin functions (standard and infrared) irscc1 [ensci] irscircr [iren] irscc2 [te] irscc2 [re] txd pin rxd pin 1000 hi-z (1) 1. after completion of transmission in progress. input ignored (terminate externally) 1001 hi-z (1) input sampled, pin should idle high 1 0 1 0 output sci (idle high) input ignored (terminate externally) 1 0 1 1 output sci (idle high) input sampled, pin should idle high 1100 hi-z (1) input ignored (terminate externally) 1101 hi-z (1) input sampled, pin should idle high 1 1 1 0 output ir sci (idle high) input ignored (terminate externally) 1 1 1 1 output ir sci (idle high) input sampled, pin should idle high 0 x x x pins under port control (standard i/o port) infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 194 freescale semiconductor irsci status register 1 (irscs1) irsci status register 2 (irscs2) irsci data register (irscdr) irsci baud rate register (irscbr) irsci infrared control register (irscircr) 12.9.1 irsci control register 1 sci control register 1: enables loop mode operation enables the sci controls output polarity controls character length controls sci wakeup method controls idle character detection enables parity function controls parity type loops ?loop mode select bit this read/write bit enables loop mode operation for the sci only. in loop mode the rxd pin is disconnected from the sci, and the transmitter output goes into the receiver input. both the transmitter and the receiver must be enabled to use loop mode. the infrared encoder/decoder is not in the loop. reset clears the loops bit. 1 = loop mode enabled 0 = normal operation enabled ensci ?enable sci bit this read/write bit enables the sci and the sci baud rate generator. clearing ensci sets the scte and tc bits in sci status register 1 and disables transmitter interrupts. reset clears the ensci bit. 1 = sci enabled 0 = sci disabled address: $0040 bit 7654321bit 0 read: loops ensci 0 m wake ilty pen pty write: reset:00000000 figure 12-12. irsci control register 1 (irscc1) i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 195 m ?mode (character length) bit this read/write bit determines whether sci characters are eight or nine bits long. (see table 12-6 .) the ninth bit can serve as an extra stop bit, as a receiver wakeup signal, or as a parity bit. reset clears the m bit. 1 = 9-bit sci characters 0 = 8-bit sci characters wake ?wakeup condition bit this read/write bit determines which condition wakes up the sci: a logic 1 (address mark) in the most significant bit position of a received character or an idle condition on the rxd pin. reset clears the wake bit. 1 = address mark wakeup 0 = idle line wakeup ilty ?idle line type bit this read/write bit determines when the sci starts counting logic 1s as idle character bits. the counting begins either after the start bit or after the stop bit. if the count begins after the start bit, then a string of logic 1s preceding the stop bit may cause false recognition of an idle character. beginning the count after the stop bit avoids false idle character recognition, but requires properly synchronized transmissions. reset clears the ilty bit. 1 = idle character bit count begins after stop bit 0 = idle character bit count begins after start bit pen ?parity enable bit this read/write bit enables the sci parity function. (see table 12-6 .) when enabled, the parity function inserts a parity bit in the most significant bit position. (see figure 12-6 .) reset clears the pen bit. 1 = parity function enabled 0 = parity function disabled pty ?parity bit this read/write bit determines whether the sci generates and checks for odd parity or even parity. (see table 12-6 .) reset clears the pty bit. 1 = odd parity 0 = even parity note changing the pty bit in the middle of a transmission or reception can generate a parity error. table 12-6. character format selection control bits character format m pen:pty start bits data bits parity stop bits character length 0 0x 1 8 none 1 10 bits 1 0x 1 9 none 1 11 bits 0 10 1 7 even 1 10 bits 0 11 1 7 odd 1 10 bits 1 10 1 8 even 1 11 bits 1 11 1 8 odd 1 11 bits infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 196 freescale semiconductor 12.9.2 irsci control register 2 irsci control register 2: enables the following cpu interrupt requests: enables the scte bit to generate transmitter cpu interrupt requests enables the tc bit to generate transmitter cpu interrupt requests enables the scrf bit to generate receiver cpu interrupt requests enables the idle bit to generate receiver cpu interrupt requests enables the transmitter enables the receiver enables sci wakeup transmits sci break characters sctie ?sci transmit interrupt enable bit this read/write bit enables the scte bit to generate sci transmitter cpu interrupt requests. reset clears the sctie bit. 1 = scte enabled to generate cpu interrupt 0 = scte not enabled to generate cpu interrupt tcie ?transmission complete interrupt enable bit this read/write bit enables the tc bit to generate sci transmitter cpu interrupt requests. reset clears the tcie bit. 1 = tc enabled to generate cpu interrupt requests 0 = tc not enabled to generate cpu interrupt requests scrie ?sci receive interrupt enable bit this read/write bit enables the scrf bit to generate sci receiver cpu interrupt requests. reset clears the scrie bit. 1 = scrf enabled to generate cpu interrupt 0 = scrf not enabled to generate cpu interrupt ilie ?idle line interrupt enable bit this read/write bit enables the idle bit to generate sci receiver cpu interrupt requests. reset clears the ilie bit. 1 = idle enabled to generate cpu interrupt requests 0 = idle not enabled to generate cpu interrupt requests te ?transmitter enable bit setting this read/write bit begins the transmission by sending a preamble of 10 or 11 logic 1s from the transmit shift register to the txd pin. if software clears the te bit, the transmitter completes any transmission in progress before the txd returns to the idle condition (logic 1). clearing and then setting te during a transmission queues an idle character to be sent after the character currently being transmitted. reset clears the te bit. 1 = transmitter enabled 0 = transmitter disabled address: $0041 bit 7654321bit 0 read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 figure 12-13. irsci control register 2 (irscc2) i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 197 note writing to the te bit is not allowed when the enable sci bit (ensci) is clear. ensci is in sci control register 1. re ?receiver enable bit setting this read/write bit enables the receiver. clearing the re bit disables the receiver but does not affect receiver interrupt flag bits. reset clears the re bit. 1 = receiver enabled 0 = receiver disabled note writing to the re bit is not allowed when the enable sci bit (ensci) is clear. ensci is in sci control register 1. rwu ?receiver wakeup bit this read/write bit puts the receiver in a standby state during which receiver interrupts are disabled. the wake bit in irscc1 determines whether an idle input or an address mark brings the receiver out of the standby state and clears the rwu bit. reset clears the rwu bit. 1 = standby state 0 = normal operation sbk ?send break bit setting and then clearing this read/write bit transmits a break character followed by a logic 1. the logic 1 after the break character guarantees recognition of a valid start bit. if sbk remains set, the transmitter continuously transmits break characters with no logic 1s between them. reset clears the sbk bit. 1 = transmit break characters 0 = no break characters being transmitted note do not toggle the sbk bit immediately after setting the scte bit. toggling sbk before the preamble begins causes the sci to send a break character instead of a preamble. 12.9.3 irsci control register 3 irsci control register 3: stores the ninth sci data bit received and the ninth sci data bit to be transmitted enables the following interrupts: receiver overrun interrupts noise error interrupts framing error interrupts parity error interrupts address: $0042 bit 7654321bit 0 read: r8 t8 dmare dmate orie neie feie peie write: reset:uu000000 = unimplemented u = unaffected figure 12-14. irsci control register 3 (irscc3) infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 198 freescale semiconductor r8 ?received bit 8 when the sci is receiving 9-bit characters, r8 is the read-only ninth bit (bit 8) of the received character. r8 is received at the same time that the irscdr receives the other 8 bits. when the sci is receiving 8-bit characters, r8 is a copy of the eighth bit (bit 7). reset has no effect on the r8 bit. t8 ?transmitted bit 8 when the sci is transmitting 9-bit characters, t8 is the read/write ninth bit (bit 8) of the transmitted character. t8 is loaded into the transmit shift register at the same time that the irscdr is loaded into the transmit shift register. reset has no effect on the t8 bit. dmare ?dma receive enable bit caution the dma module is not included on this mcu. writing a logic 1 to dmare or dmate may adversely affect mcu performance. 1 = dma not enabled to service sci receiver dma service requests generated by the scrf bit (sci receiver cpu interrupt requests enabled) 0 = dma not enabled to service sci receiver dma service requests generated by the scrf bit (sci receiver cpu interrupt requests enabled) dmate ?dma transfer enable bit caution the dma module is not included on this mcu. writing a logic 1 to dmare or dmate may adversely affect mcu performance. 1 = scte dma service requests enabled; scte cpu interrupt requests disabled 0 = scte dma service requests disabled; scte cpu interrupt requests enabled orie ?receiver overrun interrupt enable bit this read/write bit enables sci error cpu interrupt requests generated by the receiver overrun bit, or. reset clears orie. 1 = sci error cpu interrupt requests from or bit enabled 0 = sci error cpu interrupt requests from or bit disabled neie ?receiver noise error interrupt enable bit this read/write bit enables sci error cpu interrupt requests generated by the noise error bit, ne. reset clears neie. 1 = sci error cpu interrupt requests from ne bit enabled 0 = sci error cpu interrupt requests from ne bit disabled feie ?receiver framing error interrupt enable bit this read/write bit enables sci error cpu interrupt requests generated by the framing error bit, fe. reset clears feie. 1 = sci error cpu interrupt requests from fe bit enabled 0 = sci error cpu interrupt requests from fe bit disabled peie ?receiver parity error interrupt enable bit this read/write bit enables sci error cpu interrupt requests generated by the parity error bit, pe. (see 12.9.4 irsci status register 1 .) reset clears peie. 1 = sci error cpu interrupt requests from pe bit enabled 0 = sci error cpu interrupt requests from pe bit disabled i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 199 12.9.4 irsci status register 1 sci status register 1 contains flags to signal these conditions: transfer of irscdr data to transmit shift register complete transmission complete transfer of receive shift register data to irscdr complete receiver input idle receiver overrun noisy data framing error parity error scte ?sci transmitter empty bit this clearable, read-only bit is set when the irscdr transfers a character to the transmit shift register. scte can generate an sci transmitter cpu interrupt request. when the sctie bit in irscc2 is set, scte generates an sci transmitter cpu interrupt request. in normal operation, clear the scte bit by reading irscs1 with scte set and then writing to irscdr. reset sets the scte bit. 1 = irscdr data transferred to transmit shift register 0 = irscdr data not transferred to transmit shift register tc ?transmission complete bit this read-only bit is set when the scte bit is set, and no data, preamble, or break character is being transmitted. tc generates an sci transmitter cpu interrupt request if the tcie bit in irscc2 is also set. tc is automatically cleared when data, preamble or break is queued and ready to be sent. there may be up to 1.5 transmitter clocks of latency between queueing data, preamble, and break and the transmission actually starting. reset sets the tc bit. 1 = no transmission in progress 0 = transmission in progress scrf ?sci receiver full bit this clearable, read-only bit is set when the data in the receive shift register transfers to the sci data register. scrf can generate an sci receiver cpu interrupt request. when the scrie bit in irscc2 is set, scrf generates a cpu interrupt request. in normal operation, clear the scrf bit by reading irscs1 with scrf set and then reading the irscdr. reset clears scrf. 1 = received data available in irscdr 0 = data not available in irscdr idle ?receiver idle bit this clearable, read-only bit is set when 10 or 11 consecutive logic 1s appear on the receiver input. idle generates an sci receiver cpu interrupt request if the ilie bit in irscc2 is also set. clear the idle bit by reading irscs1 with idle set and then reading the irscdr. after the receiver is enabled, address: $0043 bit 7654321bit 0 read: scte tc scrf idle or nf fe pe write: reset:11000000 = unimplemented figure 12-15. irsci status register 1 (irscs1) infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 200 freescale semiconductor it must receive a valid character that sets the scrf bit before an idle condition can set the idle bit. also, after the idle bit has been cleared, a valid character must again set the scrf bit before an idle condition can set the idle bit. reset clears the idle bit. 1 = receiver input idle 0 = receiver input active (or idle since the idle bit was cleared) or ?receiver overrun bit this clearable, read-only bit is set when software fails to read the irscdr before the receive shift register receives the next character. the or bit generates an sci error cpu interrupt request if the orie bit in irscc3 is also set. the data in the shift register is lost, but the data already in the irscdr is not affected. clear the or bit by reading irscs1 with or set and then reading the irscdr. reset clears the or bit. 1 = receive shift register full and scrf = 1 0 = no receiver overrun software latency may allow an overrun to occur between reads of irscs1 and irscdr in the flag-clearing sequence. figure 12-16 shows the normal flag-clearing sequence and an example of an overrun caused by a delayed flag-clearing sequence. the delayed read of irscdr does not clear the or bit because or was not set when irscs1 was read. byte 2 caused the overrun and is lost. the next flag-clearing sequence reads byte 3 in the irscdr instead of byte 2. in applications that are subject to software latency or in which it is important to know which byte is lost due to an overrun, the flag-clearing routine can check the or bit in a second read of irscs1 after reading the data register. figure 12-16. flag clearing sequence byte 1 normal flag clearing sequence read irscs1 scrf = 1 read irscdr byte 1 scrf = 1 scrf = 1 byte 2 byte 3 byte 4 or = 0 read irscs1 scrf = 1 or = 0 read irscdr byte 2 scrf = 0 read irscs1 scrf = 1 or = 0 scrf = 1 scrf = 0 read irscdr byte 3 scrf = 0 byte 1 read irscs1 scrf = 1 read irscdr byte 1 scrf = 1 scrf = 1 byte 2 byte 3 byte 4 or = 0 read irscs1 scrf = 1 or = 1 read irscdr byte 3 delayed flag clearing sequence or = 1 scrf = 1 or = 1 scrf = 0 or = 1 scrf = 0 or = 0 i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 201 nf ?receiver noise flag bit this clearable, read-only bit is set when the sci detects noise on the rxd pin. nf generates an sci error cpu interrupt request if the neie bit in irscc3 is also set. clear the nf bit by reading irscs1 and then reading the irscdr. reset clears the nf bit. 1 = noise detected 0 = no noise detected fe ?receiver framing error bit this clearable, read-only bit is set when a logic 0 is accepted as the stop bit. fe generates an sci error cpu interrupt request if the feie bit in irscc3 also is set. clear the fe bit by reading irscs1 with fe set and then reading the irscdr. reset clears the fe bit. 1 = framing error detected 0 = no framing error detected pe ?receiver parity error bit this clearable, read-only bit is set when the sci detects a parity error in incoming data. pe generates an sci error cpu interrupt request if the peie bit in irscc3 is also set. clear the pe bit by reading irscs1 with pe set and then reading the irscdr. reset clears the pe bit. 1 = parity error detected 0 = no parity error detected 12.9.5 irsci status register 2 irsci status register 2 contains flags to signal the following conditions: break character detected incoming data bkf ?break flag bit this clearable, read-only bit is set when the sci detects a break character on the rxd pin. in irscs1, the fe and scrf bits are also set. in 9-bit character transmissions, the r8 bit in irscc3 is cleared. bkf does not generate a cpu interrupt request. clear bkf by reading irscs2 with bkf set and then reading the irscdr. once cleared, bkf can become set again only after logic 1s again appear on the rxd pin followed by another break character. reset clears the bkf bit. 1 = break character detected 0 = no break character detected address: $0044 bit 7654321bit 0 read: bkf rpf write: reset:00000000 = unimplemented figure 12-17. irsci status register 2 (irscs2) infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 202 freescale semiconductor rpf ?reception in progress flag bit this read-only bit is set when the receiver detects a logic 0 during the rt1 time period of the start bit search. rpf does not generate an interrupt request. rpf is reset after the receiver detects false start bits (usually from noise or a baud rate mismatch) or when the receiver detects an idle character. polling rpf before disabling the sci module or entering stop mode can show whether a reception is in progress. 1 = reception in progress 0 = no reception in progress 12.9.6 irsci data register the irsci data register is the buffer between the internal data bus and the receive and transmit shift registers. reset has no effect on data in the irsci data register. r7/t7?0/t0 ?receive/transmit data bits reading the irscdr accesses the read-only received data bits, r7?0. writing to the irscdr writes the data to be transmitted, t7?0. reset has no effect on the irscdr. note do not use read/modify/write instructions on the irsci data register. 12.9.7 irsci baud rate register the baud rate register selects the baud rate for both the receiver and the transmitter. cks ?baud clock input select this read/write bit selects the source clock for the baud rate generator. reset clears the cks bit, selecting cgmxclk. 1 = bus clock drives the baud rate generator 0 = cgmxclk drives the baud rate generator scp1 and scp0 ?sci baud rate prescaler bits these read/write bits select the baud rate prescaler divisor as shown in table 12-7 . reset clears scp1 and scp0. address: $0045 bit 7654321bit 0 read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset figure 12-18. irsci data register (irscdr) address: $0046 bit 7654321bit 0 read: cks 0 scp1 scp0 r scr2 scr1 scr0 write: reset:00000000 = unimplemented r = reserved figure 12-19. irsci baud rate register (irscbr) i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 203 scr2?cr0 ?sci baud rate select bits these read/write bits select the sci baud rate divisor as shown in table 12-8 . reset clears scr2?cr0. use this formula to calculate the sci baud rate: where: sci clock source = f bus or cgmxclk (selected by cks bit) pd = prescaler divisor bd = baud rate divisor table 12-9 shows the sci baud rates that can be generated with a 4.9152-mhz bus clock when f bus is selected as sci clock source. table 12-7. sci baud rate prescaling scp1 and scp0 prescaler divisor (pd) 00 1 01 3 10 4 11 13 table 12-8. irsci baud rate selection scr2, scr1, and scr0 baud rate divisor (bd) 000 1 001 2 010 4 011 8 100 16 101 32 110 64 111 128 baud rate sci clock source 16 pd bd -------------------------------------------- - = infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 204 freescale semiconductor table 12-9. irsci baud rate selection examples scp1 and scp0 prescaler divisor (pd) scr2, scr1, and scr0 baud rate divisor (bd) baud rate (f bus = 4.9152 mhz) 00 1 000 1 00 1 001 2 00 1 010 4 76800 00 1 011 8 38400 00 1 100 16 19200 00 1 101 32 9600 00 1 110 64 4800 00 1 111 128 2400 01 3 000 1 01 3 001 2 51200 01 3 010 4 25600 01 3 011 8 12800 01 3 100 16 6400 01 3 101 32 3200 01 3 110 64 1600 01 3 111 128 800 10 4 000 1 76800 10 4 001 2 38400 10 4 010 4 19200 10 4 011 8 9600 10 4 100 16 4800 10 4 101 32 2400 10 4 110 64 1200 10 4 111 128 600 11 13 000 1 23632 11 13 001 2 11816 11 13 010 4 5908 11 13 011 8 2954 11 13 100 16 1477 11 13 101 32 739 11 13 110 64 369 11 13 111 128 185 i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 205 12.9.8 irsci infrared control register the infrared control register contains the control bits for the infrared sub-module. enables the infrared sub-module selects the infrared transmitter narrow pulse width tnp1 and tnp0 ?transmitter narrow pulse bits these read/write bits select the infrared transmitter narrow pulse width as shown in table 12-10 . reset clears tnp1 and tnp0. iren ?infrared enable bit this read/write bit enables the infrared sub-module for encoding and decoding the sci data stream. when this bit is clear, the infrared sub-module is disabled. reset clears the iren bit. 1 = infrared sub-module enabled 0 = infrared sub-module disabled address: $0047 bit 7654321bit 0 read: r 000 r tnp1 tnp0 iren write: reset:00000000 = unimplemented r = reserved figure 12-20. irsci infrared control register (irscircr) table 12-10. infrared narrow pulse selection tnp1 and tnp0 prescaler divisor (pd) 00 sci transmits a 3/16 narrow pulse 01 sci transmits a 1/16 narrow pulse 10 sci transmits a 1/32 narrow pulse 11 infrared serial communications interface module (irsci) mc68hc908ap a-family data sheet, rev. 2 206 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 205 chapter 13 serial peripheral interface module (spi) 13.1 introduction this section describes the serial peripheral interface (spi) module, which allows full-duplex, synchronous, serial communications with peripheral devices. 13.2 features features of the spi module include the following: full-duplex operation master and slave modes double-buffered operation with separate transmit and receive registers four master mode frequencies (maximum = bus frequency 2) maximum slave mode frequency = bus frequency serial clock with programmable polarity and phase two separately enabled interrupts: sprf (spi receiver full) spte (spi transmitter empty) mode fault error flag with cpu interrupt capability overflow error flag with cpu interrupt capability programmable wired-or mode 13.3 pin name conventions and i/o register addresses the text that follows describes the spi. the spi i/o pin names are ss (slave select), spsck (spi serial clock), cgnd (clock ground), mosi (master out slave in), and miso (master in/slave out). the spi shares four i/o pins with four parallel i/o ports. the full names of the spi i/o pins are shown in table 13-1 . the generic pin names appear in the text that follows. figure 13-1 summarizes the spi i/o registers. table 13-1. pin name conventions spi generic pin names: miso mosi ss spsck cgnd full spi pin names: spi ptc2/miso ptc3/mosi ptc4/ ss ptc5/spsck v ss serial peripheral interface module (spi) mc68hc908ap a-family data sheet, rev. 2 206 freescale semiconductor = 13.4 functional description figure 13-2 shows the structure of the spi module. the spi module allows full-duplex, synchronous, serial communication between the mcu and peripheral devices, including other mcus. software can poll the spi status flags or spi operation can be interrupt-driven. the following paragraphs describe the operation of the spi module. 