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| m68hc08 microcontrollers freescale.com mc68hc908mr32 mc68hc908mr16 data sheet mc68hc908mr32 rev. 6.1 07/2005
mc68hc908mr32 ? mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 3 freescale? and the freescale logo are trade marks of freescale semiconductor, inc. this product incorporates superflash? technology licensed from sst. ? freescale semiconductor, inc., 2005. all rights reserved. mc68hc908mr32 mc68hc908mr16 data sheet to provide the most up-to-date information, the revisi on 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://freescale.com revision history mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 4 freescale semiconductor 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. revision history date revision level description page number(s) august, 2001 3.0 figure 2-1. mc68hc908mr32 memory map ? added flash block protect register (flbpr) at address location $ff7e 29 figure a-1. mc68hc908mr16 memory map ? added flash block protect register (flbpr) at address location $ff7e 306 october, 2001 4.0 3.3.3 conversion time ? reworked equations and text for clarity. 50 december, 2001 5.0 figure 18-8. monitor mode circuit ? pta7 and connecting circuitry added 279 table 18-2. monitor mode signal requirements and options ? switch locations added to column headings for clarity 281 section 16. timer interface a (tima) ? timer discrepancies corrected throughout this section. 233 section 17. timer interface b (timb) ? timer discrepancies corrected throughout this section. 255 november, 2003 6.0 reformatted to meet current publication standards throughout 2.8.2 flash page erase operation ? procedure reworked for clarity 42 2.8.3 flash mass erase operation ? procedure reworked for clarity 42 2.8.4 flash program operation ? procedure reworked for clarity 43 figure 14-14. sim break stat us register (sbsr) ? clarifi ed definition of sbsw bit. 207 19.5 dc electrical characteristics ? corrected maximum value for monitor mode entry voltage (on irq ) 291 19.6 flash memory characteristics ? updated table entries 292 july, 2005 6.1 updated to meet freescale identity guidelines. throughout mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 5 list of chapters chapter 1 general descr iption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 chapter 2 memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 chapter 3 analog-to-digital co nverter (adc). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 chapter 4 clock generator module (cgm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 chapter 5 configuration regist er (config) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 chapter 6 computer operating properly (cop) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 chapter 7 central processor unit (cpu). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 chapter 8 external interrupt (i rq) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 chapter 9 low-voltage inhibit (lvi). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 chapter 10 input/output (i/o) po rts (ports) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 chapter 11 power-on reset (por) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 chapter 12 pulse-width modul ator for motor control (pwmmc) . . . . . . . . . . . . . . . . . . . 115 chapter 13 serial communications in terface module (sci) . . . . . . . . . . . . . . . . . . . . . . .157 chapter 14 system integration module (sim) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 chapter 15 serial peripheral interface module (spi) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 chapter 16 timer interface a (t ima) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 chapter 17 timer interface b (t imb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 chapter 18 development support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 chapter 19 electrical spec ifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 chapter 20 ordering information and mechanical specifications . . . . . . . . . . . . . . . . . . 275 appendix a mc68hc908mr16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 list of chapters mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 6 freescale semiconductor mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 7 table of contents chapter 1 general description 1.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 1.2 features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 1.3 mcu block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1.4 pin assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 1.4.1 power supply pins (v dd and v ss ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.4.2 oscillator pins (osc1 and osc2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.4.3 external reset pin (rst ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.4.4 external interrupt pin (irq ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.4.5 cgm power supply pins (v dda and v ssad ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 1.4.6 external filter capacitor pin (cgmxfc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1.4.7 analog power supply pins (v ddad and v ssad ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1.4.8 adc voltage decoupling capacitor pin (v refh ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1.4.9 adc voltage reference low pin (v refl ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1.4.10 port a input/output (i/o) pins (pta7?pta0). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1.4.11 port b i/o pins (ptb7/atd7?ptb0/atd0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1.4.12 port c i/o pins (ptc6?ptc2 and ptc1/atd9?ptc0/atd8). . . . . . . . . . . . . . . . . . . . . . . 23 1.4.13 port d input-only pins (ptd6/is3 ?ptd4/is1 and ptd3/fault4?ptd0/fault1) . . . . . . 23 1.4.14 pwm pins (pwm6?pwm1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 1.4.15 pwm ground pin (pwmgnd) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 1.4.16 port e i/o pins (pte7/tch3a?pte3/tcl ka and pte2/tch1b?pte0/tclkb) . . . . . . . . 24 1.4.17 port f i/o pins (ptf5/txd? ptf4/rxd and ptf3/miso?ptf0/spsck) . . . . . . . . . . . . . . 24 chapter 2 memory 2.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2.2 unimplemented memory locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2.3 reserved memory locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2.4 i/o section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 2.5 memory map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 2.6 monitor rom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2.7 random-access memory (ram) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2.8 flash memory (flash) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 2.8.1 flash control register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 2.8.2 flash page erase operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 2.8.3 flash mass erase operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 2.8.4 flash program operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 2.8.5 flash block protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 2.8.6 flash block protect register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 table of contents mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 8 freescale semiconductor 2.8.7 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 2.8.8 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 chapter 3 analog-to-digital converter (adc) 3.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 3.2 features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 3.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 3.3.1 adc port i/o pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.3.2 voltage conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.3.3 conversion time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.3.4 continuous conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.3.5 result justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.3.6 monotonicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.4 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.5 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.6 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.6.1 adc analog power pin (v ddad ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.6.2 adc analog ground pin (v ssad ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.6.3 adc voltage reference pin (v refh ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.6.4 adc voltage reference low pin (v refl ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 3.6.5 adc voltage in (advin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.6.6 adc external connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.6.6.1 v refh and v refl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.6.6.2 anx. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.6.6.3 grounding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.7 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.7.1 adc status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 3.7.2 adc data register high . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 3.7.3 adc data register low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 3.7.4 adc clock register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 chapter 4 clock generator module (cgm) 4.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.2 features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.3.1 crystal oscillator circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.3.2 phase-locked loop circuit (pll) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.3.2.1 pll circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.3.2.2 acquisition and tracking modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.3.2.3 manual and automatic pll bandwidth modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.3.2.4 programming the pll. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.3.2.5 special programming exceptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.3.3 base clock selector circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.3.4 cgm external connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 9 4.4 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 4.4.1 crystal amplifier input pin (osc1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 4.4.2 crystal amplifier output pin (osc2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 4.4.3 external filter capacitor pin (cgmxfc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 4.4.4 pll analog power pin (v dda ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 4.4.5 oscillator enable signal (simoscen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 4.4.6 crystal output frequency signal (cgmxclk) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.4.7 cgm base clock output (cgmout) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.4.8 cgm cpu interrupt (cgmint) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.5 cgm registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.5.1 pll control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4.5.2 pll bandwidth control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7 4.5.3 pll programming register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 4.6 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 4.7 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 4.8 acquisition/lock time specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.8.1 acquisition/lock time definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.8.2 parametric influences on reaction time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.8.3 choosing a filter capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.8.4 reaction time calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 chapter 5 configuration register (config) 5.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 5.2 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 5.3 configuration register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 chapter 6 computer operatin g properly (cop) 6.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 6.2 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 6.3 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 6.3.1 cgmxclk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 6.3.2 copctl write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 6.3.3 power-on reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 6.3.4 internal reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 6.3.5 reset vector fetch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 6.3.6 copd (cop disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 6.4 cop control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 6.5 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 6.6 monitor mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 6.7 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 6.8 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 table of contents mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 10 freescale semiconductor chapter 7 central processor unit (cpu) 7.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 7.2 features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 7.3 cpu registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 7.3.1 accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 7.3.2 index register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 7.3.3 stack pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 7.3.4 program counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 7.3.5 condition code register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 7.4 arithmetic/logic unit (alu) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 7.5 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 7.5.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 7.5.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 7.6 cpu during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 7.7 instruction set summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 7.8 opcode map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 chapter 8 external interrupt (irq) 8.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 8.2 features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 8.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 8.4 irq pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 8.5 irq status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 chapter 9 low-voltage inhibit (lvi) 9.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 9.2 features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 9.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 9.3.1 polled lvi operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 9.3.2 forced reset operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 9.3.3 false reset protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 9.3.4 lvi trip selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 9.4 lvi status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 9.5 lvi interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 9.6 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 9.7 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 11 chapter 10 input/output (i/o) ports (ports) 10.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 10.2 port a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 10.2.1 port a data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 10.2.2 data direction register a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 10.3 port b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 10.3.1 port b data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 10.3.2 data direction register b. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 10.4 port c. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 10.4.1 port c data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 10.4.2 data direction register c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 10.5 port d. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 10.6 port e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 10.6.1 port e data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 10.6.2 data direction register e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 10.7 port f . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 10.7.1 port f data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 10.7.2 data direction register f . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 chapter 11 power-on reset (por) 11.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 11.2 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 chapter 12 pulse-width modulator fo r motor control (pwmmc) 12.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 12.2 features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 12.3 timebase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 12.3.1 resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 12.3.2 prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 12.4 pwm generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 12.4.1 load operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 12.4.2 pwm data overflow and underflow conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 12.5 output control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 12.5.1 selecting six independent pwms or three complementary pwm pairs . . . . . . . . . . . . . 126 12.5.2 dead-time insertion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 12.5.3 top/bottom correction with motor phase current po larity sensing . . . . . . . . . . . . . . . . . 130 12.5.4 output polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 12.5.5 pwm output port control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 12.6 fault protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 12.6.1 fault condition input pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 12.6.1.1 fault pin filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 12.6.1.2 automatic mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 12.6.1.3 manual mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 table of contents mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 12 freescale semiconductor 12.6.2 software output disable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 12.6.3 output port control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 12.7 initialization and the pwmen bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 12.8 pwm operation in wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 12.9 control logic block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 12.9.1 pwm counter registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 12.9.2 pwm counter modulo registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 12.9.3 pwmx value registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 12.9.4 pwm control register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 12.9.5 pwm control register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 12.9.6 dead-time write-once register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 12.9.7 pwm disable mapping write-once register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 12.9.8 fault control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 12.9.9 fault status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 12.9.10 fault acknowledge register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 12.9.11 pwm output control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 12.10 pwm glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 chapter 13 serial communications in terface module (sci) 13.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 13.2 features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 13.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 13.3.1 data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 13.3.2 transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 13.3.2.1 character length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 13.3.2.2 character transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 13.3.2.3 break characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 13.3.2.4 idle characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 13.3.2.5 inversion of transmitted output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3 13.3.2.6 transmitter interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 13.3.3 receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 13.3.3.1 character length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 13.3.3.2 character reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 13.3.3.3 data sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 13.3.3.4 framing errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 13.3.3.5 receiver wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 13.3.3.6 receiver interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 13.3.3.7 error interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 13.4 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 13.5 sci during break module interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 13.6 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 13.6.1 ptf5/txd (transmit data). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 13.6.2 ptf4/rxd (receive data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 13.7 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 13.7.1 sci control register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 13.7.2 sci control register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 13 13.7.3 sci control register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 13.7.4 sci status register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 13.7.5 sci status register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 13.7.6 sci data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 13.7.7 sci baud rate register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 chapter 14 system integrati on module (sim) 14.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 14.2 sim bus clock control and generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 14.2.1 bus timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 14.2.2 clock startup from por or lvi reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 14.2.3 clocks in wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 14.3 reset and system initializat ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 14.3.1 external pin reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 14.3.2 active resets from intern al sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 14.3.2.1 power-on reset (por) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 14.3.2.2 computer operating properly (cop) reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 14.3.2.3 illegal opcode reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 14.3.2.4 illegal address reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 14.3.2.5 forced monitor mode entry reset (menrst) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 14.3.2.6 low-voltage inhibit (lvi) reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 86 14.4 sim counter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 14.4.1 sim counter during power-on reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 14.4.2 sim counter and reset states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6 14.5 exception control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 14.5.1 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 14.5.1.1 hardware interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 14.5.1.2 software interrupt (swi) instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 14.5.2 reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 14.6 low-power mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 14.6.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 14.6.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 14.7 sim registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 14.7.1 sim break status register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 14.7.2 sim reset status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 14.7.3 sim break flag control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3 chapter 15 serial peripheral interface module (spi) 15.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 15.2 features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 15.3 pin name conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 15.4 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 15.4.1 master mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 15.4.2 slave mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 15.5 transmission formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 table of contents mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 14 freescale semiconductor 15.5.1 clock phase and polarity controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 9 15.5.2 transmission format when cpha = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 15.5.3 transmission format when cpha = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 15.5.4 transmission initiation latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 15.6 error conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 15.6.1 overflow error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 15.6.2 mode fault error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 15.7 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 15.8 resetting the spi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 15.9 queuing transmission data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 15.10 low-power mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 15.11 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 15.11.1 miso (master in/slave out). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 15.11.2 mosi (master out/slave in). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 15.11.3 spsck (serial clock) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 15.11.4 ss (slave select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 15.11.5 v ss (clock ground) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 15.12 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 15.12.1 spi control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 15.12.2 spi status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 15.12.3 spi data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 chapter 16 timer interface a (tima) 16.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 16.2 features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 16.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 16.3.1 tima counter prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 16.3.2 input capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 16.3.3 output compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 16.3.3.1 unbuffered output compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 16.3.3.2 buffered output compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 21 16.3.4 pulse-width modulation (pwm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 16.3.4.1 unbuffered pwm signal generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 16.3.4.2 buffered pwm signal generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 16.3.4.3 pwm initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 16.4 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 16.5 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 16.6 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 16.6.1 tima clock pin (pte3/tclka) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 16.6.2 tima channel i/o pins (pte4/tch0a?pte7/tch3a) . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 16.7 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 16.7.1 tima status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 16.7.2 tima counter registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 16.7.3 tima counter modulo registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 16.7.4 tima channel status and control registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 16.7.5 tima channel registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232 mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 15 chapter 17 timer interface b (timb) 17.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 17.2 features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 17.3 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 17.3.1 timb counter prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 17.3.2 input capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 17.3.3 output compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 17.3.3.1 unbuffered output compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 17.3.3.2 buffered output compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 40 17.3.4 pulse-width modulation (pwm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 17.3.4.1 unbuffered pwm signal generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 17.3.4.2 buffered pwm signal generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 17.3.4.3 pwm initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 17.4 interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 17.5 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 17.6 i/o signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 17.6.1 timb clock pin (pte0/tclkb) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 17.6.2 timb channel i/o pins (pte1/tch0b?pte2/tch1b) . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 17.7 i/o registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 17.7.1 timb status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 17.7.2 timb counter registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 17.7.3 timb counter modulo registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 17.7.4 timb channel status and control registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 17.7.5 timb channel registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 chapter 18 development support 18.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 18.2 break module (brk) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 18.2.1 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 18.2.1.1 flag protection during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 18.2.1.2 cpu during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 53 18.2.1.3 tim1 and tim2 during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 18.2.1.4 cop during break in terrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 53 18.2.2 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 18.2.2.1 wait mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 18.2.2.2 stop mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 18.2.3 break module registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 18.2.3.1 break status and control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 18.2.3.2 break address registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 18.2.3.3 break status register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 18.2.3.4 break flag control register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 55 table of contents mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 16 freescale semiconductor 18.3 monitor rom (mon) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255 18.3.1 functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 18.3.1.1 entering monitor mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 18.3.1.2 normal monitor mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 18.3.1.3 forced monitor mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 18.3.1.4 data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 18.3.1.5 echoing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 18.3.1.6 break signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 18.3.1.7 commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 18.3.1.8 baud rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 18.3.2 security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 chapter 19 electrical specifications 19.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 19.2 absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 19.3 functional operating range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 19.4 thermal characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 19.5 dc electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 19.6 flash memory characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 19.7 control timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 19.8 serial peripheral interface characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 19.9 timer interface module characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 72 19.10 clock generation module component specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 19.11 cgm operating conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 19.12 cgm acquisition/lock time specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 19.13 analog-to-digital converter (adc) characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274 chapter 20 ordering information and m echanical specifications 20.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 20.2 order numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 20.3 64-pin plastic quad flat pack (qfp) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 76 20.4 56-pin shrink dual in-line package (s dip) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 appendix a mc68hc908mr16 mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 17 chapter 1 general description 1.1 introduction the mc68hc908mr32 is a member of the low-cost , high-performance m68hc08 family of 8-bit microcontroller units (mcus). all mcus in the fa mily use the enhanced m68hc 08 central processor unit (cpu08) and are available with a variety of mo dules, memory sizes and types, and package types. the information contained in this document pertain s to the mc68hc908mr16 with the exceptions shown in appendix a mc68hc908mr16 . 1.2 features features include: high-performance m68hc08 architecture fully upward-compatible object code wi th m6805, m146805, and m68hc05 families 8-mhz internal bus frequency on-chip flash memory with in-circuit programming capabilities of flash program memory: mc68hc908mr32 ? 32 kbytes mc68hc908mr16 ? 16 kbytes on-chip programming firmware fo r use with host personal computer flash data security (1) 768 bytes of on-chip random-access memory (ram) 12-bit, 6-channel center-aligned or edge- aligned pulse-width modulator (pwmmc) serial peripheral interface module (spi) serial communications interface module (sci) 16-bit, 4-channel timer interface module (tima) 16-bit, 2-channel timer interface module (timb) clock generator module (cgm) low-voltage inhibit (lvi) module with software selectable trip points 10-bit, 10-channel analog-to-digital converter (adc) system protection features: ? optional computer operating properly (cop) reset ? low-voltage detection with optional reset ? illegal opcode or address detection with optional reset ? fault detection with optional pwm disabling 1. no security feature is absolutely secure . however, freescale?s strategy is to make reading or copying the flash difficult fo r unauthorized users. general description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 18 freescale semiconductor available packages: ? 64-pin plastic quad flat pack (qfp) ? 56-pin shrink dual in-line package (sdip) low-power design, fully static with wait mode master reset pin (rst ) and power-on reset (por) stop mode as an option break module (brk) supports setting the in-circuit simulator (ics) single break point features of the cpu08 include: enhanced m68hc05 programming model extensive loop control functions 16 addressing modes (eight more than the m68hc05) 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 c language support 1.3 mcu block diagram figure 1-1 shows the structure of the mc68hc908mr32. mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 19 mcu block diagram figure 1-1. mcu block diagram clock generator module system integration module serial communications interface module serial peripheral interface module (2) timer interface module a low-voltage inhibit module power-on reset module computer operating properly module arithmetic/logic unit cpu registers m68hc08 cpu control and status registers ? 112 bytes user flash ? 32,256 bytes user ram ? 768 bytes monitor rom ? 240 bytes user flash vector space ? 46 bytes irq module power pta ddra ddrb ptb ddrc ptc ptd ddre pte ptf ddrf internal bus osc1 osc2 cgmxfc rst irq v ss v dd v ddad pta7?pta0 pte7/tch3a pte6/tch2a pte5/tch1a pte4/tch0a pte3/tclka pte2/tch1b (1) pte1/tch0b (1) pte0/tclkb (1) ptf5/txd ptf4/rxd ptf3/miso (1) ptf2/mosi (1) ptf1/ss (1) ptf0/spsck (1) timer interface module b pulse-width modulator module ptb7/atd7 ptb6/atd6 ptb5/atd5 ptb4/atd4 ptb3/atd3 ptb2/atd2 ptb1/atd1 ptb0/atd0 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1/atd9 (1) ptc0/atd8 ptd6/is3 ptd5/is2 ptd4/is1 ptd3/fault4 ptd2/fault3 ptd1/fault2 ptd0/fault1 pwm6?pwm1 analog-to-digital converter module v ssad v ddad v ssad (3) pwmgnd v refl (3) v refh notes: 1. these pins are not available in the 56-pin sdip package. 2. this module is not available in the 56-pin sdip package. 3. in the 56-pin sdip package, these pins are bonded together. single break module general description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 20 freescale semiconductor 1.4 pin assignments figure 1-2 shows the 64-pin qfp pin assignments and figure 1-3 shows the 56-pin sdip pin assignments. figure 1-2. 64-pin qfp pin assignments ptc1/atd9 pta2 v ss ptc0/atd8 ptb7/atd7 ptb6/atd6 ptb5/atd5 ptb4/atd4 ptb3/atd3 ptb2/atd2 v ddad v ssad v refl v refh ptc2 ptc3 ptc4 ptc5 irq ptf5/txd ptf4/rxd ptf3/miso ptf2/mosi ptf1/ss ptf0/spsck v dd pte7/tch3a pte6/tch2a pte5/tch1a pte4/tch0a pte3/tclka pte2/tch1b pte1/tch0b pta1 pta0 v ssad osc2 osc1 cgmxfc v ddad rst ptb1/atd1 ptb0/atd0 pta7 pta6 pta5 pta4 pta3 ptd1/fault2 ptc6 ptd0/fault1 ptd2/fault3 ptd3/fault4 ptd4/is1 ptd5/is2 ptd6/is3 pwm1 pwm2 pwm3 pwm4 pte0/tclkb 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 pwmgnd pwm5 pwm6 pin assignments mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 21 figure 1-3. 56-pin sdip pin assignments pta2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 pta3 pta4 pta5 pta6 pta7 ptb0/atd0 ptb1/atd1 ptb2/atd2 ptb3/atd3 ptb4/atd4 ptb5/atd5 ptb6/atd5 ptb7/atd7 ptc0/atd8 v ddad v ssad /v refl v refh ptc2 ptc3 ptc4 ptc5 ptc6 ptd0/fault1 ptd1/fault2 ptd2/fault3 ptd3/fault4 ptd4/is1 ptd5/is2 ptd6/is3 pwm1 pwm2 pwm3 pwm4 pwmgnd pwm5 pwm6 nc pte3/tclka pte4/tch0a pte5/tch1a pte6/tch2a pte7/tch3a v dd v ss ptf4/rxd ptf5/txd irq rst v dda cgmxfc osc1 osc2 v ssa pta0 pta1 note: ptc1, pte0, pte1, pte2, pt f0, ptf1, ptf2, and ptf3 are removed from this package. general description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 22 freescale semiconductor 1.4.1 power supply pins (v dd and v ss ) v dd and v ss are the power supply and ground pins. th e mcu operates from a single power supply. 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 1-4 shows. place the c1 bypass capacitor as close to the mcu as possible. use a high-frequency-response ceramic capacitor for c1. c2 is an optional bulk current bypass capacitor for use in applications that require the port pins to source high-current levels. figure 1-4. power supply bypassing 1.4.2 oscillator pins (osc1 and osc2) the osc1 and osc2 pins are the connections for the on-chip oscillator circuit. for more detailed information, see chapter 4 clock generator module (cgm) . 1.4.3 external reset pin (rst ) a logic 0 on the rst pin forces the mcu to a known startup state. rst is bidirectional, allowing a reset of the entire system. it is driven low when any internal reset source is asserted. see chapter 14 system integration module (sim) . 1.4.4 external interrupt pin (irq ) irq is an asynchronous external interrupt pin. see chapter 8 external interrupt (irq) . 1.4.5 cgm power supply pins (v dda and v ssad ) v dda and v ssad are the power supply pins for the analog portion of the clock generator module (cgm). decoupling of these pins should be per the digital supply. see chapter 4 clock generator module (cgm) . mcu v dd c2 c1 0.1 f v ss v dd + note: component values shown r epresent typical applications. 1?10 f pin assignments mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 23 1.4.6 external filter capacitor pin (cgmxfc) cgmxfc is an external filter c apacitor connection for the cgm. see chapter 4 clock generator module (cgm) . 1.4.7 analog power supply pins (v ddad and v ssad ) v ddad and v ssad are the power supply pins for the analog-to-dig ital converter. decoupling of these pins should be per the digital supply. see chapter 3 analog-to-digital converter (adc) . 1.4.8 adc voltage decoupling capacitor pin (v refh ) v refh is the power supply for setting the reference voltage. connect the v refh pin to the same voltage potential as v ddad . see chapter 3 analog-to-digital converter (adc) . 1.4.9 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 ssad . see chapter 3 analog-to-digital converter (adc) . 1.4.10 port a input/outp ut (i/o) pins (pta7?pta0) pta7?pta0 are general-purpose bidirectional input/output (i/o) port pins. see chapter 10 input/output (i/o) ports (ports) . 1.4.11 port b i/o pi ns (ptb7/atd7?ptb0/atd0) port b is an 8-bit special function port that shares a ll eight pins with the analog-to-digital converter (adc). see chapter 3 analog-to-digital converter (adc) and chapter 10 input/output (i/o) ports (ports) . 1.4.12 port c i/o pins (ptc 6?ptc2 and ptc1/atd9?ptc0/atd8) ptc6?ptc2 are general-purpose bidirectional i/o port pins chapter 10 input/output (i/o) ports (ports) . ptc1/atd9?ptc0/atd8 are special functi on port pins that are shared with the analog-to-digital converter (adc). see chapter 3 analog-to-digital converter (adc) and chapter 10 input/output (i/o) ports (ports) . 1.4.13 port d input -only pins (ptd6/is3 ?ptd4/is1 and ptd3/fault4?ptd0/fault1) ptd6/is3 ?ptd4/is1 are special function input-only port pins that also serve as current sensing pins for the pulse-width modulator module (pwmmc). ptd3/fault4?ptd0/fault1 are special function port pins that also serve as f ault pins for the pwmmc. see chapter 12 pulse-width modulator for motor control (pwmmc) and chapter 10 input/output (i/o) ports (ports) . 1.4.14 pwm pins (pwm6?pwm1) pwm6?pwm1 are dedicated pins used for the outputs of the pulse-width modulator module (pwmmc). these are high-current sink pins. see chapter 12 pulse-width modulator for motor control (pwmmc) and chapter 19 electrical specifications . general description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 24 freescale semiconductor 1.4.15 pwm gr ound pin (pwmgnd) pwmgnd is the ground pin for the pulse-width modulator module (pwmmc). this dedicated ground pin is used as the ground for the six high-current pwm pins. see chapter 12 pulse-width modulator for motor control (pwmmc) . 1.4.16 port e i/o pi ns (pte7/tch3a?pte3/tclka and pte2/tch1b?pte0/tclkb) port e is an 8-bit special function port that shares it s pins with the two timer interface modules (tima and timb). see chapter 16 timer interface a (tima) , chapter 17 timer interface b (timb) , and chapter 10 input/output (i/o) ports (ports) . 1.4.17 port f i/ o pins (ptf5/txd?ptf4/rxd and ptf3/miso?ptf0/spsck) port f is a 6-bit special function port that shares tw o of its pins with the seri al communications interface module (sci) and four of its pins with the serial peripheral interface module (spi). see chapter 15 serial peripheral interface module (spi) , chapter 13 serial communications interface module (sci) , and chapter 10 input/output (i/o) ports (ports) . mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 25 chapter 2 memory 2.1 introduction the central processor unit (cpu08) can address 64 kb ytes of memory space. the memory map, shown in figure 2-1 , includes: 32 kbytes of flash 768 bytes of random-access memory (ram) 46 bytes of user-defined vectors 240 bytes of monitor read-only memory (rom) 2.2 unimplemented memory locations some addresses are unimplemented. accessing an uni mplemented address can cause an illegal address reset. in the memory map and in the input/output (i/o) register summary, unimplemented addresses are shaded. some i/o bits are read only; the write function is unimplemented. writing to a read-only i/o bit has no effect on microcontroller unit (mcu) operation. in r egister figures, the write fu nction of read-only bits is shaded. similarly, some i/o bits are write only; the read func tion is unimplemented. reading of write-only i/o bits has no effect on mcu operation. in register figur es, the read function of write-only bits is shaded. 2.3 reserved memory locations some addresses are reserved. writing to a reserv ed address can have unpredictable effects on mcu operation. in the memory map ( figure 2-1 ) and in the i/o register summary ( figure 2-2 ) reserved addresses are marked with the word reserved. some i/o bits are reserved. writing to a reserved bit can have unpredictable effects on mcu operation. in register figures, reserved bits are marked with the letter r. memory mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 26 freescale semiconductor 2.4 i/o section addresses $0000?$005f, shown in figure 2-2 , contain most of the control, status, and data registers. additional i/o registers have these addresses: $fe00, sim break status register (sbsr) $fe01, sim reset status register (srsr) $fe03, sim break flag control register (sbfcr) $fe07, flash control register (flcr) $fe0c, break address register high (brkh) $fe0d, break address register low (brkl) $fe0e, break status and control register (brkscr) $fe0f, lvi status and control register (lviscr) $ff7e, flash block protect register (flbpr) $ffff, cop control register (copctl) 2.5 memory map figure 2-1 shows the memory map for the mc68hc908mr32 while the memory map for the mc68hc908mr16 is shown in appendix a mc68hc908mr16 memory map mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 27 $0000 $005f i/o registers ? 96 bytes $0060 $035f ram ? 768 bytes $0360 $7fff unimplemented ? 31,904 bytes $8000 $fdff flash ? 32,256 bytes $fe00 sim break status register (sbsr) $fe01 sim reset status register (srsr) $fe02 reserved $fe03 sim break flag control register (sbfcr) $fe04 reserved $fe05 reserved $fe06 reserved $fe07 reserved $fe08 flash control register (flcr) $fe09 unimplemented $fe0a unimplemented $fe0b unimplemented $fe0c sim break address register high (brkh) $fe0d sim break address register low (brkl) $fe0e sim break flag control register (sbfcr) $fe0f lvi status and control register (lviscr) $fe10 $feff monitor rom ? 240 bytes $ff00 $ff7d unimplemented ? 126 bytes $ff7e flash block protect register (flbpr) $ff7f $ffd1 unimplemented ? 83 bytes $ffd2 $ffff vectors ? 46 bytes figure 2-1. mc68hc908mr32 memory map memory mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 28 freescale semiconductor addr. register name bit 7 6 5 4 3 2 1 bit 0 $0000 port a data register (pta) see page 103. read: pta7 pta6 pta5 pta4 pta3 pta2 pta1 pta0 write: reset: unaffected by reset $0001 port b data register (ptb) see page 104. read: ptb7 ptb6 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 write: reset: unaffected by reset $0002 port c data register (ptc) see page 106. read: 0 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1 ptc0 write: r reset: unaffected by reset $0003 port d data register (ptd) see page 107. read: 0 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 write: r r r r r r r r reset: unaffected by reset $0004 data direction register a (ddra) see page 103. read: ddra7 ddra6 ddra5 ddra4 ddra3 ddra2 ddra1 ddra0 write: reset: 0 0 0 0 0 0 0 0 $0005 data direction register b (ddrb) see page 105. read: ddrb7 ddrb6 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 write: reset: 0 0 0 0 0 0 0 0 $0006 data direction register c (ddrc) see page 106. read: 0 ddrc6 ddrc5 ddrc4 ddrc3 ddrc2 ddrc1 ddrc0 write: r reset: 0 0 0 0 0 0 0 0 $0007 unimplemented $0008 port e data register (pte) see page 108. read: pte7 pte6 pte5 pte4 pte3 pte2 pte1 pte0 write: reset: unaffected by reset $0009 port f data register (ptf) see page 110. read: 0 0 ptf5 ptf4 ptf3 ptf2 ptf1 ptf0 write: r r reset: unaffected by reset $000a unimplemented $000b unimplemented $000c data direction register e (ddre) see page 109. read: ddre7 ddre6 ddre5 ddre4 ddre3 ddre2 ddre1 ddre0 write: reset: 0 0 0 0 0 0 0 0 $000d data direction register f (ddrf) see page 110. read: 0 0 ddrf5 ddrf4 ddrf3 ddrf2 ddrf1 ddrf0 write: r r reset: 0 0 0 0 0 0 u = unaffected x = indeterminate r = reserved bold = buffered = unimplemented figure 2-2. control, status, and data registers summary (sheet 1 of 8) memory map mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 29 $000e tima status/control register (tasc) see page 226. read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst r reset: 0 0 1 0 0 0 0 0 $000f tima counter register high (tacnth) see page 227. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: r r r r r r r r reset: 0 0 0 0 0 0 0 0 $0010 tima counter register low (tacntl) see page 227. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: r r r r r r r r reset: 0 0 0 0 0 0 0 0 $0011 tima counter modulo register high (tamodh) see page 228. read: bit 15 14 13 12 11 10 9 bit 8 write: reset: 1 1 1 1 1 1 1 1 $0012 tima counter modulo register low (tamodl) see page 228. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 1 1 1 1 1 1 1 1 $0013 tima channel 0 status/control register (tasc0) see page 229. read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset: 0 0 0 0 0 0 0 0 $0014 tima channel 0 register high (tach0h) see page 232. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset $0015 tima channel 0 register low (tach0l) see page 232. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset $0016 tima channel 1 status/control register (tasc1) see page 232. read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 r reset: 0 0 0 0 0 0 0 0 $0017 tima channel 1 register high (tach1h) see page 232. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset $0018 tima channel 1 register low (tach1l) see page 232. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset $0019 tima channel 2 status/control register (tasc2) see page 229. read: ch2f ch2ie ms2b ms2a els2b els2a tov2 ch2max write: 0 reset: 0 0 0 0 0 0 0 0 addr. register name bit 7 6 5 4 3 2 1 bit 0 u = unaffected x = indeterminate r = reserved bold = buffered = unimplemented figure 2-2. control, status, and data registers summary (sheet 2 of 8) memory mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 30 freescale semiconductor $001a tima channel 2 register high (tach2h) see page 232. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset $001b tima channel 2 register low (tach2l) see page 232. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset $001c tima channel 3 status/control register (tasc3) see page 229. read: ch3f ch3ie 0 ms3a els3b els3a tov3 ch3max write: 0 r reset: 0 0 0 0 0 0 0 0 $001d tima channel 3 register high (tach3h) see page 232. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset $001e tima channel 3 register low (tach3l) see page 232. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset $001f configuration register (config) see page 74. read: edge botneg topneg indep lvirst lvipwr stope copd write: reset: 0 0 0 0 1 1 0 0 $0020 pwm control register 1 (pctl1) see page 146. read: disx disy pwmint pwmf isens1 isens0 ldok pwmen write: reset: 0 0 0 0 0 0 0 0 $0021 pwm control register 2 (pctl2) see page 148. read: ldfq1 ldfq0 0 ipol1 ipol2 ipol3 prsc1 prsc0 write: reset: 0 0 0 0 0 0 0 0 $0022 fault control register (fcr) see page 150. read: fint4 fmode4 fint3 fmode3 fint2 fmode2 fint1 fmode1 write: reset: 0 0 0 0 0 0 0 0 $0023 fault status register (fsr) see page 152. read: fpin4 fflag4 fpin3 fflag3 fpin2 fflag2 fpin1 fflag1 write: reset: u 0 u 0 u 0 u 0 $0024 fault acknowledge register (ftack) see page 153. read: 0 0 dt6 dt5 dt4 dt3 dt2 dt1 write: ftack4 ftack3 ftack2 ftack1 reset: 0 0 0 0 0 0 0 0 $0025 pwm output control register (pwmout) see page 154. read: 0 outctl out6 out5 out4 out3 out2 out1 write: reset: 0 0 0 0 0 0 0 0 addr. register name bit 7 6 5 4 3 2 1 bit 0 u = unaffected x = indeterminate r = reserved bold = buffered = unimplemented figure 2-2. control, status, and data registers summary (sheet 3 of 8) memory map mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 31 $0026 pwm counter register high (pcnth) see page 143. read: 0 0 0 0 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $0027 pwm counter register low (pcntl) see page 143. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $0028 pwm counter modulo register high (pmodh) see page 144. read: 0 0 0 0 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 x x x x $0029 pwm counter modulo register low (pmodl) see page 144. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: x x x x x x x x $002a pwm 1 value register high (pval1h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $002b pwm 1 value register low (pval1l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $002c pwm 2 value register high (pval2h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $002d pwm 2 value register low (pval2l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $002e pwm 3 value register high (pval3h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $002f pwm 3 value register low (pval3l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $0030 pwm 4 value register high (pval4h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $0031 pwm 4 value register low (pval4l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 addr. register name bit 7 6 5 4 3 2 1 bit 0 u = unaffected x = indeterminate r = reserved bold = buffered = unimplemented figure 2-2. control, status, and data registers summary (sheet 4 of 8) memory mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 32 freescale semiconductor $0032 pwm 5 value register high (pmval5h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $0033 pwm 5 value register low (pval5l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $0034 pwm 6 value register high (pval6h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $0035 pwm 6 value register low (pmval6l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $0036 dead-time write-once register (deadtm) see page 150. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 1 1 1 1 1 1 1 1 $0037 pwm disable mapping write-once register (dismap) see page 137. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 1 1 1 1 1 1 1 1 $0038 sci control register 1 (scc1) see page 169. read: loops ensci txinv m wake ilty pen pty write: reset: 0 0 0 0 0 0 0 0 $0039 sci control register 2 (scc2) see page 171. read: sctie tcie scrie ilie te re rwu sbk write: reset: 0 0 0 0 0 0 0 0 $003a sci control register 3 (scc3) see page 173. read: r8 t8 00 orie neie feie peie write: r r r reset: u u 0 0 0 0 0 0 $003b sci status register 1 (scs1) see page 174. read: scte tc scrf idle or nf fe pe write: r r r r r r r r reset: 1 1 0 0 0 0 0 0 $003c sci status register 2 (scs2) see page 176. read: 0 0 0 0 0 0 bkf rpf write: r r r r r r r r reset: 0 0 0 0 0 0 0 0 $003d sci data register (scdr) see page 177. read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset addr. register name bit 7 6 5 4 3 2 1 bit 0 u = unaffected x = indeterminate r = reserved bold = buffered = unimplemented figure 2-2. control, status, and data registers summary (sheet 5 of 8) memory map mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 33 $003e sci baud rate register (scbr) see page 177. read: 0 0 scp1 scp0 0 scr2 scr1 scr0 write: r r r reset: 0 0 0 0 0 0 0 0 $003f irq status/control register (iscr) see page 94. read: 0 0 0 0 irqf 0 imask1 mode1 write: r r r r ack1 reset: 0 0 0 0 0 0 0 0 $0040 adc status and control register (adscr) see page 52. read: coco aien adco adch4 adch3 adch2 adch1 adch0 write: r reset: 0 0 0 1 1 1 1 1 $0041 adc data register high right justified mode (adrh) see page 54. read: 0 0 0 0 0 0 ad9 ad8 write: r r r r r r r r reset: unaffected by reset $0042 adc data register low right justified mode (adrl) see page 54. read: ad7 ad6 ad5 ad4 ad3 ad2 ad1 ad0 write: r r r r r r r r reset: unaffected by reset $0043 adc clock register (adclk) see page 55. read: adiv2 adiv1 adiv0 adiclk mode1 mode0 0 0 write: r reset: 0 0 0 0 0 1 0 0 $0044 spi control register (spcr) see page 211. read: sprie r spmstr cpol cpha spwom spe sptie write: reset: 0 0 1 0 1 0 0 0 $0045 spi status and control register (spscr) see page 212. read: sprf errie ovrf modf spte modfen spr1 spr0 write: r r r r reset: 0 0 0 0 1 0 0 0 $0046 spi data register (spdr) see page 214. read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset $0047 $0050 unimplemented $0051 timb status/control register (tbsc) see page 244. read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst r reset: 0 0 1 0 0 0 0 0 $0052 timb counter register high (tbcnth) see page 246. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: r r r r r r r r reset: 0 0 0 0 0 0 0 0 addr. register name bit 7 6 5 4 3 2 1 bit 0 u = unaffected x = indeterminate r = reserved bold = buffered = unimplemented figure 2-2. control, status, and data registers summary (sheet 6 of 8) memory mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 34 freescale semiconductor $0053 timb counter register low (tbcntl) see page 246. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: r r r r r r r r reset: 0 0 0 0 0 0 0 0 $0054 timb counter modulo register high (tbmodh) see page 246. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 1 1 1 1 1 1 1 1 $0055 timb counter modulo register low (tbmodl) see page 246. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 1 1 1 1 1 1 1 1 $0056 timb channel 0 status/control register (tbsc0) see page 247. read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset: 0 0 0 0 0 0 0 0 $0057 timb channel 0 register high (tbch0h) see page 250. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset $0058 timb channel 0 register low (tbch0l) see page 250. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset $0059 timb channel 1 status/control register (tbsc1) see page 247. read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 r reset: 0 0 0 0 0 0 0 0 $005a timb channel 1 register high (tbch1h) see page 250. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset $005b timb channel 1 register low (tbch1l) see page 250. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset $005c pll control register (pctl) see page 66. read: pllie pllf pllon bcs 1111 write: r r r r r reset: 0 0 1 0 1 1 1 1 $005d pll bandwidth control register (pbwc) see page 67. read: auto lock acq xld 0000 write: r r r r r reset: 0 0 0 0 0 0 0 0 $005e pll programming register (ppg) see page 68. read: mul7 mul6 mul5 mul4 vrs7 vrs6 vrs5 vrs4 write: reset: 0 1 1 0 0 1 1 0 $005f unimplemented addr. register name bit 7 6 5 4 3 2 1 bit 0 u = unaffected x = indeterminate r = reserved bold = buffered = unimplemented figure 2-2. control, status, and data registers summary (sheet 7 of 8) memory map mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 35 $fe00 sim break status register (sbsr) see page 191. read: rr r r r rbwr write: reset: 0 $fe01 sim reset status register (srsr) see page 192. read: por pin cop ilop ilad menrst lvi 0 write: r r r r r r r r reset: 1 0 0 0 0 0 0 0 $fe03 sim break flag control register (sbfcr) see page 193. read: bcfe r r r r r r r write: reset: 0 $fe08 flash control register (flcr) see page 38. read: 0 0 0 0 hven mass erase pgm write: reset: 0 0 0 0 0 0 0 0 $fe0c break address register high (brkh) see page 254. read: bit 15 14 13 12 11 10 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $fe0d break address register low (brkl) see page 254. read: bit 7 6 5 4 3 2 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $fe0e break status and control register (brkscr) see page 254. read: brke brka 00 0 000 write: reset: 0 0 0 0 0 0 0 0 $fe0f lvi status and control register (lviscr) see page 99. read: lviout 0 trpsel 00000 write: r r r r r r r reset: 0 0 0 0 0 0 0 0 $ff7e flash block protect register (flbpr) see page 43. read: bpr7 bpr6 bpr5 bpr4 bpr3 bpr2 bpr1 bpr0 write: reset: 0 0 0 0 0 0 0 0 $ffff cop control register (copctl) see page 77. read: low byte of reset vector write: clear cop counter reset: unaffected by reset addr. register name bit 7 6 5 4 3 2 1 bit 0 u = unaffected x = indeterminate r = reserved bold = buffered = unimplemented figure 2-2. control, status, and data registers summary (sheet 8 of 8) memory mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 36 freescale semiconductor table 2-1 is a list of vector locations. table 2-1. vector addresses address vector low $ffd2 sci transmit vector (high) $ffd3 sci transmit vector (low) $ffd4 sci receive vector (high) $ffd5 sci receive vector (low) $ffd6 sci error vector (high) $ffd7 sci error vector (low) $ffd8 spi transmit vector (high) (1) $ffd9 spi transmit vector (low) (1) $ffda spi receive vector (high) (1) $ffdb spi receive vector (low) (1) $ffdc a/d vector (high) $ffdd a/d vector (low) $ffde timb overflow vector (high) $ffdf timb overflow vector (low) $ffe0 timb channel 1 vector (high) $ffe1 timb channel 1 vector (low) $ffe2 timb channel 0 vector (high) $ffe3 timb channel 0 vector (low) $ffe4 tima overflow vector (high) $ffe5 tima overflow vector (low) $ffe6 tima channel 3 vector (high) $ffe7 tima channel 3 vector (low) $ffe8 tima channel 2 vector (high) $ffe9 tima channel 2 vector (low) $ffea tima channel 1 vector (high) $ffeb tima channel 1 vector (low) $ffec tima channel 0 vector (high) $ffed tima channel 0 vector (low) 1. the spi module is not available in the 56-pin sdip package. priority monitor rom mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 37 2.6 monitor rom the 240 bytes at addresses $fe10?$feff are reserved rom addresses that contain the instructions for the monitor functions. see 18.3 monitor rom (mon) . 2.7 random-access memory (ram) addresses $0060?$035f are ram locations. the location of the stack ram is programmable. the 16-bit stack pointer allows the stack to be anywhere in the 64-kbyte 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 input/output (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. before processing an interrupt, the central processor unit (cpu) uses five bytes of the stack to save the contents of the cpu registers. note for m68hc05 and m1468hc05 compatibility, the h register is not stacked. $ffee pwmmc vector (high) $ffef pwmmc vector (low) $fff0 fault 4 (high) $fff1 fault 4 (low) $fff2 fault 3 (high) $fff3 fault 3 (low) $fff4 fault 2 (high) $fff5 fault 2 (low) $fff6 fault 1 (high) $fff7 fault 1 (low) $fff8 pll vector (high) $fff9 pll vector (low) $fffa irq vector (high) $fffb irq vector (low) $fffc swi vector (high) $fffd swi vector (low) high $fffe reset vector (high) $ffff reset vector (low) table 2-1. vector addresses (continued) address vector priority memory mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 38 freescale semiconductor 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 subrouti nes. the cpu may overwrite data in the ram during a subroutine or during the interrupt stacking operation. 2.8 flash memory (flash) the flash memory is an array of 32,256 bytes with an additional 46 bytes of user vectors and one byte of block protection. note an erased bit reads as a 1 and a programmed bit reads as a 0. program and erase operations are facilitated through c ontrol bits in a memory mapped register. details for these operations appear later in this section. memory in the flash array is organized into two rows per page. the page size is 128 bytes per page. the minimum erase page size is 128 bytes. programming is performed on a row basis, 64 bytes at a time. the address ranges for the user memory and vectors are: $8000?$fdff, user memory $ff7e, block protect register (flbpr) $fe08, flash control register (flcr) $ffd2?$ffff, reserved for user-defined interrupt and reset vectors programming tools are available from freescale. cont act a local freescale representative for more information. note a security feature prevents viewing of the flash contents. (1) 2.8.1 flash control register the flash control register (flcr) controls flash program and erase operations. 1. no security feature is absolutely secure . however, freescale?s strategy is to make reading or copying the flash difficult fo r unauthorized users. address: $fe08 bit 7654321bit 0 read:0000 hven mass erase pgm write: reset:00000000 = unimplemented figure 2-3. flash control register (flcr) flash memory (flash) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 39 hven ? high-voltage enable bit this read/write bit enables the charge pump to dr ive 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 setting this read/write bit configures the 32-kbyte flash array for mass erase operation. mass erase is disabled if any flash block is protected 1 = mass erase operation selected 0 = mass erase operation unselected erase ? erase control bit this read/write bit configures t he 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 unselected pgm ? program control bit this read/write bit configures the memory for progr am 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 unselected 2.8.2 flash page erase operation use this step-by-step procedure to erase a page (128 bytes) of flash memory. 1. set the erase bit and clear the mass bit in the flash control register. 2. read the flash block protect register. 3. write any data to any flash location within the address range of the block to be erased. 4. wait for a time, t nvs (minimum 10 s). 5. set the hven bit. 6. wait for a time, t erase (minimum 1 ms or 4 ms). 7. clear the erase bit. 8. wait for a time, t nvh (minimum 5 s). 9. clear the hven bit. 10. after time, t rcv (typical 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 shown, other unrelated operations may occur between the steps. in applications that require more than 1000 program /erase cycles, use the 4 ms page erase specification to get improved long-term reliability. any application can use this 4 ms page erase specification. however, in applications where a flash location will be erased and reprogrammed less than 1000 times, and speed is important, use the 1 ms page erase specification to get a shorter cycle time. memory mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 40 freescale semiconductor 2.8.3 flash m ass erase operation use this step-by-step procedure to erase the entire flash memory. 1. set both the erase bit and the mass bit in the flash control register. 2. read the flash block protect register. 3. write any data to any flash address (1) within the flash memory address range. 4. wait for a time, t nvs (minimum 10 s). 5. set the hven bit. 6. wait for a time, t merase (minimum 4 ms). 7. clear the erase and mass bits. note mass erase is disabled whenever any block is protected (flbpr does not equal $ff). 8. wait for a time, t nvhl (minimum 100 s). 9. clear the hven bit. 10. after time, t rcv (typical 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 shown, other unrelated operations may occur between the steps. 1. when in monitor mode, with security sequence failed (see 18.3.2 security ), write to the flash block protect register instead of any flash address. flash memory (flash) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 41 2.8.4 flash program operation use the following step-by-step procedure to program a row of flash memory. figure 2-4 shows a flowchart of the programming algorithm. note only bytes which are currently $ff may be programmed. 1. set the pgm bit. this configures the memory for program operation and enables the latching of address and data for programming. 2. read the flash block protect register. 3. write any data to any flash location within the address range desired. 4. wait for a time, t nvs (minimum 10 s). 5. set the hven bit. 6. wait for a time, t pgs (minimum 5 s). 7. write data to the flash address being programmed (1) . 8. wait for time, t prog (minimum 30 s). 9. repeat step 7 and 8 until all desir ed bytes within the row are programmed. 10. clear the pgm bit (1) . 11. wait for time, t nvh (minimum 5 s). 12. clear the hven bit. 13. after time, t rcv (typical 1 s), the memory can be accessed in read mode again. note the cop register at location $ffff should not be written between steps 5-12, when the hven bit is set. since this register is located at a valid flash address, unpredictable behavior may occur if this location is written while hven is set. this program sequence is repeated throughout the memory until all data is programmed. 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. do not exceed t prog maximum, see 19.6 flash memory characteristics . 1. the time between each flash address ch ange, or the time between the last fl ash address programmed to clearing pgm bit, must not exceed the maximum programming time, t prog maximum. memory mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 42 freescale semiconductor figure 2-4. flash programming flowchart set hven bit read the flash block protect register 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? yes no end of programming the time between each flash address change (step 7 to step 7), or must not exceed th e maximum programming time, t prog max. the time between the last flash address programmed to clearing pgm bit (step 7 to step 10) note: 1 2 3 4 5 6 7 8 10 11 12 13 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 (flash) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 43 2.8.5 flash bl ock 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 for protecting a bloc k of memory from unintentional erase or program operations due to system malfunction. this protecti on is done by using 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 at 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 in performing a program or erase operation, the flash block protect register must be read after setting the pgm or erase bit and before asserting the hven bit when the flbpr is programmed with all 0s, the entire memory is protected from being programmed and erased. when all the bits are erased (all 1s), the en tire memory is accessible for program and erase. when bits within the flbpr are programmed, they lock a block of memory, whose address ranges are shown in 2.8.6 flash block protect register . once the flbpr is programmed with a value other than $ff, any erase or program of the flbpr or the pr otected block of flash memory is prohibited. mass erase is disabled whenever any bloc k is protected (flbpr does not equal $ff). the flbpr itself can be erased or programmed only with an external voltage, v tst , present on the irq pin. this voltage also allows entry from reset into the monitor mode. 2.8.6 flash bloc k protect register the flash block protect register (flbpr) is impl emented as a byte within the flash memory, and therefore can be written only during a programming sequence of the flash memory. the value in this register determines the starting location of the protected range within the flash memory. bpr[7:0] ? flash block protect bits these eight bits represent bits [14:7] of a 16-bit memory address. bit 15 is 1 and bits [6:0] are 0s. 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 star t address to the end of flash memory at $ffff. with this mechanism, the protect start address can be xx00 and xx80 (128 bytes page boundaries) within the flash memory. address: $ff7e bit 7654321bit 0 read: bpr7 bpr6 bpr5 bpr4 bpr3 bpr2 bpr1 bpr0 write: reset:00000000 u = unaffected by reset. initial value from factory is 1. write to this register by a programming sequence to the flash memory. figure 2-5. flash block protect register (flbpr) memory mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 44 freescale semiconductor figure 2-6. flash block protect start address refer to table 2-2 for examples of the protect start address. 2.8.7 wait mode putting the mcu into wait mode while the flash is in read mode does not affect the operation of the flash memory directly, but there will not be any memory activity since the cpu is inactive. the wait instruction should not be executed while performing a program or erase operation on the flash. otherwise, the operation will discont inue, and the flash will be on standby mode. 2.8.8 stop mode putting the mcu into stop mode while the flash is in read mode does not affect the operation of the flash memory directly, but there will not be any memory activity since the cpu is inactive. the stop instruction should not be executed while performing a program or erase operation on the flash, otherwise the operation will discontinue, and the flash will be on standby mode note standby mode is the power-saving mode of the flash module in which all internal control signals to the flash are inactive and the current consumption of the flash is at a minimum. table 2-2. examples of protect start address bpr[7:0] start of address of protect range $00 the entire flash memory is protected. $01 ( 0000 0001 ) $8080 (1 000 0000 1 000 0000) $02 ( 0000 0010 ) $8100 (1 000 0001 0 000 0000) and so on... $fe ( 1111 1110 ) $ff00 (1 111 1111 0 000 0000) $ff the entire flash memory is not protected. note: the end address of the protected range is always $ffff. 1 flbpr value 16-bit memory address 0000000 start address of flash block protect mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 45 chapter 3 analog-to-digital converter (adc) 3.1 introduction this section describes the 10-bit analog-to-digital converter (adc). 3.2 features features of the adc module include: 10 channels with multiplexed input linear successive approximation 10-bit resolution, 8-bit accuracy single or continuous conversion conversion complete flag or conversion complete interrupt selectable adc clock left or right justified result left justified sign data mode high impedance buffered adc input 3.3 functional description ten adc channels are available for sampling extern al sources at pins ptc1/atd9:ptc0/atd8 and ptb7/atd7:ptb0/atd0. to achieve the best possi ble accuracy, these pins are implemented as input-only pins when the analog-to-digital (a/d) feature is enabled. an analog multiplexer allows the single adc to select one of the 10 adc channels as adc vo ltage in (adcvin). adcvin is converted by the successive approximation algorithm. when the conversion is completed, the adc places the result in the adc data register (adrh and adrl) and sets a flag or generates an interrupt. see figure 3-2 . mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 46 freescale semiconductor analog-to-digital converter (adc) figure 3-1. block diagram highlighting adc block and pins clock generator module system integration module serial communications interface module serial peripheral interface module (2) timer interface module a low-voltage inhibit module power-on reset module computer operating properly module arithmetic/logic unit cpu registers m68hc08 cpu control and status registers ? 112 bytes user flash ? 32,256 bytes user ram ? 768 bytes monitor rom ? 240 bytes user flash vector space ? 46 bytes irq module power pta ddra ddrb ptb ddrc ptc ptd ddre pte ptf ddrf internal bus osc1 osc2 cgmxfc rst irq v ss v dd v ddad pta7?pta0 pte7/tch3a pte6/tch2a pte5/tch1a pte4/tch0a pte3/tclka pte2/tch1b (1) pte1/tch0b (1) pte0/tclkb (1 ) ptf5/txd ptf4/rxd ptf3/miso (1) ptf2/mosi (1) ptf1/ss (1) ptf0/spsck (1) timer interface module b pulse-width modulator module ptb7/atd7 ptb6/atd6 ptb5/atd5 ptb4/atd4 ptb3/atd3 ptb2/atd2 ptb1/atd1 ptb0/atd0 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1/atd9 (1) ptc0/atd8 ptd6/is3 ptd5/is2 ptd4/is1 ptd3/fault4 ptd2/fault3 ptd1/fault2 ptd0/fault1 pwm6?pwm1 analog-to-digital converter module v ssad v dda v ssa (3) pwmgnd v refl (3) v refh notes: 1. these pins are not available in the 56-pin sdip package. 2. this module is not available in the 56-pin sdip package. 3. in the 56-pin sdip package, these pins are bonded together. single break module functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 47 figure 3-2. adc block diagram 3.3.1 adc port i/o pins ptc1/atd9:ptc0/atd8 and ptb7/atd7:ptb0/atd0 are general-purpose i/o pins that are shared with the adc channels. the channel select bits define which adc channel/p ort pin will be used as the input signal. the adc overrides the port logic when that port is selected by the adc multiplexer. the remaining adc channels/port pins are controlled by the port logi c and can be used as general-purpose input/output (i/o) pins. writes to the port register or ddr will not have any effect on the port pin that is selected by the adc. read of a port pin which is in use by the adc will return a 0. 3.3.2 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 straight-line linear conversions. 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. see 19.13 analog-to-digital converter (adc) characteristics . read ptb/ptc ptb/cx interrupt logic channel select adc clock generator conversion complete adc voltage in advin adc clock cgmxclk bus clock adch[4:0] adc data registers adiv[2:0] adiclk aien coco disable adc channel x internal data bus analog-to-digital converter (adc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 48 freescale semiconductor 3.3.3 conversion time conversion starts after a write to the adscr. a conversion is between 16 and 17 adc clock cycles, therefore: the adc conversion time is determined by the clock source chosen and the divide ratio selected. the clock source is either the bus cl ock or cgmxclk and is selectable by adiclk located in the adc clock register. for example, if cgmxclk is 4 mhz and is selected as the adc input clock source, the adc input clock divide-by-4 pres cale is selected and the cpu bus frequency is 8 mhz: note the adc frequency must be between f adic minimum and f adic maximum to meet a/d spec ifications. see 19.13 analog-to-digital converter (adc) characteristics . since an adc cycle may be comprised of several bus cycles (eight, 136 minus 128, in the previous example) and the start of a conversion is initiated by a bus cycle write to the adscr, from zero to eight 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. 3.3.4 continuous conversion in continuous conversion mode, the adc data regist ers adrh and adrl will be filled with new data after each conversion. data from the pr evious conversion will be overwri tten whether that data has been read or not. conversions will c ontinue until the adco bit is cleared. the coco bit is set after each conversion and will stay set until the next read of the adc data register. when a conversion is in process and the adscr is written, the current conversion data should be discarded to prevent an incorrect reading. 3.3.5 result justification the conversion result may be formatted in four different ways: 1. left justified 2. right justified 3. left justified sign data mode 4. 8-bit truncation mode all four of these modes are controlled using mode0 and mode1 bits located in the adc clock register (adcr). left justification will place the eight most signific ant 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 two least 16 to17 adc cycles conversion time = adc frequency number of bus cycles = conv ersion time x cpu bus frequency 16 to 17 adc cycles conversion time = 4 mhz/4 number of bus cycles = 16 s x 8 mhz = 128 to 136 cycles = 16 to 17 s functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 49 significant bits (lsb), located in the adc data regist er low, adrl, can be ignored. however, adrl must be read after adrh or else the interlocking wi ll 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 lsbs 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 just ified mode with one exception. the msb of the 10-bit result, ad9 located in adrh, is complemented. th is 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. note quantization error is affected when only the most significant eight bits are used as a result. see figure 3-3 . figure 3-3. 8-bit truncation mode error 3.3.6 monotonicity the conversion process is monot onic and has no missing codes. ideal 10-bit characteristic with quantization = 1/2 ideal 8-bit characteristic with quantization = 1/2 10-bit truncated to 8-bit result when truncation is used, error from ideal 8-bit = 3/8 lsb due to non-ideal quantization. 000 001 002 003 004 005 006 007 008 009 00a 00b 000 001 002 003 8-bit resul t 10-bit result input voltage represented as 10-bit input voltage represented as 8-bit 1/2 2 1/2 4 1/2 6 1/2 8 1/2 1 1/2 3 1/2 5 1/2 7 1/2 9 1/2 1/2 2 1/2 1 1/2 analog-to-digital converter (adc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 50 freescale semiconductor 3.4 interrupts when the aien bit is set, the adc module is capable of generating a cpu interrupt after each adc conversion. a cpu interrupt is generated if the coco bit is at 0. the coco bit is not used as a conversion complete flag when interrupts are enabled. 3.5 wait mode the wait instruction can put the mcu in low power-consumption standby mode. the adc continues normal operation du ring 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 adch[4:0] in the adc status and control register before executing the wait instruction. 3.6 i/o signals the adc module has 10 input signals that are shared with port b and port c. 3.6.1 adc analog power pin (v ddad ) the adc analog portion uses v ddad as its power pin. connect the v ddad pin to the same voltage potential as v dd . external filtering may be necessary to ensure clean v ddad for good results. note route v ddad carefully for maximum noise immunity and place bypass capacitors as close as possible to the package. 3.6.2 adc analog ground pin (v ssad ) the adc analog portion uses v ssad as its ground pin. connect the v ssad pin to the same voltage potential as v ss . 3.6.3 adc voltage reference 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 ddad . there will be a finite current associated with v refh . see chapter 19 electrical specifications . note route v refh carefully for maximum nois e immunity and place bypass capacitors as close as possible to the package. 3.6.4 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 ssad . a finite current will be associated with v refl . see chapter 19 electrical specifications . note in the 56-pin shrink dual in-line package (sdip), v refl and v ssad are tied together. i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 51 3.6.5 adc voltage in (advin) advin is the input voltage signal from one of the 10 adc channels to the adc module. 3.6.6 adc external connections this section describes the adc external connections: v refh and v refl , anx, and grounding. 3.6.6.1 v refh and v refl both ac and dc current are drawn through the v refh and v refl loop. the ac current is in the form of current spikes required to supply c harge to the capacitor array at each successive approximation step. the current flows through the internal resistor string. the best external component to meet both these current demands is a capacitor in the 0.01 f to 1 f range with good high frequency characteristics. this capacitor is connected between v refh and v refl and must be placed as close as possible to the package pins. resistance in the path is not recomm ended because the dc current will cause a voltage drop which could result in conversion errors. 3.6.6.2 anx empirical data shows that capacitors from the analog inputs to v refl improve adc performance. 0.01- f and 0.1- f capacitors with good high-frequency characteristics are sufficient. these capacitors must be placed as close as possi ble to the package pins. 3.6.6.3 grounding in cases where separate power supplies are used for analog and digital power, the ground connection between these supplies should be at the v ssad pin. this should be the only ground connection between these supplies if possible. the v ssa pin makes a good single point ground location. connect the v refl pin to the same potential as v ssad at the single point ground location. 3.7 i/o registers these i/o registers control and monitor operation of the adc: adc status and control register, adscr adc data registers, adrh and ardl adc clock register, adclk analog-to-digital converter (adc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 52 freescale semiconductor 3.7.1 adc status and control register this section describes the function of the adc status and control register (adscr). writing adscr aborts the current conversion and initiates a new conversion. coco ? conversions complete bit in non-interrupt mode (aien = 0), coco is a read-only bit that is set at the end of each conversion. coco will stay set until cleared by a read of the adc data register. reset clears this bit. in interrupt mode (aien = 1), coco is a read-only bit that is not set at the end of a conversion. it always reads as a 0. 1 = conversion completed (aien = 0) 0 = conversion not completed (aien = 0) or cpu interrupt enabled (aien = 1) note the write function of the coco bit is reserved. when writing to the adscr register, always have a 0 in the coco bit position. aien ? adc interrupt enable bit when this bit is set, an interrupt is generated at th e end of an adc conversion. the interrupt signal is cleared when the data register is read or the status/control register 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 adr register at the end of each conversion. only one conver sion is allowed when this bit is cleared. reset clears the adco bit. 1 = continuous adc conversion 0 = one adc conversion adch[4:0] ? adc channel select bits adch4, adch3, adch2, adch1, and adch0 form a 5-bi t field which is used to select one of 10 adc channels. the adc channels are detailed in table 3-1 . note take care to prevent switching noise from corrupting the analog signal when simultaneously using a port pin as both an analog and digital input. the adc subsystem is turned off when the channel select bits are all set to 1. this feature allows for reduced power consumption for the mcu when the adc is not used. note recovery from the disabled state requi res one conversion cycle to stabilize. address: $0040 bit 7654321bit 0 read: coco aien adco adch4 adch3 adch2 adch1 adch0 write: r reset:00011111 r= reserved figure 3-4. adc status and control register (adscr) i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 53 the voltage levels supplied from internal reference nodes as specified in table 3-1 are used to verify the operation of the adc both in production test and for user applications. table 3-1. mux channel select adch4 adch3 adch2 adch1 adch0 input select 00000 ptb0/atd0 00001 ptb1/atd1 00010 ptb2/atd2 00011 ptb3/atd3 00100 ptb4/atd4 00101 ptb5/atd5 00110 ptb6/atd6 00111 ptb7/atd7 01000 ptc0/atd8 01001 ptc1/atd9 (1) 1. atd9 is not available in the 56-pin sdip package. 01010 unused (2) 01011 ? 01100 ? 01101 ? 01110 ? 01111 ? 10000 ? 11010 unused (2) 2. used for factory testing. 11011 reserved (3) 3. if any unused channels are selected, the resulting adc conversion will be unknown. 