13.4.1 master mode the spi operates in master mode when the spi master bit, spmstr, is set. note configure the spi modules as master or slave before enabling them. enable the master spi before enabling the slave spi. disable the slave spi before disabling the master spi. (see 13.13.1 spi control register .) only a master spi module can initiate transmissions. software begins the transmission from a master spi module by writing to the transmit data register. if the shift register is empty, the byte immediately transfers to the shift register, setting the spi transmitter empty bit, spte. the byte begins shifting out on the mosi pin under the control of the serial clock. (see figure 13-3 .) the spr1 and spr0 bits control the baud rate generator and determine the speed of the shift register. (see 13.13.2 spi status and control register .) through the spsck pin, the baud rate generator of the master also controls the shift register of the slave peripheral. as the byte shifts out on the mosi pin of the master, another byte shifts in from the slave on the master? miso pin. the transmission ends when the receiver full bit, sprf, becomes set. at the same time that sprf becomes set, the byte from the slave transfers to the receive data register. in normal operation, sprf signals the end of a transmission. software clears sprf by reading the spi status and control register with sprf set and then reading the spi data register. writing to the spi data register clears the spte bit. addr. register name bit 7 654321bit 0 $0010 spi control register (spcr) read: sprie r spmstr cpol cpha spwom spe sptie write: reset:00101000 $0011 spi status and control register (spscr) read: sprf errie ovrf modf spte modfen spr1 spr0 write: reset:00001000 $0012 spi data register (spdr) read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset = unimplemented r = reserved figure 13-1. spi i/o register summary functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 207 figure 13-2. spi module block diagram figure 13-3. full-duplex master-slave connections transmitter cpu interrupt request reserved receiver/error cpu interrupt request 76543210 spr1 spmstr transmit data register shift register spr0 cgmout 2 clock select 2 clock divider 8 32 128 clock logic cpha cpol spi sprie r spe spwom sprf spte ovrf reserved m s pin control logic receive data register sptie spe internal bus from sim modfen errie control modf spmstr mosi miso spsck ss shift register shift register baud rate generator master mcu slave mcu v dd mosi mosi miso miso spsck spsck ss ss serial peripheral interface module (spi) mc68hc908ap a-family data sheet, rev. 2 208 freescale semiconductor 13.4.2 slave mode the spi operates in slave mode when the spmstr bit is clear. in slave mode, the spsck pin is the input for the serial clock from the master mcu. before a data transmission occurs, the ss pin of the slave spi must be at logic 0. ss must remain low until the transmission is complete. (see 13.7.2 mode fault error .) in a slave spi module, data enters the shift register under the control of the serial clock from the master spi module. after a byte enters the shift register of a slave spi, it transfers to the receive data register, and the sprf bit is set. to prevent an overflow condition, slave software then must read the receive data register before another full byte enters the shift register. the maximum frequency of the spsck for an spi configured as a slave is the bus clock speed (which is twice as fast as the fastest master spsck clock that can be generated). the frequency of the spsck for an spi configured as a slave does not have to correspond to any spi baud rate. the baud rate only controls the speed of the spsck generated by an spi configured as a master. therefore, the frequency of the spsck for an spi configured as a slave can be any frequency less than or equal to the bus speed. when the master spi starts a transmission, the data in the slave shift register begins shifting out on the miso pin. the slave can load its shift register with a new byte for the next transmission by writing to its transmit data register. the slave must write to its transmit data register at least one bus cycle before the master starts the next transmission. otherwise, the byte already in the slave shift register shifts out on the miso pin. data written to the slave shift register during a transmission remains in a buffer until the end of the transmission. when the clock phase bit (cpha) is set, the first edge of spsck starts a transmission. when cpha is clear, the falling edge of ss starts a transmission. (see 13.5 transmission formats .) note spsck must be in the proper idle state before the slave is enabled to prevent spsck from appearing as a clock edge. 13.5 transmission formats during an spi transmission, data is simultaneously transmitted (shifted out serially) and received (shifted in serially). a serial clock synchronizes shifting and sampling on the two serial data lines. a slave select line allows selection of an individual slave spi device; slave devices that are not selected do not interfere with spi bus activities. on a master spi device, the slave select line can optionally be used to indicate multiple-master bus contention. 13.5.1 clock phase and polarity controls software can select any of four combinations of serial clock (spsck) phase and polarity using two bits in the spi control register (spcr). the clock polarity is specified by the cpol control bit, which selects an active high or low clock and has no significant effect on the transmission format. the clock phase (cpha) control bit selects one of two fundamentally different transmission formats. the clock phase and polarity should be identical for the master spi device and the communicating slave device. in some cases, the phase and polarity are changed between transmissions to allow a master device to communicate with peripheral slaves having different requirements. note before writing to the cpol bit or the cpha bit, disable the spi by clearing the spi enable bit (spe). transmission formats mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 209 13.5.2 transmission format when cpha = 0 figure 13-4 shows an spi transmission in which cpha is logic 0. the figure should not be used as a replacement for data sheet parametric information. two waveforms are shown for spsck: one for cpol = 0 and another for cpol = 1. the diagram may be interpreted as a master or slave timing diagram since the serial clock (spsck), master in/slave out (miso), and master out/slave in (mosi) pins are directly connected between the master and the slave. the miso signal is the output from the slave, and the mosi signal is the output from the master. the ss line is the slave select input to the slave. the slave spi drives its miso output only when its slave select input ( ss) is at logic 0, so that only the selected slave drives to the master. the ss pin of the master is not shown but is assumed to be inactive. the ss pin of the master must be high or must be reconfigured as general-purpose i/o not affecting the spi. (see 13.7.2 mode fault error .) when cpha = 0, the first spsck edge is the msb capture strobe. therefore, the slave must begin driving its data before the first spsck edge, and a falling edge on the ss pin is used to start the slave data transmission. the slave? ss pin must be toggled back to high and then low again between each byte transmitted as shown in figure 13-5 . figure 13-4. transmission format (cpha = 0) figure 13-5. cpha/ ss timing when cpha = 0 for a slave, the falling edge of ss indicates the beginning of the transmission. this causes the spi to leave its idle state and begin driving the miso pin with the msb of its data. once the transmission begins, no new data is allowed into the shift register from the transmit data register. therefore, the spi data register of the slave must be loaded with transmit data before the falling edge of ss. any data written after the falling edge is stored in the transmit data register and transferred to the shift register after the current transmission. bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 lsb msb bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 lsb msb 12345678 spsck cycle # for reference spsck; cpol = 0 spsck; cpol =1 mosi from master miso from slave ss; to slave capture strobe byte 1 byte 3 miso/mosi byte 2 master ss slave ss cpha = 0 slave ss cpha = 1 serial peripheral interface module (spi) mc68hc908ap a-family data sheet, rev. 2 210 freescale semiconductor 13.5.3 transmission format when cpha = 1 figure 13-6 shows an spi transmission in which cpha is logic 1. the figure should not be used as a replacement for data sheet parametric information. two waveforms are shown for spsck: one for cpol = 0 and another for cpol = 1. the diagram may be interpreted as a master or slave timing diagram since the serial clock (spsck), master in/slave out (miso), and master out/slave in (mosi) pins are directly connected between the master and the slave. the miso signal is the output from the slave, and the mosi signal is the output from the master. the ss line is the slave select input to the slave. the slave spi drives its miso output only when its slave select input ( ss) is at logic 0, so that only the selected slave drives to the master. the ss pin of the master is not shown but is assumed to be inactive. the ss pin of the master must be high or must be reconfigured as general-purpose i/o not affecting the spi. (see 13.7.2 mode fault error .) when cpha = 1, the master begins driving its mosi pin on the first spsck edge. therefore, the slave uses the first spsck edge as a start transmission signal. the ss pin can remain low between transmissions. this format may be preferable in systems having only one master and only one slave driving the miso data line. figure 13-6. transmission format (cpha = 1) when cpha = 1 for a slave, the first edge of the spsck indicates the beginning of the transmission. this causes the spi to leave its idle state and begin driving the miso pin with the msb of its data. once the transmission begins, no new data is allowed into the shift register from the transmit data register. therefore, the spi data register of the slave must be loaded with transmit data before the first edge of spsck. any data written after the first edge is stored in the transmit data register and transferred to the shift register after the current transmission. 13.5.4 transmission initiation latency when the spi is configured as a master (spmstr = 1), writing to the spdr starts a transmission. cpha has no effect on the delay to the start of the transmission, but it does affect the initial state of the spsck signal. when cpha = 0, the spsck signal remains inactive for the first half of the first spsck cycle. when cpha = 1, the first spsck cycle begins with an edge on the spsck line from its inactive to its active level. the spi clock rate (selected by spr1:spr0) affects the delay from the write to spdr and the start of the spi transmission. (see figure 13-7 .) the internal spi clock in the master is a free-running derivative of the internal mcu clock. to conserve power, it is enabled only when both the spe and spmstr bits are set. spsck edges occur halfway through the low time of the internal mcu clock. since the spi clock is free-running, it is uncertain where the write to the spdr occurs relative to the slower spsck. this uncertainty causes the variation in the initiation delay shown in figure 13-7 . this delay is no longer than a single spi bit time. that is, the maximum delay is two mcu bus cycles for div2, eight mcu bus cycles for div8, 32 mcu bus cycles for div32, and 128 mcu bus cycles for div128. bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 lsb msb bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 lsb msb 12345678 spsck cycle # for reference spsck; cpol = 0 spsck; cpol =1 mosi from master miso from slave ss ; to slave capture strobe queuing transmission data mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 211 figure 13-7. transmission start delay (master) 13.6 queuing transmission data the double-buffered transmit data register allows a data byte to be queued and transmitted. for an spi configured as a master, a queued data byte is transmitted immediately after the previous transmission has completed. the spi transmitter empty flag (spte) indicates when the transmit data buffer is ready to accept new data. write to the transmit data register only when the spte bit is high. figure 13-8 shows the timing associated with doing back-to-back transmissions with the spi (spsck has cpha: cpol = 1:0). write to spdr initiation delay bus mosi spsck cpha = 1 spsck cpha = 0 spsck cycle number msb bit 6 12 clock write to spdr earliest latest spsck = internal clock 2; earliest latest 2 possible start points spsck = internal clock 8; 8 possible start points earliest latest spsck = internal clock 32; 32 possible start points earliest latest spsck = internal clock 128; 128 possible start points write to spdr write to spdr write to spdr bus clock bit 5 3 bus clock bus clock bus clock initiation delay from write spdr to transfer begin serial peripheral interface module (spi) mc68hc908ap a-family data sheet, rev. 2 212 freescale semiconductor figure 13-8. sprf/spte cpu interrupt timing the transmit data buffer allows back-to-back transmissions without the slave precisely timing its writes between transmissions as in a system with a single data buffer. also, if no new data is written to the data buffer, the last value contained in the shift register is the next data word to be transmitted. for an idle master or idle slave that has no data loaded into its transmit buffer, the spte is set again no more than two bus cycles after the transmit buffer empties into the shift register. this allows the user to queue up a 16-bit value to send. for an already active slave, the load of the shift register cannot occur until the transmission is completed. this implies that a back-to-back write to the transmit data register is not possible. the spte indicates when the next write can occur. 13.7 error conditions the following flags signal spi error conditions: overflow (ovrf) ?failing to read the spi data register before the next full byte enters the shift register sets the ovrf bit. the new byte does not transfer to the receive data register, and the unread byte still can be read. ovrf is in the spi status and control register. mode fault error (modf) ?the modf bit indicates that the voltage on the slave select pin ( ss) is inconsistent with the mode of the spi. modf is in the spi status and control register. bit 3 mosi spsck spte write to spdr 1 cpu writes byte 2 to spdr, queueing byte 2 cpu writes byte 1 to spdr, clearing spte bit. byte 1 transfers from transmit data 3 1 2 2 3 5 register to shift register, setting spte bit. sprf read spscr msb bit 6 bit 5 bit 4 bit 2 bit 1 lsb msb bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 lsb msb bit 6 byte 2 transfers from transmit data cpu writes byte 3 to spdr, queueing byte byte 3 transfers from transmit data 5 8 10 8 10 4 first incoming byte transfers from shift 6 cpu reads spscr with sprf bit set. 4 6 9 second incoming byte transfers from shift 9 11 and clearing spte bit. register to shift register, setting spte bit. register to receive data register, setting sprf bit. 3 and clearing spte bit. register to shift register, setting spte bit. register to receive data register, setting sprf bit. 12 cpu reads spdr, clearing sprf bit. bit 5 bit 4 byte 1 byte 2 byte 3 7 12 read spdr 7 cpu reads spdr, clearing sprf bit. 11 cpu reads spscr with sprf bit set. cpha:cpol = 1:0 error conditions mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 213 13.7.1 overflow error the overflow flag (ovrf) becomes set if the receive data register still has unread data from a previous transmission when the capture strobe of bit 1 of the next transmission occurs. the bit 1 capture strobe occurs in the middle of spsck cycle 7. (see figure 13-4 and figure 13-6 .) if an overflow occurs, all data received after the overflow and before the ovrf bit is cleared does not transfer to the receive data register and does not set the spi receiver full bit (sprf). the unread data that transferred to the receive data register before the overflow occurred can still be read. therefore, an overflow error always indicates the loss of data. clear the overflow flag by reading the spi status and control register and then reading the spi data register. ovrf generates a receiver/error cpu interrupt request if the error interrupt enable bit (errie) is also set. the sprf, modf, and ovrf interrupts share the same cpu interrupt vector. (see figure 13-11 .) it is not possible to enable modf or ovrf individually to generate a receiver/error cpu interrupt request. however, leaving modfen low prevents modf from being set. if the cpu sprf interrupt is enabled and the ovrf interrupt is not, watch for an overflow condition. figure 13-9 shows how it is possible to miss an overflow. the first part of figure 13-9 shows how it is possible to read the spscr and spdr to clear the sprf without problems. however, as illustrated by the second transmission example, the ovrf bit can be set in between the time that spscr and spdr are read. figure 13-9. missed read of overflow condition in this case, an overflow can be missed easily. since no more sprf interrupts can be generated until this ovrf is serviced, it is not obvious that bytes are being lost as more transmissions are completed. to prevent this, either enable the ovrf interrupt or do another read of the spscr following the read of the spdr. this ensures that the ovrf was not set before the sprf was cleared and that future transmissions can set the sprf bit. figure 13-10 illustrates this process. generally, to avoid this second spscr read, enable the ovrf to the cpu by setting the errie bit. read read ovrf sprf byte 1 byte 2 byte 3 byte 4 byte 1 sets sprf bit. cpu reads spscr with sprf bit set cpu reads byte 1 in spdr, byte 2 sets sprf bit. cpu reads spscr with sprf bit set byte 3 sets ovrf bit. byte 3 is lost. cpu reads byte 2 in spdr, clearing sprf bit, byte 4 fails to set sprf bit because 1 1 2 3 4 5 6 7 8 2 3 4 5 6 7 8 clearing sprf bit. but not ovrf bit. ovrf bit is not cleared. byte 4 is lost. and ovrf bit clear. and ovrf bit clear. spscr spdr serial peripheral interface module (spi) mc68hc908ap a-family data sheet, rev. 2 214 freescale semiconductor figure 13-10. clearing sprf when ovrf interrupt is not enabled 13.7.2 mode fault error setting the spmstr bit selects master mode and configures the spsck and mosi pins as outputs and the miso pin as an input. clearing spmstr selects slave mode and configures the spsck and mosi pins as inputs and the miso pin as an output. the mode fault bit, modf, becomes set any time the state of the slave select pin, ss, is inconsistent with the mode selected by spmstr. to prevent spi pin contention and damage to the mcu, a mode fault error occurs if: the ss pin of a slave spi goes high during a transmission the ss pin of a master spi goes low at any time for the modf flag to be set, the mode fault error enable bit (modfen) must be set. clearing the modfen bit does not clear the modf flag but does prevent modf from being set again after modf is cleared. modf generates a receiver/error cpu interrupt request if the error interrupt enable bit (errie) is also set. the sprf, modf, and ovrf interrupts share the same cpu interrupt vector. (see figure 13-11 .) it is not possible to enable modf or ovrf individually to generate a receiver/error cpu interrupt request. however, leaving modfen low prevents modf from being set. in a master spi with the mode fault enable bit (modfen) set, the mode fault flag (modf) is set if ss goes to logic 0. a mode fault in a master spi causes the following events to occur: if errie = 1, the spi generates an spi receiver/error cpu interrupt request. the spe bit is cleared. the spte bit is set. the spi state counter is cleared. the data direction register of the shared i/o port regains control of port drivers. read read ovrf sprf byte 1 byte 2 byte 3 byte 4 1 byte 1 sets sprf bit. cpu reads spscr with sprf bit set cpu reads byte 1 in spdr, cpu reads spscr again byte 2 sets sprf bit. cpu reads spscr with sprf bit set byte 3 sets ovrf bit. byte 3 is lost. cpu reads byte 2 in spdr, cpu reads spscr again cpu reads byte 2 spdr, byte 4 sets sprf bit. cpu reads spscr. cpu reads byte 4 in spdr, cpu reads spscr again 1 2 3 clearing sprf bit. 4 to check ovrf bit. 5 6 7 8 9 clearing sprf bit. to check ovrf bit. 10 clearing ovrf bit. 11 12 13 14 2 3 4 5 6 7 8 9 10 11 12 13 14 clearing sprf bit. to check ovrf bit. spi receive complete and ovrf bit clear. and ovrf bit clear. spscr spdr interrupts mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 215 note to prevent bus contention with another master spi after a mode fault error, clear all spi bits of the data direction register of the shared i/o port before enabling the spi. when configured as a slave (spmstr = 0), the modf flag is set if ss goes high during a transmission. when cpha = 0, a transmission begins when ss goes low and ends once the incoming spsck goes back to its idle level following the shift of the eighth data bit. when cpha = 1, the transmission begins when the spsck leaves its idle level and ss is already low. the transmission continues until the spsck returns to its idle level following the shift of the last data bit. (see 13.5 transmission formats .) note setting the modf flag does not clear the spmstr bit. the spmstr bit has no function when spe = 0. reading spmstr when modf = 1 shows the difference between a modf occurring when the spi is a master and when it is a slave. when cpha = 0, a modf occurs if a slave is selected ( ss is at logic 0) and later unselected ( ss is at logic 1) even if no spsck is sent to that slave. this happens because ss at logic 0 indicates the start of the transmission (miso driven out with the value of msb) for cpha = 0. when cpha = 1, a slave can be selected and then later unselected with no transmission occurring. therefore, modf does not occur since a transmission was never begun. in a slave spi (mstr = 0), the modf bit generates an spi receiver/error cpu interrupt request if the errie bit is set. the modf bit does not clear the spe bit or reset the spi in any way. software can abort the spi transmission by clearing the spe bit of the slave. note a logic 1 voltage on the ss pin of a slave spi puts the miso pin in a high impedance state. also, the slave spi ignores all incoming spsck clocks, even if it was already in the middle of a transmission. to clear the modf flag, read the spscr with the modf bit set and then write to the spcr register. this entire clearing mechanism must occur with no modf condition existing or else the flag is not cleared. 13.8 interrupts four spi status flags can be enabled to generate cpu interrupt requests. table 13-2. spi interrupts flag request spte transmitter empty spi transmitter cpu interrupt request (sptie = 1, spe = 1) sprf receiver full spi receiver cpu interrupt request (sprie = 1) ovrf over?w spi receiver/error interrupt request (errie = 1) modf mode fault spi receiver/error interrupt request (errie = 1) serial peripheral interface module (spi) mc68hc908ap a-family data sheet, rev. 2 216 freescale semiconductor reading the spi status and control register with sprf set and then reading the receive data register clears sprf. the clearing mechanism for the spte flag is always just a write to the transmit data register. the spi transmitter interrupt enable bit (sptie) enables the spte flag to generate transmitter cpu interrupt requests, provided that the spi is enabled (spe = 1). the spi receiver interrupt enable bit (sprie) enables the sprf bit to generate receiver cpu interrupt requests, regardless of the state of the spe bit. (see figure 13-11 .) the error interrupt enable bit (errie) enables both the modf and ovrf bits to generate a receiver/error cpu interrupt request. the mode fault enable bit (modfen) can prevent the modf flag from being set so that only the ovrf bit is enabled by the errie bit to generate receiver/error cpu interrupt requests. figure 13-11. spi interrupt request generation the following sources in the spi status and control register can generate cpu interrupt requests: spi receiver full bit (sprf) the sprf bit becomes set every time a byte transfers from the shift register to the receive data register. if the spi receiver interrupt enable bit, sprie, is also set, sprf generates an spi receiver/error cpu interrupt request. spi transmitter empty (spte) the spte bit becomes set every time a byte transfers from the transmit data register to the shift register. if the spi transmit interrupt enable bit, sptie, is also set, spte generates an spte cpu interrupt request. 13.9 resetting the spi any system reset completely resets the spi. partial resets occur whenever the spi enable bit (spe) is low. whenever spe is low, the following occurs: the spte flag is set. any transmission currently in progress is aborted. spte sptie sprf sprie r errie modf ovrf spe cpu interrupt request cpu interrupt request not available spi transmitter not available spi receiver/error low-power modes mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 217 the shift register is cleared. the spi state counter is cleared, making it ready for a new complete transmission. all the spi port logic is defaulted back to being general-purpose i/o. these items are reset only by a system reset: all control bits in the spcr register all control bits in the spscr register (modfen, errie, spr1, and spr0) the status flags sprf, ovrf, and modf by not resetting the control bits when spe is low, the user can clear spe between transmissions without having to set all control bits again when spe is set back high for the next transmission. by not resetting the sprf, ovrf, and modf flags, the user can still service these interrupts after the spi has been disabled. the user can disable the spi by writing 0 to the spe bit. the spi can also be disabled by a mode fault occurring in an spi that was configured as a master with the modfen bit set. 13.10 low-power modes the wait and stop instructions put the mcu in low power-consumption standby modes. 13.10.1 wait mode the spi module remains active after the execution of a wait instruction. in wait mode the spi module registers are not accessible by the cpu. any enabled cpu interrupt request from the spi module can bring the mcu out of wait mode. if spi module functions are not required during wait mode, reduce power consumption by disabling the spi module before executing the wait instruction. to exit wait mode when an overflow condition occurs, enable the ovrf bit to generate cpu interrupt requests by setting the error interrupt enable bit (errie). (see 13.8 interrupts .) 13.10.2 stop mode the spi module is inactive after the execution of a stop instruction. the stop instruction does not affect register conditions. spi operation resumes after an external interrupt. if stop mode is exited by reset, any transfer in progress is aborted, and the spi is reset. 13.11 spi during break interrupts the system integration module (sim) controls whether status bits in other modules can be cleared during the break state. the bcfe bit in the sim break flag control register (sbfcr) enables software to clear status bits during the break state. (see chapter 7 system integration module (sim) .) to allow software to clear status bits during a break interrupt, write a logic 1 to the bcfe bit. if a status bit is cleared during the break state, it remains cleared when the mcu exits the break state. to protect status bits during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), software can read and write i/o registers during the break state without affecting status bits. some status bits have a 2-step read/write clearing procedure. if software does the first step on such a bit before the break, the bit cannot change during the break state as long as bcfe is at logic 0. after the break, doing the second step clears the status bit. serial peripheral interface module (spi) mc68hc908ap a-family data sheet, rev. 2 218 freescale semiconductor since the spte bit cannot be cleared during a break with the bcfe bit cleared, a write to the transmit data register in break mode does not initiate a transmission nor is this data transferred into the shift register. therefore, a write to the spdr in break mode with the bcfe bit cleared has no effect. 13.12 i/o signals the spi module has five i/o pins and shares four of them with a parallel i/o port. they are: miso ?data received mosi ?data transmitted spsck ?serial clock ss ?slave select cgnd ?clock ground (internally connected to v ss ) the spi has limited inter-integrated circuit (i 2 c) capability (requiring software support) as a master in a single-master environment. to communicate with i 2 c peripherals, mosi becomes an open-drain output when the spwom bit in the spi control register is set. in i 2 c communication, the mosi and miso pins are connected to a bidirectional pin from the i 2 c peripheral and through a pullup resistor to v dd . 13.12.1 miso (master in/slave out) miso is one of the two spi module pins that transmits serial data. in full duplex operation, the miso pin of the master spi module is connected to the miso pin of the slave spi module. the master spi simultaneously receives data on its miso pin and transmits data from its mosi pin. slave output data on the miso pin is enabled only when the spi is configured as a slave. the spi is configured as a slave when its spmstr bit is logic 0 and its ss pin is at logic 0. to support a multiple-slave system, a logic 1 on the ss pin puts the miso pin in a high-impedance state. when enabled, the spi controls data direction of the miso pin regardless of the state of the data direction register of the shared i/o port. 13.12.2 mosi (master out/slave in) mosi is one of the two spi module pins that transmits serial data. in full-duplex operation, the mosi pin of the master spi module is connected to the mosi pin of the slave spi module. the master spi simultaneously transmits data from its mosi pin and receives data on its miso pin. when enabled, the spi controls data direction of the mosi pin regardless of the state of the data direction register of the shared i/o port. 13.12.3 spsck (serial clock) the serial clock synchronizes data transmission between master and slave devices. in a master mcu, the spsck pin is the clock output. in a slave mcu, the spsck pin is the clock input. in full-duplex operation, the master and slave mcus exchange a byte of data in eight serial clock cycles. when enabled, the spi controls data direction of the spsck pin regardless of the state of the data direction register of the shared i/o port. i/o signals mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 219 13.12.4 ss (slave select) the ss pin has various functions depending on the current state of the spi. for an spi configured as a slave, the ss is used to select a slave. for cpha = 0, the ss is used to define the start of a transmission. (see 13.5 transmission formats .) since it is used to indicate the start of a transmission, the ss must be toggled high and low between each byte transmitted for the cpha = 0 format. however, it can remain low between transmissions for the cpha = 1 format. see figure 13-12 . figure 13-12. cpha/ ss timing when an spi is configured as a slave, the ss pin is always configured as an input. it cannot be used as a general-purpose i/o regardless of the state of the modfen control bit. however, the modfen bit can still prevent the state of the ss from creating a modf error. (see 13.13.2 spi status and control register .) note a logic 1 voltage on the ss pin of a slave spi puts the miso pin in a high-impedance state. the slave spi ignores all incoming spsck clocks, even if it was already in the middle of a transmission. when an spi is configured as a master, the ss input can be used in conjunction with the modf flag to prevent multiple masters from driving mosi and spsck. (see 13.7.2 mode fault error .) for the state of the ss pin to set the modf flag, the modfen bit in the spsck register must be set. if the modfen bit is low for an spi master, the ss pin can be used as a general-purpose i/o under the control of the data direction register of the shared i/o port. with modfen high, it is an input-only pin to the spi regardless of the state of the data direction register of the shared i/o port. the cpu can always read the state of the ss pin by configuring the appropriate pin as an input and reading the port data register. (see table 13-3 .) table 13-3. spi con?uration spe spmstr modfen spi configuration state of ss logic 0 x (1) x not enabled general-purpose i/o; ss ignored by spi 1 0 x slave input-only to spi 1 1 0 master without modf general-purpose i/o; ss ignored by spi 1 1 1 master with modf input-only to spi note 1. x = don? care byte 1 byte 3 miso/mosi byte 2 master ss slave ss cpha = 0 slave ss cpha = 1 serial peripheral interface module (spi) mc68hc908ap a-family data sheet, rev. 2 220 freescale semiconductor 13.12.5 cgnd (clock ground) cgnd is the ground return for the serial clock pin, spsck, and the ground for the port output buffers. it is internally connected to v ss as shown in table 13-1 . 13.13 i/o registers three registers control and monitor spi operation: spi control register (spcr) spi status and control register (spscr) spi data register (spdr) 13.13.1 spi control register the spi control register: enables spi module interrupt requests configures the spi module as master or slave selects serial clock polarity and phase configures the spsck, mosi, and miso pins as open-drain outputs enables the spi module sprie ?spi receiver interrupt enable bit this read/write bit enables cpu interrupt requests generated by the sprf bit. the sprf bit is set when a byte transfers from the shift register to the receive data register. reset clears the sprie bit. 1 = sprf cpu interrupt requests enabled 0 = sprf cpu interrupt requests disabled spmstr ?spi master bit this read/write bit selects master mode operation or slave mode operation. reset sets the spmstr bit. 1 = master mode 0 = slave mode cpol ?clock polarity bit this read/write bit determines the logic state of the spsck pin between transmissions. (see figure 13-4 and figure 13-6 .) to transmit data between spi modules, the spi modules must have identical cpol values. reset clears the cpol bit. cpha ?clock phase bit address: $0010 bit 7654321bit 0 read: sprie r spmstr cpol cpha spwom spe sptie write: reset:00101000 = unimplemented r = reserved figure 13-13. spi control register (spcr) i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 221 this read/write bit controls the timing relationship between the serial clock and spi data. (see figure 13-4 and figure 13-6 .) to transmit data between spi modules, the spi modules must have identical cpha values. when cpha = 0, the ss pin of the slave spi module must be set to logic 1 between bytes. (see figure 13-12 .) reset sets the cpha bit. serial peripheral interface module (spi) mc68hc908ap a-family data sheet, rev. 2 222 freescale semiconductor spwom ?spi wired-or mode bit this read/write bit disables the pullup devices on pins spsck, mosi, and miso so that those pins become open-drain outputs. 1 = wired-or spsck, mosi, and miso pins 0 = normal push-pull spsck, mosi, and miso pins spe ?spi enable this read/write bit enables the spi module. clearing spe causes a partial reset of the spi. (see 13.9 resetting the spi .) reset clears the spe bit. 1 = spi module enabled 0 = spi module disabled sptie?spi transmit interrupt enable this read/write bit enables cpu interrupt requests generated by the spte bit. spte is set when a byte transfers from the transmit data register to the shift register. reset clears the sptie bit. 1 = spte cpu interrupt requests enabled 0 = spte cpu interrupt requests disabled 13.13.2 spi status and control register the spi status and control register contains flags to signal these conditions: receive data register full failure to clear sprf bit before next byte is received (overflow error) inconsistent logic level on ss pin (mode fault error) transmit data register empty the spi status and control register also contains bits that perform these functions: enable error interrupts enable mode fault error detection select master spi baud rate sprf ?spi receiver full bit this clearable, read-only flag is set each time a byte transfers from the shift register to the receive data register. sprf generates a cpu interrupt request if the sprie bit in the spi control register is set also. during an sprf cpu interrupt, the cpu clears sprf by reading the spi status and control register with sprf set and then reading the spi data register. reset clears the sprf bit. 1 = receive data register full 0 = receive data register not full address $0011 bit 7654321bit 0 read: sprf errie ovrf modf spte modfen spr1 spr0 write: reset:00001000 = unimplemented figure 13-14. spi status and control register (spscr) i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 223 errie ?error interrupt enable bit this read/write bit enables the modf and ovrf bits to generate cpu interrupt requests. reset clears the errie bit. 1 = modf and ovrf can generate cpu interrupt requests 0 = modf and ovrf cannot generate cpu interrupt requests ovrf ?over?w bit this clearable, read-only flag is set if software does not read the byte in the receive data register before the next full byte enters the shift register. in an overflow condition, the byte already in the receive data register is unaffected, and the byte that shifted in last is lost. clear the ovrf bit by reading the spi status and control register with ovrf set and then reading the receive data register. reset clears the ovrf bit. 1 = overflow 0 = no overflow modf ?mode fault bit this clearable, read-only flag is set in a slave spi if the ss pin goes high during a transmission with the modfen bit set. in a master spi, the modf flag is set if the ss pin goes low at any time with the modfen bit set. clear the modf bit by reading the spi status and control register (spscr) with modf set and then writing to the spi control register (spcr). reset clears the modf bit. 1 = ss pin at inappropriate logic level 0 = ss pin at appropriate logic level spte ?spi transmitter empty bit this clearable, read-only flag is set each time the transmit data register transfers a byte into the shift register. spte generates an spte cpu interrupt request if the sptie bit in the spi control register is set also. note do not write to the spi data register unless the spte bit is high. during an spte cpu interrupt, the cpu clears the spte bit by writing to the transmit data register. reset sets the spte bit. 1 = transmit data register empty 0 = transmit data register not empty modfen ?mode fault enable bit this read/write bit, when set to 1, allows the modf flag to be set. if the modf flag is set, clearing the modfen does not clear the modf flag. if the spi is enabled as a master and the modfen bit is low, then the ss pin is available as a general-purpose i/o. if the modfen bit is set, then this pin is not available as a general-purpose i/o. when the spi is enabled as a slave, the ss pin is not available as a general-purpose i/o regardless of the value of modfen. (see 13.12.4 ss (slave select) .) if the modfen bit is low, the level of the ss pin does not affect the operation of an enabled spi configured as a master. for an enabled spi configured as a slave, having modfen low only prevents the modf flag from being set. it does not affect any other part of spi operation. (see 13.7.2 mode fault error .) spr1 and spr0 ?spi baud rate select bits in master mode, these read/write bits select one of four baud rates as shown in table 13-4 . spr1 and spr0 have no effect in slave mode. reset clears spr1 and spr0. serial peripheral interface module (spi) mc68hc908ap a-family data sheet, rev. 2 224 freescale semiconductor use this formula to calculate the spi baud rate: where: cgmout = base clock output of the clock generator module (cgm) bd = baud rate divisor 13.13.3 spi data register the spi data register consists of the read-only receive data register and the write-only transmit data register. writing to the spi data register writes data into the transmit data register. reading the spi data register reads data from the receive data register. the transmit data and receive data registers are separate registers that can contain different values. (see figure 13-2 .) r7?0/t7?0 ?receive/transmit data bits note do not use read-modify-write instructions on the spi data register since the register read is not the same as the register written. table 13-4. spi master baud rate selection spr1 and spr0 baud rate divisor (bd) 00 2 01 8 10 32 11 128 address: $0012 bit 7654321bit 0 read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset figure 13-15. spi data register (spdr) baud rate cgmout 2bd -------------------------- = mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 225 chapter 14 multi-master iic interface (mmiic) 14.1 introduction the multi-master iic (mmiic) interface is a two wire, bidirectional serial bus which provides a simple, efficient way for data exchange between devices. the interface is designed for internal serial communication between the mcu and other iic devices. it has hardware generated start and stop signals; and byte by byte interrupt driven software algorithm. this bus is suitable for applications which need frequent communications over a short distance between a number of devices. it also provides a flexibility that allows additional devices to be connected to the bus. the maximum data rate is 100k-bps, and the maximum communication distance and number of devices that can be connected is limited by a maximum bus capacitance of 400pf. this mmiic interface is also smbus (system management bus) version 1.0 and 1.1 compatible, with hardware cyclic redundancy code (crc) generation, making it suitable for smart battery applications. 14.2 features features of the mmic module include: full smbus version 1.0/1.1 compliance multi-master iic bus standard software programmable for one of eight different serial clock frequencies software controllable acknowledge bit generation interrupt driven byte by byte data transfer calling address identification interrupt arbitration loss detection and no-ack awareness in master mode and automatic mode switching from master to slave auto detection of r/w bit and switching of transmit or receive mode accordingly detection of start, repeated start, and stop signals auto generation of start and stop condition in master mode repeated start generation master clock generator with eight selectable baud rates automatic recognition of the received acknowledge bit busy detection software enabled 8-bit crc generation/decoding multi-master iic interface (mmiic) mc68hc908ap a-family data sheet, rev. 2 226 freescale semiconductor 14.3 i/o pins the mmiic module uses two i/o pins, shared with standard port i/o pins. the full name of the mmiic i/o pins are listed in table 14-1 . the generic pin name appear in the text that follows. the sda and sdl pins are open-drain. when configured as general purpose output pins (ptb0 and ptb1), pullup resistors must be connected to these pins. 14.4 multi-master iic system configuration the multi-master iic system uses a serial data line sda and a serial clock line scl for data transfer. all devices connected to it must have open collector (drain) outputs and the logical-and function is performed on both lines by two pull-up resistors. table 14-1. pin name conventions mmiic generic pin names: full mcu pin names: pin selected for mmiic function by: sda ptb0/sda mmen bit in mmcr1 ($0049) scl ptb1/scl addr. register name bit 7 654321bit 0 $0048 mmiic address register (mmadr) read: mmad7 mmad6 mmad5 mmad4 mmad3 mmad2 mmad1 mmextad write: reset:10100000 $0049 mmiic control register 1 (mmcr1) read: mmen mmien 00 mmtxak repsen mmcrcbyte 0 write: mmclrbb reset:00000000 $004a mmiic control register 2 (mmcr2) read: mmalif mmnakif mmbb mmast mmrw 00 mmcrcef write: 0 0 reset:0000000un affected $004b mmiic status register (mmsr) read: mmrxif mmtxif mmatch mmsrw mmrxak mmcrcbf mmtxbe mmrxbf write: 0 0 reset:00001010 $004c mmiic data transmit register (mmdtr) read: mmtd7 mmtd6 mmtd5 mmtd4 mmtd3 mmtd2 mmtd1 mmtd0 write: reset:00000000 $004d mmiic data receive register (mddrr) read: mmrd7 mmrd6 mmrd5 mmrd4 mmrd3 mmrd2 mmrd1 mmrd0 write: reset:00000000 $004e mmiic crc data register (mmcrdr) read: mmcrcd7 mmcrcd6 mmcrcd5 mmcrcd4 mmcrcd3 mmcrcd2 mmcrcd1 mmcrcd0 write: reset:00000000 $004f mmiic frequency divider register (mmfdr) read: 00000 mmbr2 mmbr1 mmbr0 write: reset:00000100 = unimplemented figure 14-1. mmiic i/o register summary multi-master iic bus protocol mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 227 14.5 multi-master iic bus protocol normally a standard communication is composed of four parts: 1. start signal, 2. slave address transmission, 3. data transfer, and 4. stop signal. these are described briefly in the following sections and illustrated in figure 14-2 . figure 14-2. multi-master iic bus transmission signal diagram 14.5.1 start signal when the bus is free, (i.e. no master device is engaging the bus both scl and sda lines are at logic high) a master may initiate communication by sending a start signal. as shown in figure 14-2 , a start signal is defined as a high to low transition of sda while scl is high. this signal denotes the beginning of a new data transfer (each data transfer may contain several bytes of data) and wakes up all slaves. 14.5.2 slave address transmission the first byte transferred immediately after the start signal is the slave address transmitted by the master. this is a 7-bit calling address followed by a r/w-bit. the r/w-bit dictates to the slave the desired direction of the data transfer. a logic 0 indicates that the master wishes to transmit data to the slave; a logic 1 indicates that the master wishes to receive data from the slave. 10 1 00011 1 0 1 10011 10 1 00011 1 0 1 10011 scl sda scl sda msb lsb msb lsb msb lsb msb lsb start stop repeated start stop 9th clock pulse 9th clock pulse ack no ack signal signal signal signal signal ack no ack start data must be stable when scl is high multi-master iic interface (mmiic) mc68hc908ap a-family data sheet, rev. 2 228 freescale semiconductor only the slave with a matched address will respond by sending back an acknowledge bit by pulling sda low on the 9th clock cycle. (see figure 14-2 .) 14.5.3 data transfer once a successful slave addressing is achieved, the data transfer can proceed byte by byte in the direction specified by the r/w-bit sent by the calling master. each data byte is 8 bits. data can be changed only when scl is low and must be held stable when scl is high as shown in figure 14-2 . the msb is transmitted first and each byte has to be followed by an acknowledge bit. this is signalled by the receiving device by pulling the sda low on the 9th clock cycle. therefore, one complete data byte transfer requires 9 clock cycles. if the slave receiver does not acknowledge the master, the sda line should be left high by the slave. the master can then generate a stop signal to abort the data transfer or a start signal (repeated start) to commence a new transfer. if the master receiver does not acknowledge the slave transmitter after a byte has been transmitted, it means an ?nd of data to the slave. the slave should release the sda line for the master to generate a stop or start signal. 14.5.4 repeated start signal as shown in figure 14-2 , a repeated start signal is used to generate start signal without first generating a stop to terminate the communication. this is used by the master to communicate with another slave or with the same slave in a different mode (transmit/receive mode) without releasing the bus. 14.5.5 stop signal the master can terminate the communication by generating a stop signal to free the bus. however, the master may generate a start signal followed by a calling command without first generating a stop signal. this is called repeat start. a stop signal is defined as a low to high transition of sda while scl is at logic high (see figure 14-2 ). 14.5.6 arbitration procedure the interface circuit is a multi-master system which allows more than one master to be connected. if two or more masters try to control the bus at the same time, a clock synchronization procedure determines the bus clock. the clock low period is equal to the longest clock low period and the clock high period is equal to the shortest one among the masters. a data arbitration procedure determines the priority. a master will lose arbitration if it transmits a logic 1 while another transmits a logic 0. the losing master will immediately switch over to slave receive mode and stops its data and clock outputs. the transition from master to slave will not generate a stop condition. meanwhile a software bit will be set by hardware to indicates loss of arbitration. 14.5.7 clock synchronization since wired-and logic is performed on scl line, a high to low transition on the scl line will affect the devices connected to the bus. the devices start counting their low period once a device? clock has gone low, it will hold the scl line low until the clock high state is reached. however, the change of low to high mmiic i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 229 in this device clock may not change the state of the scl line if another device clock is still in its low period. therefore the synchronized clock scl will be held low by the device which last releases scl to logic high. devices with shorter low periods enter a high wait state during this time. when all devices concerned have counted off their low period, the synchronized scl line will be released and go high, and all devices will start counting their high periods. the first device to complete its high period will again pull the scl line low. figure 14-3 illustrates the clock synchronization waveforms. figure 14-3. clock synchronization 14.5.8 handshaking the clock synchronization mechanism can be used as a handshake in data transfer. a slave device may hold the scl low after completion of one byte data transfer and will halt the bus clock, forcing the master clock into a wait state until the slave releases the scl line. 14.5.9 packet error code the packet error code (pec) for the mmiic interface is in the form a cyclic redundancy code (crc). the pec is generated by hardware for every transmitted and received byte of data. the transmission of the generated pec is controlled by user software. the crc data register, mmcrcdr, contains the generated pec byte, with three other bits in the mmiic control registers and status register monitoring and controlling the pec byte. 14.6 mmiic i/o registers these i/o registers control and monitor mmiic operation: mmiic address register (mmadr) ?$0048 mmiic control register 1 (mmcr1) ?$0049 mmiic control register 2 (mmcr2) ?$004a mmiic status register (mmsr) ?$004b mmiic data transmit register (mmdtr) ?