1 1 1 0 0 unused (2) 1 1 1 0 1 v refh 1 1 1 1 0 v refl 1 1 1 1 1 adc power off analog-to-digital converter (adc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 54 freescale semiconductor 3.7.2 adc data register high in left justified mode, this 8-bit result register holds the eight msbs of the 10-bit result. this register is updated each time an adc single c hannel conversion complete s. reading adrh latches the contents of adrl until adrl is read. until adrl is read, all subsequent adc results will be lost. in right justified mode, this 8-bit result register holds the two msbs of the 10-bit result. all other bits read as 0. this register is updated each time a singl e channel adc conversion completes. reading adrh latches the contents of adrl until adrl is read. un til adrl is read, all subsequent adc results will be lost. 3.7.3 adc data register low in left justified mode, this 8-bit result register holds the two lsbs of the 10-bit result. all other bits read as 0. this register is updated each time a single chann el adc conversion completes. reading adrh latches the contents of adrl until adrl is read. until adrl is read, all subsequent adc results will be lost. in right justified mode, this 8-bit result register holds the eight lsbs of the 10-bit result. this register is updated each time an adc conversion completes. re ading adrh latches the contents of adrl until adrl is read. until adrl is read, all subsequent adc results will be lost. address: $0041 bit 7654321bit 0 read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write:rrrrrrrr reset: unaffected by reset r= reserved figure 3-5. adc data register high (adrh) left justified mode address: $0041 bit 7654321bit 0 read:000000ad9ad8 write:rrrrrrrr reset: unaffected by reset r= reserved figure 3-6. adc data register high (adrh) right justified mode address: $0042 bit 7654321bit 0 read:ad1ad0000000 write:rrrrrrrr reset: unaffected by reset r= reserved figure 3-7. adc data register low (adrl) left justified mode i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 55 in 8-bit mode, this 8-bit result register holds the ei ght msbs of the 10-bit result. this register is updated each time an adc conversion completes. in 8-bit mode , this register contains no interlocking with adrh. 3.7.4 adc clock register this register selects the clock frequency for the adc, selecting between modes of operation. adiv2:adiv0 ? adc clock prescaler bits adiv2, adiv1, and adiv0 form a 3-bit field which se lects the divide ratio used by the adc to generate the internal adc clock. table 3-2 shows the available clock configurations. address: $0042 bit 7654321bit 0 read: ad7 ad6 ad5 ad4 ad3 ad2 ad1 ad0 write:rrrrrrrr reset: unaffected by reset r= reserved figure 3-8. adc data register low (adrl) right justified mode address: $0042 bit 7654321bit 0 read: ad9 ad8 ad7 ad6 ad5 ad4 ad3 ad2 write:rrrrrrrr reset: unaffected by reset r= reserved figure 3-9. adc data register low (adrl) 8-bit mode address: $0043 bit 7654321bit 0 read: adiv2 adiv1 adiv0 adiclk mode1 mode0 0 0 write: r reset:00000100 r= reserved figure 3-10. adc clock register (adclk) table 3-2. 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?t care analog-to-digital converter (adc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 56 freescale semiconductor adiclk ? adc input clock select bit adiclk selects either bus clock or cgmxclk as t he 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 1 mhz, cgmxclk can be used as the clock source for the adc. if cgmxclk is less t han 1 mhz, 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. see 19.13 analog-to-digital converter (adc) characteristics . 1 = internal bus clock 0 = external clock, cgmxclk mode1:mode0 ? modes of result justification bits mode1:mode0 selects among 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. 00 = 8-bit truncation mode 01 = right justified mode 10 = left justified mode 11 = left justified sign data mode cgmxclk or bus frequency f adic = adiv[2:0] mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 57 chapter 4 clock generator module (cgm) 4.1 introduction this section describes the clock generator module (cgm, version a). the cgm generates the crystal clock signal, cgmxclk, which operates at the fre quency of the crystal. the cgm also generates the base clock signal, cgmout, from which the system in tegration module (sim) derives the system clocks. cgmout is based on either the crystal clock divide d by two or the phase-locked loop (pll) clock, cgmvclk, divided by two. the pll is a frequency gen erator designed for use with crystals or ceramic resonators. the pll can generate an 8-mhz bus fr equency without using a 32-mhz external clock. 4.2 features features of the cgm include: pll with output frequency in integer multiples of the crystal reference programmable hardware voltage-controlled oscillator (vco) for low-jitter operation automatic bandwidth control mode for low-jitter operation automatic frequency lock detector central processor unit (cpu) interrupt on entry or exit from locked condition 4.3 functional description the cgm consists of three major submodules: 1. crystal oscillator circuit ? the crystal oscillat or circuit generates the constant crystal frequency clock, cgmxclk. 2. phase-locked loop (pll) ? the pll generat es the programmable vco frequency clock, cgmvclk. 3. base clock selector circuit ? this software-cont rolled circuit selects either cgmxclk divided by two or the vco clock, cgmvclk, divided by two as the base cl ock, cgmout. the sim derives the system clocks from cgmout. figure 4-1 shows the structure of the cgm. clock generator module (cgm) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 58 freescale semiconductor figure 4-1. cgm block diagram addr. register name bit 7654321bit 0 $005c pll control register (pctl) see page 66. read: pllie pllf pllon bcs 1111 write: r r r r r reset:00101111 $005d pll bandwidth control register (pbwc) see page 67. read: auto lock acq xld 0000 write: r r r r r reset:00000000 $005e pll programming register (ppg) see page 68. read: mul7 mul6 mul5 mul4 vrs7 vrs6 vrs5 vrs4 write: reset:01100110 r=reserved figure 4-2. cgm i/o register summary bcs phase detector loop filter frequency divider voltage controlled oscillator bandwidth control lock detector clock cgmxclk cgmout cgmvdv cgmvclk simoscen crystal oscillator interrupt control cgmint cgmrdv pll analog 2 cgmrclk select circuit lock auto acq vrs[7:4] pllie pllf mul[7:4] cgmxfc v ss v dda osc1 osc2 to sim to sim ptc2 monitor mode a b s* user mode *when s = 1, cgmout = b functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 59 4.3.1 crystal os cillator circuit the crystal oscillator circuit consists of an inverting am plifier and an external crystal. the osc1 pin is the input to the amplifier and the osc2 pin is the out put. the simoscen signal from the system integration module (sim) enables the crystal oscillator circuit. the cgmxclk signal is the output of the crystal oscillator circuit and runs at a rate equal to the crystal frequency. cgmxclk is then buffered to pr oduce cgmrclk, the pll reference clock. cgmxclk can be used by other modules which require precise timing for operation. the duty cycle of cgmxclk is not guaranteed to be 50 percent and depends on external factors, including the crystal and related external components. an externally generated clock also can feed the osc1 pin of the crystal osci llator circuit. connect the external clock to the osc1 pin and let the osc2 pin float. 4.3.2 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. 4.3.2.1 pll circuits the pll consists of these circuits: voltage-controlled oscillator (vco) modulo vco frequency divider 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, incl uding 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 wi thin this range. by design, f vrs is equal to the nominal center-of-range frequency, f nom , (4.9152 mhz) times a linear factor, l or (l) f nom . cgmrclk is the pll reference clock, a buffered ve rsion of cgmxclk. cgmrclk runs at a frequency, f rclk , and is fed to the pll through a buffer. the buffer output is the final reference clock, cgmrdv, running at a frequency, f rdv =f rclk . the vco?s output clock, cgmvclk, running at a frequency, f vclk , is fed back through a programmable modulo divider. the modulo divider reduc es the vco clock by a factor, n. the divider?s output is the vco feedback clock, cgmvdv, running at a frequency, f vdv =f vclk/n . (see 4.3.2.4 programming the pll for more information.) the phase detector then compares the vco feedback cloc k, 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 c onnected to cgmxfc based on the width and direction of the correction pulse. the fi lter can make fast or slow corrections depending on its mode, described in 4.3.2.2 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. clock generator module (cgm) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 60 freescale semiconductor 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 th e pll and the lock condition based on this comparison. 4.3.2.2 acquisition and tracking modes the pll filter is manually or automatically configurable into one of two operating modes: 1. acquisition mode ? in acquisiti on mode, the filter can make large frequency corrections to the vco. this mode is used at pll startup or when the pll has suffered a severe noise hit and the vco frequency is far off the desired freq uency. when in acquisition mode, the acq bit is clear in the pll bandwidth control register. see 4.5.2 pll bandwidth control register . 2. 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 4.3.3 base clock selector circuit . the pll is au tomatically in tracking mode when not in acqui sition mode or when the acq bit is set. 4.3.2.3 manual and automatic pll bandwidth modes the pll can change the bandwidth or operational mode of the loop filter manua lly or automatically. in automatic bandwidth control mode (auto = 1), th e lock detector automatically switches between acquisition and tracking modes. automatic bandwidth c ontrol mode also is used to determine when the vco clock, cgmvclk, is safe to use as th e source for the base clock, cgmout. see 4.5.2 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 startup, 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 4.3.3 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 appr opriate action, depending on the application. see 4.6 interrupts for information and precautions on using interrupts. these conditions apply when the pll is in automatic bandwidth control mode: the acq bit (see 4.5.2 pll bandwidth control register ) is a read-only indicator of the mode of the filter. for more information, see 4.3.2.2 acquisition and tracking modes . the acq bit is set when the vco frequency is within a certain tolerance, ? trk , and is cleared when the vco frequency is out of a certain tolerance, ? unt . for more information, see 4.8 acquisition/lock time specifications . the lock bit is a read-only indica tor of the locked state of the pll. the lock bit is set when the vco freq uency is within a certain tolerance, ? lock , and is cleared when the vco frequency is out of a certain tolerance, ? unl . for more information, see 4.8 acquisition/lock time specifications . cpu interrupts can occur if enabled (pllie = 1) when the pll?s lock c ondition changes, toggling the lock bit. for more information, see 4.5.1 pll control register . functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 61 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 and require fast startup. these 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 4.8 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. 4.3.2.4 programming the pll use this 9-step procedure to program the pll. table 4-1 lists the variables used and their meaning. 1. choose the desired bus frequency, f busdes . example: f busdes = 8 mhz 2. calculate the desired vco frequency, f vclkdes . f vclkdes = 4 x f busdes example: f vclkdes = 4 x 8 mhz = 32 mhz 3. using a reference frequency, f rclk , equal to the crystal frequency, calculate the vco frequency multiplier, n. round the result to the nearest integer. 4. calculate the vco frequency, f vclk . table 4-1. variable definitions variable definition f busdes desired bus clock frequency f vclkdes desired vco clock frequency f rclk chosen reference crystal frequency f vclk calculated vco clock frequency f bus calculated bus clock frequency f nom nominal vco center frequency f vrs shifted fco center frequency f vclkdes f rclk n = example: n = 32 mhz 4 mhz = 8 mhz f vclk = n x f rclk example: f vclk = 8 x 4 mhz = 32 mhz clock generator module (cgm) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 62 freescale semiconductor 5. calculate the bus frequency, f bus , and compare f bus with f busdes . 6. if the calculated f bus is not within the tolerance limits of the application, select another f busdes or another f rclk . 7. using the value 4.9152 mhz for f nom , calculate the vco linear range multiplier, l. the linear range multiplier controls the frequency range of the pll. 8. calculate the vco center-of-range frequency, f vrs . the center-or-range frequency is the midpoint between the minimum and maximum frequencies attainable by the pll. f vrs = l x f nom example: f vrs = 7 x 4.9152 mhz = 34.4 mhz for proper operation, caution exceeding the recommended maximum bus frequency or vco frequency can crash the mcu. 9. program the pll registers accordingly: a. in the upper four bits of the pll programming register (ppg), program the binary equivalent of n. b. in the lower four bits of the pll programming register (ppg), program the binary equivalent of l. 4.3.2.5 special programming exceptions the programming method described in 4.3.2.4 programming the pll does not account for possible exceptions. a value of 0 for n or l is meaningless when used in the equations given. to account for these exceptions: a 0 value for 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 4.3.3 base clock selector circuit . 4.3.3 base clock se lector circuit this circuit is used to select either the crystal cl ock, cgmxclk, or the vco clock, cgmvclk, as the source of the base clock, cgmout. the two input cl ocks go through a transition c ontrol circuit that waits up to three cgmxclk cycles and three cgmvclk cycles to change from one clock source to the other. during this time, cgmout is held in stasis. the outpu t of the transition control circuit is then divided by f bus = f vclk 4 example: n = 32 mhz 4 mhz = 8 mhz example: l = 32 mhz 4.9152 mhz = 7 mhz l = round f vclk f nom ( ) f vrs ? f vclk | f nom 2 functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 63 two to correct the duty cycle. therefore, the bus cl ock frequency, which is one-half of the base clock frequency, is one-fourth the frequency of the selected clock (cgmxclk or cgmvclk). the bcs bit in the pll control register (pctl) selects which clock drives cgmout. the 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 vco clock is selected. the pll cannot be turned on or off simultaneously with the selection or deselection of the vco clock. the 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 crysta l clock would be forced as the source of the base clock. 4.3.4 cgm exte rnal connections in its typical configuration, the cgm requires seven ex ternal components. five of these are for the crystal oscillator and two are for the pll. the crystal oscillator is normally connected in a pierce oscillator configuration, as shown in figure 4-3 . figure 4-3 shows only the logical representation of the internal components and may not represent actual circuitry. figure 4-3. cgm external connections the oscillator configuration uses five components: 1. crystal, x 1 2. fixed capacitor, c 1 3. tuning capacitor, c 2 (can also be a fixed capacitor) 4. feedback resistor, r b 5. series resistor, r s (optional) 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?s data for more information. c1 c2 c f simoscen cgmxclk r b x1 r s * c byp osc1 osc2 v ss cgmxfc v dda v dd *rs can be 0 (shorted) when used with higher frequency crystals. refer to manufacturer?s data. clock generator module (cgm) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 64 freescale semiconductor figure 4-3 also shows the external components for the pll: bypass capacitor, c byp filter capacitor, c f note routing should be done with great care to minimize signal cross talk and noise. (see 4.8 acquisition/lock time specifications for routing information and more information on the filter capacitor?s value and its effects on pll performance.) 4.4 i/o signals this section describes the cgm input/output (i/o) signals. 4.4.1 crystal amplifi er input pin (osc1) the osc1 pin is an input to the crystal oscillator amplifier. 4.4.2 crystal amplifi er output pin (osc2) the osc2 pin is the output of the cr ystal oscillator inverting amplifier. 4.4.3 external filter capacitor pin (cgmxfc) the cgmxfc pin is required by the loop filter to filt er out phase corrections. a sm all external capacitor is connected to this pin. note to prevent noise problems, c f should be placed as close to the cgmxfc pin as possible, with minimum routing distances and no routing of other signals across the c f connection. 4.4.4 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. 4.4.5 oscillator e nable signal (simoscen) the simoscen signal comes from the system integr ation module (sim) and enables the oscillator and pll. cgm registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 65 4.4.6 crystal output frequency signal (cgmxclk) cgmxclk is the crystal oscillator output signal. it runs at the full speed of the crystal (f xclk ) and comes directly from the crys tal oscillator circuit. figure 4-3 shows only the logical relation of cgmxclk to osc1 and osc2 and may not represent the actual circui try. the duty cycle of cgmxclk is unknown and may depend on the crystal and other external factors. also, the frequency and amplitude of cgmxclk can be unstable at startup. 4.4.7 cgm base cl ock 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, cg mxclk, divided by two or the vco clock, cgmvclk, divided by two. 4.4.8 cgm cpu interrupt (cgmint) cgmint is the interrupt signal generated by the pll lock detector. 4.5 cgm registers these registers control and monitor operation of the cgm: pll control register (pctl) ? see 4.5.1 pll control register pll bandwidth control register (pbwc) ? see 4.5.2 pll bandwidth control register pll programming register (ppg) ? see 4.5.3 pll programming register figure 4-4 is a summary of the cgm registers. addr. register name bit 7654321bit 0 $005c pll control register (pctl) see page 66. read: pllie pllf pllon bcs 1111 write: r r r r r reset:00101111 $005d pll bandwidth control register (pbwc) see page 67. read: auto lock acq xld 0000 write: r r r r r reset:00000000 $005e pll programming register (ppg) see page 68. read: mul7 mul6 mul5 mul4 vrs7 vrs6 vrs5 vrs4 write: reset:01100110 r = reserved notes: 1. when auto = 0, pllie is forced to logic 0 and is read-only. 2. when auto = 0, pllf and lock read as logic 0. 3. when auto = 1, acq is read-only. 4. when pllon = 0 or vrs[ 7:4] = $0, bcs is forced to logic 0 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 4-4. cgm i/o register summary clock generator module (cgm) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 66 freescale semiconductor 4.5.1 pll control register the pll control register (pctl) contains the interrupt enable and flag bits, the on/off switch, and the base clock selector bit. 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 b andwidth 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 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 readi ng 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 th e base clock, cgmout (bcs = 1). see 4.3.3 base clock selector circuit . reset sets this bit so that the l oop 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 crystal oscillator output, cgmxclk, or the vco clock, cgmvclk, 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 cgmv clk cycles to complete the transition from one source clock to the other. during the trans ition, cgmout is held in stasis. see 4.3.3 base clock selector circuit . reset clears the bcs bit. 1 = cgmvclk divided by two drives cgmout 0 = cgmxclk divided by two drives cgmout note pllon and bcs have built-in protecti on that prevents the base clock selector circuit from selecting the vco clock as the source of the base clock address: $005c bit 7654321bit 0 read: pllie pllf pllon bcs 1111 write: r rrrr reset:00101111 r = reserved figure 4-5. pll control register (pctl) cgm registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 67 if the pll is off. therefore, pllon cannot be cleared when bcs is set, and bcs cannot be set when pllon is cl ear. if the pll is off (pllon = 0), selecting cgmvclk requires two writes to the pll control register. see 4.3.3 base clock selector circuit . pctl[3:0] ? unimplemented bits these bits provide no function and always read as logic 1s. 4.5.2 pll bandwidth control register the pll bandwidth control register (pbwc): selects automatic or manual (softw are-controlled) bandwidth control mode indicates when the pll is locked in automatic bandwidth control mode, indicates wh en 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 b andwidth 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. 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: $005d bit 7654321bit 0 read: auto lock acq xld 0000 write: r rrrr reset:00000000 r = reserved figure 4-6. pll bandwidth control register (pbwc) clock generator module (cgm) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 68 freescale semiconductor xld ? crystal loss detect bit when the vco output, cgmvclk, is driving cgmout, this read/write bit ca n indicate whether the crystal reference frequency is active or not. to chec k the status of the crystal reference, follow these steps: 1. write a logic 1 to xld. 2. wait n 4 cycles. (n is the vco frequency multiplier.) 3. read xld. the crystal loss detect function works only when the bcs bit is set, selecting cgmvclk to drive cgmout. when bcs is clear, xld always reads as logic 0. 1 = crystal reference is not active. 0 = crystal reference is active. pbwc[3:0] ? reserved for test these bits enable test functions not available in us er mode. to ensure software portability from development systems to user applications, software should write 0s to pbwc[3:0] whenever writing to pbwc. 4.5.3 pll programming register the pll programming register (ppg) contains t he programming information for the modulo feedback divider and the programming information for the hardware configuration of the vco. mul[7:4] ? multiplier select bits these read/write bits control the modulo feedback di vider that selects the vco frequency multiplier, n. see 4.3.2.1 pll circuits and 4.3.2.4 programming the pll . a value of $0 in the multiplier select bits configures the modulo feedback divider the same as a va lue of $1. reset initializes these bits to $6 to give a default multiply value of 6. address: $005e bit 7654321bit 0 read: mul7 mul6 mul5 mul4 vrs7 vrs6 vrs5 vrs4 write: reset:01100110 figure 4-7. pll programming register (ppg) table 4-2. vco frequency multiplier (n) selection mul7:mul6:mul5:mul4 vco fr equency multiplier (n) 0000 1 0001 1 0010 2 0011 3 1101 13 1110 14 1111 15 interrupts mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 69 note the multiplier select bits have built-in protection that prevents them from being written when the pll is on (pllon = 1). vrs[7:4] ? vco range select bits these read/write bits control the hardware center-of-range linear multiplier l, which controls the hardware center-of-range frequency f vrs . see 4.3.2.1 pll circuits , 4.3.2.4 programming the pll and 4.5.1 pll control register . vrs[7:4] cannot be written when the pllon bit in the pll control register (pctl) is set. see 4.3.2.5 special programming exceptions . a value of $0 in the vco range select bits disables the pll and clears the bcs bit in the pctl. see 4.3.3 base clock selector circuit and 4.3.2.5 special programming exceptions for more information. reset initializes the bits to $6 to give a default range multiply value of 6. note the vco range select bits have built-in protection that prevents them from being written when the pll is on (pllon = 1) and prevents selection of the vco clock as the source of the base clock (bcs = 1) if the vco range select bits are all clear. the vco range select bits must be programmed correctly. incorrect programming may result in failure of the pll to achieve lock. 4.6 interrupts when the auto bit is set in the pll bandwidth c ontrol 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 vco clock, cgmvclk, divided by two can be selected as the cgmout source by setting bcs in the pctl. when the pll exits lock, the 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 cgmvclk divi ded 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. 4.7 wait mode the wait instruction puts the mcu in low power-consumption standby 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). less power-sensitive applications can dis engage the pll without turning it off. applications that require the pll to wake the mcu from wait mode also can deselect the pll output without turning off the pll. clock generator module (cgm) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 70 freescale semiconductor 4.8 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 ensure s the highest stability and lowest acquisition/lock times. 4.8.1 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 sp ecified 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 acquisiti on time tolerance. if a command instructs the system to change from 0 hz to 1 mhz, the acquisition time is the time taken for the frequency to reach 1 mhz 50 khz. fifty khz = 5% of the 1-mhz step input. if the system is operating at 1 mhz and suffers a ?100-khz noise hit, the acquisition time is the time taken to return from 900 khz to 1 mhz 5 khz. five khz = 5% of the 100-khz step input. other systems refer to acquisition and lock times as t he 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 beca use the system requires the output frequency to be within a certain tolerance of the desired frequenc y regardless of the size of the initial error. the discrepancy in these definitions makes it difficul t to specify an acquisition or lock time for a typical pll. therefore, the definitions for acquisition and lock times for this module are: acquisition time, t acq , is the time the pll takes to reduce the error between the actual output frequency and the desired output frequency to less than the tracking mode entry tolerance, ? trk . acquisition time is based on an initial frequency error, (f des ? f orig )/f des , of not more than 100 percent. in automatic bandwidth control mode (see 4.3.2.3 manual and automatic pll bandwidth modes ), acquisition time expires when the acq bit becomes set in the pll bandwidth control register (pbwc). lock time, t lock , is the time the pll takes to reduce the error between the actual output frequency and the desired output frequency to less than the lock mode entry tolerance, ? lock . lock time is based on an initial frequency error, (f des ? f orig )/f des , of not more than 100 percent. in automatic bandwidth control mode, lock time expires when the lock bit becomes set in the pll bandwidth control register (pbwc). see 4.3.2.3 manual and automatic pll bandwidth modes . obviously, the acquisition and lock times can vary according to how large the frequency error is and may be shorter or longer in many cases. 4.8.2 parametric in fluences on reaction time acquisition and lock times are designed to be as short as possible while still pr oviding 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 reacti on 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 acquisition/lock ti me specifications mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 71 required to reduce the frequency error. therefore, the slower the reference the longer it takes to make these corrections. this parameter is also under user control via the choice of crystal frequency, f xclk . another critical parameter is the external filter capacitor. the pll modifies the voltage on the vco by adding or subtracting charge from this capacitor. therefore, the rate at which the voltage changes for a given frequency error (thus change in charge) is pr oportional to the capacitor size. 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 4.8.3 choosing a filter capacitor . 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. va riable supplies, such as batteries, are acceptable if they vary within a known range at very slow sp eeds. noise on the power s upply is not acceptable, because it causes small frequency errors which continually change the acquisition time of the pll. temperature and processing also can affect acquisition time because the electrical characteristics of the pll change. the part operates as spec ified as long as thes e influences stay within the specified limits. external factors, however, can caus e drastic changes in the operation of the pll. these factors include noise injected into the pll through the filter capaci tor filter, capacitor leakage, stray impedances on the circuit board, and even humidity or circuit board contamination. 