$004c mmiic data receive register (mmdrr) ?$004d mmiic crc data register (mmcrcdr) ?$004e mmiic frequency divide register (mmfdr) ?$004f scl1 scl2 scl internal counter reset wait start counting high period multi-master iic interface (mmiic) mc68hc908ap a-family data sheet, rev. 2 230 freescale semiconductor 14.6.1 mmiic address register (mmadr) mmad[7:1] ?multi-master address these seven bits represent the mmiic interface? own specific slave address when in slave mode, and the calling address when in master mode. software must update mmad[7:1] as the calling address while entering master mode and restore its own slave address after master mode is relinquished. this register is cleared as $a0 upon reset. mmextad ?multi-master expanded address this bit is set to expand the address of the mmiic in slave mode. when set, the mmiic will acknowledge the following addresses from a calling master: $mmad[7:1], 0000000, and 0001100. reset clears this bit. 1 = mmiic responds to the following calling addresses: $mmad[7:1], 0000000, and 0001100. 0 = mmiic responds to address $mmad[7:1] for example, when mmadr is configured as: the mmiic module will respond to the calling address: or the general calling address: or the calling address: note that bit-0 of the 8-bit calling address is the mmrw bit from the calling master. address: $0048 bit 7654321bit 0 read: mmad7 mmad6 mmad5 mmad4 mmad3 mmad2 mmad1 mmextad write: reset: 10100000 figure 14-4. mmiic address register (mmadr) mmad7 mmad6 mmad5 mmad4 mmad3 mmad2 mmad1 mmextad 11010101 bit 765432bit 1 1101010 0000000 bit 765432bit 1 0001100 mmiic i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 231 14.6.2 mmiic control register 1 (mmcr1) mmen ?mmiic enable this bit is set to enable the multi-master iic module. when mmen = 0, module is disabled and all flags will restore to its power-on default states. reset clears this bit. 1 = mmiic module enabled 0 = mmiic module disabled mmien ?mmiic interrupt enable when this bit is set, the mmtxif, mmrxif, mmalif, and mmnakif flags are enabled to generate an interrupt request to the cpu. when mmien is cleared, the these flags are prevented from generating an interrupt request. reset clears this bit. 1 = mmtxif, mmrxif, mmalif, and/or mmnakif bit set will generate interrupt request to cpu 0 = mmtxif, mmrxif, mmalif, and/or mmnakif bit set will not generate interrupt request to cpu mmclrbb ?mmiic clear busy flag writing a logic 1 to this write-only bit clears the mmbb flag. mmclrbb always reads as a logic 0. reset clears this bit. 1 = clear mmbb flag 0 = no affect on mmbb flag mmtxak ?mmiic transmit acknowledge enable this bit is set to disable the mmiic from sending out an acknowledge signal to the bus at the 9th clock bit after receiving 8 data bits. when mmtxak is cleared, an acknowledge signal will be sent at the 9th clock bit. reset clears this bit. 1 = mmiic does not send acknowledge signals at 9th clock bit 0 = mmiic sends acknowledge signal at 9th clock bit repsen ?repeated start enable this bit is set to enable repeated start signal to be generated when in master mode transfer (mmast = 1). the repsen bit is cleared by hardware after the completion of repeated start signal or when the mmast bit is cleared. reset clears this bit. 1 = repeated start signal will be generated if mmast bit is set 0 = no repeated start signal will be generated mmcrcbyte ?mmiic crc byte in receive mode, this bit is set by software to indicate that the next receiving byte will be the packet error checking (pec) data. in master receive mode, after completion of crc generation on the received pec data, an acknowledge signal is sent if mmtxak = 0; no acknowledge is sent if mmtxak = 1. in slave receive mode, no acknowledge signal is sent if a crc error is detected on the received pec data. if no crc error is detected, an acknowledge signal is sent if mmtxak = 0; no acknowledge is sent if mmtxak = 1. address: $0049 bit 7654321bit 0 read: mmen mmien 00 mmtxak repsen mmcrcbyte 0 write: mmclrbb reset:00000000 = unimplemented figure 14-5. mmiic control register 1 (mmcr1) multi-master iic interface (mmiic) mc68hc908ap a-family data sheet, rev. 2 232 freescale semiconductor under normal operation, the user software should clear mmtxak bit before setting mmcrcbyte bit to ensure that an acknowledge signal is sent when no crc error is detected. the mmcrcbyte bit should not be set in transmit mode. this bit is cleared by the next start signal. reset also clears this bit. 1 = next receiving byte is the packet error checking (pec) data 0 = next receiving byte is not pec data 14.6.3 mmiic control register 2 (mmcr2) mmalif ?arbitration loss interrupt flag this flag is set when software attempt to set mmast but the mmbb has been set by detecting the start condition on the lines or when the mmiic is transmitting a "1" to sda line but detected a "0" from sda line in master mode ?an arbitration loss. this bit generates an interrupt request to the cpu if the mmien bit in mmcr1 is set. this bit is cleared by writing "0" to it or by reset. 1 = lost arbitration in master mode 0 = no arbitration lost mmnakif ?no acknowledge interrupt flag (master mode) this flag is only set in master mode (mmast = 1) when there is no acknowledge bit detected after one data byte or calling address is transferred. this flag also clears mmast. mmnakif generates an interrupt request to cpu if the mmien bit in mmcr1 is set. this bit is cleared by writing "0" to it or by reset. 1 = no acknowledge bit detected 0 = acknowledge bit detected mmbb ?mmiic bus busy flag this flag is set after a start condition is detected (bus busy), and is cleared when a stop condition (bus idle) is detected or the mmiic is disabled. reset clears this bit. 1 = start condition detected 0 = stop condition detected or mmiic is disabled mmast ?mmiic master control this bit is set to initiate a master mode transfer. in master mode, the module generates a start condition to the sda and scl lines, followed by sending the calling address stored in mmadr. when the mmast bit is cleared by mmnakif set (no acknowledge) or by software, the module generates the stop condition to the lines after the current byte is transmitted. if an arbitration loss occurs (mmalif = 1), the module reverts to slave mode by clearing mmast, and releasing sda and scl lines immediately. this bit is cleared by writing "0" to it or by reset. 1 = master mode operation 0 = slave mode operation address: $004a bit 7654321bit 0 read: mmalif mmnakif mmbb mmast mmrw 00 mmcrcef write: 0 0 reset:0000000un affected = unimplemented figure 14-6. mmiic control register 2 (mmcr2) mmiic i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 233 mmrw ?mmiic master read/write this bit is transmitted out as bit 0 of the calling address when the module sets the mmast bit to enter master mode. the mmrw bit determines the transfer direction of the data bytes that follows. when it is "1", the module is in master receive mode. when it is "0", the module is in master transmit mode. reset clears this bit. 1 = master mode receive 0 = master mode transmit mmcrcef ?mmiic crc error flag this flag is set when a crc error is detected, and cleared when no crc error is detected. the mmcrcef is only meaningful after receiving a pec data. this flag is unaffected by reset. 1 = crc error detected on pec byte 0 = no crc error detected on pec byte 14.6.4 mmiic status register (mmsr) mmrxif ?mmiic receive interrupt flag this flag is set after the data receive register (mmdrr) is loaded with a new received data. once the mmdrr is loaded with received data, no more received data can be loaded to the mmdrr register until the cpu reads the data from the mmdrr to clear mmrxbf flag. mmrxif generates an interrupt request to cpu if the mmien bit in mmcr is also set. this bit is cleared by writing "0" to it or by reset; or when the mmen = 0. 1 = new data in data receive register (mmdrr) 0 = no data received mmtxif ?mmiic transmit interrupt flag this flag is set when data in the data transmit register (mmdtr) is downloaded to the output circuit, and that new data can be written to the mmdtr. mmtxif generates an interrupt request to cpu if the mmien bit in mmcr is also set. this bit is cleared by writing "0" to it or when the mmen = 0. 1 = data transfer completed 0 = data transfer in progress mmatch ?mmiic address match flag this flag is set when the received data in the data receive register (mmdrr) is a calling address which matches with the address or its extended addresses (mmextad = 1) specified in the address register (mmadr). the mmatch flag is set at the 9th clock of the calling address and will be cleared on the 9th clock of the next receiving data. note: slave transmits do not clear mmatch. 1 = received address matches mmadr 0 = received address does not match address: $004b bit 7654321bit 0 read: mmrxif mmtxif mmatch mmsrw mmrxak mmcrcbf mmtxbe mmrxbf write: 00 reset: 00001010 = unimplemented figure 14-7. mmiic status register (mmsr) multi-master iic interface (mmiic) mc68hc908ap a-family data sheet, rev. 2 234 freescale semiconductor mmsrw ?mmiic slave read/write select this bit indicates the data direction when the module is in slave mode. it is updated after the calling address is received from a master device. mmsrw = 1 when the calling master is reading data from the module (slave transmit mode). mmsrw = 0 when the master is writing data to the module (receive mode). 1 = slave mode transmit 0 = slave mode receive mmrxak ?mmiic receive acknowledge when this bit is cleared, it indicates an acknowledge signal has been received after the completion of eight data bits transmission on the bus. when mmrxak is set, it indicates no acknowledge signal has been detected at the 9th clock; the module will release the sda line for the master to generate stop or repeated start condition. reset sets this bit. 1 = no acknowledge signal received at 9th clock 0 = acknowledge signal received at 9th clock mmcrcbf ?crc data buffer full flag this flag is set when the crc data register (mmcrcdr) is loaded with a crc byte for the current received or transmitted data. in transmit mode, after a byte of data has been sent (mmtxif = 1), the mmcrcbf will be set when the crc byte has been generated and ready in the mmcrcdr. the content of the mmcrcdr should be copied to the mmdtr for transmission. in receive mode, the mmcrcbf is set when the crc byte has been generated and ready in mmcrcdr, for the current byte of received data. the mmcrcbf bit is cleared when the crc data register is read. reset also clears this bit. 1 = data ready in crc data register (mmcrcdr) 0 = data not ready in crc data register (mmcrcdr) mmtxbe ?mmiic transmit buffer empty this flag indicates the status of the data transmit register (mmdtr). when the cpu writes the data to the mmdtr, the mmtxbe flag will be cleared. mmtxbe is set when mmdtr is emptied by a transfer of its data to the output circuit. reset sets this bit. 1 = data transmit register empty 0 = data transmit register full mmrxbf ?mmiic receive buffer full this flag indicates the status of the data receive register (mmdrr). when the cpu reads the data from the mmdrr, the mmrxbf flag will be cleared. mmrxbf is set when mmdrr is full by a transfer of data from the input circuit to the mmdrr. reset clears this bit. 1 = data receive register full 0 = data receive register empty 14.6.5 mmiic data transmit register (mmdtr) address: $004c bit 7654321bit 0 read: mmtd7 mmtd6 mmtd5 mmtd4 mmtd3 mmtd2 mmtd1 mmtd0 write: reset:00000000 figure 14-8. mmiic data transmit register (mmdtr) mmiic i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 235 when the mmiic module is enabled, mmen = 1, data written into this register depends on whether module is in master or slave mode. in slave mode, the data in mmdtr will be transferred to the output circuit when: the module detects a matched calling address (mmatch = 1), with the calling master requesting data (mmsrw = 1); or the previous data in the output circuit has be transmitted and the receiving master returns an acknowledge bit, indicated by a received acknowledge bit (mmrxak = 0). if the calling master does not return an acknowledge bit (mmrxak = 1), the module will release the sda line for master to generate a stop or repeated start condition. the data in the mmdtr will not be transferred to the output circuit until the next calling from a master. the transmit buffer empty flag remains cleared (mmtxbe = 0). in master mode, the data in mmdtr will be transferred to the output circuit when: the module receives an acknowledge bit (mmrxak = 0), after setting master transmit mode (mmrw = 0), and the calling address has been transmitted; or the previous data in the output circuit has be transmitted and the receiving slave returns an acknowledge bit, indicated by a received acknowledge bit (mmrxak = 0). if the slave does not return an acknowledge bit (mmrxak = 1), the master will generate a stop or repeated start condition. the data in the mmdtr will not be transferred to the output circuit. the transmit buffer empty flag remains cleared (mmtxbe = 0). the sequence of events for slave transmit and master transmit are illustrated in figure 14-12 . 14.6.6 mmiic data receive register (mmdrr) when the mmiic module is enabled, mmen = 1, data in this read-only register depends on whether module is in master or slave mode. in slave mode, the data in mmdrr is: the calling address from the master when the address match flag is set (mmatch = 1); or the last data received when mmatch = 0. in master mode, the data in the mmdrr is: the last data received. when the mmdrr is read by the cpu, the receive buffer full flag is cleared (mmrxbf = 0), and the next received data is loaded to the mmdrr. each time when new data is loaded to the mmdrr, the mmrxif interrupt flag is set, indicating that new data is available in mmdrr. the sequence of events for slave receive and master receive are illustrated in figure 14-12 . address: $004d bit 7654321bit 0 read: mmrd7 mmrd6 mmrd5 mmrd4 mmrd3 mmrd2 mmrd1 mmrd0 write: reset:00000000 = unimplemented figure 14-9. mmiic data receive register (mmdrr) multi-master iic interface (mmiic) mc68hc908ap a-family data sheet, rev. 2 236 freescale semiconductor 14.6.7 mmiic crc data register (mmcrcdr) when the mmiic module is enabled, mmen = 1, and the crc buffer full flag is set (mmcrcbf = 1), data in this read-only register contains the generated crc byte for the last byte of received or transmitted data. a crc byte is generated for each received and transmitted data byte and loaded to the crc data register. the mmcrcbf bit will be set to indicate the crc byte is ready in the crc data register. reading the crc data register clears the mmcrcbf bit. if the crc data register is not read, the mmcrcbf bit will be cleared by hardware before the next crc byte is loaded. 14.6.8 mmiic frequency divider register (mmfdr) the three bits in the frequency divider register (mmfdr) selects the divider to divide the bus clock to the desired baud rate for the mmiic data transfer. table 14-2 shows the divider values for mmbr[2:0]. address: $004e bit 7654321bit 0 read: mmcrcd7 mmcrcd6 mmcrcd5 mmcrcd4 mmcrcd3 mmcrcd2 mmcrcd1 mmcrcd0 write: reset:00000000 = unimplemented figure 14-10. mmiic crc data register (mmcrcdr) address: $004f bit 7654321bit 0 read: 00000 mmbr2 mmbr1 mmbr0 write: reset:00000100 = unimplemented figure 14-11. mmiic frequency divider register (mmfdr) program algorithm mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 237 note the frequency of the mmiic baud rate is only guaranteed for 100khz to 10khz. the divider is available for the flexibility on bus frequency selection. 14.7 program algorithm when the mmiic module detects an arbitration loss in master mode, it releases both sda and scl lines immediately. but if there are no further stop conditions detected, the module will hang up. therefore, it is recommended to have time-out software to recover from this condition. the software can start the time-out counter by looking at the mmbb (bus busy) flag and reset the counter on the completion of one byte transmission. if a time-out has occurred, software can clear the mmen bit (disable mmiic module) to release the bus, and hence clear the mmbb flag. this is the only way to clear the mmbb flag by software if the module hangs up due to a no stop condition received. the mmiic can resume operation again by setting the mmen bit. table 14-2. mmiic baud rate selection mmbr2 mmbr1 mmbr0 divider mmiic baud rates for bus clocks: 8mhz 4mhz 2mhz 1mhz 0 0 0 20 400khz 200khz 100khz 50khz 0 0 1 40 200khz 100khz 50khz 25khz 0 1 0 80 100khz 50khz 25khz 12.5khz 0 1 1 160 50khz 25khz 12.5khz 6.25khz 1 0 0 320 25khz 12.5khz 6.25khz 3.125khz 1 0 1 640 12.5khz 6.25khz 3.125khz 1.5625khz 1 1 0 1280 6.25khz 3.125khz 1.5625khz 0.78125khz 1 1 1 2560 3.125khz 1.5625khz 0.78125khz 0.3906khz multi-master iic interface (mmiic) mc68hc908ap a-family data sheet, rev. 2 238 freescale semiconductor 14.7.1 data sequence figure 14-12. data transfer sequences for master/slave transmit/receive modes start address ack tx data1 mmtxbe=0 mmrw=0 mmast=1 mmtxif=1 mmtxbe=1 mmnakif=1 mmast=0 mmtxbe=1 (a) master transmit mode (b) master receive mode (c) slave transmit mode mmtxif=1 mmtxbe=0 ack tx datan ack stop mmtxif=1 mmtxbe=1 start address ack rx data1 mmrxbf=0 mmast=1 mmtxbe=0 mmrxbf=1 mmrxif=1 mmnakif=1 mmast=0 mmrxif=1 mmrxbf=1 ack rx datan nak stop 1 start address ack tx data1 mmtxbe=1 mmrxbf=0 mmnakif=1 mmtxbe=0 mmtxbe=1 (d) slave receive mode mmtxif=1 ack tx datan nak stop mmrxbf=1 mmrxif=1 mmatch=1 mmsrw=1 mmtxif=1 mmtxbe=1 0 start address ack rx data1 mmrxbf=1 mmrxif=1 mmrxif=1 mmrxbf=1 ack rx datan ack stop mmtxbe=0 mmrxbf=0 mmrxbf=1 mmrxif=1 mmatch=1 mmsrw=0 data1 mmdrr datan mmdrr data1 mmdtr data2 mmdtr datan+2 mmdtr data1 mmdtr data2 mmdtr data3 mmdtr datan+2 mmdtr (dummy data mmdtr) mmrw=1 data1 mmdrr datan mmdrr 0 1 shaded data packets indicate transmissions by the mcu smbus protocols with pec and without pec mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 239 14.8 smbus protocols with pec and without pec following is a description of the various mmiic bus protocols with and without a packet error code (pec). 14.8.1 quick command figure 14-13. quick command 14.8.2 send byte figure 14-14. send byte 14.8.3 receive byte figure 14-15. receive byte start slave address ack stop rw master to slave slave to master command bit acknowledge stop condition start condition 17111 start slave address ack w command code ack stop ack stop pec start slave address ack w command code ack (a) send byte protocol (b) send byte protocol with pec start slave address ack r data byte nak stop nak stop pec start slave address ack r data byte ack (b) receive byte protocol with pec (a) receive byte protocol multi-master iic interface (mmiic) mc68hc908ap a-family data sheet, rev. 2 240 freescale semiconductor 14.8.4 write byte/word figure 14-16. write byte/word 14.8.5 read byte/word figure 14-17. read byte/word ack command code ack data byte low ack data byte high ack stop ack command code ack data byte ack stop ack stop pec start slave address w start slave address w ack command code ack data byte ack start slave address w (a) write byte protocol (b) write byte protocol with pec (c) write word protocol ack command code ack data byte low ack data byte high ack ack stop pec start slave address w (d) write word protocol with pec stop ack command code ack data byte low ack data byte high pec data byte high ack nak ack nak start ack command code ack data byte low ack ack start stop start slave address w start slave address w slave address r slave address r (d) read word protocol with pec (c) read word protocol (b) read byte protocol with pec ack command code ack data byte nak ack command code ack nak stop pec ack start ack data byte ack start start slave address w start slave address w slave address r slave address r stop (a) read byte protocol smbus protocols with pec and without pec mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 241 14.8.6 process call figure 14-18. process call 14.8.7 block read/write figure 14-19. block read/write nak stop ack command code data byte low ack ack data byte high ack data byte low data byte high ack nak ack stop pec start slave address w start slave address r ack command code data byte low ack ack data byte high ack data byte low data byte high ack ack ack stop start slave address w start slave address r (b) process call with pec (a) process call ack command code ack byte count = n ack data byte 1 ack data byte 2 ack data byte n nak stop start ack ack command code ack byte count = n ack data byte 1 ack data byte 2 ack data byte n ack stop start slave address w start slave address w slave address r data byte 1 ack command code ack byte count = n ack ack data byte 2 ack data byte n nak stop start ack start slave address w slave address r data byte 1 pec ack (d) block write with pec (c) block write (b) block read with pec ack command code ack byte count = n ack data byte 1 ack data byte 2 ack data byte n ack stop start slave address w pec ack (a) block read multi-master iic interface (mmiic) mc68hc908ap a-family data sheet, rev. 2 242 freescale semiconductor 14.9 smbus protocol implementation figure 14-20. smbus protocol implementation start address ack command ack 0 start ack stop rx data1 ack nak rx datan address 1 ack prepare for master mode action: 1. load slave address to mmadr 2. clear mmrw 3. load command to mmdtr 4. set mmast operation: prepare for repeated start flags: mmtxif set mmrxak clear operation: action: 1. set mmrw 2. set repsen 3. clear mmtxak 4. load dummy ($ff) to mmdtr get ready to receive data flags: mmtxif set mmrxak clear operation: action: load dummy ($ff) to mmdtr generate stop flags: mmrxif set operation: action: read datan from mmdrr read received data and prepare for stop flags: mmrxif set operation: action: 1. set mmtxak 2. read data(n-1) from mmdrr 3. clear mmast read received data flags: mmrxif set operation: action: read data1 from mmdrr master mode start address ack command ack 0 start ack stop tx data1 ack nak tx datan address 1 ack slave address match and flags: mmrxif set mmatch set operation: action: 1. check mmsrw 2. read slave address read and decode received command flags: mmrxif set mmatch clear operation: action: load data1 to mmdtr last data sent flags: mmtxif set mmrxak set operation: action: load dummy ($ff) to mmdtr last data is going to be sent flags: mmtxif set operation: action: load dummy ($ff) to mmdtr transmit data flags: mmtxif set operation: action: load data3 to mmdtr prepare for slave mode action: 1. load slave address to mmadr 2. clear mmtxak 3. clear mmast operation: mmsrw depends on 8th slave address match and flags: mmrxif set mmatch set operation: action: check mmsrw mmsrw depends on 8th mmrxak clear mmrxak clear transmit data flags: mmtxif set operation: action: load data2 to mmdtr check for data direction bit of calling address byte get ready to transmit data bit of calling address byte slave mode shaded data packets indicate transmissions by the mcu mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 243 chapter 15 analog-to-digital converter (adc) 15.1 introduction this section describes the analog-to-digital converter (adc). the adc is a 8-channel 10-bit linear successive approximation adc. 15.2 features features of the adc module include: eight channels with multiplexed input high impedance buffered input linear successive approximation with monotonicity 10-bit resolution single or continuous conversion auto-scan conversion on four channels conversion complete flag or conversion complete interrupt selectable adc clock conversion result justification 8-bit truncated mode right justified mode left justified mode left justified sign mode addr. register name bit 7 654321bit 0 $0057 adc status and control register (adscr) read: coco aien adco adch4 adch3 adch2 adch1 adch0 write: reset:00011111 $0058 adc clock control register (adiclk) read: adiv2 adiv1 adiv0 adiclk mode1 mode0 00 write: r reset:00000100 $0059 adc data register high 0 (adrh0) read: adx adx adx adx adx adx adx adx write: rrrrrrrr reset:00000000 $005a adc data register low 0 (adrl0) read: adx adx adx adx adx adx adx adx write: rrrrrrrr reset:00000000 $005b adc data register low 1 (adrl1) read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write: rrrrrrrr reset:00000000 figure 15-1. adc i/o register summary analog-to-digital converter (adc) mc68hc908ap a-family data sheet, rev. 2 244 freescale semiconductor 15.3 functional description the adc provides eight pins for sampling external sources at pins pta0/adc0?ta7/adc7. an analog multiplexer allows the single adc converter to select one of eight adc channels as adc voltage in (v adin ). v adin is converted by the successive approximation register-based analog-to-digital converter. when the conversion is completed, adc places the result in the adc data register, high and low byte (adrh0 and adrl0), and sets a flag or generates an interrupt. an additional three adc data registers (adrl1?drl3) are available to store the individual converted data for adc channels adc1?dc3 when the auto-scan mode is enabled. data from channel adc0 is stored in adrl0 in the auto-scan mode. figure 15-2 shows the structure of the adc module. 15.3.1 adc port i/o pins pta0?ta7 are general-purpose i/o pins that are shared with the adc channels. the channel select bits, adch[4:0], define which adc channel/port pin will be used as the input signal. the adc overrides the port i/o logic by forcing that pin as input to the adc. the remaining adc channels/port pins are controlled by the port i/o logic and can be used as general-purpose i/o. writes to the port data register or data direction register will not have any affect on the port pin that is selected by the adc. read of a port pin which is in use by the adc will return the pin condition if the corresponding ddr bit is at logic 0. if the ddr bit is at logic 1, the value in the port data latch is read. 15.3.2 voltage conversion when the input voltage to the adc equals v refh , the adc converts the signal to $3ff (full scale). if the input voltage equals v refl , the adc converts it to $000. input voltages between v refh and v refl are a straight-line linear conversion. all other input voltages will result in $3ff if greater than v refh and $000 if less than v refl . note input voltage should not exceed the analog supply voltages. $005c adc data register low 2 (adrl3) read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write: rrrrrrrr reset:00000000 $005d adc data register low 3 (adrl3) read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write: rrrrrrrr reset:00000000 $005e adc auto-scan control register (adascr) read: 00000 auto1 auto0 ascan write: reset:00000000 = unimplemented r = reserved figure 15-1. adc i/o register summary functional description mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 245 figure 15-2. adc block diagram 15.3.3 conversion time conversion starts after a write to the adscr. one conversion will take between 16 and 17 adc clock cycles, therefore: adc data registers internal data bus read ddrax write ddrax reset write ptax read ptax ptax/adcx ddrax ptax interrupt logic channel select 10-bit adc clock generator conversion complete adc (v adin ) adciclk cgmxclk bus clock ascan disable disable (8 channels) adiv[2:0] adiclk voltage in vrefl vrefh adch[4:0] adc0?dc7 mux 2-bit up-counter coco aien adrh0 adrl1 adrl0 adrl2 adrl3 auto[1:0] 16 to17 adc cycles conversion time = adc frequency number of bus cycles = conversion time bus frequency analog-to-digital converter (adc) mc68hc908ap a-family data sheet, rev. 2 246 freescale semiconductor the adc conversion time is determined by the clock source chosen and the divide ratio selected. the clock source is either the bus clock or cgmxclk and is selectable by the adiclk bit located in the adc clock register. the divide ratio is selected by the adiv[2:0] bits. for example, if a 4mhz cgmxclk is selected as the adc input clock source, with a divide-by-four prescale, and the bus speed is set at 2mhz: note the adc frequency must be between f adic minimum and f adic maximum to meet a/d specifications. (see 22.5 5v dc electrical characteristics .) . since an adc cycle may be comprised of several bus cycles (four in the previous example) and the start of a conversion is initiated by a bus cycle write to the adscr, from zero to four additional bus cycles may occur before the start of the initial adc cycle. this results in a fractional adc cycle and is represented as the 17th cycle. 15.3.4 continuous conversion in the continuous conversion mode, the adc continuously converts the selected channel, filling the adc data register with new data after each conversion. data from the previous conversion will be overwritten whether that data has been read or not. conversions will continue until the adco bit is cleared. the coco bit is set after each conversion and can be cleared by writing to the adc status and control register or reading of the adrl0 data register. 15.3.5 auto-scan mode in auto-scan mode, the adc input channel is selected by the value of the 2-bit up-counter, instead of the channel select bits, adch[4:0]. the value of the counter also defines the data register adrlx to be used to store the conversion result. when ascan bit is set, a write to adc status and control register (adscr) will reset the auto-scan up-counter and adc conversion will start on the channel 0 up to the channel number defined by the integer value of auto[1:0]. after a channel conversion is completed, data is stored in adrlx and the coco-bit will be set. the counter value will be incremented by 1 and a new conversion will start. this process will continue until the counter value reaches the value of auto[1:0]. when this happens, it indicates that the current channel is the last channel to be converted. upon the completion on the last channel, the counter value will not be incremented and no further conversion will be performed. to start another auto-scan cycle, a write to adscr must be performed. note the system only provides 8-bit data storage in auto-scan code, user must clear mode[1:0] bits to select 8-bit truncation mode before entering auto-scan mode. it is recommended that user should disable the auto-scan function before switching channel and also before entering stop mode. 16 to17 adc cycles conversion time = 4mhz 4 number of bus cycles = 16 s 2mhz = 32 to 34 cycles = 16 to 17 s interrupts mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 247 15.3.6 result justification the conversion result may be formatted in four different ways. left justified right justified left justified sign data mode 8-bit truncation all four of these modes are controlled using mode0 and mode1 bits located in the adc clock control register (adiclk). left justification will place the eight most significant bits (msb) in the corresponding adc data register high (adrh). this may be useful if the result is to be treated as an 8-bit result where the least significant two bits, located in the adc data register low (adrl) can be ignored. however, you must read adrl after adrh or else the interlocking will prevent all new conversions from being stored. right justification will place only the two msbs in the corresponding adc data register high (adrh) and the eight lsb bits in adc data register low (adrl). this mode of operation typically is used when a 10-bit unsigned result is desired. left justified sign data mode is similar to left justified mode with one exception. the msb of the 10-bit result, ad9 located in adrh is complemented. this mode of operation is useful when a result, represented as a signed magnitude from mid-scale, is needed. finally, 8-bit truncation mode will place the eight msbs in adc data register low (adrl). the two lsbs are dropped. this mode of operation is used when compatibility with 8-bit adc designs are required. no interlocking between adrh and adrl is present. 15.3.7 data register interlocking reading adrh in any 10-bit mode latches the contents of adrl until adrl is read. until adrl is read all subsequent adc results will be lost. this register interlocking can also be reset by a write to the adc status and control register, or adc clock control register. a power-on reset or reset will also clear the interlocking. note that an external conversion request will not reset the lock. 15.3.8 monotonicity the conversion process is monotonic and has no missing codes. 15.4 interrupts when the aien bit is set, the adc module is capable of generating a cpu interrupt after each adc conversion or after an auto-scan conversion cycle. a cpu interrupt is generated if the coco bit is at logic 0. the coco bit is not used as a conversion complete flag when interrupts are enabled. the interrupt vector is defined in table 2-1 . vector addresses . 15.5 low-power modes the stop and wait instructions put the mcu in low power-consumption standby modes. analog-to-digital converter (adc) mc68hc908ap a-family data sheet, rev. 2 248 freescale semiconductor 15.5.1 wait mode the adc continues normal operation in wait mode. any enabled cpu interrupt request from the adc can bring the mcu out of wait mode. if the adc is not required to bring the mcu out of wait mode, power down the adc by setting the adch[4:0] bits to logic 1? before executing the wait instruction. 15.5.2 stop mode the adc module is inactive after the execution of a stop instruction. any pending conversion is aborted. adc conversions resume when the mcu exits stop mode. allow one conversion cycle to stabilize the analog circuitry before attempting a new adc conversion after exiting stop mode. 15.6 i/o signals the adc module has eight channels shared with port a i/o pins. 15.6.1 adc voltage in (v adin ) v adin is the input voltage signal from one of the eight adc channels to the adc module. 15.6.2 adc analog power pin (v dda ) the adc analog portion uses v dda as its power pin. connect the v dda pin to the same voltage potential as v dd . external filtering may be necessary to ensure clean v dda for good results. note route v dda carefully for maximum noise immunity and place bypass capacitors as close as possible to the package. 15.6.3 adc analog ground pin (v ssa ) the adc analog portion uses v ssa as its ground pin. connect the v ssa pin to the same voltage potential as v ss . 15.6.4 adc voltage reference high pin (v refh ) v refh is the power supply for setting the reference voltage v refh . connect the v refh pin to the same voltage potential as v dda . there will be a finite current associated with v refh (see chapter 22 electrical specifications ). note route v refh carefully for maximum noise immunity and place bypass capacitors as close as possible to the package. 15.6.5 adc voltage reference low pin (v refl ) v refl is the lower reference supply for the adc. connect the v refl pin to the same voltage potential as v ssa . there will be a finite current associated with v refl (see chapter 22 electrical specifications ). i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 249 15.7 i/o registers these i/o registers control and monitor adc operation: adc status and control register (adscr) ?$0057 adc clock control register (adiclk) ?$0058 adc data register high:low 0 (adrh0:adrl0) ?$0059:$005a adc data register low 1? (adrl1?drl3) ?$005b?005d adc auto-scan control register (adascr) ?$005e 15.7.1 adc status and control register function of the adc status and control register is described here. coco ?conversions complete bit when the aien bit is a logic 0, the coco is a read-only bit which is set each time a conversion is completed. this bit is cleared whenever the adscr is written, or whenever the adc clock control register is written, or whenever the adc data register low, adrlx, is read. if the aien bit is logic 1, the coco bit always read as logic 0. adc interrupt will be generated at the end if an adc conversion. reset clears the coco bit. 1 = conversion completed (aien = 0) 0 = conversion not completed (aien = 0)/cpu interrupt (aien=1) aien ?adc interrupt enable bit when this bit is set, an interrupt is generated at the end of an adc conversion. the interrupt signal is cleared when the data register, adr0, is read or the adscr is written. reset clears the aien bit. 1 = adc interrupt enabled 0 = adc interrupt disabled adco ?adc continuous conversion bit when set, the adc will convert samples continuously and update the adc data register at the end of each conversion. only one conversion is allowed when this bit is cleared. reset clears the adco bit. 1 = continuous adc conversion 0 = one adc conversion this bit should not be set when auto-scan mode is enabled; i.e. when ascan=1. adch[4:0] ?adc channel select bits adch[4:0] form a 5-bit field which is used to select one of the adc channels when not in auto-scan mode. the five channel select bits are detailed in table 15-1 . note care should be taken when using a port pin as both an analog and a digital input simultaneously to prevent switching noise from corrupting the analog signal. recovery from the disabled state requires one conversion cycle to stabilize. address: $0057 read: coco aien adco adch4 adch3 adch2 adch1 adch0 write: reset:00011111 figure 15-3. adc status and control register (adscr) analog-to-digital converter (adc) mc68hc908ap a-family data sheet, rev. 2 250 freescale semiconductor 15.7.2 adc clock control register the adc clock control register (adiclk) selects the clock frequency for the adc. adiv[2:0] ?adc clock prescaler bits adiv2, adiv1, and adiv0 form a 3-bit field which selects the divide ratio used by the adc to generate the internal adc clock. table 15-2 shows the available clock configurations. the adc clock should be set to between 500khz and 1mhz. table 15-1. mux channel select adch4 adch3 adch2 adch1 adch0 adc channel input select 00000 adc0 pta0 00001 adc1 pta1 00010 adc2 pta2 00011 adc3 pta3 00100 adc4 pta4 00101 adc5 pta5 00110 adc6 pta6 00111 adc7 pta7 0 1 1 1 0 1 0 0 0 0 adc8 adc28 reserved 11 1 0 1 adc29 v refh (see note 2) 11 1 1 0 adc30 v refl (see note 2) 11 1 1 1 adc powered-off notes: 1. if any unused channels are selected, the resulting adc conversion will be unknown. 2. the voltage levels supplied from internal reference nodes as specified in the table are used to verify the operation of the adc converter both in production test and for user applications. address: $0058 read: adiv2 adiv1 adiv0 adiclk mode1 mode0 00 write: r reset:00000100 = unimplemented r = reserved figure 15-4. adc clock control register (adiclk) i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 251 adiclk ?adc input clock select bit adiclk selects either bus clock or cgmxclk as the input clock source to generate the internal adc clock. reset selects cgmxclk as the adc clock source. if the external clock (cgmxclk) is equal to or greater than 1mhz, cgmxclk can be used as the clock source for the adc. if cgmxclk is less than 1mhz, use the pll-generated bus clock as the clock source. as long as the internal adc clock is at f adic , correct operation can be guaranteed. 1 = internal bus clock 0 = external clock, cgmxclk mode1 and mode0 ?modes of result justification mode1 and mode0 selects between four modes of operation. the manner in which the adc conversion results will be placed in the adc data registers is controlled by these modes of operation. reset returns right-justified mode. 15.7.3 adc data register 0 (adrh0 and adrl0) the adc data register 0 consist of a pair of 8-bit registers: high byte (adrh0), and low byte (adrl0). this pair form a 16-bit register to store the 10-bit adc result for the selected adc result justification mode. in 8-bit truncated mode, the adrl0 holds the eight most significant bits (msbs) of the 10-bit result. the adrl0 is updated each time an adc conversion completes. in 8-bit truncated mode, adrl0 contains no interlocking with adrh0. (see figure 15-5 . adrh0 and adrl0 in 8-bit truncated mode .) table 15-2. adc clock divide ratio adiv2 adiv1 adiv0 adc clock rate 0 0 0 adc input clock 1 0 0 1 adc input clock 2 0 1 0 adc input clock 4 0 1 1 adc input clock 8 1 x x adc input clock 16 x = don? care table 15-3. adc mode select mode1 mode0 justification mode 0 0 8-bit truncated mode 0 1 right justi?d mode 1 0 left justi?d mode 1 1 left justi?d sign data mode cgmxclk or bus frequency f adic = adiv[2:0] analog-to-digital converter (adc) mc68hc908ap a-family data sheet, rev. 2 252 freescale semiconductor in right justified mode the adrh0 holds the two msbs, and the adrl0 holds the eight least significant bits (lsbs), of the 10-bit result. adrh0 and adrl0 are updated each time a single channel adc conversion completes. reading adrh0 latches the contents of adrl0. until adrl0 is read all subsequent adc results will be lost. (see figure 15-6 . adrh0 and adrl0 in right justified mode .) in left justified mode the adrh0 holds the eight most significant bits (msbs), and the adrl0 holds the two least significant bits (lsbs), of the 10-bit result. the adrh0 and adrl0 are updated each time a single channel adc conversion completes. reading adrh0 latches the contents of adrl0. until adrl0 is read all subsequent adc results will be lost. (see figure 15-7 . adrh0 and adrl0 in left justified mode .) in left justified sign mode the adrh0 holds the eight msbs with the msb complemented, and the adrl0 holds the two least significant bits (lsbs), of the 10-bit result. the adrh0 and adrl0 are updated each time a single channel adc conversion completes. reading adrh0 latches the contents of adrl0. until adrl0 is read all subsequent adc results will be lost. (see figure 15-8 adrh0 and adrl0 in left justified sign data mode .) addr. register name bit 7 654321bit 0 $0059 adc data register high 0 (adrh0) read: 00000000 write: rrrrrrrr reset:00000000 $005a adc data register low 0 (adrl0) read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write: rrrrrrrr reset:00000000 figure 15-5. adrh0 and adrl0 in 8-bit truncated mode addr. register name bit 7 654321bit 0 $0059 adc data register high 0 (adrh0) read: 000000ad9ad8 write: rrrrrrrr reset:00000000 $005a adc data register low 0 (adrl0) read: ad7 ad6 ad5 ad4 ad3 ad2 ad1 ad0 write: rrrrrrrr reset:00000000 figure 15-6. adrh0 and adrl0 in right justified mode addr. register name bit 7 654321bit 0 $0059 adc data register high 0 (adrh0) read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write: rrrrrrrr reset:00000000 $005a adc data register low 0 (adrl0) read: ad1 ad0 000000 write: rrrrrrrr reset:00000000 figure 15-7. adrh0 and adrl0 in left justified mode i/o registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 253 15.7.4 adc auto-scan mode data registers (adrl1?drl3) the adc data registers 1 to 3 (adrl1?drl3), are 8-bit registers for conversion results in 8-bit truncated mode, for channels adc1 to adc3, when the adc is operating in auto-scan mode (mode[1:0] = 00). 15.7.5 adc auto-scan control register (adascr) the adc auto-scan control register (adascr) enables and controls the adc auto-scan function. auto[1:0] ?auto-scan mode channel select bits auto1 and auto0 form a 2-bit field which is used to define the number of auto-scan channels used when in auto-scan mode. reset clears these bits. addr. register name bit 7 654321bit 0 $0059 adc data register high 0 (adrh0) read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write: rrrrrrrr reset:00000000 $005a adc data register low 0 (adrl0) read: ad1 ad0 000000 write: rrrrrrrr reset:00000000 figure 15-8 adrh0 and adrl0 in left justified sign data mode address: adrl1, $005b; adrl2, $005c; and adrl3, $005d read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write: rrrrrrrr reset:00000000 r = reserved figure 15-9. adc data register low 1 to 3 (adrl1?drl3) address: $005e read: 00000 auto1 auto0 ascan write: reset:00000000 = unimplemented r = reserved figure 15-10. adc scan control register (adascr) table 15-4. auto-scan mode channel select auto1 auto0 auto-scan channels 0 0 adc0 only 0 1 adc0 to adc1 1 0 adc0 to adc2 1 1 adc0 to adc3 analog-to-digital converter (adc) mc68hc908ap a-family data sheet, rev. 2 254 freescale semiconductor ascan ?auto-scan mode enable bit this bit enable/disable the auto-scan mode. reset clears this bit. 1 = auto-scan mode is enabled 0 = auto-scan mode is disabled auto-scan mode should not be enabled when adc continuous conversion is enabled; i.e. when adco=1. mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 255 chapter 16 input/output (i/o) ports 16.1 introduction thirty-two (32) bidirectional input-output (i/o) pins form four parallel ports. all i/o pins are programmable as inputs or outputs. note connect any unused i/o pins to an appropriate logic level, either v dd or v ss . although the i/o ports do not require termination for proper operation, termination reduces excess current consumption and the possibility of electrostatic damage. addr. register name bit 7 654321bit 0 $0000 port a data register (pta) read: pta7 pta6 pta5 pta4 pta3 pta2 pta1 pta0 write: reset: unaffected by reset $0001 port b data register (ptb) read: ptb7 ptb6 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 write: reset: unaffected by reset $0002 port c data register (ptc) read: ptc7 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1 ptc0 write: reset: unaffected by reset $0003 port d data register (ptd) read: ptd7 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 write: reset: unaffected by reset $0004 data direction register a (ddra) read: ddra7 ddra6 ddra5 ddra4 ddra3 ddra2 ddra1 ddra0 write: reset: 00000000 $0005 data direction register b (ddrb) read: ddrb7 ddrb6 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 write: reset: 00000000 $0006 data direction register c (ddrc) read: ddrc7 ddrc6 ddrc5 ddrc4 ddrc3 ddrc2 ddrc1 ddrc0 write: reset: 00000000 $0007 data direction register d (ddrd) read: ddrd7 ddrd6 ddrd5 ddrd4 ddrd3 ddrd2 ddrd1 ddrd0 write: reset: 00000000 $000c port-a led control register (leda) read: leda7 leda6 leda5 leda4 leda3 leda2 leda1 leda0 write: reset: 00000000 figure 16-1. i/o port register summary input/output (i/o) ports mc68hc908ap a-family data sheet, rev. 2 256 freescale semiconductor table 16-1. port control register bits summary port bit ddr module control pin module register control bit a 0 ddra0 adc adscr ($0057) adch[4:0] pta0/adc0 1 ddra1 pta1/adc1 2 ddra2 pta2/adc2 3 ddra3 pta3/adc3 4 ddra4 pta4/adc4 5 ddra5 pta5/adc5 6 ddra6 pta6/adc6 7 ddra7 pta7/adc7 b 0 ddrb0 mbus mmcr1 ($0049) mmen ptb0/sda (1) 1. pin is open-drain when configured as output. pullup resistor must be connected when configured as output. 1 ddrb1 ptb1/scl (1) 2 ddrb2 sci scc1 ($0013) ensci ptb2/txd (1) 3 ddrb3 ptb3/rxd (1) 4 ddrb4 tim1 t1sc0 ($0025) els0b:els0a ptb4/t1ch0 (2) 2. pin has schmitt trigger when configured as input. 5 ddrb5 t1sc1 ($0028) els1b:els1a ptb5/t1ch1 (2) 6 ddrb6 tim2 t2sc0 ($0030) els0b:els0a ptb6/t2ch0 (2) 7 ddrb7 t2sc1 ($0033) els1b:els1a ptb7/t2ch1 (2) c 0 ddrc0 irq2 intscr2 ($001c) imask2 ptc0/ irq2 (2) 1 ddrc1 ptc1 2 ddrc2 spi spcr ($0010) spe ptc2/miso 3 ddrc3 ptc3/mosi 4 ddrc4 ptc4/ ss 5 ddrc5 ptc5/spsck 6 ddrc6 irsci irscc1 ($0040) ensci ptc6/sctxd (1) 7 ddrc7 ptc7/scrxd (1) d 0 ddrd0 kbi kbier ($001b) kbie0 ptd0/kbi0 (2) 1 ddrd1 kbie1 ptd1/kbi1 (2) 2 ddrd2 kbie2 ptd2/kbi2 (2) 3 ddrd3 kbie3 ptd3/kbi3 (2) 4 ddrd4 kbie4 ptd4/kbi4 (2) 5 ddrd5 kbie5 ptd5/kbi5 (2) 6 ddrd6 kbie6 ptd6/kbi6 (2) 7 ddrd7 kbie7 ptd7/kbi7 (2) port a mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 257 16.2 port a port a is an 8-bit special-function port that shares all of its pins with the analog-to-digital converter (adc) module. port a pins also have led direct drive capability. 16.2.1 port a data register (pta) the port a data register contains a data latch for each of the eight port a pins. pta[7:0] ?port a data bits these read/write bits are software-programmable. data direction of each port a pin is under the control of the corresponding bit in data direction register a. reset has no effect on port a data. adc7?dc0 ?adc channels 7 to 0 adc7?dc0 are pins used for the input channels to the analog-to-digital converter module. the channel select bits, adch[4:0], in the adc status and control register define which port pin will be used as an adc input and overrides any control from the port i/o logic. note care must be taken when reading port a while applying analog voltages to adc7?dc0 pins. if the appropriate adc channel is not enabled, excessive current drain may occur if analog voltages are applied to the ptax/adcx pin, while pta is read as a digital input. those ports not selected as analog input channels are considered digital i/o ports. led drive ?direct led drive pins pta7?ta0 pins can be configured for direct led drive. see 16.2.3 port-a led control register (leda) . 16.2.2 data direction register (ddra) data direction register a determines whether each port a pin is an input or an output. writing a logic 1 to a ddra bit enables the output buffer for the corresponding port a pin; a logic 0 disables the output buffer. address: $0000 bit 7654321bit 0 read: pta7 pta6 pta5 pta4 pta3 pta2 pta1 pta0 write: reset: unaffected by reset alternative function: adc7 adc6 adc5 adc4 adc3 adc2 adc1 adc0 additional function: led drive led drive led drive led drive led drive led drive led drive led drive figure 16-2. port a data register (pta) address: $0004 bit 7654321bit 0 read: ddra7 ddra6 ddra5 ddra4 ddra3 ddra2 ddra1 ddra0 write: reset:00000000 figure 16-3. data direction register a (ddra) input/output (i/o) ports mc68hc908ap a-family data sheet, rev. 2 258 freescale semiconductor ddra[7:0] ?data direction register a bits these read/write bits control port a data direction. reset clears ddra[7:0], configuring all port a pins as inputs. 