4.8.3 choosing a filter capacitor as described in 4.8.2 parametric influences on reaction time , the external filter capacitor, c f , is critical to the stability and reaction time of the pll. t he pll is also dependent on reference frequency and supply voltage. the value of the capacitor must, theref ore, be chosen with supply potential and reference frequency in mind. for proper operation, the external filter capacitor must be chosen according to this equation: for acceptable values of c fact , see 4.8 acquisition/lock time specifications . for the value of v dda , choose the voltage potential at which the mcu is operating. if the power supply is variable, choose a value near the middle of the range of possible supply values. this equation does not always yield a commonly av ailable capacitor size, so round to the nearest available size. if the value is between two different sizes, choose the higher value for better stability. choosing the lower size may seem attractive for acquisition time improvement, but the pll can become unstable. also, always choose a ca pacitor with a tight tolerance ( 20 percent or better) and low dissipation. 4.8.4 reaction ti me calculation the actual acquisition and lock times can be calculated using the equations here. these equations yield nominal values under these conditions: correct selection of filter capacitor, c f , see 4.8.3 choosing a filter capacitor room temperature operation negligible external leakage on c gmxfc negligible noise c f c fact v dda f rdv -------------- - ?? ?? ?? = clock generator module (cgm) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 72 freescale semiconductor the k factor in the equations is derived from internal pll parameters. k acq is the k factor when the pll is configured in acquisition mode, and k trk is the k factor when the pll is configured in tracking mode. see 4.3.2.2 acquisition and tracking modes . note the inverse proportionality between the lock time and the reference frequency. in automatic bandwidth control mode, the acquisition and lock times are quantized into units based on the reference frequency. see 4.3.2.3 manual and automatic pll bandwidth modes a certain number of clock cycles, n acq , is required to ascertain that the pll is within the tracking mode entry tolerance, ? trk , before exiting acquisition mode. a certain number of clock cycles, n trk , is required to ascertain that the pll is within the lock mode entry tolerance, ? lock . therefore, the acquisition time, t acq , is an integer multiple of n acq /f rdv , and the acquisition to lock time, t al , is an integer multiple of n trk /f rdv . also, since the average frequency over the entire measurement perio d must be within the specified tolerance, the total time usually is longer than t lock as calculated in the previous example. in manual mode, it is usually necessary to wait considerably longer than t lock before selecting the pll clock (see 4.3.3 base clock selector circuit ) because the factors described in 4.8.2 parametric influences on reaction time may slow the lock time considerably. t acq v dda f rdv -------------- - ?? ?? ?? 8 k acq -------------- - ?? ?? = t al v dda f rdv -------------- - ?? ?? ?? 4 k trk -------------- ?? ?? = t lock t acq t al + = mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 73 chapter 5 configuration register (config) 5.1 introduction this section describes the configurat ion register (config). this register contains bits that configure these options: resets caused by the low-voltage inhibit (lvi) module power to the lvi module computer operating properly (cop) module top-side pulse-width modulator (pwm) polarity bottom-side pwm polarity edge-aligned versus center-aligned pwms six independent pwms versus three complementary pwm pairs 5.2 functional description the configuration register (config) is used in the initialization of various options. the configuration register 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 microcontroller unit (mcu), it is recommended that this register be written immediately after reset. the configuration register is located at $001f and may be read at anytime. note on a flash device, the options are one-time writeable by the user after each reset. the registers are not in the flash memory but are special registers containing one-time writ eable latches after each reset. upon a reset, the configuration register defaults to predetermined settings as shown in figure 5-1 . if the lvi module and the lvi reset si gnal are enabled, a reset occurs when v dd falls to a voltage, v lvrx , and remains at or below that level for at least nine consecutive central processor un it (cpu) cycles. once an lvi reset occurs, the mcu remains in reset until v dd rises to a voltage, v lvrx . configuration register (config) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 74 freescale semiconductor 5.3 configuration register edge ? edge - align enable bit edge determines if the motor control pwm will o perate in edge-aligned mode or center-aligned mode. see chapter 12 pulse-width modulator for motor control (pwmmc) . 1 = edge-aligned mode enabled 0 = center-aligned mode enabled botneg ? bottom-side pwm polarity bit botneg determines if the bottom-side pwms wi ll have positive or negative polarity. see chapter 12 pulse-width modulator for motor control (pwmmc) . 1 = negative polarity 0 = positive polarity topneg ? top-side pwm polarity bit topneg determines if the top-side pwms will have positive or negative polarity. see chapter 12 pulse-width modulator for motor control (pwmmc) . 1 = negative polarity 0 = positive polarity indep ? independent mode enable bit indep determines if the motor control pwms will be six independent pwms or three complementary pwm pairs. see chapter 12 pulse-width modulator for motor control (pwmmc) . 1 = six independent pwms 0 = three complementary pwm pairs lvirst ? lvi reset enable bit lvirst enables the reset signal from the lvi module. see chapter 9 low-voltage inhibit (lvi) . 1 = lvi module resets enabled 0 = lvi module resets disabled lvipwr ? lvi power enable bit lvipwr enables the lvi module. chapter 9 low-voltage inhibit (lvi) 1 = lvi module power enabled 0 = lvi module power disabled stope ? stop enable bit writing a 0 or a 1 to bit 1 has no effect on mcu operation. bit 1 operates the same as the other bits within this write-once register operate. 1 = stop mode enabled 0 = stop mode disabled copd ? cop disable bit copd disables the cop module. see chapter 6 computer operating properly (cop) . 1 = cop module disabled 0 = cop module enabled address: $001f bit 7654321bit 0 read: edge botneg topneg indep lvirst lvipwr stope copd write: reset:00001100 figure 5-1. configuration register (config) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 75 chapter 6 computer operating properly (cop) 6.1 introduction this section describes the computer operating proper ly module, a free-running counter that generates a reset if allowed to overflow. the computer operati ng properly (cop) module helps software recover from runaway code. prevent a cop reset by periodically clearing the cop counter. 6.2 functional description figure 6-1 shows the structure of the cop module. a summar y of the input/output (i/o) register is shown in figure 6-2 . figure 6-1. cop block diagram copctl write cgmxclk reset vector fetch sim reset circuit sim reset status register internal reset sources(1) sim clear bits 12?4 13-bit sim counter clear all bits 6-bit cop counter copd (from config) reset copctl write clear cop module cop counter note 1. see 14.3.2 active resets from internal sources . computer operating properly (cop) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 76 freescale semiconductor the cop counter is a free-running, 6-bit counter preceded by the 13-bit system integration module (sim) counter. if not cleared by software, the cop counter overflows and generates an asynchronous reset after 2 18 ?2 4 cgmxclk cycles. with a 4.9152-mhz crystal, t he cop timeout period is 53.3 ms. writing any value to location $ffff before overflow occu rs clears the cop counter and prevents reset. a cop reset pulls the rst pin low for 32 cgmxclk cycles and sets the cop bit in the sim reset status register (srsr). see 14.7.2 sim reset status register . note place cop clearing instructions in the main program and not in an interrupt subroutine. such an interrupt s ubroutine could keep the cop from generating a reset even while the main program is not working properly. 6.3 i/o signals this section describes the signals shown in figure 6-1 . 6.3.1 cgmxclk cgmxclk is the crystal oscillator output signal. cg mxclk frequency is equal to the crystal frequency. 6.3.2 copctl write writing any value to the cop control register (copctl) (see 6.4 cop control register ) clears the cop counter and clears bits 12?4 of the sim counter. reading the cop control register returns the reset vector. 6.3.3 powe r-on reset the power-on reset (por) circuit in the sim clears the sim counter 4096 cgmxclk cycles after power-up. 6.3.4 internal reset an internal reset clears the sim counter and the cop counter. 6.3.5 reset vector fetch a reset vector fetch occurs when the vector address appears on the data bus. a reset vector fetch clears the sim counter. addr. register name bit 7654321bit 0 $ffff cop control register (copctl) see page 77. read: low byte of reset vector write: clear cop counter reset: unaffected by reset figure 6-2. cop i/o register summary cop control register mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 77 6.3.6 copd (cop disable) the copd signal reflects the state of the cop disable bit (copd) in the configur ation register (config). see chapter 5 configuration register (config) . 6.4 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. 6.5 interrupts the cop does not generate cpu interrupt requests. 6.6 monitor mode the cop is disabled in monitor mode when v hi is present on the irq pin or on the rst pin. 6.7 wait mode the wait instruction puts the mcu in low power-consumption standby mode. the cop continues to operate during wait mode. 6.8 stop mode stop mode turns off the cgmxclk input to the co p 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. address: $ffff bit 7654321bit 0 read: low byte of reset vector write: clear cop counter reset: unaffected by reset figure 6-3. cop control register (copctl) computer operating properly (cop) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 78 freescale semiconductor mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 79 chapter 7 central processor unit (cpu) 7.1 introduction the m68hc08 cpu (central processor unit) is an e nhanced and fully object-code- compatible version of the m68hc05 cpu. the cpu08 reference manual (document order number cpu08rm/ad) contains a description of the cpu instruction set, addressing modes, and architecture. 7.2 features features of the cpu include: object code fully upward-compatible with m68hc05 family 16-bit stack pointer with stack manipulation instructions 16-bit index register with x-re gister 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 7.3 cpu registers figure 7-1 shows the five cpu registers. cpu registers are not part of the memory map. central processor unit (cpu) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 80 freescale semiconductor figure 7-1. cpu registers 7.3.1 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. 7.3.2 index register the 16-bit index register allows i ndexed 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, th e 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 7-2. accumulator (a) bit 151413121110987654321 bit 0 read: write: reset:00000000 xxxxxxxx x = indeterminate figure 7-3. index register (h:x) 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?s complement overflow flag v11hinzc h x 0 0 0 0 7 15 15 15 70 cpu registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 81 7.3.3 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 a ddressing modes, the stack pointer can function as an index register to access data on t he 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 random-access memory (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. 7.3.4 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 increm ents 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 151413121110987654321 bit 0 read: write: reset:0000000011111111 figure 7-4. stack pointer (sp) bit 151413121110987654321 bit 0 read: write: reset: loaded with vector from $fffe and $ffff figure 7-5. program counter (pc) central processor unit (cpu) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 82 freescale semiconductor 7.3.5 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 per manently to 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. th e 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 cp u 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 compatibil ity, 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. after the i bit is cleared, the highest-priori ty 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 bit 7654321bit 0 read: v11hinzc write: reset:x11x1xxx x = indeterminate figure 7-6. condition code register (ccr) arithmetic/logic unit (alu) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 83 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 7.4 arithmetic/logic unit (alu) the alu performs the arithmetic and logic operations defined by the instruction set. refer to the cpu08 reference manual (document order number cpu08rm/ad) for a description of the instructions and addressing modes and more detail about the architecture of the cpu. 7.5 low-power modes the wait and stop instructions put the mcu in low power-consumption standby modes. 7.5.1 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 cl ear. after exit by reset, the i bit is set. disables the cpu clock 7.5.2 stop mode the stop instruction: clears the interrupt mask (i bit) in the conditi on 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 ru nning after the oscillator stabilization delay. 7.6 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 in struction, the break inte rrupt 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. central processor unit (cpu) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 84 freescale semiconductor 7.7 instruction set summary table 7-1 provides a summary of the m68hc08 instruction set. table 7-1. instruction set summary (sheet 1 of 6) 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) ? 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) ? 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 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 ? ? ? 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) ?? 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 ?? 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 c b0 b7 0 b0 b7 c instruction set summary mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 85 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 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 ? ? ? 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 ????? 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 ????? 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 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 ?????0inh 98 1 cli clear interrupt mask i 0 ??0???inh 9a 2 table 7-1. instruction set summary (sheet 2 of 6) source form operation description effect on ccr address mode opcode operand cycles vh i nzc central processor unit (cpu) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 86 freescale semiconductor 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 0??01? 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) ?? 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?? 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) ?? 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) ?? 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?? inh 72 2 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 ?? ? 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 ???? 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?? ? 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 ?? ? dir inh inh ix1 ix sp1 3c 4c 5c 6c 7c 9e6c dd ff ff 4 1 1 4 3 5 table 7-1. instruction set summary (sheet 3 of 6) source form operation description effect on ccr address mode opcode operand cycles vh i nzc instruction set summary mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 87 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?? ? 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?? ? imm dir 45 55 ii jj dd 3 4 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?? ? 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) ?? 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 ??0 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?? ? 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???0inh 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) ?? 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 ? ? ? 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 table 7-1. instruction set summary (sheet 4 of 6) 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) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 88 freescale semiconductor pula pull a from stack sp (sp + 1); pull ( a ) ??????inh 86 2 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 ?? 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 ?? 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) 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) ?? 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 ?????1inh 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?? ? 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 ? ? ? dir 35 dd 4 stop enable interrupts, stop processing, refer to mcu documentation i 0; stop processing ??0???inh 8e 1 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?? ? 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) ?? 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 table 7-1. instruction set summary (sheet 5 of 6) source form operation description effect on ccr address mode opcode operand cycles vh i nzc c b0 b7 b0 b7 c opcode map mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 89 7.8 opcode map see table 7-2 . 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) 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 ? ? ? 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 bit 0; inhibit cpu clocking until interrupted ??0???inh 8f 1 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 pos t increment addressing mode rr relati ve program counter offset byte ee ff high and low bytes of offset in indexed, 16-bit offs et 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 undefined h index register high byte v overflow 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 des tination 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, pos t increment addressing mode ? if ix2 indexed, 16-bit offset addressing mode : concatenated with m memory location set or cleared n negative bit ? not affected table 7-1. instruction set summary (sheet 6 of 6) source form operation description effect on ccr address mode opcode operand cycles vh i nzc mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 90 freescale semiconductor central processor unit (cpu) table 7-2. 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 1 2 3 4 5 6 9e6 7 8 9 a b c d 9ed e 9ee f 0 5 brset0 3dir 4 bset0 2dir 3 bra 2rel 4 neg 2dir 1 nega 1inh 1 negx 1inh 4 neg 2ix1 5 neg 3 sp1 3 neg 1ix 7 rti 1inh 3 bge 2rel 2 sub 2imm 3 sub 2dir 4 sub 3ext 4 sub 3ix2 5 sub 4 sp2 3 sub 2ix1 4 sub 3 sp1 2 sub 1ix 1 5 brclr0 3dir 4 bclr0 2dir 3 brn 2rel 5 cbeq 3dir 4 cbeqa 3imm 4 cbeqx 3imm 5 cbeq 3ix1+ 6 cbeq 4 sp1 4 cbeq 2ix+ 4 rts 1inh 3 blt 2rel 2 cmp 2imm 3 cmp 2dir 4 cmp 3ext 4 cmp 3ix2 5 cmp 4 sp2 3 cmp 2ix1 4 cmp 3 sp1 2 cmp 1ix 2 5 brset1 3dir 4 bset1 2dir 3 bhi 2rel 5 mul 1inh 7 div 1inh 3 nsa 1inh 2 daa 1inh 3 bgt 2rel 2 sbc 2imm 3 sbc 2dir 4 sbc 3ext 4 sbc 3ix2 5 sbc 4 sp2 3 sbc 2ix1 4 sbc 3 sp1 2 sbc 1ix 3 5 brclr1 3dir 4 bclr1 2dir 3 bls 2rel 4 com 2dir 1 coma 1inh 1 comx 1inh 4 com 2ix1 5 com 3 sp1 3 com 1ix 9 swi 1inh 3 ble 2rel 2 cpx 2imm 3 cpx 2dir 4 cpx 3ext 4 cpx 3ix2 5 cpx 4 sp2 3 cpx 2ix1 4 cpx 3 sp1 2 cpx 1ix 4 5 brset2 3dir 4 bset2 2dir 3 bcc 2rel 4 lsr 2dir 1 lsra 1inh 1 lsrx 1inh 4 lsr 2ix1 5 lsr 3 sp1 3 lsr 1ix 2 ta p 1inh 2 txs 1inh 2 and 2imm 3 and 2dir 4 and 3ext 4 and 3ix2 5 and 4 sp2 3 and 2ix1 4 and 3 sp1 2 and 1ix 5 5 brclr2 3dir 4 bclr2 2dir 3 bcs 2rel 4 sthx 2dir 3 ldhx 3imm 4 ldhx 2dir 3 cphx 3imm 4 cphx 2dir 1 tpa 1inh 2 tsx 1inh 2 bit 2imm 3 bit 2dir 4 bit 3ext 4 bit 3ix2 5 bit 4 sp2 3 bit 2ix1 4 bit 3 sp1 2 bit 1ix 6 5 brset3 3dir 4 bset3 2dir 3 bne 2rel 4 ror 2dir 1 rora 1inh 1 rorx 1inh 4 ror 2ix1 5 ror 3 sp1 3 ror 1ix 2 pula 1inh 2 lda 2imm 3 lda 2dir 4 lda 3ext 4 lda 3ix2 5 lda 4 sp2 3 lda 2ix1 4 lda 3 sp1 2 lda 1ix 7 5 brclr3 3dir 4 bclr3 2dir 3 beq 2rel 4 asr 2dir 1 asra 1inh 1 asrx 1inh 4 asr 2ix1 5 asr 3 sp1 3 asr 1ix 2 psha 1inh 1 ta x 1inh 2 ais 2imm 3 sta 2dir 4 sta 3ext 4 sta 3ix2 5 sta 4 sp2 3 sta 2ix1 4 sta 3 sp1 2 sta 1ix 8 5 brset4 3dir 4 bset4 2dir 3 bhcc 2rel 4 lsl 2dir 1 lsla 1inh 1 lslx 1inh 4 lsl 2ix1 5 lsl 3 sp1 3 lsl 1ix 2 pulx 1inh 1 clc 1inh 2 eor 2imm 3 eor 2dir 4 eor 3ext 4 eor 3ix2 5 eor 4 sp2 3 eor 2ix1 4 eor 3 sp1 2 eor 1ix 9 5 brclr4 3dir 4 bclr4 2dir 3 bhcs 2rel 4 rol 2dir 1 rola 1inh 1 rolx 1inh 4 rol 2ix1 5 rol 3 sp1 3 rol 1ix 2 pshx 1inh 1 sec 1inh 2 adc 2imm 3 adc 2dir 4 adc 3ext 4 adc 3ix2 5 adc 4 sp2 3 adc 2ix1 4 adc 3 sp1 2 adc 1ix a 5 brset5 3dir 4 bset5 2dir 3 bpl 2rel 4 dec 2dir 1 deca 1inh 1 decx 1inh 4 dec 2ix1 5 dec 3 sp1 3 dec 1ix 2 pulh 1inh 2 cli 1inh 2 ora 2imm 3 ora 2dir 4 ora 3ext 4 ora 3ix2 5 ora 4 sp2 3 ora 2ix1 4 ora 3 sp1 2 ora 1ix b 5 brclr5 3dir 4 bclr5 2dir 3 bmi 2rel 5 dbnz 3dir 3 dbnza 2inh 3 dbnzx 2inh 5 dbnz 3ix1 6 dbnz 4 sp1 4 dbnz 2ix 2 pshh 1inh 2 sei 1inh 2 add 2imm 3 add 2dir 4 add 3ext 4 add 3ix2 5 add 4 sp2 3 add 2ix1 4 add 3 sp1 2 add 1ix c 5 brset6 3dir 4 bset6 2dir 3 bmc 2rel 4 inc 2dir 1 inca 1inh 1 incx 1inh 4 inc 2ix1 5 inc 3 sp1 3 inc 1ix 1 clrh 1inh 1 rsp 1inh 2 jmp 2dir 3 jmp 3ext 4 jmp 3ix2 3 jmp 2ix1 2 jmp 1ix d 5 brclr6 3dir 4 bclr6 2dir 3 bms 2rel 3 tst 2dir 1 tsta 1inh 1 tstx 1inh 3 tst 2ix1 4 tst 3 sp1 2 tst 1ix 1 nop 1inh 4 bsr 2rel 4 jsr 2dir 5 jsr 3ext 6 jsr 3ix2 5 jsr 2ix1 4 jsr 1ix e 5 brset7 3dir 4 bset7 2dir 3 bil 2rel 5 mov 3dd 4 mov 2dix+ 4 mov 3imd 4 mov 2ix+d 1 stop 1inh * 2 ldx 2imm 3 ldx 2dir 4 ldx 3ext 4 ldx 3ix2 5 ldx 4 sp2 3 ldx 2ix1 4 ldx 3 sp1 2 ldx 1ix f 5 brclr7 3dir 4 bclr7 2dir 3 bih 2rel 3 clr 2dir 1 clra 1inh 1 clrx 1inh 3 clr 2ix1 4 clr 3 sp1 2 clr 1ix 1 wait 1inh 1 txa 1inh 2 aix 2imm 3 stx 2dir 4 stx 3ext 4 stx 3ix2 5 stx 4 sp2 3 stx 2ix1 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 3dir cycles opcode mnemonic number of bytes / addressing mode msb lsb msb lsb mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 91 chapter 8 external interrupt (irq) 8.1 introduction this section describes the external interrupt (irq) module, which supports exte rnal interrupt functions. 8.2 features features of the irq module include: a dedicated external interrupt pin, irq hysteresis buffers 8.3 functional description a logic 0 applied to any of the external inte rrupt pins can latch a cpu interrupt request. figure 8-1 shows the structure of the irq module. figure 8-1. irq module block diagram addr. register name bit 7654321bit 0 $003f irq status/control register (iscr) see page 94. read:0000 irqf 0 imask1 mode1 write:rrrr ack1 reset:00000000 r= reserved figure 8-2. irq i/o register summary ack1 imask1 dq ck clr irq high interrupt to mode select logic irq latch request irq v dd mode1 voltage detect synchro- nizer external interrupt (irq) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 92 freescale semiconductor interrupt signals on the irq pin are latched into the irq1 latch. an interrupt latch remains set until one of the following actions occurs: vector fetch ? a vector fetch automatically gener ates an interrupt acknowledge signal that clears the latch that caused the vector fetch. software clear ? software can clear an interrupt latch by writing to the appropriate acknowledge bit in the interrupt status and control register (i scr). writing a logic 1 to the ack1 bit clears the irq1 latch. reset ? a reset automatically clears both interrupt latches. the external interrupt pins are falling-edge- triggered and are software-configurable to be both falling-edge and low-level-triggered. the mode1 bit in the iscr controls the tri ggering sensitivity of the irq pin. when the interrupt pin is edge-triggered only, the interr upt latch remains set until a vector fetch, software clear, or reset occurs. when the interrupt pin is both falling-edge and low-level-triggered, the interrupt latch remains set until both of these occur: vector fetch, software clear, or reset return of the interrupt pin to logic 1 the vector fetch or software clear can occur before or after the interrupt pin returns to logic 1. as long as the pin is low, the interrupt request remains pending. when set, the imask1 bit in the iscr masks all external interrupt requests. a latched interrupt request is not presented to the interrupt priori ty logic unless the imask bit is clear. note the interrupt mask (i) in the condi tion code register (ccr) masks all interrupt requests, including exte rnal interrupt requests. (see figure 8-3 .) 8.4 irq pin 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 mode1 bit is set, the irq pin is both falling-edge-sensitive and low-level- sensitive. with mode1 set, both of these actions must occur to clear the irq1 latch: vector fetch, software clear, or reset ? a vect or fetch generates an interrupt acknowledge signal to clear the latch. software can generate the inte rrupt acknowledge signal by writing a logic 1 to the ack1 bit in the interrupt status and contro l register (iscr). the ack1 bit is useful in applications that poll the irq pin and require software to clear the irq1 latch. writing to the ack1 bit can also prevent spurious interrupts due to noise. setting ack1 does not affect subsequent transitions on the irq pin. a falling edge that occurs after writing to the ack1 bit latches another interrupt request. if the irq1 mask bit, imask1, is clear, the cpu loads the program counter with the vector address at locations $fffa and $fffb. return of the irq pin to logic 1 ? as long as the irq pin is at logic 0, the irq1 latch remains set. irq pin mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 93 figure 8-3. irq interrupt flowchart from reset i bit set? fetch next yes no interrupt? instruction swi instruction? rti instruction? no stack cpu registers no set i bit load pc with interrupt vector no yes unstack cpu registers execute instruction yes yes external interrupt (irq) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 94 freescale semiconductor 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 mode1 bit is set, the irq pin is both falling-edge-sensitive and low-level- sensitive. with mode1 set, both of these actions must occur to clear the irq1 latch: vector fetch, software clear, or reset ? a vect or fetch generates an interrupt acknowledge signal to clear the latch. software can generate the inte rrupt acknowledge signal by writing a logic 1 to the ack1 bit in the interrupt status and contro l register (iscr). the ack1 bit is useful in applications that poll the irq pin and require software to clear the irq1 latch. writing to the ack1 bit can also prevent spurious interrupts due to noise. setting ack1 does not affect subsequent transitions on the irq pin. a falling edge that occurs after writing to the ack1 bit latches another interrupt request. if the irq1 mask bit, imask1, is clear, the cpu loads the program counter with the vector address at locations $fffa and $fffb. return of the irq pin to logic 1 ? as long as the irq pin is at logic 0, the irq1 latch remains set. the vector fetch or software clear and the return of the irq pin to logic 1 can occur in any order. the interrupt request remains pending as long as the irq pin is at logic 0. if the mode1 bit is clear, the irq pin is falling-edge-sensit ive only. with mode1 clear, a vector fetch or software clear immediately clears the irq1 latch. use the branch if irq pin high (bih) or branch if irq pin low (bil) instruction to read the logic level on the irq pin. note when using the level-sensitive interrupt trigger, avoid false interrupts by masking interrupt requests in the interrupt routine. 8.5 irq status and control register the irq status and control register (iscr) has these functions: clears the irq interrupt latch masks irq interrupt requests controls triggering sensitivity of the irq interrupt pin ack1 ? irq interrupt request acknowledge bit writing a logic 1 to this write-only bit clears the irq latch. ack1 always reads as logic 0. reset clears ack1. address: $003f bit 7654321bit 0 read:0000 irqf 0 imask1 mode1 write:rrrr ack1 reset:00000000 r= reserved figure 8-4. irq status and control register (iscr) irq status and control register mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 95 imask1 ? irq interrupt mask bit writing a logic 1 to this read/write bit disables irq interrupt requests. reset clears imask1. 1 = irq interrupt requests disabled 0 = irq interrupt requests enabled mode1 ? irq edge/level select bit this read/write bit controls the triggering sensitivity of the irq pin. reset clears mode1. 1 = irq interrupt requests on falling edges and low levels 0 = irq interrupt requests on falling edges only irqf ? irq flag this read-only bit acts as a status flag, indicating an irq event occurred. 1 = external irq event occurred. 0 = external irq event did not occur. external interrupt (irq) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 96 freescale semiconductor mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 97 chapter 9 low-voltage inhibit (lvi) 9.1 introduction this section describes the low-voltage inhibit (lvi) module, which monitors the voltage on the v dd pin and can force a reset when the v dd voltage falls to the lvi trip voltage. 9.2 features features of the lvi module include: programmable lvi reset programmable power consumption digital filtering of v dd pin level selectable lvi trip voltage 9.3 functional description figure 9-1 shows the structure of the lvi module. the lvi is enabled out of reset. the lvi module contains a bandgap reference circuit and comparator. the lvi power bit, lvipwr, enables the lvi to monitor v dd voltage. the lvi reset bit, lvirst, enables the lvi module to generate a reset when v dd falls below a voltage, v lvrx , and remains at or below that level for nine or more consecutive cgmxclk. v lvrx and v lvhx are determined by the trpsel bit in the lviscr (see figure 9-2 ). lvipwr and lvirst are in the configuration register (config). see chapter 5 configuration register (config) . figure 9-1. lvi module block diagram low v dd lvirst v dd > lvitrip = 0 v dd < lvitrip = 1 lviout lvipwr detector v dd lvi reset from config from config v dd digital filter cpu clock anlgtrip trpsel from lviscr low-voltage inhibit (lvi) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 98 freescale semiconductor once an lvi reset o ccurs, the mcu remains in reset until v dd rises above a voltage, v lvrx + v lvhx . v dd must be above v lvrx + v lvhx for only one cpu cycle to bring the mcu out of reset. see 14.3.2.6 low-voltage inhibit (lvi) reset . the output of the comparator controls the state of the lviout flag in the lvi status register (lviscr). an lvi reset also drives the rst pin low to provide low-voltage protec tion to external peripheral devices. see 19.5 dc electrical characteristics . 9.3.1 polled lvi operation in applications that can operate at v dd levels below v lvrx , software can monitor v dd by polling the lviout bit. in the configuration register, the lvipwr bit must be 1 to enable the lvi module, and the lvirst bit must be 0 to disable lvi resets. see chapter 5 configuration register (config) . trpsel in the lviscr selects v lvrx . 9.3.2 forced reset operation in applications that require v dd to remain above v lvrx , enabling lvi resets allows the lvi module to reset the mcu when v dd falls to the v lvrx level and remains at or below that level for nine or more consecutive cpu cycles. in the config register, the lvipwr and lvirst bits must be 1s to enable the lvi module and to enabl e lvi resets. trpsel in the lviscr selects v lvrx . 9.3.3 false reset protection the v dd pin level is digitally filtered to reduce false resets due to power supply noise. in order for the lvi module to reset the mcu, v dd must remain at or below v lvrx for nine or more consecutive cpu cycles. v dd must be above v lvrx + v lvhx for only one cpu cycle to bring the mcu out of reset. trpsel in the lviscr selects v lvrx + v lvhx . 9.3.4 lvi trip selection the trpsel bit allows the user to chose between 5 percent and 10 percent tolerance when monitoring the supply voltage. the 10 percent option is enabled out of reset. wr iting a 1 to trpsel will enable 5 percent option. note the microcontroller is guaranteed to operate at a minimum supply voltage. the trip point (vlvr1 or vlvr2) may be lower than this. see 19.5 dc electrical characteristics . addr. register name bit 7654321bit 0 $fe0f lvi status and control register (lviscr) see page 99. read: lviout 0 trpsel 00000 write:rr rrrrr reset:00000000 r =reserved figure 9-2. lvi i/o register summary lvi status and control register mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 99 9.4 lvi status and control register the lvi status register (lviscr) flags v dd voltages below the v lvrx level . lviout ? lvi output bi t this read-only flag becomes set when the v dd voltage falls below the v lvrx voltage for 32 to 40 cgmxclk cycles. see table 9-1 . reset clears the lviout bit. trpsel ? lvi trip select bit this bit selects the lvi trip point. reset clears this bit. 1 = 5 percent tolerance. the trip point and recovery point are determined by v lvr1 and v lvh1 , respectively. 0 = 10 percent tolerance. the trip point and recovery point are determined by v lvr2 and v lvh2 , respectively. note if lvirst and lvipwr are 0s, note that when changing the tolerance, lvi reset will be generated if the supply voltage is below the trip point. 9.5 lvi interrupts the lvi module does not generate interrupt requests. 9.6 wait mode the wait instruction puts the mcu in low power-consumption standby mode. with the lvipwr bit in the configur ation register programmed to 1, the lvi module is active after a wait instruction. address: $fe0f bit 7654321bit 0 read: lviout 0 trpsel 00000 write:rr rrrrr reset:00000000 r =reserved figure 9-3. lvi status and control register (lviscr) table 9-1. lviout bit indication v dd lviout at level: for number of cgmxclk cycles: v dd > v lv r x + v lv h x any 0 v dd < v lvr x < 32 cgmxclk cycles 0 v dd < v lvr x between 32 & 40 cgmxclk cycles 0 or 1 v dd < v lvr x > 40 cgmxclk cycles 1 v lv r x < v dd < v lv r x + v lv h x any previous value low-voltage inhibit (lvi) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 100 freescale semiconductor with the lvirst bit in the confi guration register programmed to 1, the lvi module can generate a reset and bring the mcu out of wait mode. 9.7 stop mode if enabled, the lvi module remains active in st op mode. if enabled to generate resets, the lvi module can generate a reset and bring the mcu out of stop mode. mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 101 chapter 10 input/output (i/o) ports (ports) 10.1 introduction thirty-seven bidirectional input-output (i/o) pins and seven input pins fo rm six parallel ports. all i/o pins are programmable as inputs or outputs. when using the 56-pin package version: set the data direction register bits in ddrc such that bit 1 is written to a logic 1 (along with any other output bits on port c). set the data direction register bits in ddre such t hat bits 0, 1, and 2 are written to a logic 1 (along with any other output bits on port e). set the data direction register bits in ddrf such that bits 0, 1, 2, and 3 are written to a logic 1 (along with any other output bits on port f). note connect any unused i/o pins to an appropriate logic level, either v dd or v ss . although pwm6?pwm1 do not require termination for proper operation, termination reduces excess current consumption and the possibility of electrostatic damage. addr. register name bit 7 6 5 4 3 2 1 bit 0 $0000 port a data register (pta) see page 103. read: pta7 pta6 pta5 pta4 pta3 pta2 pta1 pta0 write: reset: unaffected by reset $0001 port b data register (ptb) see page 104. read: ptb7 ptb6 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 write: reset: unaffected by reset $0002 port c data register (ptc) see page 106. read: 0 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1 ptc0 write: r reset: unaffected by reset $0003 port d data register (ptd) see page 107. read: 0 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 write:rrrrrrrr reset: unaffected by reset $0004 data direction register a (ddra) see page 103. read: ddra7 ddra6 ddra5 ddra4 ddra3 ddra2 ddra1 ddra0 write: reset:00000000 r= reserved = unimplemented figure 10-1. i/o port register summary input/output (i/o) ports (ports) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 102 freescale semiconductor $0005 data direction register b (ddrb) see page 105. read: ddrb7 ddrb6 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 write: reset:00000000 $0006 data direction register c (ddrc) see page 106. read: 0 ddrc6 ddrc5 ddrc4 ddrc3 ddrc2 ddrc1 ddrc0 write: r reset:00000000 $0007 unimplemented $0008 port e data register (pte) see page 108. read: pte7 pte6 pte5 pte4 pte3 pte2 pte1 pte0 write: reset: unaffected by reset $0009 port f data register (ptf) see page 110. read: 0 0 ptf5 ptf4 ptf3 ptf2 ptf1 ptf0 write: r r reset: unaffected by reset $000a unimplemented $000b unimplemented $000c data direction register e (ddre) see page 109. read: ddre7 ddre6 ddre5 ddre4 ddre3 ddre2 ddre1 ddre0 write: reset:00000000 $000d data direction register f (ddrf) see page 110. read: 0 0 ddrf5 ddrf4 ddrf3 ddrf2 ddrf1 ddrf0 write: r r reset: 000000 addr. register name bit 7 6 5 4 3 2 1 bit 0 r= reserved = unimplemented figure 10-1. i/o port register summary (continued) port a mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 103 10.2 port a port a is an 8-bit, general-purpose, bidirectional i/o port. 10.2.1 port a data register the port a data register (pta) 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 regi ster a. reset has no effect on port a data. 10.2.2 data dir ection register a data direction register a (ddra) 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. ddra[7:0] ? data direction register a bits these read/write bits contro l 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 writin g to the port a data register before changing data direction regist er a bits from 0 to 1. figure 10-4 shows the port a i/o logic. address: $0000 bit 7654321bit 0 read: pta7 pta6 pta5 pta4 pta3 pta2 pta1 pta0 write: reset: unaffected by reset figure 10-2. port a data register (pta) address: $0004 bit 7654321bit 0 read: ddra7 ddra6 ddra5 ddra4 ddra3 ddra2 ddra1 ddra0 write: reset:00000000 figure 10-3. data direction register a (ddra) input/output (i/o) ports (ports) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 104 freescale semiconductor figure 10-4. port a i/o circuit when bit ddrax is a logic 1, reading address $0000 reads the ptax data latch. when bit 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 10-1 summarizes the operation of the port a pins. 10.3 port b port b is an 8-bit, general-purpose, bidirectional i/o port that shares its pins with the analog-to-digital convertor (adc) module. 10.3.1 port b data register the port b data register (ptb) 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 regi ster b. reset has no effect on port b data. table 10-1. 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?t 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] address: $0001 bit 7654321bit 0 read: ptb7 ptb6 ptb5 ptb4 ptb3 ptb2 ptb1 ptb0 write: reset: unaffected by reset figure 10-5. port b data register (ptb) read ddra ($0004) write ddra ($0004) reset write pta ($0000) read pta ($0000) ptax ddrax ptax internal data bus port b mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 105 10.3.2 data dir ection register b data direction register b (ddrb) 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 contro l 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 writin g to the port b data register before changing data direction regist er b bits from 0 to 1. figure 10-7 shows the port b i/o logic. figure 10-7. port b i/o circuit when bit ddrbx is a logic 1, reading address $0001 reads the ptbx data latch. when bit 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 10-2 summarizes the operation of the port b pins. address: $0005 bit 7654321bit 0 read: ddrb7 ddrb6 ddrb5 ddrb4 ddrb3 ddrb2 ddrb1 ddrb0 write: reset:00000000 figure 10-6. data direction register b (ddrb) table 10-2. 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?t 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] read ddrb ($0005) write ddrb ($0005) reset write ptb ($0001) read ptb ($0001) ptbx ddrbx ptbx internal data bus input/output (i/o) ports (ports) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 106 freescale semiconductor 10.4 port c port c is a 7-bit, general-purpose, bidi rectional i/o port that shares two of its pins with the analog-to-digital convertor module (adc). 10.4.1 port c data register the port c data register (ptc) contains a dat a latch for each of the seven port c pins. ptc[6:0] ? port c data bits these read/write bits are software-programmable. da ta 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. 10.4.2 data dir ection register c data direction register c (ddrc) determines whether ea ch port c pin is an input or an output. writing a logic 1 to a ddrc bit enables the output buffer for t he corresponding port c pin; a logic 0 disables the output buffer. ddrc[6:0] ? data direction register c bits these read/write bits control port c data direction. reset clears ddrc[6:0], 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 writin g to the port c data register before changing data direction regist er c bits from 0 to 1. address: $0002 bit 7654321bit 0 read: 0 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1 ptc0 write: r reset: unaffected by reset r = reserved figure 10-8. port c data register (ptc) address: $0006 bit 7654321bit 0 read: 0 ddrc6 ddrc5 ddrc4 ddrc3 ddrc2 ddrc1 ddrc0 write: r reset:00000000 r= reserved figure 10-9. data direction register c (ddrc) port d mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 107 figure 10-10 shows the port c i/o logic. figure 10-10. port c i/o circuit when bit ddrcx is a logic 1, r eading address $0002 reads the ptcx data latch. when bit 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 10-3 summarizes the operation of the port c pins. 10.5 port d port d is a 7-bit, input-only port that shares its pi ns with the pulse width modulator for motor control module (pmc). the port d data register (ptd) contains a data latch for each of the seven port pins. ptd[6:0] ? port d data bits these read/write bits are software programmable. reset has no effect on port d data. table 10-3. 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?t care input, hi-z (2) 2. hi-z = high impedance ddrc[6:0] pin ptc[6:0] (3) 3. writing affects data register, but does not affect input. 1 x output ddrc[6:0] ptc[6:0] ptc[6:0] address: $0003 bit 7654321bit 0 read: 0 ptd6 ptd5 ptd4 ptd3 ptd2 ptd1 ptd0 write:rrrrrrrr reset: unaffected by reset r = reserved figure 10-11. port d data register (ptd) read ddrc ($0006) write ddrc ($0006) reset write ptc ($0002) read ptc ($0002) ptcx ddrcx ptcx internal data bus input/output (i/o) ports (ports) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 108 freescale semiconductor figure 10-12 shows the port d input logic. figure 10-12. port d input circuit reading address $0003 reads the voltage level on the pin. table 10- 4 summarizes the operation of the port d pins. 10.6 port e port e is an 8-bit, special function port that shares fi ve of its pins with the timer interface module (tim) and two of its pins with the serial communications interface module (sci). 10.6.1 port e data register the port e data register (pte) contains a data latch for each of the eight port e pins. pte[7:0] ? port e data bits pte[7:0] are read/write, software-programmable bits . data direction of each port e pin is under the control of the corresponding bit in data direction register e. note data direction register e (ddre) does not affect the data direction of port e pins that are being used by the tima or timb. however, the ddre bits always determine whether reading port e returns the states of the latches or the states of the pins. table 10-4. port d pin functions ptd bit pin mode accesses to ptd read write x (1) 1. x = don?t care input, hi-z (2) 2. hi-z = high impedance pin ptd[6:0] (3) 3. writing affects data regist er, but does not affect input. address: $0008 bit 7654321bit 0 read: pte7 pte6 pte5 pte4 pte3 pte2 pte1 pte0 write: reset: unaffected by reset figure 10-13. port e data register (pte) read ptd ($0003) ptdx internal data bus port e mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 109 10.6.2 data dir ection register e data direction register e (ddre) determines whether each port e pin is an input or an output. writing a logic 1 to a ddre bit enables the output buffer for the corresponding port e pin; a logic 0 disables the output buffer. ddre[7:0] ? data direction register e bits these read/write bits contro l port e data direction. reset clears ddre[7:0], configuring all port e pins as inputs. 1 = corresponding port e pin configured as output 0 = corresponding port e pin configured as input note avoid glitches on port e pins by writin g to the port e data register before changing data direction regist er e bits from 0 to 1. figure 10-15 shows the port e i/o logic. figure 10-15. port e i/o circuit when bit ddrex is a logic 1, reading address $0008 reads the ptex data latch. when bit ddrex is a logic 0, reading address $0008 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. table 10- 5 summarizes the operation of the port e pins. address: $000c bit 7654321bit 0 read: ddre7 ddre6 ddre5 ddre4 ddre3 ddre2 ddre1 ddre0 write: reset:00000000 figure 10-14. data direction register e (ddre) table 10-5. port e pin functions ddre bit pte bit i/o pin mode accesses to ddre accesses to pte read/write read write 0 x (1) 1. x = don?t care input, hi-z (2) 2. hi-z = high impedance ddre[7:0] pin pte[7:0] (3) 3. writing affects data register, but does not affect input. 1 x output ddre[7:0] pte[7:0] pte[7:0] read ddre ($000c) write ddre ($000c) reset write pte ($0008) read pte ($0008) ptex ddrex ptex internal data bus input/output (i/o) ports (ports) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 110 freescale semiconductor 10.7 port f port f is a 6-bit, special function port that shares four of its pins with the serial peripheral interface module (spi) and two pins with the serial communications interface (sci). 10.7.1 port f data register the port f data register (ptf) contains a data latch for each of the six port f pins. ptf[5:0] ? port f data bits these read/write bits are software programmable. data direction of each port f pin is under the control of the corresponding bit in data direction re gister f. reset has no effect on ptf[5:0]. note data direction register f (ddrf) does not affect the data direction of port f pins that are being used by the spi or sci module. however, the ddrf bits always determine whether reading port f returns the states of the latches or the states of the pins. 10.7.2 data dir ection register f data direction register f (ddrf) determines whether each port f pin is an input or an output. writing a logic 1 to a ddrf bit enables the output buffer for the corresponding port f pin; a logic 0 disables the output buffer. ddrf[5:0] ? data direction register f bits these read/write bits control port f data direction. reset clears ddrf[5:0], configuring all port f pins as inputs. 1 = corresponding port f pin configured as output 0 = corresponding port f pin configured as input note avoid glitches on port f pins by writ ing to the port f data register before changing data direction regist er f bits from 0 to 1. address: $0009 bit 7654321bit 0 read: 0 0 ptf5 ptf4 ptf3 ptf2 ptf1 ptf0 write: r r reset: unaffected by reset r = reserved figure 10-16. port f data register (ptf) address: $000d bit 7654321bit 0 read: 0 0 ddrf5 ddrf4 ddrf3 ddrf2 ddrf1 ddrf0 write: r r read: 000000 r = reserved figure 10-17. data direction register f (ddrf) port f mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 111 figure 10-18 shows the port f i/o logic. figure 10-18. port f i/o circuit when bit ddrfx is a logic 1, r eading address $0009 read s the ptfx data latch. when bit ddrfx is a logic 0, reading address $0009 reads the voltage level on the pin. the data latch can always be written, regardless of the state of its data direction bit. table 10- 6 summarizes the operation of the port f pins. table 10-6. port f pin functions ddrf bit ptf bit i/o pin mode accesses to ddrf accesses to ptf read/write read write 0 x (1) 1. x = don?t care input, hi-z (2) 2. hi-z = high impedance ddrf[6:0] pin ptf[6:0] (3) 3. writing affects data register, but does not affect input. 1 x output ddrf[6:0] ptf[6:0] ptf[6:0] read ddrf ($000d) write ddrf ($000d) reset write ptf ($0009) read ptf ($0009) ptfx ddrfx ptfx internal data bus input/output (i/o) ports (ports) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 112 freescale semiconductor mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 113 chapter 11 power-on reset (por) 11.1 introduction this section describes the power-on reset (por) module. 11.2 functional description the por module provides a known, stable signal to the microcontroller unit (mcu) at power-on. this signal tracks v dd until the mcu generates a feedback signal to indi cate that it is properly initialized. at this time, the por drives its output low. the por is not a brown-out detector, low-voltage detector, or glitch detector. v dd at the por must go completely to 0 to reset the microcontroller unit (m cu). to detect power-loss conditions, use a low-voltage inhibit module (lvi) or other suitable circuit. power-on reset (por) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 114 freescale semiconductor mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 115 chapter 12 pulse-width modulator for motor control (pwmmc) 12.1 introduction this section describes the pulse-width modulator for motor control (pwmmc, version a). the pwm module can generate three complementary pwm pairs or six independent pwm signals. these pwm signals can be center-aligned or edge-aligned. a block diagram of the pwm module is shown in figure 12-2 . a12-bit timer pwm counter is common to all six channels. pwm resolution is one clock period for edge-aligned operation and two clock periods for center-aligned operation. the clock period is dependent on the internal operating frequency (f op ) and a programmable prescaler. the highest resolution for edge-aligned operation is 125 ns (f op = 8 mhz). the highest resoluti on for center-aligned operation is 250 ns (f op =8mhz). when generating complementary pwm signals, the module features automatic dead-time insertion to the pwm output pairs and transparent toggling of pw m data based upon sensed motor phase current polarity. a summary of the pwm registers is shown in figure 12-3 . 12.2 features features of the pwmmc include: three complementary pwm pairs or six independent pwm signals edge-aligned pwm signals or center-aligned pwm signals pwm signal polarity control 20-ma current sink capability on pwm pins manual pwm output control through software programmable fault protection complementary mode featuring: ? dead-time insertion ? separate top/bottom pulse width correction via current sensing or programmable software bits mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 116 freescale semiconductor pulse-width modulator fo r motor control (pwmmc) figure 12-1. block diagram highlighting pwmmc block and pins clock generator module system integration module serial communications interface module serial peripheral interface module (2) timer interface module a low-voltage inhibit module power-on reset module computer operating properly module arithmetic/logic unit cpu registers m68hc08 cpu control and status registers ? 112 bytes user flash ? 32,256 bytes user ram ? 768 bytes monitor rom ? 240 bytes user flash vector space ? 46 bytes irq module power pta ddra ddrb ptb ddrc ptc ptd ddre pte ptf ddrf internal bus osc1 osc2 cgmxfc rst irq v ss v dd v ddad pta7?pta0 pte7/tch3a pte6/tch2a pte5/tch1a pte4/tch0a pte3/tclka pte2/tch1b (1) pte1/tch0b (1) pte0/tclkb (1) ptf5/txd ptf4/rxd ptf3/miso (1) ptf2/mosi (1) ptf1/ss (1) ptf0/spsck (1) timer interface module b pulse-width modulator module ptb7/atd7 ptb6/atd6 ptb5/atd5 ptb4/atd4 ptb3/atd3 ptb2/atd2 ptb1/atd1 ptb0/atd0 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1/atd9(1) ptc0/atd8 ptd6/is3 ptd5/is2 ptd4/is1 ptd3/fault4 ptd2/fault3 ptd1/fault2 ptd0/fault1 pwm6?pwm1 analog-to-digital converter module v ssad v dda v ssa (3) pwmgnd v refl (3) v refh notes: 1. these pins are not available in the 56-pin sdip package. 2. this module is not available in the 56-pin sdip package. 3. in the 56-pin sdip package, these pins are bonded together. single break module features mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 117 figure 12-2. pwm module block diagram addr. register name bit 7 6 5 4 3 2 1 bit 0 $0020 pwm control register 1 (pctl1) see page 146. read: disx disy pwmint pwmf isens1 isens0 ldok pwmen write: reset: 0 0 0 0 0 0 0 0 $0021 pwm control register 2 (pctl2) see page 148. read: ldfq1 ldfq0 0 ipol1 ipol2 ipol3 prsc1 prsc0 write: reset: 0 0 0 0 0 0 0 0 $0022 fault control register (fcr) see page 150. read: fint4 fmode4 fint3 fmode3 fint2 fmode2 fint1 fmode1 write: reset: 0 0 0 0 0 0 0 0 $0023 fault status register (fsr) see page 152. read: fpin4 fflag4 fpin3 fflag3 fpin2 fflag2 fpin1 fflag1 write: reset: u 0 u 0 u 0 u 0 $0024 fault acknowledge register (ftack) see page 153. read: 0 0 dt6 dt5 dt4 dt3 dt2 dt1 write: ftack4 ftack3 ftack2 ftack1 reset: 0 0 0 0 0 0 0 0 r = reserved bold = buffered x = indeterminate figure 12-3. register summary (sheet 1 of 3) pwm1 pin pwm2 pin pwm channels 3 and 4 pwm3 pin pwm4 pin pwm channels 5 and 6 pwm5 pin pwm6 pin timebase cpu bus output control coil current polarity pins 3 4 fault interrupt pins 12 control logic block 8 pwm channels 1 and 2 fault protection pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 118 freescale semiconductor $0025 pwm output control register (pwmout) see page 154. read: 0 outctl out6 out5 out4 out3 out2 out1 write: reset: 0 0 0 0 0 0 0 0 $0026 pwm counter register high (pcnth) see page 143. read: 0 0 0 0 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $0027 pwm counter register low (pcntl) see page 143. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $0028 pwm counter modulo register high (pmodh) see page 144. read: 0 0 0 0 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 x x x x $0029 pwm counter modulo register low (pmodl) see page 144. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: x x x x x x x x $002a pwm 1 value register high (pval1h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $002b pwm 1 value register low (pval1l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $002c pwm 2 value register high (pval2h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $002d pwm 2 value register low (pval2l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $002e pwm 3 value register high (pval3h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $002f pwm 3 value register low (pval3l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 addr. register name bit 7 6 5 4 3 2 1 bit 0 r = reserved bold = buffered x = indeterminate figure 12-3. register summary (sheet 2 of 3) features mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 119 $0030 pwm 4 value register high (pval4h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $0031 pwm 4 value register low (pval4l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $0032 pwm 5 value register high (pval5h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $0033 pwm 5 value register low (pval5l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $0034 pwm 6 value register high (pval6h) see page 145. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 0 0 0 0 0 0 0 0 $0035 pwm 6 value register low (pmval6l) see page 145. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 0 0 0 0 0 0 0 0 $0036 dead-time write-once register (deadtm) see page 150. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 1 1 1 1 1 1 1 1 $0037 pwm disable mapping write-once register (dismap) see page 150. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 1 1 1 1 1 1 1 1 addr. register name bit 7 6 5 4 3 2 1 bit 0 r = reserved bold = buffered x = indeterminate figure 12-3. register summary (sheet 3 of 3) pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 120 freescale semiconductor 12.3 timebase this section provides a discussion of the timebase. 12.3.1 resolution in center-aligned mode, a 12-bit up/down counter is used to create the pwm period. therefore, the pwm resolution in center-aligned mode is two cl ocks (highest resolution is 250 ns @ f op = 8 mhz) as shown in figure 12-4 . the up/down counter uses the value in the timer modulus register to determine its maximum count. the pwm period will equal: [(timer modulus) x (pwm clock period) x 2]. figure 12-4. center-aligned pwm (positive polarity) up/down counter modulus = 4 pwm = 0 pwm = 1 pwm = 2 pwm = 3 pwm = 4 period = 8 x (pwm clock period) timebase mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 121 for edge-aligned mode, a 12-bit up-onl y counter is used to create the pwm period. therefore, the pwm resolution in edge-aligned mode is one clock (highest resolution is125 ns @ f op = 8 mhz) as shown in figure 12-5 . again, the timer modulus register is used to determine the maximum count. the pwm period will equal: (timer modulus) x (pwm clock period) center-aligned operation versus edge-aligned oper ation is determined by the option edge. see 5.2 functional description . figure 12-5. edge-aligned pwm (positive polarity) up-only counter modulus = 4 pwm = 0 pwm = 1 pwm = 2 pwm = 3 pwm = 4 period = 4 x (pwm clock period) pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 122 freescale semiconductor 12.3.2 prescaler to permit lower pwm frequencies, a prescaler is prov ided which will divide the pwm clock frequency by 1, 2, 4, or 8. table 12-1 shows how setting the prescaler bits in pwm control register 2 affects the pwm clock frequency. this prescaler is buffered and will not be used by the pwm generator until the ldok bit is set and a new pwm reload cycle begins. 