1 = corresponding port a pin configured as output 0 = corresponding port a pin configured as input note avoid glitches on port a pins by writing to the port a data register before changing data direction register a bits from 0 to 1. figure 16-4 shows the port a i/o logic. figure 16-4. port a i/o circuit when ddrax is a logic 1, reading address $0000 reads the ptax data latch. when ddrax is a logic 0, reading address $0000 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. table 16-2 summarizes the operation of the port a pins. table 16-2. port a pin functions ddra bit pta bit i/o pin mode accesses to ddra accesses to pta read/write read write 0 x (1) 1. x = don? care. input, hi-z (2) 2. hi-z = high impedance. ddra[7:0] pin pta[7:0] (3) 3. writing affects data register, but does not affect input. 1 x output ddra[7:0] pta[7:0] pta[7:0] read ddra ($0004) write ddra ($0004) reset write pta ($0000) read pta ($0000) ptax ddrax ptax internal data bus port b mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 259 16.2.3 port-a led control register (leda) the port-a led control register (leda) controls the direct led drive capability on pta7?ta0 pins. each bit is individually configurable and requires that the data direction register, ddra, bit be configured as an output. leda[7:0] ?port a led drive enable bits these read/write bits are software programmable to enable the direct led drive on an output port pin. 1 = corresponding port a pin is configured for direct led drive, with 15ma current sinking capability 0 = corresponding port a pin is configured for standard drive 16.3 port b port b is an 8-bit special-function port that shares two of its pins with the multi-master iic (mmiic) module, two of its pins with sci module, and four of its pins with two timer interface (tim1 and tim2) modules. note ptb3?tb0 are open-drain pins when configured as outputs regardless whether the pins are used as general purpose i/o pins, mmiic pins, or sci pins. therefore, when configured as general purpose output pins, mmiic pins, or sci pins (the txd pin), pullup resistors must be connected to these pins. 16.3.1 port b data register (ptb) the port b data register contains a data latch for each of the eight port b pins. ptb[7:0] ?port b data bits these read/write bits are software-programmable. data direction of each port b pin is under the control of the corresponding bit in data direction register b. reset has no effect on port b data. address: $000c bit 7654321bit 0 read: leda7 leda6 leda5 leda4 leda3 leda2 leda1 leda0 write: reset:00000000 figure 16-5. port a led control register (leda) address: $0001 bit 7654321bit 0 read: ptb7 ptb6 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 write: reset: unaffected by reset alternative function: t2ch1 t2ch0 t1ch1 t1ch0 rxd txd scl sda figure 16-6. port b data register (ptb) input/output (i/o) ports mc68hc908ap a-family data sheet, rev. 2 260 freescale semiconductor sda and scl ?multi-master iic data and clock the sda and scl pins are multi-master iic data and clock pins. setting the mmen bit in the mmiic control register 1 (mmcr1) configures the ptb0/sda and ptb1/scl pins for mmiic function and overrides any control from the port i/o logic. txd and rxd ?sci transmit and receive data the txd and rxd pins are sci transmit and receive data pins. setting the ensci bit in the sci control register 1 (scc1) configures the ptb2/txd and ptb3/rxd pins for sci function and overrides any control from the port i/o logic. t1ch0 and t1ch1 ?timer 1 channel i/o the t1ch0 and t1ch1 pins are the tim1 input capture/output compare pins. the edge/level select bits, elsxb:elsxa, determine whether the ptb4/t1ch0?tb5/t1ch1 pins are timer channel i/o pins or general-purpose i/o pins. t2ch0 and t2ch1 ?timer 2 channel i/o the t2ch0 and t2ch1 pins are the tim2 input capture/output compare pins. the edge/level select bits, elsxb:elsxa, determine whether the ptb6/t2ch0?tb7/t2ch1 pins are timer channel i/o pins or general-purpose i/o pins. 16.3.2 data direction register b (ddrb) data direction register b determines whether each port b pin is an input or an output. writing a logic 1 to a ddrb bit enables the output buffer for the corresponding port b pin; a logic 0 disables the output buffer. ddrb[7:0] ?data direction register b bits these read/write bits control port b data direction. reset clears ddrb[7:0], configuring all port b pins as inputs. 1 = corresponding port b pin configured as output 0 = corresponding port b pin configured as input note avoid glitches on port b pins by writing to the port b data register before changing data direction register b bits from 0 to 1. figure 16-8 shows the port b i/o logic. address: $0005 bit 7654321bit 0 read: ddrb7 ddrb6 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 write: reset:00000000 figure 16-7. data direction register b (ddrb) port c mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 261 figure 16-8. port b i/o circuit when ddrbx is a logic 1, reading address $0001 reads the ptbx data latch. when ddrbx is a logic 0, reading address $0001 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. table 16-3 summarizes the operation of the port b pins. 16.4 port c port c is an 8-bit special-function port that shares one of its pins with the irq2, four of its pins with the spi module, and two of its pins with the irsci module. 16.4.1 port c data register (ptc) the port c data register contains a data latch for each of the eight port c pins. table 16-3. port b pin functions ddrb bit ptb bit i/o pin mode accesses to ddrb accesses to ptb read/write read write 0 x (1) 1. x = don? care. input, hi-z (2) 2. hi-z = high impedance. ddrb[7:0] pin ptb[7:0] (3) 3. writing affects data register, but does not affect input. 1 x output ddrb[7:0] ptb[7:0] ptb[7:0] address: $0002 bit 7654321bit 0 read: ptc7 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1 ptc0 write: reset: unaffected by reset alternative function: scrxd sctxd spsck ss mosi miso irq2 figure 16-9. port c data register (ptc) read ddrb ($0005) write ddrb ($0005) reset write ptb ($0001) read ptb ($0001) ptbx # ddrbx ptbx internal data bus # ptb3?tb0 are open-drain pins when con?ured as outputs. ptb7?tb4 have schmitt trigger inputs. input/output (i/o) ports mc68hc908ap a-family data sheet, rev. 2 262 freescale semiconductor ptc[7:0] ?port c data bits these read/write bits are software-programmable. data direction of each port c pin is under the control of the corresponding bit in data direction register c. reset has no effect on port c data. irq2 ?irq2 input pin the ptc0/ irq2 pin is always available as input pin to the irq2 module. care must be taken to available unwanted interrupts when this pin is used as general purpose i/o. ptc0/ irq2 pin has an internal pullup, and can be disabled by setting the puc0enb bit in the irq2 status and control register (intscr2). miso, mosi, ss, and spsck ?spi data i/o, select, and clock pins these pins are the spi data in/out, select, and clock pins. setting the spe bit in the spi control register (spcr) configures ptc2/miso, ptc3/mosi, ptc4/ ss, and ptc5/spsck pins for spi function and overrides any control from the port i/o logic. sctxd and scrxd ?irsci transmit and receive data the sctxd and scrxd pins are irsci transmit and receive data pins. setting the ensci bit in the irsci control register 1 (irscc1) configures the ptc6/sctxd and ptc7/scrxd pins for irsci function and overrides any control from the port i/o logic. 16.4.2 data direction register c (ddrc) data direction register c determines whether each port c pin is an input or an output. writing a logic 1 to a ddrc bit enables the output buffer for the corresponding port c pin; a logic 0 disables the output buffer. ddrc[7:0] ?data direction register c bits these read/write bits control port c data direction. reset clears ddrc[7:0], configuring all port c pins as inputs. 1 = corresponding port c pin configured as output 0 = corresponding port c pin configured as input note avoid glitches on port c pins by writing to the port c data register before changing data direction register c bits from 0 to 1. figure 16-11 shows the port c i/o logic. note for those devices packaged in a 42-pin shrink dual in-line package, ptc0 and ptc1 are not connected. ddrc0 and ddrc1 should be set to a 1 to configure ptc0 and ptc1 as outputs. address: $0006 bit 7654321bit 0 read: ddrc7 ddrc6 ddrc5 ddrc4 ddrc3 ddrc2 ddrc1 ddrc0 write: reset:00000000 figure 16-10. data direction register c (ddrc) port d mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 263 figure 16-11. port c i/o circuit when ddrcx is a logic 1, reading address $0002 reads the ptcx data latch. when ddrcx is a logic 0, reading address $0002 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. table 16-4 summarizes the operation of the port c pins. 16.5 port d port d is an 8-bit special function port that shares all of its pins with the keyboard interrupt module. 16.5.1 port d data register (ptd) the port d data register contains a data latch for each of the eight port d pins. table 16-4. port c pin functions ddrc bit ptc bit i/o pin mode accesses to ddrc accesses to ptc read/write read write 0 x (1) 1. x = don? care. input, hi-z (2) 2. hi-z = high impedance. ddrc[7:0] pin ptc[7:0] (3) 3. writing affects data register, but does not affect input. 1 x output ddrc[7:0] ptc[7:0] ptc[7:0] address: $0003 bit 7654321bit 0 read: ptd7 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 write: reset: unaffected by reset alternative function: kbi7 kbi6 kbi5 kbi4 kbi3 kbi2 kbi1 kbi0 figure 16-12. port d data register (ptd) read ddrc ($0006) write ddrc ($0006) reset write ptc ($0002) read ptc ($0002) ptcx # ddrcx ptcx internal data bus # ptc0 has schmitt trigger input. input/output (i/o) ports mc68hc908ap a-family data sheet, rev. 2 264 freescale semiconductor ptd[7:0] ?port d data bits these read/write bits are software programmable. data direction of each port d pin is under the control of the corresponding bit in data direction register d. reset has no effect on port d data. kbi7?bi0 ?keyboard interrupt inputs the keyboard interrupt enable bits, kbie[7:0], in the keyboard interrupt enable register (kbier), enable the port d pins as external interrupt pins. see chapter 18 keyboard interrupt module (kbi) . 16.5.2 data direction register d (ddrd) data direction register d determines whether each port d pin is an input or an output. writing a logic 1 to a ddrd bit enables the output buffer for the corresponding port d pin; a logic 0 disables the output buffer. ddrd[7:0] ?data direction register d bits these read/write bits control port d data direction. reset clears ddrd[7:0], configuring all port d pins as inputs. 1 = corresponding port d pin configured as output 0 = corresponding port d pin configured as input note avoid glitches on port d pins by writing to the port d data register before changing data direction register d bits from 0 to 1. figure 16-14 shows the port d i/o logic. figure 16-14. port d i/o circuit when bit ddrdx is a logic 1, reading address $0003 reads the ptdx data latch. when bit ddrdx is a logic 0, reading address $0003 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. address: $0007 bit 7654321bit 0 read: ddrd7 ddrd6 ddrd5 ddrd4 ddrd3 ddrd2 ddrd1 ddrd0 write: reset:00000000 figure 16-13. data direction register d (ddrd) read ddrd ($0007) write ddrd ($0007) reset write ptd ($0003) read ptd ($0003) ptdx # ddrdx ptdx internal data bus kbiex # ptd7?td0 have schmitt trigger inputs. port d mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 265 table 16-5 summarizes the operation of the port d pins. table 16-5. port d pin functions ddrd bit ptd bit i/o pin mode accesses to ddrd accesses to ptd read/write read write 0 x (1) 1. x = don? care. input, hi-z (2) 2. hi-z = high impedance. ddrd[7:0] pin ptd[7:0] (3) 3. writing affects data register, but does not affect input. 1 x output ddrd[7:0] ptd[7:0] ptd[7:0] input/output (i/o) ports mc68hc908ap a-family data sheet, rev. 2 266 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 267 chapter 17 external interrupt (irq) 17.1 introduction the external interrupt (irq) module provides two maskable interrupt inputs: irq1 and irq2. 17.2 features features of the irq module include: a dedicated external interrupt pin, irq1 an external interrupt pin shared with a port pin, ptc0/ irq2 separate irq interrupt control bits for irq1 and irq2 hysteresis buffers programmable edge-only or edge and level interrupt sensitivity automatic interrupt acknowledge internal pullup resistor, with disable option on irq2 note references to either irq1 or irq2 may be made in the following text by omitting the irq number. for example, irqf may refer generically to irq1f and irq2f, and imask may refer to imask1 and imask2. 17.3 functional description a logic 0 applied to the external interrupt pin can latch a cpu interrupt request. figure 17-2 and figure 17-3 shows the structure of the irq module. interrupt signals on the irq pin are latched into the irq latch. an interrupt latch remains set until one of the following actions occurs: vector fetch a vector fetch automatically generates an interrupt acknowledge signal that clears the latch that caused the vector fetch. addr. register name bit 7 654321bit 0 $001c irq2 status and control register (intscr2) read: 0 puc0enb 0 0 irq2f 0 imask2 mode2 write: ack2 reset:00000000 $001e irq1 status and control register (intscr1) read: 0000i rq1f 0 imask1 mode1 write: ack1 reset:00000000 = unimplemented figure 17-1. external interrupt i/o register summary external interrupt (irq) mc68hc908ap a-family data sheet, rev. 2 268 freescale semiconductor software clear software can clear an interrupt latch by writing to the appropriate acknowledge bit in the interrupt status and control register (intscr). writing a logic 1 to the ack bit clears the irq latch. reset ?a reset automatically clears the interrupt latch. the external interrupt pin is falling-edge-triggered and is software-configurable to be either falling-edge or falling-edge and low-level-triggered. the mode bit in the intscr controls the triggering sensitivity of the irq pin. when an interrupt pin is edge-triggered only, the interrupt remains set until a vector fetch, software clear, or reset occurs. when an interrupt pin is both falling-edge and low-level-triggered, the interrupt remains set until both of the following occur: vector fetch or software clear return of the interrupt pin to logic 1 the vector fetch or software clear may occur before or after the interrupt pin returns to logic 1. as long as the pin is low, the interrupt request remains pending. a reset will clear the latch and the mode1 control bit, thereby clearing the interrupt even if the pin stays low. when set, the imask bit in the intscr mask all external interrupt requests. a latched interrupt request is not presented to the interrupt priority logic unless the imask bit is clear. note the interrupt mask (i) in the condition code register (ccr) masks all interrupt requests, including external interrupt requests. figure 17-2. irq1 block diagram reset imask1 dq ck clr irq1 high interrupt to mode select logic request v dd mode1 voltage detect synchronizer irq1f to cpu for bil/bih instructions vector fetch decoder internal address bus ack1 v dd internal pullup device irq1 irq1 and irq2 pins mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 269 figure 17-3. irq2 block diagram 17.4 irq1 and irq2 pins a logic 0 on the irq pin can latch an interrupt request into the irq latch. a vector fetch, software clear, or reset clears the irq latch. if the mode bit is set, the irq pin is both falling-edge-sensitive and low-level-sensitive. with mode set, both of the following actions must occur to clear irq: vector fetch or software clear a vector fetch generates an interrupt acknowledge signal to clear the latch. software may generate the interrupt acknowledge signal by writing a logic 1 to the ack bit in the interrupt status and control register (intscr). the ack bit is useful in applications that poll the irq pin and require software to clear the irq latch. writing to the ack bit prior to leaving an interrupt service routine can also prevent spurious interrupts due to noise. setting ack does not affect subsequent transitions on the irq pin. a falling edge that occurs after writing to the ack bit another interrupt request. if the irq mask bit, imask, is clear, the cpu loads the program counter with the vector address at location defined in table 2-1 . vector addresses . return of the irq pin to logic 1 ?as long as the irq pin is at logic 0, irq remains active. the vector fetch or software clear and the return of the irq pin to logic 1 may occur in any order. the interrupt request remains pending as long as the irq pin is at logic 0. a reset will clear the latch and the mode control bit, thereby clearing the interrupt even if the pin stays low. if the mode bit is clear, the irq pin is falling-edge-sensitive only. with mode clear, a vector fetch or software clear immediately clears the irq latch. the irqf bit in the intscr register can be used to check for pending interrupts. the irqf bit is not affected by the imask bit, which makes it useful in applications where polling is preferred. use the bih or bil instruction to read the logic level on the irq1 pin. note the bih and bil instructions do not read the logic level on the irq2 pin. reset imask2 dq ck clr irq2 interrupt request v dd mode2 irq2f vector fetch decoder internal address bus ack2 v dd internal pullup device irq2 puc0enb synchronizer external interrupt (irq) mc68hc908ap a-family data sheet, rev. 2 270 freescale semiconductor note when using the level-sensitive interrupt trigger, avoid false interrupts by masking interrupt requests in the interrupt routine. the irq1 pin has a permanent internal pullup device connected, while the irq2 pin has an optional pullup device that can be enabled or disabled by the puc0enb bit in the intscr2 register. 17.5 irq module during break interrupts the bcfe bit in the sim break flag control register (sbfcr) enables software to clear the latch during the break state. (see chapter 21 break module (brk) .) to allow software to clear the irq latch during a break interrupt, write a logic 1 to the bcfe bit. if a latch is cleared during the break state, it remains cleared when the mcu exits the break state. to protect cpu interrupt flags during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), writing to the ack bit in the irq status and control register during the break state has no effect on the irq interrupt flags. 17.6 irq registers each irq is controlled and monitored by an status and control register. irq1 status and control register ?$001e irq2 status and control register ?$001c 17.6.1 irq1 status and control register the irq1 status and control register (intscr1) controls and monitors operation of irq1. the intscr1 has the following functions: shows the state of the irq1 flag clears the irq1 latch masks irq1 interrupt request controls triggering sensitivity of the irq1 interrupt pin irq1f ?irq1 flag bit this read-only status bit is high when the irq1 interrupt is pending. 1 = irq1 interrupt pending 0 = irq1 interrupt not pending ack1 ?irq1 interrupt request acknowledge bit writing a logic 1 to this write-only bit clears the irq1 latch. ack1 always reads as logic 0. reset clears ack1. address: $001e bit 7654321bit 0 read: 0000i rq1f 0 imask1 mode1 write: ack1 reset:00000000 = unimplemented figure 17-4. irq1 status and control register (intscr1) irq registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 271 imask1 ?irq1 interrupt mask bit writing a logic 1 to this read/write bit disables irq1 interrupt requests. reset clears imask1. 1 = irq1 interrupt requests disabled 0 = irq1 interrupt requests enabled mode1 ?irq1 edge/level select bit this read/write bit controls the triggering sensitivity of the irq1 pin. reset clears mode1. 1 = irq1 interrupt requests on falling edges and low levels 0 = irq1 interrupt requests on falling edges only 17.6.2 irq2 status and control register the irq2 status and control register (intscr2) controls and monitors operation of irq2. the intscr2 has the following functions: enables/disables the internal pullup device on irq2 pin shows the state of the irq2 flag clears the irq2 latch masks irq2 interrupt request controls triggering sensitivity of the irq2 interrupt pin puc0enb irq2 pin pullup enable bit. setting this bit to logic 1 disables the pullup on ptc0/ irq2 pin. reset clears this bit. 1 = irq2 pin internal pullup is disabled 0 = irq2 pin internal pullup is enabled irq2f ?irq2 flag bit this read-only status bit is high when the irq2 interrupt is pending. 1 = irq2 interrupt pending 0 = irq2 interrupt not pending ack2 ?irq2 interrupt request acknowledge bit writing a logic 1 to this write-only bit clears the irq2 latch. ack2 always reads as logic 0. reset clears ack2. imask2 ?irq2 interrupt mask bit writing a logic 1 to this read/write bit disables irq2 interrupt requests. reset clears imask2. 1 = irq2 interrupt requests disabled 0 = irq2 interrupt requests enabled mode2 ?irq2 edge/level select bit this read/write bit controls the triggering sensitivity of the irq2 pin. reset clears mode2. 1 = irq2 interrupt requests on falling edges and low levels 0 = irq2 interrupt requests on falling edges only address: $001c bit 7654321bit 0 read: 0 puc0enb 0 0 irq2f 0 imask2 mode2 write: ack2 reset:00000000 = unimplemented figure 17-5. irq2 status and control register (intscr2) external interrupt (irq) mc68hc908ap a-family data sheet, rev. 2 272 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 273 chapter 18 keyboard interrupt module (kbi) 18.1 introduction the keyboard interrupt module (kbi) provides eight independently maskable external interrupts which are accessible via ptd0?td7. when a port pin is enabled for keyboard interrupt function, an internal 30k ? pullup device is also enabled on the pin. 18.2 features features of the keyboard interrupt module include the following: eight keyboard interrupt pins with pullup devices separate keyboard interrupt enable bits and one keyboard interrupt mask programmable edge-only or edge- and level- interrupt sensitivity exit from low-lower modes 18.3 i/o pins the eight keyboard interrupt pins are shared with standard port i/o pins. the full name of the kbi pins are listed in table 18-1 . the generic pin name appear in the text that follows. addr. register name bit 7 654321bit 0 $001a keyboard status and control register (kbscr) read: 0000 keyf 0 imaskk modek write: ackk reset:00000000 $001b keyboard interrupt enable register (kbier) read: kbie7 kbie6 kbie5 kbie4 kbie3 kbie2 kbie1 kbie0 write: reset:00000000 = unimplemented figure 18-1. kbi i/o register summary table 18-1. pin name conventions kbi generic pin name full mcu pin name pin selected for kbi function by kbiex bit in kbier kbi0?bi7 ptd0/kbi0?td7/kbi7 kbie0?bie7 keyboard interrupt module (kbi) mc68hc908ap a-family data sheet, rev. 2 274 freescale semiconductor 18.4 functional description figure 18-2. keyboard interrupt block diagram writing to the kbie7?bie0 bits in the keyboard interrupt enable register independently enables or disables each port d pin as a keyboard interrupt pin. enabling a keyboard interrupt pin in port d also enables its internal pull-up device. a logic 0 applied to an enabled keyboard interrupt pin latches a keyboard interrupt request. a keyboard interrupt is latched when one or more keyboard pins goes low after all were high. the modek bit in the keyboard status and control register controls the triggering mode of the keyboard interrupt. if the keyboard interrupt is edge-sensitive only, a falling edge on a keyboard pin does not latch an interrupt request if another keyboard pin is already low. to prevent losing an interrupt request on one pin because another pin is still low, software can disable the latter pin while it is low. if the keyboard interrupt is falling edge- and low level-sensitive, an interrupt request is present as long as any keyboard pin is low. if the modek bit is set, the keyboard interrupt pins are both falling edge- and low level-sensitive, and both of the following actions must occur to clear a keyboard interrupt request: vector fetch or software clear a vector fetch generates an interrupt acknowledge signal to clear the interrupt request. software may generate the interrupt acknowledge signal by writing a logic 1 to the ackk bit in the keyboard status and control register kbscr. the ackk bit is useful in applications that poll the keyboard interrupt pins and require software to clear the keyboard interrupt request. writing to the ackk bit prior to leaving an interrupt service routine can also prevent spurious interrupts due to noise. setting ackk does not affect subsequent transitions on the keyboard interrupt pins. a falling edge that occurs after writing to the ackk bit latches another interrupt request. if the keyboard interrupt mask bit, imaskk, is clear, the cpu loads the program counter with the vector address at locations $ffe0 and $ffe1. return of all enabled keyboard interrupt pins to logic 1 ?as long as any enabled keyboard interrupt pin is at logic 0, the keyboard interrupt remains set. the vector fetch or software clear and the return of all enabled keyboard interrupt pins to logic 1 may occur in any order. kbie0 kbie7 . . . dq ck clr v dd modek imaskk keyboard interrupt ff vector fetch decoder ackk internal bus reset kbi7 kbi0 synchronizer keyf keyboard interrupt request to pullup enable to pullup enable keyboard interrupt registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 275 if the modek bit is clear, the keyboard interrupt pin is falling-edge-sensitive only. with modek clear, a vector fetch or software clear immediately clears the keyboard interrupt request. reset clears the keyboard interrupt request and the modek bit, clearing the interrupt request even if a keyboard interrupt pin stays at logic 0. the keyboard flag bit (keyf) in the keyboard status and control register can be used to see if a pending interrupt exists. the keyf bit is not affected by the keyboard interrupt mask bit (imaskk) which makes it useful in applications where polling is preferred. to determine the logic level on a keyboard interrupt pin, use the data direction register to configure the pin as an input and read the data register. note setting a keyboard interrupt enable bit (kbiex) forces the corresponding keyboard interrupt pin to be an input, overriding the data direction register. however, the data direction register bit must be a logic 0 for software to read the pin. 18.4.1 keyboard initialization when a keyboard interrupt pin is enabled, it takes time for the internal pull-up to reach a logic 1. therefore a false interrupt can occur as soon as the pin is enabled. to prevent a false interrupt on keyboard initialization: 1. mask keyboard interrupts by setting the imaskk bit in the keyboard status and control register. 