12.4 pwm generators pulse-width modulator (pwm) generators are discussed in this subsection. 12.4.1 load operation to help avoid erroneous pulse widths and pwm periods, the modulus, prescaler, and pwm value registers are buffered. new pwm values, counter mo dulus values, and prescalers can be loaded from their buffers into the pwm module every one, two, four, or eight pwm cycles. ldfq1 and ldfq0 in pwm control register 2 are used to contro l this reload frequency, as shown in table 12-2 . when a reload cycle arrives, regardless of whether an actual reload occu rs (as determined by the ldok bit), the pwm reload flag bit in pwm control register 1 will be set. if the pwmint bit in pwm control register 1 is set, a cpu interrupt request will be generated when pwmf is set. software can use this interrupt to calculate new pwm parameters in real time for the pwm module. table 12-1. pwm prescaler prescaler bits prsc1 and prsc0 pwm clock frequency 00 f op 01 f op /2 10 f op /4 11 f op /8 table 12-2. pwm reload frequency reload frequency bits ldfq1 and ldfq0 pwm reload frequency 00 every pwm cycle 01 every 2 pwm cycles 10 every 4 pwm cycles 11 every 8 pwm cycles pwm generators mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 123 for ease of software, the ldfqx bits are buffered. when the ldfqx bits are changed, the reload frequency will not change until the previous reload cycle is completed. see figure 12-6 . note when reading the ldfqx bits, the value is the buffered value (for example, not necessarily the value being acted upon). figure 12-6. reload frequency change pwmint enables cpu interrupt requests as shown in figure 12-7 . when this bit is set, cpu interrupt requests are generated when the pwmf bit is set. when the pwmint bit is clear, pwm interrupt requests are inhibited. pwm reloads will still occur at the reload rate, but no interrupt requests will be generated. figure 12-7. pwm interrupt requests to prevent a partial reload of pwm parameters from occurring while the software is still calculating them, an interlock bit controlled from so ftware is provided. this bit informs the pwm module that all the pwm parameters have been calculated, and it is ?okay? to use them. a new modulus, prescaler, and/or pwm value cannot be loaded into the pwm module until the ldok bit in pwm control register 1 is set. when the ldok bit is set, these new values are loaded in to a second set of registers and used by the pwm generator at the beginning of the next pwm reload cycle as shown in figure 12-8 , figure 12-9 , figure 12-10 , and figure 12-11 . after these values are loaded, the ldok bit is cleared. note when the pwm module is enabled (via th e pwmen bit), a load will occur if the ldok bit is set. even if it is not set, an interrupt will occur if the pwmint bit is set. to prevent this, the software should clear the pwmint bit before enabling the pwm module. reload reload reload reloadreloadreload reload change reload frequency to every 4 cycles change reload frequency to every cycle latch v dd cpu interrupt reset d ck pwmint pwmf pwm reload read pwmf as 1, write pwmf as 0 or reset request pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 124 freescale semiconductor figure 12-8. center-aligned pwm value loading figure 12-9. center-aligned loading of modulus figure 12-10. edge-aligned pwm value loading ldok = 1 modulus = 3 pwm value = 1 ldok = 1 modulus = 3 pwm value = 2 up/down counter pwm ldfq1:ldfq0 = 00 (reload every cycle) ldok = 0 modulus = 3 pwm value = 2 ldok = 0 modulus = 3 pwm value = 1 pwmf set pwmf set pwmf set pwmf set ldok = 1 pwm value = 1 modulus = 2 ldok = 1 pwm value = 1 modulus = 3 ldok = 1 pwmvalue = 1 modulus = 2 ldok = 1 pwm value = 1 modulus = 1 ldok = 0 pwm value = 1 modulus = 2 up/down counter pwm ldfq1:ldfq0 = 00 (reload every cycle) pwmf set pwmf set pwmf set pwmf set pwmf set ldok = 1 modulus = 3 pwm value = 1 ldok = 1 modulus = 3 pwm value = 2 up-only counter pwm ldfq1:ldfq0 = 00 (reload every cycle) ldok = 0 modulus = 3 pwm value = 2 ldok = 0 modulus = 3 pwm value = 1 ldok = 0 modulus = 3 pwm value = 1 pwmf set pwmf set pwmf set pwmf set pwmf set pwm generators mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 125 figure 12-11. edge-aligned modulus loading 12.4.2 pwm data overflow and underflow conditions the pwm value registers are 16-bit registers. althou gh the counter is only 12 bits, the user may write a 16-bit signed value to a pwm value register. as shown in figure 12-4 and figure 12-5 , if the pwm value is less than or equal to zero, the pwm will be inacti ve for the entire period. conversely, if the pwm value is greater than or equal to the timer modulus, the pwm will be active for the entire period. refer to table 12-3 . note the terms ?active? and ?inactive? refer to the asserted and negated states of the pwm signals and should not be confused with the high-impedance state of the pwm pins. table 12-3. pwm data overflow and underflow conditions pwmvalxh:pwmvalxl con dition pwm value used $0000?$0fff normal per register contents $1000?$7fff overflow $fff $8000?$ffff underflow $000 ldok = 1 modulus = 3 pwm value = 2 ldok = 1 modulus = 4 pwm value = 2 ldok = 1 modulus = 2 pwm value = 2 up-only counter pwm ldfq1:ldfq0 = 00 (reload every cycle) ldok = 0 modulus = 1 pwm value = 2 pwmf set pwmf set pwmf set pwmf set pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 126 freescale semiconductor 12.5 output control this subsection discus ses output control. 12.5.1 selecting six i ndependent pwms or three co mplementary pwm pairs the pwm outputs can be configured as six independent pwm channels or three complementary channel pairs. the option indep determines which mode is used (see 5.2 functional description ). if complementary operation is chosen, th e pwm pins are paired as shown in figure 12-12 . operation of one pair is then determined by one pwm value register. this type of operation is meant for use in motor drive circuits such as the one in figure 12-13 . figure 12-12. complementary pairing figure 12-13. typical ac motor drive pwm value register pwms 1 and 2 pwms 3 and 4 pwms 5 and 6 output control pwm value register pwm value register pwm1 pin pwm2 pin pwm3 pin pwm4 pin pwm5 pin pwm6 pin polarity & dead-time insertion pwm 1 pwm 2 pwm 3 pwm 4 pwm 5 pwm 6 ac to motor inputs output control mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 127 when complementary operation is used, tw o additional features are provided: dead-time insertion separate top/bottom pulse width correction to co rrect for distortions caused by the motor drive characteristics if independent operation is chosen, each pwm has its own pwm value register. 12.5.2 dead-time insertion as shown in figure 12-13 , in complementary mode, each pwm pair can be used to drive top-side/bottom-side transistors. when controlling dc-to-ac inverters such as th is, the top and bottom pwms in one pair should never be active at the same time. in figure 12-13 , if pwm1 and pwm2 were on at the same time, large currents would flow through the two transistors as they discharge the bus capacitor. the igbts could be weakened or destroyed. simply forcing the two pwms to be inversions of each other is not always sufficient. since a time delay is associated with turning off the transistors in the motor drive, there must be a dead-time between the deactivation of one pwm and the activation of the other. a dead-time can be specified in the dead-time write- once register. this 8-bit value specifies the number of cpu clock cycles to use for the dead-time. the dead-time is not affected by changes in the pwm period caused by the prescaler. dead-time insertion is achieved by feeding the top pwm outputs of the pwm generator into dead-time generators, as shown in figure 12-14 . current sensing determines which pwm value of a pwm generator pair to use for the top pwm in the next pwm cycle. see 12.5.3 top/bottom correction with motor phase current polarity sensing . when output control is enabled, the odd out bits, rather than the pwm generator outputs, are fed into the dead-time generators. see 12.5.5 pwm output port control . whenever an input to a dead-time generator transitions , a dead-time is inserted (for example, both pwms in the pair are forced to their inactive state). the bottom pwm signal is generated from the top pwm and the dead-time. in the case of output control enabled, the odd outx bits control the top pwms, the even outx bits control the bottom pwms with respect to the odd outx bits (see table 12-6 ). figure 12-15 shows the effects of the dead-time insertion. as seen in figure 12-15 , some pulse width distortion occurs when the dead-time is inserted. the active pulse widths are reduced. for example, in figure 12-15 , when the pwm value register is equal to two, the ideal waveform (with no dead-time) has pulse widths equal to four. however, the actual pulse widths shrink to two after a dead-time of two was inserted. in this example, with the prescaler set to divide by one and center-aligned operation selected, this distortion can be compensated for by adding or subtracting half the dead-time value to or from the pw m register value. this correction is further described in 12.5.3 top/bottom correction with motor phase current polarity sensing . further examples of dead-time insertion are shown in figure 12-16 and figure 12-17 . figure 12-16 shows the effects of dead-time insertion at the duty cycl e boundaries (near 0 percent and 100 percent duty cycles). figure 12-17 shows the effects of dead-time insertion on pulse widths smaller than the dead-time. pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 128 freescale semiconductor figure 12-14. dead-time generators fault polarity/output drive pwmgen<1:6> pwmpair12 pwmpair34 pwmpair56 dead-time top/bottom generation postdt (top) top/bottom generation top/bottom generation top bottom top bottom top bottom pwm1 pwm2 pwm3 pwm4 pwm5 pwm6 6 mux pwm (top) outx select predt (top) mux pwm (top) outx select predt (top) mux pwm (top) outx select predt (top) dead-time dead-time postdt (top) dead-time dead-time postdt (top) dead-time (top) (top) (top) (pwm1) (pwm2) (pwm3) (pwm4) (pwm5) (pwm6) output control out1 out3 out5 outctl out2 out4 out6 (outctl) current sensing pwm generator output control mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 129 figure 12-15. effects of dead-time insertion figure 12-16. dead-time at duty cycle boundaries pwm value = 2 pwm value = 2 pwm value = 3 pwm1 w/ pwm2 w/ pwm1 w/ pwm2 w/ no dead-time no dead-time dead-time = 2 dead-time = 2 2 2 2 2 up/down counter modulus = 4 22 up/down counter modulus = 3 pwm value = 1 pwm value = 3 pwm value = 3 pwm1 w/ no dead-time pwm2 w/ no dead-time pwm1 w/ dead-time = 2 pwm2 w/ dead-time = 2 2 2 2 2 pwm value = 1 pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 130 freescale semiconductor figure 12-17. dead-time and small pulse widths 12.5.3 top/bottom correct ion with motor phase cu rrent polarity sensing ideally, when complementary pairs are used, the pwm pairs are inversions of each other, as shown in figure 12-18 . when pwm1 is active, pwm2 is inactive, and vice versa. in this case, the motor terminal voltage is never allowed to float and is strictly controlled by the pwm waveforms. figure 12-18. ideal complementary operation (dead-time = 0) however, when dead-time is inserted, the motor voltage is allowed to float momentarily during the dead-time interval, creating a distortion in the motor current waveform. this distortion is aggravated by dissimilar turn-on and turn-off delays of each of the transistors. 3 3 3 3 3 3 up/down counter moudulus = 3 pwm value = 2 pwm value = 3 pwm value = 2 pwm value = 1 pwm1 w/ no dead-time pwm2 w/ no dead-time pwm1 w/ dead-time = 3 pwm2 w/ dead-time = 3 up/down counter modulus = 4 pwm value = 1 pwm1 pwm2 pwm value = 2 pwm3 pwm4 pwm value = 3 pwm5 pwm6 output control mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 131 for a typical motor drive inverter as shown in figure 12-13 , for a given top/bottom transistor pair, only one of the transistors will be effective in controlling the output voltage at any given time depending on the direction of the motor current for that pair. to achiev e distortion correction, one of two different correction factors must be added to the desired pwm value, depending on whether the top or bottom transistor is controlling the output voltage. therefore, the softw are is responsible for calculating both compensated pwm values and placing them in an odd/even pwm regi ster pair. by supplying the pwm module with information regarding which transistor (top or bottom) is controlling the output voltage at any given time (for instance, the current polarity for that motor phase), the pwm module select s either the odd or even numbered pwm value register to be used by the pwm generator. current sensing or programmable software bits are t hen used to determine which pwm value to use. if the current sensed at the motor for that pwm pair is pos itive (voltage on current pin isx is low) or bit ipolx in pwm control register 2 is low, the top pwm value is used for the pwm pair. likewise, if the current sensed at the motor for that pwm pair is negative (v oltage on current pin isx is high) or bit ipolx in pwm control register 2 is high, the bottom pwm value is used. see table 12-4 . note this text assumes the user will provi de current sense circ uitry which causes the voltage at the corresponding input pin to be low for positive current and high for negative current. see figure 12-19 for current convention. in addition, it assumes the top pwms are pwms 1, 3, and 5 while the bottom pwms are pwms 2, 4, and 6. figure 12-19. current convention table 12-4. current sense pins current sense pin or bit voltage on current sense pin or ipolx bit pwm value register used pwms affected is1 or ipol1 logic 0 pwm value register 1 pwms 1 and 2 is1 or ipol1 logic 1 pwm value register 2 pwms 1 and 2 i+ i- pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 132 freescale semiconductor to allow for correction based on different current se nsing methods or correction controlled by software, the isens1 and isens0 bits in pwm control register 1 are provided to choose the correction method. these bits provide correction according to table 12-5 . if correction is to be done in software or is not necessary, setting isens1:isens0 = 00 or = 01 causes the correction to be based on bits ipol1, ipol2, and ip ol3 in pwm control register 2. if correction is not required, the user can initialize the ipolx bits and then only load one pwm value register per pwm pair. to allow the user to use a current sense scheme based upon sensed phase voltage during dead-time, setting isens1:isens0 = 10 causes the polarity of t he ix pin to be latched when both the top and bottom pwms are off (for example, during the dead-time). at the 0 percent and 100 percent duty cycle boundaries, there is no dead-time so no new current value is sensed. to accommodate other current sensing schemes, setting isens1:isens0 = 11 causes the polarity of the current sense pin to be latched half-way into the pwm cycle in center-aligned mode and at the end of the cycle in edge-aligned mode. therefore, even at 0 per cent and 100 percent duty cycle, the current is sensed. distortion correction is only available in complem entary mode. at the beginning of the pwm period, the pwm uses this latched current value or polarity bi t to decide whether the top pwm value or bottom pwm value is used. figure 12-20 shows an example of top/bottom correction for pwms 1 and 2. note the ipolx bits and the values latched on the isx pins are buffered so that only one pwm register is used per pwm cycle. if the ipolx bits or the current sense values change during a pwm period, this new value will not be used until the next pwm period. the isensx bits are not buffered; therefore, changing the current sensing method could affect the present pwm cycle. when the pwm is first enabled by setting pwmen, pwm value registers 1, 3, and 5 will be used if the isensx bits are configured for current sensing correct ion. this is because no current will have previously been sensed. table 12-5. correction methods current correction bits isens1 and isens0 correction method 00 01 bits ipol1, ipol2, and ipol3 used for correction 10 current sensing on pins is1 , is2 , and is3 occurs during the dead-time. 11 current sensing on pins is1 , is2 , and is3 occurs at the half cycle in center-aligned mode a nd at the end of the cycle in edge-aligned mode. output control mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 133 figure 12-20. top/bottom correction for pwms 1 and 2 12.5.4 output polarity the output polarity of the pwms is determined by two options: topneg and botneg. the top polarity option, topneg, controls the polarity of pwms 1, 3, and 5. the bottom polarity option, botneg, controls the polarity of pwms 2, 4, and 6. positive polarity means that when the pwm is active, the pwm output is high. conversely, negative polarity means t hat when the pwm is active, pwm output is low. see figure 12-21 . note both bits are found in the config register, which is a write-once register. this reduces the chances of the software inadvertently changing the polarity of the pwm signals and possibly damaging the motor drive hardware. pwm1 pwm2 pwm value reg. 1 = 1 pwm value reg. 2 = 2 is1 positive is1 positive is1 negative is1 negative pwm = 1 pwm = 1 pwm = 2 pwm = 2 pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 134 freescale semiconductor figure 12-21. pwm polarity up/down counter modulus = 4 pwm <= 0 pwm = 1 pwm = 2 pwm = 3 pwm >= 4 up-only counter modulus = 4 pwm <= 0 pwm = 1 pwm = 2 pwm = 3 pwm >= 4 center-aligned positive polarity edge-aligned positive polarity up/down counter modulus = 4 pwm <= 0 pwm = 1 pwm = 2 pwm = 3 pwm >= 4 up-only counter modulus = 4 pwm <= 0 pwm = 1 pwm = 2 pwm = 3 pwm >= 4 center-aligned negative polarity edge-aligned negative polarity output control mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 135 12.5.5 pwm output port control conditions may arise in which the pwm pins need to be individually controlled. this is made possible by the pwm output control register (pwmout) shown in figure 12-22 . if the outctl bit is set, the pwm pins can be contro lled by the outx bits. these bits behave according to table 12-6 . when outctl is set, the polarity options toppol and botpol will still affect the outputs. in addition, if complementary operation is in use, the pwm pairs will not be allowed to be active simultaneously, and dead-time will still not be violated. when outctl is set and complementary operation is in use, the odd outx bits are inputs to the dead-time generators as shown in figure 12-15 . dead-time is inserted whenever the odd outx bit toggles as shown in figure 12-23 . although dead-time is not inserted when the even outx bits change, there will be no dead-time violation as shown in figure 12-24 . setting the outctl bit does not disable the pwm gener ator and current sensing circuitry. they continue to run, but are no longer controlling the output pins . in addition, outctl will control the pwm pins even when pwmen = 0. when outctl is cleared, the outputs of the pwm generator become the inputs to the dead-time and output circuitry at the beginning of the next pwm cycle. note to avoid an unexpected dead-time occurrence, it is recommended that the outx bits be cleared prior to enteri ng and prior to exiting individual pwm output control mode. address: $0025 bit 7654321bit 0 read: 0 outctl out6 out5 out4 out3 out2 out1 write: reset:00000000 = unimplemented figure 12-22. pwm output control register (pwmout) table 12-6. outx bits outx bit complementary mode independent mode out1 1 ? pwm1 is active. 0 ? pwm1 is inactive. 1 ? pwm1 is active. 0 ? pwm1 is inactive. out2 1 ? pwm2 is complement of pwm 1. 0 ? pwm2 is inactive. 1 ? pwm2 is active. 0 ? pwm2 is inactive. out3 1 ? pwm3 is active. 0 ? pwm3 is inactive. 1 ? pwm3 is active. 0 ? pwm3 is inactive. out4 1 ? pwm4 is complement of pwm 3. 0 ? pwm4 is inactive. 1 ? pwm4 is active. 0 ? pwm4 is inactive. out5 1 ? pwm5 is active. 0 ? pwm5 is inactive. 1 ? pwm5 is active. 0 ? pwm5 is inactive. out6 1 ? pwm 6 is complement of pwm 5. 0 ? pwm6 is inactive. 1 ? pwm6 is active. 0 ? pwm6 is inactive. pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 136 freescale semiconductor figure 12-23. dead-time insertion during outctl = 1 figure 12-24. dead-time insertion during outctl = 1 up/down counter modulus = 4 pwm1 pwm2 dead-time = 2 outctl out1 out2 2 pwm1/pwm2 2 2 dead-time inserted as part of normal pwm operation as controlled by current sensing and pwm generator dead-time inserted due to setting of out1 bit dead-time inserted due to clearing of out1 bit pwm value = 3 dead-time up/down counter modulus = 4 dead-time = 2 outctl pwm1 pwm2 out1 out2 2 pwm1/pwm2 2 2 pwm value = 3 dead-time inserted because when outctl was set, the state of out1 was such that pwm1 was directed to toggle dead-time inserted because out1 toggles, directing pwm1 to toggle no dead-time inserted because out1 is not toggling dead-time 2 fault protection mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 137 12.6 fault protection conditions may arise in the exter nal drive circuitry which require t hat the pwm signals become inactive immediately, such as an overcurrent fault condition . furthermore, it may be desirable to selectively disable pwm(s) solely with software. one or more pwm pins can be disabled (forced to their inactive state) by applying a logic high to any of the four external fault pins or by writing a logic hi gh to either of the disable bits (disx and disy in pwm control register 1). figure 12-26 shows the structure of the pwm disabling scheme. while the pwm pins are disabled, they are forced to their inactive st ate. the pwm generator continues to run ? only the output pins are disabled. to allow for different motor configurations and the co ntrolling of more than one motor, the pwm disabling function is organized as two banks, bank x and bank y. bank information combines with information from the disable mapping register to allo w selective pwm disabling. fault pi n 1, fault pin 2, and pwm disable bit x constitute the disabling functi on of bank x. fault pin 3, fault pin 4, and pwm disable bit y constitute the disabling function of bank y. figure 12-25 and figure 12-27 show the disable mapping write-once register and the decoding scheme of the bank which sele ctively disables pwm(s). when all bits of the disable mapping register are set, any di sable condition will disable all pwms. a fault can also generate a cpu interrupt. each fault pin has its own interrupt vector. 12.6.1 fault cond ition input pins a logic high level on a fault pin disables the respec tive pwm(s) determined by the bank and the disable mapping register. each fault pin incorporates a filter to as sist in rejecting spurious faults. all of the external fault pins are software-configurable to re-enable the pw ms either with the fault pin (automatic mode) or with software (manual mode). each fault pin has an associated fmode bit to control the pwm re-enabling method. automatic mode is selected by sett ing the fmodex bit in the fault control register. manual mode is selected when fmodex is clear. address: $0037 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset:11111111 figure 12-25. pwm disable mapping write-once register (dismap) pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 138 freescale semiconductor figure 12-26. pwm disabling scheme fint2 cycle start logic high for fault bank x fmode2 disx clear by writing 1 to ftack4 interrupt request shot sq r sq r sq r one fpin2 fflag2 manual mode auto mode software x disable fault pin 2 disable the example is of fault pin 2 with disx. fault pin 4 wit h disy is logically similar and affects bank y disable. note: in manual mode (fmode = 0), faults 2 and 4 may be clea red only if a logic level low at the input of the fault pin is present. fault pin2 disable two sample filter fault pin1 fint1 cycle start logic high for fault bank x disable fmode1 clear by writing 1 to ftack1 interrupt request two shot sq r sq r sample filter one fflag1 manual mode auto mode fault pin 1 disable the example is of fault pin 1. fault pin 3 is logically similar and affects bank y disable. note: in manual mode (fmode = 0), faults 1 and 3 may be cleared regardless of the logic level at the input of the fault pin. fpin1 fault protection mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 139 figure 12-27. pwm disabling decode scheme 12.6.1.1 fault pin filter each fault pin incorporates a filter to assist in determining a genuine fault condition. after a fault pin has been logic low for one cpu cycle, a rising edge (logic high) will be synchronously sampled once per cpu cycle for two cycles. if both samples are detected logic high, the corresponding fpin bit and fflag bit will be set. the fpin bit will remain set until the corresponding fault pin is logic low and synchronously sampled once in the following cpu cycle. 12.6.1.2 automatic mode in automatic mode, the pwm(s) are disabled immediat ely once a filtered fault condition is detected (logic high). the pwm(s) remain disabled until the filtered fault condition is cleared (logic low) and a new pwm cycle begins as shown in figure 12-28 . clearing the corresponding fflagx event bit will not enable the pwms in automatic mode. the filtered fault pin?s logic state is reflected in the re spective fpinx bit. any write to this bit is overwritten by the pin state. the fflagx event bit is set with eac h rising edge of the respective fault pin after filtering has been applied. to clear the fflagx bit, the user must write a 1 to the corresponding ftackx bit. f the fintx bit is set, a fault condition resulting in setting the corresponding fflag bit will also latch a cpu interrupt request. the interrupt request latch is not cleared until one of these actions occurs: the fflagx bit is cleared by writing a 1 to the corresponding ftackx bit. the fintx bit is cleared. this will not clear the fflagx bit. a reset automatically clears all four interrupt latches. bit 7 bit 3 bit 0 bit 1 bit 2 bit 4 bit 5 bit 6 bank x disable disable disable disable disable disable disable disable bank y pwm pin 1 pwm pin 2 pwm pin 3 pwm pin 4 pwm pin 5 pwm pin 6 pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 140 freescale semiconductor figure 12-28. pwm disabling in automatic mode iif prior to a vector fetch, the interrupt request latch is cleared by one of the actions listed, a cpu interrupt will no longer be requested. a vector fetch does not alter the state of the pwms, the fflagx event flag, or fintx. note if the fflagx or fintx bits are not cleared during the interrupt service routine, the interrupt request latch will not be cleared. 