2. enable the kbi pins by setting the appropriate kbiex bits in the keyboard interrupt enable register. 3. write to the ackk bit in the keyboard status and control register to clear any false interrupts. 4. clear the imaskk bit. an interrupt signal on an edge-triggered pin can be acknowledged immediately after enabling the pin. an interrupt signal on an edge- and level-triggered interrupt pin must be acknowledged after a delay that depends on the external load. another way to avoid a false interrupt: 1. configure the keyboard pins as outputs by setting the appropriate ddr bits in data direction register. 2. write logic 1s to the appropriate data register bits. 3. enable the kbi pins by setting the appropriate kbiex bits in the keyboard interrupt enable register. 18.5 keyboard interrupt registers two registers control the operation of the keyboard interrupt module: keyboard status and control register ?$001a keyboard interrupt enable register ?$001b 18.5.1 keyboard status and control register flags keyboard interrupt requests acknowledges keyboard interrupt requests masks keyboard interrupt requests controls keyboard interrupt triggering sensitivity keyboard interrupt module (kbi) mc68hc908ap a-family data sheet, rev. 2 276 freescale semiconductor keyf ?keyboard flag bit this read-only bit is set when a keyboard interrupt is pending. reset clears the keyf bit. 1 = keyboard interrupt pending 0 = no keyboard interrupt pending ackk ?keyboard acknowledge bit writing a logic 1 to this write-only bit clears the keyboard interrupt request. ackk always reads as logic 0. reset clears ackk. imaskk ?keyboard interrupt mask bit writing a logic 1 to this read/write bit prevents the output of the keyboard interrupt mask from generating interrupt requests. reset clears the imaskk bit. 1 = keyboard interrupt requests masked 0 = keyboard interrupt requests not masked modek ?keyboard triggering sensitivity bit this read/write bit controls the triggering sensitivity of the keyboard interrupt pins. reset clears modek. 1 = keyboard interrupt requests on falling edges and low levels 0 = keyboard interrupt requests on falling edges only 18.5.2 keyboard interrupt enable register the port-d keyboard interrupt enable register enables or disables each port-d pin to operate as a keyboard interrupt pin. kbie7?bie0 ?keyboard interrupt enable bits each of these read/write bits enables the corresponding keyboard interrupt pin to latch interrupt requests. reset clears the keyboard interrupt enable register. 1 = kbix pin enabled as keyboard interrupt pin 0 = kbix pin not enabled as keyboard interrupt pin address: $001a bit 7654321bit 0 read: 0000 keyf 0 imaskk modek write: ackk reset:00000000 = unimplemented figure 18-3. keyboard status and control register (kbscr) address: $001b bit 7654321bit 0 read: kbie7 kbie6 kbie5 kbie4 kbie3 kbie2 kbie1 kbie0 write: reset:00000000 figure 18-4. keyboard interrupt enable register (kbier) low-power modes mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 277 18.6 low-power modes the wait and stop instructions put the mcu in low power-consumption standby modes. 18.6.1 wait mode the keyboard interrupt module remains active in wait mode. clearing the imaskk bit in the keyboard status and control register enables keyboard interrupt requests to bring the mcu out of wait mode. 18.6.2 stop mode the keyboard interrupt module remains active in stop mode. clearing the imaskk bit in the keyboard status and control register enables keyboard interrupt requests to bring the mcu out of stop mode. 18.7 keyboard module during break interrupts the system integration module (sim) controls whether the keyboard interrupt latch can be cleared during the break state. the bcfe bit in the sim break flag control register (bfcr) enables software to clear status bits during the break state. to allow software to clear the keyboard interrupt latch during a break interrupt, write a logic 1 to the bcfe bit. if a latch is cleared during the break state, it remains cleared when the mcu exits the break state. to protect the latch during the break state, write a logic 0 to the bcfe bit. with bcfe at logic 0 (its default state), writing to the keyboard acknowledge bit (ackk) in the keyboard status and control register during the break state has no effect. keyboard interrupt module (kbi) mc68hc908ap a-family data sheet, rev. 2 278 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 279 chapter 19 computer operating properly (cop) 19.1 introduction the computer operating properly (cop) module contains a free-running counter that generates a reset if allowed to overflow. the cop module helps software recover from runaway code. prevent a cop reset by clearing the cop counter periodically. the cop module can be disabled through the copd bit in the configuration register 1 (config1). 19.2 functional description figure 19-1 shows the structure of the cop module. figure 19-1. cop block diagram the cop counter is a free-running 6-bit counter preceded by a 12-bit prescaler counter. if not cleared by software, the cop counter overflows and generates an asynchronous reset after 2 18 ? 4 or 2 13 ? 4 iclk cycles, depending on the state of the cop rate select bit, coprs, in the config1 register. with a2 13 ? 4 iclk cycle overflow option, a 88-khz iclk gives a cop timeout period of ~93ms. writing any value to location $ffff before an overflow occurs prevents a cop reset by clearing the cop counter and stages 12 through 5 of the prescaler. copctl write iclk reset vector fetch reset circuit reset status register internal reset sources 12-bit cop prescaler clear all stages 6-bit cop counter cop disable reset copctl write clear copen (from sim) cop counter cop clock cop timeout stop instruction (copd from config1) cop rate sel (coprs from config1) clear stages 5?2 computer operating properly (cop) mc68hc908ap a-family data sheet, rev. 2 280 freescale semiconductor note service the cop immediately after reset and before entering or after exiting stop mode to guarantee the maximum time before the first cop counter overflow. a cop reset pulls the rst pin low for 32 iclk cycles and sets the cop bit in the sim reset status register (srsr). in monitor mode, the cop is disabled if the rst pin or the irq1 is held at v tst . during the break state, v tst on the rst pin disables the cop. note place cop clearing instructions in the main program and not in an interrupt subroutine. such an interrupt subroutine could keep the cop from generating a reset even while the main program is not working properly. 19.3 i/o signals the following paragraphs describe the signals shown in figure 19-1 . 19.3.1 iclk iclk is the internal oscillator output signal. see chapter 22 electrical specifications for iclk frequency specification. 19.3.2 stop instruction the stop instruction clears the cop prescaler. 19.3.3 copctl write writing any value to the cop control register (copctl) (see 19.4 cop control register ) clears the cop counter and clears bits 12 through 5 of the prescaler. reading the cop control register returns the low byte of the reset vector. 19.3.4 power-on reset the power-on reset (por) circuit clears the cop prescaler 4096 iclk cycles after power-up. 19.3.5 internal reset an internal reset clears the cop prescaler and the cop counter. 19.3.6 reset vector fetch a reset vector fetch occurs when the vector address appears on the data bus. a reset vector fetch clears the cop prescaler. 19.3.7 copd (cop disable) the copd signal reflects the state of the cop disable bit (copd) in the config1 register. (see figure 19-2 . configuration register 1 (config1) .) cop control register mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 281 19.3.8 coprs (cop rate select) the coprs signal reflects the state of the cop rate select bit (coprs) in the config1 register. coprs ?cop rate select bit coprs selects the cop time out period. reset clears coprs. 1 = cop time out period = 2 13 ?2 4 iclk cycles 0 = cop time out period = 2 18 ?2 4 iclk cycles copd ?cop disable bit copd disables the cop module. 1 = cop module disabled 0 = cop module enabled 19.4 cop control register the cop control register is located at address $ffff and overlaps the reset vector. writing any value to $ffff clears the cop counter and starts a new timeout period. reading location $ffff returns the low byte of the reset vector. 19.5 interrupts the cop does not generate cpu interrupt requests. 19.6 monitor mode when monitor mode is entered with v tst on the irq1 pin, the cop is disabled as long as v tst remains on the irq1 pin or the rst pin. when monitor mode is entered by having blank reset vectors and not having v tst on the irq1 pin, the cop is automatically disabled until a por occurs. 19.7 low-power modes the wait and stop instructions put the mcu in low power-consumption standby modes. address: $001f bit 7654321bit 0 read: coprs lvistop lvirstd lvipwrd lviregd ssrec stop copd write: reset:00000000 figure 19-2. configuration register 1 (config1) address: $ffff bit 7654321bit 0 read: low byte of reset vector write: clear cop counter reset: unaffected by reset figure 19-3. cop control register (copctl) computer operating properly (cop) mc68hc908ap a-family data sheet, rev. 2 282 freescale semiconductor 19.7.1 wait mode the cop remains active during wait mode. to prevent a cop reset during wait mode, periodically clear the cop counter in a cpu interrupt routine. 19.7.2 stop mode stop mode turns off the iclk input to the cop and clears the cop prescaler. service the cop immediately before entering or after exiting stop mode to ensure a full cop timeout period after entering or exiting stop mode. to prevent inadvertently turning off the cop with a stop instruction, a configuration option is available that disables the stop instruction. when the stop bit in the configuration register has the stop instruction is disabled, execution of a stop instruction results in an illegal opcode reset. 19.8 cop module during break mode the cop is disabled during a break interrupt when v tst is present on the rst pin. mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 283 chapter 20 low-voltage inhibit (lvi) 20.1 introduction this section describes the low-voltage inhibit (lvi) module. the lvi module monitors the voltage on the v dd pin and v reg pin, and can force a reset when v dd voltage falls below v tripf1 ,orv reg voltage falls below v tripf2 . note the v reg pin is the output of the internal voltage regulator and is guaranteed to meet operating specification as long as v dd is within the mcu operating voltage. the lvi feature is intended to provide the safe shutdown of the microcontroller and thus protection of related circuitry prior to any application v dd voltage collapsing completely to an unsafe level. it is not intended that users operate the microcontroller at lower than the specified operating voltage, v dd . 20.2 features features of the lvi module include: independent voltage monitoring circuits for v dd and v reg independent disable for v dd and v reg lvi circuits programmable lvi reset programmable stop mode operation 20.3 functional description figure 20-2 shows the structure of the lvi module. the lvi is enabled out of reset. the lvi module contains independent bandgap reference circuit and comparator for monitoring the v dd voltage and the v reg voltage. an lvi reset performs a mcu internal reset and drives the rst pin low to provide low-voltage protection to external peripheral devices. lvistop, lvipwrd, lvirstd, and lviregd are in the config1 register. see chapter 3 configuration & mask option registers (config & mor) for details of the lvi configuration bits. once addr. register name bit 7 654321bit 0 $fe0f lvi status register (lvisr) read: lviout 0000000 write: reset:00000000 = unimplemented figure 20-1. lvi i/o register summary low-voltage inhibit (lvi) mc68hc908ap a-family data sheet, rev. 2 284 freescale semiconductor an lvi reset occurs, the mcu remains in reset until v dd rises above v tripr1 and v reg rises above v tripr2 , which causes the mcu to exit reset. the output of the comparator controls the state of the lviout flag in the lvi status register (lvisr). an lvi reset also drives the rst pin low to provide low-voltage protection to external peripheral devices. figure 20-2. lvi module block diagram 20.3.1 low v dd detector the low v dd detector circuit monitors the v dd voltage and forces a lvi reset when the v dd voltage falls below the trip voltage, v tripf1 . the v dd lvi circuit can be disabled by the setting the lvipwrd bit in config1 register. 20.3.2 low v reg detector the low v reg detector circuit monitors the v reg voltage and forces a lvi reset when the v reg voltage falls below the trip voltage, v tripf2 . the v reg lvi circuit can be disabled by the setting the lviregd bit in config1 register. 20.3.3 polled lvi operation in applications that can operate at v dd levels below the v tripf1 level, software can monitor v dd by polling the lviout bit. in the config1 register, the lvipwrd bit must be at logic 0 to enable the lvi module, and the lvirstd bit must be at logic 1 to disable lvi resets. low v dd detector lvipwrd stop instruction lvi reset v dd > v tripr1 = 0 v dd v tripf1 = 1 from config1 from config1 v dd from config1 to lvisr lviout lvistop lvirstd detector low v reg lviregd stop instruction v reg v tripf2 = 1 v reg > v tripr2 = 0 from config1 v reg from config1 lvistop lvi status register mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 285 20.3.4 forced reset operation in applications that require v dd to remain above the v tripf1 level, enabling lvi resets allows the lvi module to reset the mcu when v dd falls below the v tripf1 level. in the config1 register, the lvipwrd and lvirstd bits must be at logic 0 to enable the lvi module and to enable lvi resets. 20.3.5 voltage hysteresis protection once the lvi has triggered (by having v dd fall below v tripf1 ), the lvi will maintain a reset condition until v dd rises above the rising trip point voltage, v tripr1 . this prevents a condition in which the mcu is continually entering and exiting reset if v dd is approximately equal to v tripf1 . v tripr1 is greater than v tripf1 by the hysteresis voltage, v hys . 20.4 lvi status register the lvi status register (lvisr) indicates if the v dd voltage was detected below v tripf1 or v reg voltage was detected below v tripf2 . lviout ?lvi output bit this read-only flag becomes set when the v dd or v reg falls below their respective trip voltages. reset clears the lviout bit. 20.5 lvi interrupts the lvi module does not generate interrupt requests. address: $fe0f bit 7654321bit 0 read: lviout 0000000 write: reset:00000000 = unimplemented figure 20-3. lvi status register table 20-1. lviout bit indication v dd , v reg lviout v dd > v tripr1 and v reg > v tripr2 0 v dd < v tripf1 or v dd < v tripf2 1 v tripf1 < v dd < v tripr1 or v tripf2 < v reg < v tripr2 previous value low-voltage inhibit (lvi) mc68hc908ap a-family data sheet, rev. 2 286 freescale semiconductor 20.6 low-power modes the stop and wait instructions put the mcu in low power-consumption standby modes. 20.6.1 wait mode if enabled, the lvi module remains active in wait mode. if enabled to generate resets, the lvi module can generate a reset and bring the mcu out of wait mode. 20.6.2 stop mode if enabled in stop mode (lvistop = 1), the lvi module remains active in stop mode. if enabled to generate resets (lvirstd = 0), the lvi module can generate a reset and bring the mcu out of stop mode. mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 287 chapter 21 break module (brk) 21.1 introduction this section describes the break module. the break module can generate a break interrupt that stops normal program flow at a defined address to enter a background program. 21.2 features features of the break module include: accessible input/output (i/o) registers during the break interrupt cpu-generated break interrupts software-generated break interrupts cop disabling during break interrupts 21.3 functional description when the internal address bus matches the value written in the break address registers, the break module issues a breakpoint signal to the cpu. the cpu then loads the instruction register with a software interrupt instruction (swi) after completion of the current cpu instruction. the program counter vectors to $fffc and $fffd ($fefc and $fefd in monitor mode). addr. register name bit 7 654321bit 0 $fe00 sim break status register (sbsr) read: rrrrrr sbsw r write: note reset: 0 $fe03 sim break flag control register (sbfcr) read: bcfe rrrrrrr write: reset: 0 $fe0c break address register high (brkh) read: bit 15 14 13 12 11 10 9 bit 8 write: reset: 00000000 $fe0d break address register low (brkl) read: bit 7654321bit 0 write: reset: 00000000 $fe0e break status and control register (brkscr) read: brke brka 000000 write: reset: 00000000 note: writing a logic 0 clears bw. = unimplemented r = reserved figure 21-1. break module i/o register summary break module (brk) mc68hc908ap a-family data sheet, rev. 2 288 freescale semiconductor the following events can cause a break interrupt to occur: a cpu-generated address (the address in the program counter) matches the contents of the break address registers. software writes a logic 1 to the brka bit in the break status and control register. when a cpu-generated address matches the contents of the break address registers, the break interrupt begins after the cpu completes its current instruction. a return-from-interrupt instruction (rti) in the break routine ends the break interrupt and returns the mcu to normal operation. figure 21-2 shows the structure of the break module. figure 21-2. break module block diagram 21.3.1 flag protection during break interrupts the bcfe bit in the sim break flag control register (sbfcr) enables software to clear status bits during the break state. 21.3.2 cpu during break interrupts the cpu starts a break interrupt by: loading the instruction register with the swi instruction loading the program counter with $fffc and $fffd ($fefc and $fefd in monitor mode) the break interrupt begins after completion of the cpu instruction in progress. if the break address register match occurs on the last cycle of a cpu instruction, the break interrupt begins immediately. 21.3.3 timi and tim2 during break interrupts a break interrupt stops the timer counters. 21.3.4 cop during break interrupts the cop is disabled during a break interrupt when v tst is present on the rst pin. 21.4 low-power modes the wait and stop instructions put the mcu in low power-consumption standby modes. iab15?ab8 iab7?ab0 8-bit comparator 8-bit comparator control break address register low break address register high iab15?ab0 break break module registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 289 21.4.1 wait mode if enabled, the break module is active in wait mode. in the break routine, the user can subtract one from the return address on the stack if sbsw is set. (see chapter 7 system integration module (sim) ) clear the bw bit by writing logic 0 to it. 21.4.2 stop mode a break interrupt causes exit from stop mode and sets the sbsw bit in the break status register. 21.5 break module registers these registers control and monitor operation of the break module: break status and control register (brkscr) break address register high (brkh) break address register low (brkl) sim break status register (sbsr) sim break flag control register (sbfcr) 21.5.1 break status and control register the break status and control register (brkscr) contains break module enable and status bits. brke ?break enable bit this read/write bit enables breaks on break address register matches. clear brke by writing a logic 0 to bit 7. reset clears the brke bit. 1 = breaks enabled on 16-bit address match 0 = breaks disabled on 16-bit address match brka ?break active bit this read/write status and control bit is set when a break address match occurs. writing a logic 1 to brka generates a break interrupt. clear brka by writing a logic 0 to it before exiting the break routine. reset clears the brka bit. 1 = (when read) break address match 0 = (when read) no break address match address: $fe0e bit 7654321bit 0 read: brke brka 000000 write: reset:00000000 = unimplemented figure 21-3. break status and control register (brkscr) break module (brk) mc68hc908ap a-family data sheet, rev. 2 290 freescale semiconductor 21.5.2 break address registers the break address registers (brkh and brkl) contain the high and low bytes of the desired breakpoint address. reset clears the break address registers. 21.5.3 sim break status register the sim break status register (sbsr) contains a flag to indicate that a break caused an exit from wait mode. the flag is useful in applications requiring a return to wait mode after exiting from a break interrupt. sbsw ?break wait bit this status bit is set when a break interrupt causes an exit from wait mode or stop mode. clear sbsw by writing a logic 0 to it. reset clears sbsw. 1 = stop mode or wait mode was exited by break interrupt 0 = stop mode or wait mode was not exited by break interrupt sbsw can be read within the break interrupt routine. the user can modify the return address on the stack by subtracting 1 from it. the following code is an example. address: $fe0c bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 figure 21-4. break address register high (brkh) address: $fe0d bit 7654321bit 0 read: bit 7654321bit 0 write: reset:00000000 figure 21-5. break address register low (brkl) address: $fe00 bit 7654321bit 0 read: rrrrrr sbsw r write: note reset: 0 note: writing a logic 0 clears sbsw. r = reserved figure 21-6. sim break status register (sbsr) break module registers mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 291 21.5.4 sim break flag control register the sim break flag control register (sbfcr) contains a bit that enables software to clear status bits while the mcu is in a break state. bcfe ?break clear flag enable bit this read/write bit enables software to clear status bits by accessing status registers while the mcu is in a break state. to clear status bits during the break state, the bcfe bit must be set. 1 = status bits clearable during break 0 = status bits not clearable during break ; ; ; this code works if the h register has been pushed onto the stack in the break service routine software. this code should be executed at the end of the break service routine software. hibyte equ 5 lobyte equ 6 ; if not sbsw, do rti brclr sbsw,sbsr, return ; ; see if wait mode or stop mode was exited by break. tst lobyte,sp ;if returnlo is not zero, bne dolo ;then just decrement low byte. dec hibyte,sp ;else deal with high byte, too. dolo dec lobyte,sp ;point to wait/stop opcode. return pulh rti ;restore h register. address: $fe03 bit 7654321bit 0 read: bcfe rrrrrrr write: reset: 0 r = reserved figure 21-7. sim break flag control register (sbfcr) break module (brk) mc68hc908ap a-family data sheet, rev. 2 292 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 293 chapter 22 electrical specifications 22.1 introduction this section contains electrical and timing specifications. 22.2 absolute maximum ratings maximum ratings are the extreme limits to which the mcu can be exposed without permanently damaging it. note this device is not guaranteed to operate properly at the maximum ratings. refer to 5v dc electrical characteristics for guaranteed operating conditions. note this device contains circuitry to protect the inputs against damage due to high static voltages or electric fields; however, it is advised that normal precautions be taken to avoid application of any voltage higher than maximum-rated voltages to this high-impedance circuit. for proper operation, it is recommended that v in and v out be constrained to the range v ss (v in or v out ) v dd . reliability of operation is enhanced if unused inputs are connected to an appropriate logic voltage level (for example, either v ss or v dd .) table 22-1. absolute maximum ratings characteristic (1) 1. voltages referenced to v ss . symbol value unit supply voltage v dd 0.3 to +6.0 v input voltage all pins (except irq1) irq1 pin v in v ss 0.3 to v dd +0.3 v ss 0.3 to 8.5 v v maximum current per pin excluding v dd and v ss i 25 ma maximum current out of v ss i mvss 100 ma maximum current into v dd i mvdd 100 ma storage temperature t stg 55 to +150 c electrical specifications mc68hc908ap a-family data sheet, rev. 2 294 freescale semiconductor 22.3 functional operating range 22.4 thermal characteristics table 22-2. operating range characteristic symbol value unit operating temperature range t a 40 to +85 c operating voltage range v dd 4.5 to 5.5 (1) 1. functionality of the device has been characterized down to the lvi trip voltage, but user should ensure that the device supply voltage is within the specified range of 4.5 to 5.5v after power-up in order for the lvi circuit to configure properly. v table 22-3. thermal characteristics characteristic symbol value unit thermal resistance 42-pin sdip 44-pin qfp 48-pin lqfp ja 60 95 80 c/w c/w c/w i/o pin power dissipation p i/o user determined w power dissipation (1) 1. power dissipation is a function of temperature. p d p d = (i dd v dd ) + p i/o = k/(t j + 273 c) w constant (2) 2. k constant unique to the device. k can be determined for a known t a and measured p d. with this value of k, p d and t j can be determined for any value of t a . k p d x(t a + 273 c) + p d 2 ja w/ c average junction temperature t j t a + (p d ja ) c maximum junction temperature t jm 100 c 5v dc electrical characteristics mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 295 22.5 5v dc electrical characteristics table 22-4. dc electrical characteristics (5v) characteristic (1) symbol min typ (2) max unit output high voltage (i load = ?2ma) pta[0:7], ptb[4:7], ptc[0:5], ptd[0:7] (i load = ?5ma) pta[0:7], ptb[4:7], ptc[0:5], ptd[0:7] v oh v oh v dd 0.8 v dd 1.0 v v output low voltage (i load = 6 ma) pta[0:7], ptb[4:7], ptc[0:5], ptd[0:7] (i load = 12ma) ptb[0:3], ptc[6:7] (i load = 15ma) pta[0:7], ptb[4:7], ptc[0:5], ptd[0:7] (i load = 15ma) ptb[0:3], ptc[6:7] (i load = 15ma) as txd, rxd, sctxd, scrxd (i load = see table 22-8 ) as sda, scl v ol v ol v ol v ol v olsci v oliic 0.4 0.4 0.8 0.6 0.4 0.4 v v v v v v led sink current (v ol = 3v) pta[0:7] i ol 91525ma input high voltage pta[0:7], ptb[0:7], ptc[0:7], ptd[0:7], rst, irq1 osc1 v ih 0.7 v dd 0.7 v reg v dd v reg v v input low voltage pta[0:7], ptb[0:7], ptc[0:7], ptd[0:7], rst, irq1 osc1 v il v ss v ss 0.3 v dd 0.3 v reg v v v dd supply current, f op = 8 mhz run (3) wait (4) 10 2.5 20 10 ma ma stop (25 c) with osc, tbm, and lvi modules on (5) with osc and tbm modules on (5) all modules off (6) i dd 1 160 20 2.1 250 125 ma a a stop (?0 to 85 c) with osc, tbm, and lvi modules on (5) with osc and tbm modules on (5) all modules off (6) 1.2 180 42 2.5 300 250 ma a a digital i/o ports hi-z leakage current i il 10 a input current i in 1 a capacitance ports (as input or output) c out c in 12 8 pf pf por rearm voltage (7) v por 0 100 mv por rise time ramp rate (8) r por 0.035 v/ms monitor mode entry voltage v tst 1.4 v dd 8.5 v electrical specifications mc68hc908ap a-family data sheet, rev. 2 296 freescale semiconductor 22.6 5v control timing pullup resistors (9) ptd[0:7] rst, irq1, irq2 r pu1 r pu2 21 21 27 27 39 39 k ? k ? low-voltage inhibit, trip falling voltage1 v tripf1 2.90 3.10 3.30 v low-voltage inhibit, trip rising voltage1 v tripr1 3.25 3.45 3.65 v low-voltage inhibit, trip voltage2 v tripf2 2.25 2.45 2.65 v v reg (10) v reg 2.25 2.50 2.75 v 1. v dd = 4.5 to 5.5 vdc, v ss = 0 vdc, t a = t l to t h , unless otherwise noted. 2. typical values reflect average measurements at midpoint of voltage range, 25 c only. 3. run (operating) i dd measured using external 32mhz clock to osc1; all inputs 0.2 v from rail; no dc loads; less than 100pf on all outputs; c l = 20 pf on osc2; all ports configured as inputs; osc2 capacitance linearly affects run i dd ; measured with all modules enabled. 4. wait i dd measured using external 32mhz to osc1; all inputs 0.2 v from rail; no dc loads; less than 100 pf on all outputs. c l = 20 pf on osc2; all ports configured as inputs; osc2 capacitance linearly affects wait i dd . 5. stop i dd measured using external 8mhz clock to osc1; no port pins sourcing current. 6. stop i dd measured with osc1 grounded; no port pins sourcing current. 7. maximum is highest voltage that por is guaranteed. the rearm voltage is triggered by v reg . 8. if minimum v dd is not reached before the internal por reset is released, rst must be driven low externally until minimum v dd is reached. 9. r pu1 and r pu2 are measured at v dd = 5.0v 10. measured from v dd = v tripf1 (min) to 5.5 v. table 22-5. control timing (5v) characteristic (1) 1. v dd = 4.5 to 5.5 vdc, v ss = 0 vdc; timing shown with respect to 20% v dd and 70% v dd , unless otherwise noted. symbol min max unit internal operating frequency (2) 2. some modules may require a minimum frequency greater than dc for proper operation; see appropriate table for this in- formation. f op 8 mhz rst input pulse width low (3) 3. minimum pulse width reset is guaranteed to be recognized. it is possible for a smaller pulse width to cause a reset. t irl 750 ns table 22-4. dc electrical characteristics (5v) characteristic (1) symbol min typ (2) max unit 5v oscillator characteristics mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 297 22.7 5v oscillator characteristics figure 22-1. rc vs. frequency table 22-6. oscillator speci?ations (5v) characteristic (1) 1. the oscillator circuit operates at v reg . symbol min typ max unit internal oscillator clock frequency f iclk 64k 88k (2) 2. typical value reflect average measurements at midpoint of voltage range, 25 c only. 104k hz external reference clock to osc1 (3) 3. no more than 10% duty cycle deviation from 50%. the max. frequency is limited by an emc filter. f osc dc 32m hz crystal reference frequency (4) 4. fundamental mode crystals only. f xtalclk 1m 8m hz crystal load capacitance (5) 5. consult crystal vendor data sheet. c l crystal ?ed capacitance (5) c 1 2 c l crystal tuning capacitance (5) c 2 2 c l feedback bias resistor r b ?m ? series resistor (5) r s ? ? external rc clock frequency f rcclk 7.6m hz rc oscillator external r r ext see figure 22-1 ? rc oscillator external c c ext ?0 pf r ext c ext osc1 v reg mcu 0 0 1020304050 8 6 4 2 resistor, r ext (k ? ) rc frequency, f rcclk (mhz) c ext = 10 pf v dd = 5v, @ 25 c electrical specifications mc68hc908ap a-family data sheet, rev. 2 298 freescale semiconductor 22.8 5v adc electrical characteristics table 22-7. adc electrical characteristics (5v) characteristic (1) 1. v dd = 4.5 to 5.5 vdc, v ss = 0 vdc, t a = t l to t h , unless otherwise noted. symbol min max unit notes supply voltage v dda 4.5 5.5 v v dda is an dedicated pin and should be tied to v dd on the pcb with proper decoupling. input range v adin 0 v dda v v adin v dda resolution b ad 10 10 bits absolute accuracy a ad 1.5 lsb includes quantization. 0.5 lsb = 1 adc step. adc internal clock f adic 500k 1.048m hz t adic = 1/f adic conversion range r ad v refl v refh v adc voltage reference high v refh v dda + 0.1 v adc voltage reference low v refl v ssa ?0.1 ? conversion time t adc 16 17 t adic cycles sample time t ads 5 t adic cycles monotonicity m ad guaranteed zero input reading z adi 000 001 hex v adin = v refl full-scale reading f adi 3fd 3ff hex v adin = v refh input capacitance c adi 20 pf not tested. input impedance r adi 20m ? v refh /v refl i vref 1.6 ma not tested. mmiic electrical characteristics mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 299 22.9 mmiic electrical characteristics figure 22-2. mmiic signal timings see table 22-9 for mmiic timing parameters. table 22-8. mmiic dc electrical characteristics characteristic (1) 1. v dd = 4.5 to 5.5vdc, v ss = 0 vdc, t a = t l to t h , unless otherwise noted. symbol min typ max unit comments input low v il ?.5 0.8 v data, clock input low. input high v ih 2.1 5.5 v data, clock input high. output low v ol 0.4 v data, clock output low; @i pullup,max input leakage i leak 5 a input leakage current pullup current i pullup 100 350 a current through pull-up resistor or current source. see note. (2) 2. the i pullup (max) specification is determined primarily by the need to accommodate a maximum of 1.1k ? equivalent se- ries resistor of removable smbus devices, such as the smart battery, while maintaining the v ol (max) of the bus. sda scl t hd.sta t low t high t su.dat t hd.dat t su.sta t su.sto electrical specifications mc68hc908ap a-family data sheet, rev. 2 300 freescale semiconductor table 22-9. mmiic interface input/output signal timing characteristic symbol min typ max unit comments operating frequency f smb 10 100 khz mmiic operating frequency bus free time t buf 4.7 s bus free time between stop and start condition repeated start hold time. t hd.sta 4.0 s hold time after (repeated) start condition. after this period, the ?st clock is generated. repeated start setup time. t su.sta 4.7 s repeated start condition setup time. stop setup time t su.sto 4.0 s stop condition setup time. hold time t hd.dat 300 ns data hold time. setup time t su.dat 250 ns data setup time. clock low time-out t timeout 25 35 ms clock low time-out. (1) clock low t low 4.7 s clock low period clock high t high 4.0 s clock high period. (2) slave clock low extend time t low.sext 25 ms cumulative clock low extend time (slave device) (3) master clock low extend time t low.mext 10 ms cumulative clock low extend time (master device) (4) fall time t f 300 ns clock/data fall time (5) rise time t r 1000 ns clock/data rise time (5) 1. devices participating in a transfer will timeout when any clock low exceeds the value of t timeout min. of 25ms. devices that have detected a timeout condition must reset the communication no later than t timeout max of 35ms. the maximum value specified must be adhered to by both a master and a slave as it incorporates the cumulative limit for both a master (10 ms) and a slave (25 ms). software should turn-off the mmiic module to release the sda and scl lines. 2. t high max provides a simple guaranteed method for devices to detect the idle conditions. 3. t low.sext is the cumulative time a slave device is allowed to extend the clock cycles in one message from the initial start to the stop. if a slave device exceeds this time, it is expected to release both its clock and data lines and reset itself. 4. t low.mext is the cumulative time a master device is allowed to extend its clock cycles within each byte of a message as defined from start-to-ack, ack-to-ack, or ack-to-stop. 5. rise and fall time is defined as follows: t r = (v ilmax ?0.15) to (v ihmin + 0.15), t f = 0.9 v dd to (v ilmax ?0.15). cgm electrical specification mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 301 22.10 cgm electrical specification table 22-10. cgm electrical speci?ations characteristic symbol min typ max unit reference frequency f rdv 1 8 mhz range nominal multiplies f nom 125 khz vco center-of-range frequency f vrs 125k 40m hz vco range linear range multiplier l 1 255 vco power-of-two-range multiplier 2 e 1? vco multiply factor n 1 4095 vco prescale multiplier 2 p 1? reference divider factor r 1 1 15 vco operating frequency f vclk 125k 40m hz manual acquisition time t lock 50 ms automatic lock time t lock 50 ms pll jitter (1) 1. deviation of average bus frequency over 2ms. n = vco multiplier. f j 0 f rclk 0.025% 2 p n/4 hz electrical specifications mc68hc908ap a-family data sheet, rev. 2 302 freescale semiconductor 22.11 5v spi characteristics table 22-11. spi characteristics (5v) diagram number (1) 1. numbers refer to dimensions in figure 22-3 and figure 22-4 . characteristic (2) 2. all timing is shown with respect to 20% v dd and 70% v dd , unless noted; 100 pf load on all spi pins. symbol min max unit operating frequency master slave f op(m) f op(s) f op /128 dc f op /2 f op mhz mhz 1 cycle time master slave t cyc (m) t cyc(s) 2 1 128 t cyc t cyc 2 enable lead time t lead(s) 1 t cyc 3 enable lag time t lag(s) 1 t cyc 4 clock (spsck) high time master slave t sckh(m) t sckh(s) t cyc ?5 1/2 t cyc ?5 64 t cyc ns ns 5 clock (spsck) low time master slave t sckl(m) t sckl(s) t cyc ?5 1/2 t cyc ?5 64 t cyc ns ns 6 data setup time (inputs) master slave t su(m) t su(s) 30 30 ns ns 7 data hold time (inputs) master slave t h(m) t h(s) 30 30 ns ns 8 access time, slave (3) cpha = 0 cpha = 1 3. time to data active from high-impedance state t a(cp0) t a(cp1) 0 0 40 40 ns ns 9 disable time, slave (4) 4. hold time to high-impedance state t dis(s) ?0ns 10 data valid time, after enable edge master slave (5) 5. with 100 pf on all spi pins t v(m) t v(s) 50 50 ns ns 11 data hold time, outputs, after enable edge master slave t ho(m) t ho(s) 0 0 ns ns 5v spi characteristics mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 303 figure 22-3. spi master timing note note: this first clock edge is generated internally, but is not seen at the spsck pin. ss pin of master held high msb in ss input spsck output spsck output miso input mosi output note 4 5 5 1 4 bits 6? lsb in master msb out bits 6? master lsb out 11 10 11 7 6 note note: this last clock edge is generated internally, but is not seen at the spsck pin. ss pin of master held high msb in ss input spsck output spsck output miso input mosi output note 4 5 5 1 4 bits 6? lsb in master msb out bits 6? master lsb out 10 11 10 7 6 a) spi master timing (cpha = 0) b) spi master timing (cpha = 1) cpol = 0 cpol = 1 cpol = 0 cpol = 1 electrical specifications mc68hc908ap a-family data sheet, rev. 2 304 freescale semiconductor figure 22-4. spi slave timing note: not defined but normally msb of character just received slave ss input spsck input spsck input miso input mosi output 4 5 5 1 4 msb in bits 6? 8 6 10 5 11 note slave lsb out 9 3 lsb in 2 7 bits 6? msb out note: not defined but normally lsb of character previously transmitted slave ss input spsck input spsck input miso output mosi input 4 5 5 1 4 msb in bits 6? 8 6 10 note slave lsb out 9 3 lsb in 2 7 bits 6? msb out 10 a) spi slave timing (cpha = 0) b) spi slave timing (cpha = 1) 11 11 cpol = 0 cpol = 1 cpol = 0 cpol = 1 memory characteristics mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 305 22.12 memory characteristics table 22-12. memory characteristics characteristic symbol min. max. unit data retention voltage v rdr 1.3 v number of rows per page 8 rows number of bytes per page 512 bytes read bus clock frequency f read (1) 1. f read is defined as the frequency range for which the flash memory can be read. 32k 8m hz page erase time t erase (2) 2. if the page erase time is longer than t erase (min.), there is no erase-disturb, but it reduces the endurance of the flash memory. 20 ms mass erase time t me (3) 3. if the mass erase time is longer than t me (min.), there is no erase-disturb, but it reduces the endurance of the flash memory. 200 ms pgm/erase to hven setup time t nvs 5 s high-voltage hold time t nvh 5 s high-voltage hold time (mass erase) t nvh1 100 s program hold time t pgs 10 s program time t prog 20 40 s address/data setup time t ads 20 ns address/data hold time t adh ?0 ns recovery time t rcv (4) 4. it is defined as the time it needs before the flash can be read after turning off the high voltage charge pump, by clearing hven to logic 0. 1 s cumulative hv period t hv (5) 5. t hv is the cumulative high voltage programming time to the same row before next erase, and the same address can not be programmed twice before next erase. ?8ms row erase endurance (6) 6. the minimum row endurance value specifies each row of the flash memory is guaranteed to work for at least this many erase/program cycles. 10k cycles row program endurance (7) 7. the minimum row endurance value specifies each row of the flash memory is guaranteed to work for at least this many erase/program cycle. 10k cycles data retention time (8) 8. the flash is guaranteed to retain data over the entire operating temperature range for at least the minimum time specified. 10 years electrical specifications mc68hc908ap a-family data sheet, rev. 2 306 freescale semiconductor mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 307 chapter 23 mechanical specifications 23.1 introduction this section gives the dimensions for: 48-pin plastic low-profile quad flat pack (case #932) 44-pin plastic quad flat pack (case #824a) 42-pin shrink dual in-line package (case #858) mechanical specifications mc68hc908ap a-family data sheet, rev. 2 308 freescale semiconductor 23.2 48-pin low-profile quad flat pack (lqfp) figure 23-1. 48-pin lqfp (case #932) a a1 z 0.200 ab t? 4x z 0.200 ac t? 4x b b1 1 12 13 24 25 36 37 48 s1 s v v1 p ae ae t, u, z detail y detail y base metal n j f d t? m 0.080 z ac section ae?e ad g 0.080 ac m top & bottom l w k aa e c h 0.250 r 9 detail ad notes: 1. dimensioning and tolerancing per asme y14.5m, 1994. 2. controlling dimension: millimeter. 3. datum plane ab is located at bottom of lead and is coincident with the lead where the lead exits the plastic body at the bottom of the parting line. 4. datums t, u, and z to be determined at datum plane ab. 5. dimensions s and v to be determined at seating plane ac. 6. dimensions a and b do not include mold protrusion. allowable protrusion is 0.250 per side. dimensions a and b do include mold mismatch and are determined at datum plane ab. 7. dimension d does not include dambar protrusion. dambar protrusion shall not cause the d dimension to exceed 0.350. 8. minimum solder plate thickness shall be 0.0076. 9. exact shape of each corner is optional. t u z ab ac gauge plane dim a min max 7.000 bsc millimeters a1 3.500 bsc b 7.000 bsc b1 3.500 bsc c 1.400 1.600 d 0.170 0.270 e 1.350 1.450 f 0.170 0.230 g 0.500 bsc h 0.050 0.150 j 0.090 0.200 k 0.500 0.700 m 12 ref n 0.090 0.160 p 0.250 bsc l 1 5 r 0.150 0.250 s 9.000 bsc s1 4.500 bsc v 9.000 bsc v1 4.500 bsc w 0.200 ref aa 1.000 ref 44-pin quad flat pack (qfp) mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 309 23.3 44-pin quad flat pack (qfp) figure 23-2. 44-pin qfp (case #824a) notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: millimeter. 3. datum plane ??is located at bottom of lead and is coincident with the lead where the lead exits the plastic body at the bottom of the parting line. 4. datums ?? ??and ??to be determined at datum plane ?? 5. dimensions s and v to be determined at seating plane ?? 6. dimensions a and b do not include mold protrusion. allowable protrusion is 0.25 (0.010) per side. dimensions a and b do include mold mismatch and are determined at datum plane ?? 7. dimension d does not include dambar protrusion. allowable dambar protrusion shall be 0.08 (0.003) total in excess of the d dimension at maximum material condition. dambar cannot be located on the lower radius or the foot. l 33 34 23 22 44 111 12 detail a ? ? a s a? m 0.20 (0.008) d s h s a? m 0.20 (0.008) d s c 0.05 (0.002) a? s b s a? m 0.20 (0.008) d s h s a? m 0.20 (0.008) d s c 0.05 (0.002) a? v l ? ? seating plane m m e h g c ? datum plane detail c 0.10 (0.004) m ? datum plane t r k q w x detail c dim min max min max inches millimeters a 9.90 10.10 0.390 0.398 b 9.90 10.10 0.390 0.398 c 2.10 2.45 0.083 0.096 d 0.30 0.45 0.012 0.018 e 2.00 2.10 0.079 0.083 f 0.30 0.40 0.012 0.016 g 0.80 bsc 0.031 bsc h 0.25 0.010 j 0.13 0.23 0.005 0.009 k 0.65 0.95 0.026 0.037 l 8.00 ref 0.315 ref m 5 10 5 10 n 0.13 0.17 0.005 0.007 q 0 7 0 7 r 0.13 0.30 0.005 0.012 s 12.95 13.45 0.510 0.530 t 0.13 0.005 u 0 ? v 12.95 13.45 0.510 0.530 w 0.40 0.016 x 1.6 ref 0.063 ref detail a b b ?? ?? ? s a? m 0.20 (0.008) d s c f n section b? j d base metal view rotated 90 mechanical specifications mc68hc908ap a-family data sheet, rev. 2 310 freescale semiconductor 23.4 42-pin shrink dual in-line package (sdip) figure 23-3. 42-pin sdip (case #858) ? 42 22 121 ? seating plane ? s a m 0.25 (0.010) t s b m 0.25 (0.010) t l h m j 42 pl d 42 pl f g n k c notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: inch. 3. dimension l to center of lead when formed parallel. 4. dimensions a and b do not include mold flash. maximum mold flash 0.25 (0.010). dim min max min max millimeters inches a 1.435 1.465 36.45 37.21 b 0.540 0.560 13.72 14.22 c 0.155 0.200 3.94 5.08 d 0.014 0.022 0.36 0.56 f 0.032 0.046 0.81 1.17 g 0.070 bsc 1.778 bsc h 0.300 bsc 7.62 bsc j 0.008 0.015 0.20 0.38 k 0.115 0.135 2.92 3.43 l 0.600 bsc 15.24 bsc m 0 15 0 15 n 0.020 0.040 0.51 1.02 mc68hc908ap a-family data sheet, rev. 2 freescale semiconductor 311 ordering information 23.5 introduction this section contains device ordering numbers. 23.6 mc order numbers table 23-1. mc order numbers mc order number ram size (bytes) flash size (bytes) package operating temperature range mc908ap64acb 2,048 62,368 42-pin sdip 40 to +85 c mc908ap64acfb 2,048 62,368 44-pin qfp 40 to +85 c mc908ap64acfa 2,048 62,368 48-pin lqfp 40 to +85 c mc908ap32acb 2,048 32,768 42-pin sdip 40 to +85 c mc908ap32acfb 2,048 32,768 44-pin qfp 40 to +85 c mc908ap32acfa 2,048 32,768 48-pin lqfp 40 to +85 c mc908ap16acb 1,024 16,384 42-pin sdip 40 to +85 c mc908ap16acfb 1,024 16,384 44-pin qfp 40 to +85 c mc908ap16acfa 1,024 16,384 48-pin lqfp 40 to +85 c mc908ap8acb 1,024 8,192 42-pin sdip 40 to +85 c mc908ap8acfb 1,024 8,192 44-pin qfp 40 to +85 c mc908ap8acfa 1,024 8,192 48-pin lqfp 40 to +85 c mc68hc908ap a-family data sheet, rev. 2 312 freescale semiconductor how to reach us: home page: www.freescale.com e-mail: support@freescale.com usa/europe or locations not listed: freescale semiconductor technical information center, ch370 1300 n. alma school road chandler, arizona 85224 +1-800-521-6274 or +1-480-768-2130 support@freescale.com europe, middle east, and africa: freescale halbleiter deutschland gmbh technical information center schatzbogen 7 81829 muenchen, germany +44 1296 380 456 (english) +46 8 52200080 (english) +49 89 92103 559 (german) +33 1 69 35 48 48 (french) support@freescale.com japan: freescale semiconductor japan ltd. headquarters arco tower 15f 1-8-1, shimo-meguro, meguro-ku, tokyo 153-0064 japan 0120 191014 or +81 3 5437 9125 support.japan@freescale.com asia/paci?: freescale semiconductor hong kong ltd. technical information center 2 dai king street tai po industrial estate tai po, n.t., hong kong +800 2666 8080 support.asia@freescale.com for literature requests only: freescale semiconductor literature distribution center p.o. box 5405 denver, colorado 80217 1-800-441-2447 or 303-675-2140 fax: 303-675-2150 ldcforfreescalesemiconductor@hibbertgroup.com information in this document is provided solely to enable system and software implementers to use freescale semiconductor products. there are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. freescale semiconductor reserves the right to make changes without further notice to any products herein. freescale semiconductor makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does freescale semiconductor assume any liability arising out of the application or use of any product or circuit, and speci?ally disclaims any and all liability, including without limitation consequential or incidental damages. ?ypical?parameters that may be provided in freescale semiconductor data sheets and/or speci?ations can and do vary in different applications and actual performance may vary over time. all operating parameters, including ?ypicals? must be validated for each customer application by customer s technical experts. freescale semiconductor does not convey any license under its patent rights nor the rights of others. freescale semiconductor products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the freescale semiconductor product could create a situation where personal injury or death may occur. should buyer purchase or use freescale semiconductor products for any such unintended or unauthorized application, buyer shall indemnify and hold freescale semiconductor and its of?ers, employees, subsidiaries, af?iates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that freescale semiconductor was negligent regarding the design or manufacture of the part. freescale and the freescale logo are trademarks of freescale semiconductor, inc. all other product or service names are the property of their respective owners. ?freescale semiconductor, inc. 2007. all rights reserved. mc68hc908ap64a rev. 2, 01/2007 |
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