12.6.1.3 manual mode in manual mode, the pwm(s) are disabled immediatel y once a filtered fault condition is detected (logic high). the pwm(s) remain disabled until software clears the corresponding fflagx event bit and a new pwm cycle begins. in manual mode, the fault pins are grouped in pairs, each pair sharing common functionality. a fault condition on pins 1 and 3 may be cleared, allowing the pwm(s) to enable at the start of a pwm cycle regardless of the logic level at the fault pin. see figure 12-29 . a fault condition on pins 2 and 4 can only be cleared, allowing the pwm(s) to enable, if a logic low level at the fault pin is present at the start of a pwm cycle. see figure 12-30 . the function of the fault control and event bits is the same as in automatic mode except that the pwms are not re-enabled until the fflagx event bit is cleared by writing to the ftackx bit and the filtered fault condition is cleared (logic low). figure 12-29. pwm disabling in manual mode (example 1) pwm(s) enabled pwm(s) enabled pwm(s) disabled (inactive) filtered fault pin pwm(s) enabled pwm(s) enabled pwm(s) disabled fflagx cleared filtered fault pin 1 or 3 fault protection mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 141 figure 12-30. pwm disabling in manual mode (example 2) 12.6.2 software output disable setting pwm disable bit disx or disy in pwm control register 1 immediately disables the corresponding pwm pins as determined by the bank and disable ma pping register. the pwm pin(s) remain disabled until the pwm disable bit is cleared and a new pwm cycle begins as shown in figure 12-31 . setting a pwm disable bit does not latch a cpu interrupt request, and there are no event flags associated with the pwm disable bits. 12.6.3 output port control when operating the pwms using the outx bits (outct l = 1), fault protection applies as described in this section. due to the absence of periodic pwm cycles, fault conditions are cleared upon each cpu cycle and the pwm outputs are re-enabled, provided all fault clearing conditions are satisfied. figure 12-31. pwm software disable pwm(s) enabled pwm(s) enabled pwm(s) disabled fflagx cleared filtered fault pin 2 or 4 pwm(s) enabled pwm(s) enabled pwm(s) disabled disable bit pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 142 freescale semiconductor 12.7 initialization and the pwmen bit for proper operation, all registers should be initia lized and the ldok bit should be set before enabling the pwm via the pwmen bit. when the pwmen bit is fi rst set, a reload will occur immediately, setting the pwmf flag and generating an interrupt if pwmint is set. in addition, in complementary mode, pwm value registers 1, 3, and 5 will be used for the first pwm cycle if current sensing is selected. note if the ldok bit is not set when pwmen is set after a reset , the prescaler and pwm values will be 0, but the modulus will be unknown. if the ldok bit is not set after the pwmen bit has been cleared then set (without a reset ), the modulus value that was last loaded will be used. if the dead-time register (deadtm) is changed after pwmen or outctl is set, an improper dead-time insertion could occur. however, the dead-time can never be shorter than the specified value. because of the equals-comparator architecture of this pwm, the modulus = 0 case is considered illegal. therefor e, the modulus register is not reset, and a modulus value of 0 will result in waveforms inconsistent with the other modulus waveforms. see 12.9.2 pwm counter modulo registers . when pwmen is set, the pwm pins change from high impedance to outputs. at this time, assuming no fault condition is present, the pwm pins will drive ac cording to the pwm values, polarity, and dead-time. see the timing diagram in figure 12-32 . figure 12-32. pwmen and pwm pins when the pwmen bit is cleared, this will occur: pwm pins will be three-stated unless outctl = 1. pwm counter is cleared and will not be clocked. internally, the pwm generator will force its output s to 0 to avoid glitches when the pwmen is set again. when pwmen is cleared, these features remain active: all fault circuitry manual pwm pin control via the pwmout register dead-time insertion when pwm pins change via the pwmout register note the pwmf flag and pending cpu interrupts are not cleared when pwmen = 0. cpu clock pwmen pwm pins drive according to pwm value, polarity, and dead-time hi-z if outctl = 0 hi-z if outctl = 0 pwm operation in wait mode mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 143 12.8 pwm operation in wait mode when the microcontroller is put in low-power wait mode via the wait instruction, all clocks to the pwm module will continue to run. if an interrupt is issued from the pwm module (via a reload or a fault), the microcontroller will exit wait mode. clearing the pwmen bit before entering wait mode wi ll reduce power consumption in wait mode because the counter, prescaler divider, and ldfq divider wi ll no longer be clocked. in addition, power will be reduced because the pwms will no longer toggle. 12.9 control logic block this subsection provides a description of the control logic block. 12.9.1 pwm counter registers the pwm counter registers (pcnth and pcntl) disp lay the 12-bit up/down or up-only counter. when the high byte of the counter is read, the lower byte is latched. pcntl will hold this latched value until it is read. see figure 12-33 and figure 12-34 . address: $0026 bit 7654321bit 0 read:0000bit 11bit 10bit 9bit 8 write: reset:00000000 = unimplemented figure 12-33. pwm counter register high (pcnth) address: $0027 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset:00000000 = unimplemented figure 12-34. pwm counter register low (pcntl) pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 144 freescale semiconductor 12.9.2 pwm counte r modulo registers the pwm counter modulus registers (pmodh and pmodl) hold a 12-bit unsigned number that determines the maximum count for the up/down or up-only counter. in center-aligned mode, the pwm period will be twice the modulus (a ssuming no prescaler). in edge-aligned mode, the pwm period will equal the modulus. see figure 12-35 and figure 12-36 . to avoid erroneous pwm periods, this value is buffer ed and will not be used by the pwm generator until the ldok bit has been set and th e next pwm load cycle begins. note when reading this register, the value read is the buffer (not necessarily the value the pwm generator is currently using). because of the equals-comparator architecture of this pwm, the modulus = 0 case is considered illegal. therefore, the modulus register is not reset, and a modulus value of 0 will result in waveforms inconsistent with the other modulus waveforms. if a modulus of 0 is loaded, the counter will continually count down from $fff. this operation will not be tested or guaranteed (the user should consider it illegal). however, the dead-time constraints and fault conditions will still be guaranteed. address: $0028 bit 7654321bit 0 read:0000 bit 11 bit 10 bit 9 bit 8 write: reset:0000 xxxx = unimplemented x = indeterminate figure 12-35. pwm counter modulo register high (pmodh) address: $0029 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset:xxxxxxxx x = indeterminate figure 12-36. pwm counter modulo register low (pmodl) control logic block mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 145 12.9.3 pwmx value registers each of the six pwms has a 16-bit pwm value register. the 16-bit signed value stored in this register determi nes the duty cycle of the pwm. the duty cycle is defined as: (pwm value/modulus) x 100. writing a number less than or equal to 0 causes the pwm to be off for the entire pwm period. writing a number greater than or equal to the 12-bit modulus causes the pwm to be on for the entire pwm period. if the complementary mode is selected, the pwm pairs share pwm value registers. to avoid erroneous pwm pulses, this value is buffe red and will not be used by the pwm generator until the ldok bit has been set and th e next pwm load cycle begins. note when reading these registers, the value read is the buffer (not necessarily the value the pwm generator is currently using). bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset:00000000 bold = buffered figure 12-37. pwmx value registers high (pvalxh) bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset:00000000 bold = buffered figure 12-38. pwmx value registers low (pvalxl) pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 146 freescale semiconductor 12.9.4 pwm control register 1 pwm control register 1 (pctl1) controls pwm enabling/ disabling, the loading of new modulus, prescaler, pwm values, and the pwm correction method. in addition, this register contains the software disable bits to force the pwm outputs to their inactive states (according to the disable mapping register). disx ? software disable bit for bank x bit this read/write bit allows the user to disable one or more pwm pins in bank x. the pins that are disabled are determined by the di sable mapping write-once register. 1 = disable pwm pins in bank x. 0 = re-enable pwm pins at beginning of next pwm cycle. disy ? software disable bit for bank y bit this read/write bit allows the user to disable one or more pwm pins in bank y. the pins that are disabled are determined by the di sable mapping write-once register. 1 = disable pwm pins in bank y. 0 = re-enable pwm pins at beginning of next pwm cycle. pwmint ? pwm interrupt enable bit this read/write bit allows the user to enable and disable pwm cpu interrupts. if set, a cpu interrupt will be pending when the pwmf flag is set. 1 = enable pwm cpu interrupts. 0 = disable pwm cpu interrupts. note when pwmint is cleared, pending cpu interrupts are inhibited. pwmf ? pwm reload flag this read/write bit is set at the beginning of every reload cycle regardless of the state of the ldok bit. this bit is cleared by reading pwm control register 1 with the pwmf flag set, then writing a logic 0 to pwmf. if another reload occurs before the clear ing sequence is complete, then writing logic 0 to pwmf has no effect. 1 = new reload cycle began. 0 = new reload cycle has not begun. note when pwmf is cleared, pending pwm cpu interrupts are cleared (not including fault interrupts). isens1 and isens0 ? current sense correction bits these read/write bits select the top/bottom correction scheme as shown in table 12-7 . address: $0020 bit 7654321bit 0 read: disx disy pwmint pwmf isens1 isens0 ldok pwmen write: reset:00000000 figure 12-39. pwm control register 1 (pctl1) control logic block mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 147 note the isensx bits are not buffered. changing the current sensing method can affect the present pwm cycle. ldok? load ok bit this read/write bit loads the prescaler bits of the pmctl2 register and the entire pmmodh/l and pwmvalh/l registers into a set of buffers. the buffered prescaler divisor, pwm counter modulus value, and pwm pulse will take effect at the next pw m load. set ldok by reading it when it is logic 0 and then writing a logic 1 to it. ldok is automati cally cleared after the new values are loaded or can be manually cleared before a reload by writing a 0 to it. reset clears ldok. 1 = load prescaler, modulus, and pwm values. 0 = do not load new modulus, prescaler, and pwm values. note the user should initialize the pwm registers and set the ldok bit before enabling the pwm. a pwm cpu interrupt request can still be generated when ldok is 0. pwmen ? pwm module enable bit this read/write bit enables and disables the pwm generator and the pwm pins. when pwmen is clear, the pwm generator is disabled and the pwm pins are in the high-impedance state (unless outctl = 1). when the pwmen bit is set, the pwm generator and pwm pins are activated. for more information, see 12.7 initialization and the pwmen bit . 1 = pwm generator and pwm pins enabled 0 = pwm generator and pwm pins disabled table 12-7. correction methods current correction bits isens1 and isens0 correction method 00 01 bits ipol1, ipol2, and ip ol3 are used for correction. 10 current sensing on pins is1 , is2 , and is3 occurs during the dead-time. 11 current sensing on pins is1 , is2 , and is3 occurs at the half cycle in center-aligned mode and at the end of the cycle in edge-aligned mode. 1. the polarity of the isx pin is latched when both the top and bottom pwms are off. at the 0% and 100% duty cycle boundaries, there is no dead-time, so no new current value is sensed. 2. current is sensed even with 0% and 100% duty cycle. pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 148 freescale semiconductor 12.9.5 pwm control register 2 pwm control register 2 (pctl2) controls the pwm load frequency, the pwm correction method, and the pwm counter prescaler. for ease of software and to avoid erroneous pwm periods, some of these register bits are buffered. the pwm generator will not use the prescaler value until the ldok bit has been set, and a new pwm cycle is starting. the correcti on bits are used at the beginning of each pwm cycle (if the isensx bits are configured for software corre ction). the load frequency bits are not used until the current load cycle is complete. see figure 12-40 . note the user should initialize this register before enabling the pwm. ldfq1 and ldfq0 ? pwm load frequency bits these buffered read/write bits select the pwm cpu load frequency according to table 12-8 . note when reading these bits, the value read is the buffer value (not necessarily the value the pwm generator is currently using). the ldfqx bits take effect when the current load cycle is complete regardless of the state of the load okay bit, ldok. note reading the lpfqx bit reads the buffe red values and not necessarily the values currently in effect. ipol1 ? top/bottom correction bit for pwm pair 1 (pwms 1 and 2) this buffered read/write bit selects which pwm value register is used if top/bottom correction is to be achieved without current sensing. 1 = use pwm value register 2. 0 = use pwm value register 1. address: $0021 bit 7654321bit 0 read: ldfq1 ldfq0 0 ipol1 ipol2 ipol3 prsc1 prsc0 write: reset:00000000 = unimplemented bold = buffered figure 12-40. pwm control register 2 (pctl2) table 12-8. pwm reload frequency reload frequency bits ldfq1 and ldfq0 pwm reload frequency 00 every pwm cycle 01 every 2 pwm cycles 10 every 4 pwm cycles 11 every 8 pwm cycles control logic block mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 149 note when reading this bit, the value read is the buffer value (not necessarily the value the output control block is currently using). the ipolx bits take effect at the beginning of the next load cycle, regardless of the state of the load okay bit, ldok. ipol2 ? top/bottom correction bit for pwm pair 2 (pwms 3 and 4) this buffered read/write bit selects which pwm value register is used if top/bottom correction is to be achieved without current sensing. 1 = use pwm value register 4. 0 = use pwm value register 3. note when reading this bit, the value read is the buffer value (not necessarily the value the output control block is currently using). ipol3 ? top/bottom correction bit for pwm pair 3 (pwms 5 and 6) this buffered read/write bit selects which pwm value register is used if top/bottom correction is to be achieved without current sensing. 1 = use pwm value register 6. 0 = use pwm value register 5. note when reading this bit, the value read is the buffer value (not necessarily the value the output control block is currently using). prsc1 and prsc0 ? pwm prescaler bits these buffered read/write bits allow the pwm clock frequency to be modified as shown in table 12-9 . note when reading these bits, the value read is the buffer value (not necessarily the value the pwm generator is currently using). table 12-9. pwm prescaler prescaler bits prsc1 and prsc0 pwm clock frequency 00 f op 01 f op /2 10 f op /4 11 f op /8 pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 150 freescale semiconductor 12.9.6 dead-time write-once register the dead-time write-once register (deadtm) holds an 8-bit value which specifies the number of cpu clock cycles to use for the dead-time when complement ary pwm mode is selected. after this register is written for the first time, it cannot be rewritten unless a reset occurs. dead-time is not affected by changes to the prescaler value. 12.9.7 pwm disable mappi ng write-once register the pwm disable mapping write-once register (disma p) holds an 8-bit value which determines which pwm pins will be disabled if an external fault or software disable occurs. for a further description of disable mapping, see 12.6 fault protection . after this register is written for the first time, it cannot be rewritten unless a reset occurs. 12.9.8 fault control register the fault control register (fcr) controls the fault-protection circuitry. fint4 ? fault 4 interrupt enable bit this read/write bit allows the cpu interrupt caused by faults on fault pin 4 to be enabled. the fault protection circuitry is independent of this bit and will always be active. if a fault is detected, the pwm pins will still be disabled accordi ng to the disable mapping register. 1 = fault pin 4 will cause cpu interrupts. 0 = fault pin 4 will not cause cpu interrupts. address: $0036 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset:11111111 figure 12-41. dead-time write-once register (deadtm) address: $0037 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset:11111111 figure 12-42. pwm disable mapping write-once register (dismap) address: $0022 bit 7654321bit 0 read: fint4 fmode4 fint3 fmode3 fint2 fmode2 fint1 fmode1 write: reset:00000000 figure 12-43. fault control register (fcr) control logic block mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 151 fmode4 ?fault mode selection for fault pin 4 bit ( automatic versus manual mode) this read/write bit allows the user to select between automatic and manual mode faults. for further descriptions of each mode, see 12.6 fault protection . 1 = automatic mode 0 = manual mode fint3 ? fault 3 interrupt enable bit this read/write bit allows the cpu interrupt caused by faults on fault pin 3 to be enabled. the fault protection circuitry is independent of this bit and will always be active. if a fault is detected, the pwm pins will still be disabled accordi ng to the disable mapping register. 1 = fault pin 3 will cause cpu interrupts. 0 = fault pin 3 will not cause cpu interrupts. fmode3 ?fault mode selection for fault pin 3 bit ( automatic versus manual mode ) this read/write bit allows the user to select between automatic and manual mode faults. for further descriptions of each mode, see 12.6 fault protection . 1 = automatic mode 0 = manual mode fint2 ? fault 2 interrupt enable bit this read/write bit allows the cpu interrupt caused by faults on fault pin 2 to be enabled. the fault protection circuitry is independent of this bit and will always be active. if a fault is detected, the pwm pins will still be disabled accordi ng to the disable mapping register. 1 = fault pin 2 will cause cpu interrupts. 0 = fault pin 2 will not cause cpu interrupts. fmode2 ?fault mode selection for fault pin 2 bit ( automatic versus manual mode ) this read/write bit allows the user to select between automatic and manual mode faults. for further descriptions of each mode, see 12.6 fault protection . 1 = automatic mode 0 = manual mode fint1 ? fault 1 interrupt enable bit this read/write bit allows the cpu interrupt caused by faults on fault pin 1 to be enabled. the fault protection circuitry is independent of this bit and will always be active. if a fault is detected, the pwm pins will still be disabled accordi ng to the disable mapping register. 1 = fault pin 1 will cause cpu interrupts. 0 = fault pin 1 will not cause cpu interrupts. fmode1 ?faul t mode selection for fault pin 1 bit ( automatic versus manual mode) this read/write bit allows the user to select between automatic and manual mode faults. for further descriptions of each mode, see 12.6 fault protection . 1 = automatic mode 0 = manual mode pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 152 freescale semiconductor 12.9.9 fault status register the fault status register (fsr) is a read-only register that indicates the current fault status. fpin4 ? state of fault pin 4 bit this read-only bit allows the user to read the current state of fault pin 4. 1 = fault pin 4 is at logic 1. 0 = fault pin 4 is at logic 0. fflag4 ? fault event flag 4 the fflag4 event bit is set within two cpu cycles after a rising edge on fault pin 4. to clear the fflag4 bit, the user must write a 1 to the ftack4 bit in the fault acknowledge register. 1 = a fault has occurred on fault pin 4. 0 = no new fault on fault pin 4 fpin3 ? state of fault pin 3 bit this read-only bit allows the user to read the current state of fault pin 3. 1 = fault pin 3 is at logic 1. 0 = fault pin 3 is at logic 0. fflag3 ? fault event flag 3 the fflag3 event bit is set within two cpu cycles after a rising edge on fault pin 3. to clear the fflag3 bit, the user must write a 1 to the ftack3 bit in the fault acknowledge register. 1 = a fault has occurred on fault pin 3. 0 = no new fault on fault pin 3. fpin2 ? state of fault pin 2 bit this read-only bit allows the user to read the current state of fault pin 2. 1 = fault pin 2 is at logic 1. 0 = fault pin 2 is at logic 0. fflag2 ? fault event flag 2 the fflag2 event bit is set within two cpu cycles after a rising edge on fault pin 2. to clear the fflag2 bit, the user must write a 1 to the ftack2 bit in the fault acknowledge register. 1 = a fault has occurred on fault pin 2. 0 = no new fault on fault pin 2 fpin1 ? state of fault pin 1 bit this read-only bit allows the user to read the current state of fault pin 1. 1 = fault pin 1 is at logic 1. 0 = fault pin 1 is at logic 0. address: $0023 bit 7654321bit 0 read: fpin4 fflag4 fpin3 fflag3 fpin2 fflag2 fpin1 fflag1 write: reset:u0u0u0u0 = unimplemented u = unaffected figure 12-44. fault status register (fsr) control logic block mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 153 fflag1 ? fault event flag 1 the fflag1 event bit is set within two cpu cycles after a rising edge on fault pin 1. to clear the fflag1 bit, the user must write a 1 to the ftack1 bit in the fault acknowledge register. 1 = a fault has occurred on fault pin 1. 0 = no new fault on fault pin 1. 12.9.10 fault ac knowledge register the fault acknowledge register (ftack) is used to a cknowledge and clear the fflags. in addition, it is used to monitor the current sensi ng bits to test proper operation. ftack4 ? fault acknowledge 4 bit the ftack4 bit is used to acknowledge and clear ffla g4. this bit will always read 0. writing a 1 to this bit will clear fflag4. writing a 0 will have no effect. ftack3 ? fault acknowledge 3 bit the ftack3 bit is used to acknowledge and clear ffla g3. this bit will always read 0. writing a 1 to this bit will clear fflag3. writing a 0 will have no effect. ftack2 ? fault acknowledge 2 bit the ftack2 bit is used to acknowledge and clear ffla g2. this bit will always read 0. writing a 1 to this bit will clear fflag2. writing a 0 will have no effect. ftack1 ? fault acknowledge 1 bit the ftack1 bit is used to acknowledge and clear ffla g1. this bit will always read 0. writing a 1 to this bit will clear fflag1. writing a 0 will have no effect. dt6 ? dead-time 6 bit current sensing pin is3 is monitored immediately before dead-time ends due to the assertion of pwm6. dt5 ? dead-time 5 bit current sensing pin is3 is monitored immediately before dead-time ends due to the assertion of pwm5. dt4 ? dead-time 4 bit current sensing pin is2 is monitored immediately before dead-time ends due to the assertion of pwm4. dt3 ? dead-time 3 bit current sensing pin is2 is monitored immediately before dead-time ends due to the assertion of pwm3. address: $0024 bit 7654321bit 0 read: 0 0 dt6 dt5 dt4 dt3 dt2 dt1 write: ftack4 ftack3 ftack2 ftack1 reset:00000000 = unimplemented figure 12-45. fault acknowledge register (ftack) pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 154 freescale semiconductor dt2 ? dead-time 2 bit current sensing pin is1 is monitored immediately before dead-time ends due to the assertion of pwm2. dt1 ? dead-time 1 bit current sensing pin is1 is monitored immediately before dead-time ends due to the assertion of pwm1. 12.9.11 pwm output control register the pwm output control register (pwmout) is used to manually control the pwm pins. outctl? output control enable bit this read/write bit allows the user to manually control the pwm pins. when set, the pwm generator is no longer the input to the dead-time and output circuitry. the outx bits determine the state of the pwm pins. setting the outctl bit does not disable the pwm generator. the generator continues to run, but is no longer the input to the pwm dead-time and output circuitry. when outctl is cleared, the outputs of the pwm generator immediately become the inputs to the dead-time and output circuitry. 1 = pwm outputs controlled manually 0 = pwm outputs determined by pwm generator out6?out1? pwm pin output control bit s these read/write bits control the pwm pins according to table 12-10 . address: $0025 bit 7654321bit 0 read: 0 outctl out6 out5 out4 out3 out2 out1 write: reset:00000000 = unimplemented figure 12-46. pwm output control register (pwmout) table 12-10. outx bits outx bit complementary mode independent mode out1 1 ? pwm1 is active. 0 ? pwm1 is inactive. 1 ? pwm1 is active. 0 ? pwm1 is inactive. out2 1 ? pwm2 is comp lement of pwm 1. 0 ? pwm2 is inactive. 1 ? pwm2 is active. 0 ? pwm2 is inactive. out3 1 ? pwm3 is active. 0 ? pwm3 is inactive. 1 ? pwm3 is active. 0 ? pwm3 is inactive. out4 1 ? pwm4 is comp lement of pwm 3. 0 ? pwm4 is inactive. 1 ? pwm4 is active. 0 ? pwm4 is inactive. out5 1 ? pwm5 is active. 0 ? pwm5 is inactive. 1 ? pwm5 is active. 0 ? pwm5 is inactive. out6 1 ? pwm 6 is complement of pwm 5. 0 ? pwm6 is inactive. 1 ? pwm6 is active. 0 ? pwm6 is inactive. pwm glossary mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 155 12.10 pwm glossary cpu cycle ? one internal bus cycle (1/f op ) pwm clock cycle (or period) ? one tick of the pwm counter (1/f op with no prescaler). see figure 12-47 . pwm cycle (or period) center-aligned mode: the time it takes the pwm counter to count up and count down (modulus * 2/f op assuming no prescaler). see figure 12-47 . edge-aligned mode: the time it takes the pwm counter to count up (modulus/f op ). see figure 12-47 . figure 12-47. pwm clock cycle and pwm cycle definitions pwm clock cycle pwm cycle (or period) pwm pwm cycle (or period) center-aligned mode edge-aligned mode clock cycle pulse-width modulator fo r motor control (pwmmc) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 156 freescale semiconductor pwm load frequency ? frequency at which new pwm parameters get loaded into the pwm. see figure 12-48 . figure 12-48. pwm load cycle/frequency definition reload new modulus, prescaler, & pwm values if ldok = 1 reload new modulus, prescaler, & pwm values if ldok = 1 pwm load cycle ldfq1:ldfq0 = 01 ? reload every two cycles (1/pwm load frequency) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 157 chapter 13 serial communications interface module (sci) 13.1 introduction this section describes the serial communications interface module (sci, version d), which allows high-speed asynchronous communications with peri pheral devices and other microcontroller units (mcus). 13.2 features features of the sci module include: full-duplex operation standard mark/space non-retu rn-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 separate receiver and transmitter 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 mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 158 freescale semiconductor serial communications interface module (sci) figure 13-1. block diagram highlighting sci block and pins clock generator module system integration module serial communications interface module serial peripheral interface module (2) timer interface module a low-voltage inhibit module power-on reset module computer operating properly module arithmetic/logic unit cpu registers m68hc08 cpu control and status registers ? 112 bytes user flash ? 32,256 bytes user ram ? 768 bytes monitor rom ? 240 bytes user flash vector space ? 46 bytes irq module power pta ddra ddrb ptb ddrc ptc ptd ddre pte ptf ddrf internal bus osc1 osc2 cgmxfc rst irq v ss v dd v ddad pta7?pta0 pte7/tch3a pte6/tch2a pte5/tch1a pte4/tch0a pte3/tclka pte2/tch1b (1) pte1/tch0b (1) pte0/tclkb (1) ptf5/txd ptf4/rxd ptf3/miso (1) ptf2/mosi (1) ptf1/ss (1) ptf0/spsck (1) timer interface module b pulse-width modulator module ptb7/atd7 ptb6/atd6 ptb5/atd5 ptb4/atd4 ptb3/atd3 ptb2/atd2 ptb1/atd1 ptb0/atd0 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1/atd9(1) ptc0/atd8 ptd6/is3 ptd5/is2 ptd4/is1 ptd3/fault4 ptd2/fault3 ptd1/fault2 ptd0/fault1 pwm6?pwm1 analog-to-digital converter module v ssad v dda v ssa (3) pwmgnd v refl (3) v refh notes: 1. these pins are not available in the 56-pin sdip package. 2. this module is not available in the 56-pin sdip package. 3. in the 56-pin sdip package, these pins are bonded together. single break module functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 159 13.3 functional description figure 13-2 shows the structure of the sci module. the sc i allows full-duplex, asynchronous, nrz serial communication among the mcu and remote devices, in cluding 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. figure 13-2. sci module block diagram scte tc scrf idle or nf fe pe sctie tcie scrie ilie te re rwu sbk r8 t8 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 transmitter interrupt control receiver interrupt control error interrupt control control ensci loops ensci ptf4/rxd ptf5/txd internal bus txinv loops 4 16 pre- scaler baud rate generator f op serial communications in terface modu le (sci) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 160 freescale semiconductor 13.3.1 data format the sci uses the standard non-return-to-zero mark/space data format illustrated in figure 13-4 . figure 13-4. sci data formats addr. register name bit 7654321bit 0 $0038 sci control register 1 (scc1) see page 169. read: loops ensci txinv m wake ilty pen pty write: reset:00000000 $0039 sci control register 2 (scc2) see page 171. read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 $003a sci control register 3 (scc3) see page 173. read: r8 t8 00 orie neie feie peie write: r r r reset:uu000000 $003b sci status register 1 (scs1) see page 174. read: scte tc scrf idle or nf fe pe write:rrrrrrrr reset:11000000 $003c sci status register 2 (scs2) see page 176. read:000000bkfrpf write:rrrrrrrr reset:00000000 $003d sci data register (scdr) see page 177. read:r7r6r5r4r3r2r1r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset $003e sci baud rate register (scbr) see page 177. read: 0 0 scp1 scp0 0 scr2 scr1 scr0 write: r r r reset:00000000 r = reserved u = unaffected figure 13-3. sci i/o register summary 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 possible parity bit possible parity bit functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 161 13.3.2 transmitter figure 13-5 shows the structure of the sci transmitter. figure 13-5. sci transmitter pen pty h876543210l 11-bit transmit stop start t8 scte sctie tcie sbk tc f op parity generation msb sci data register load from scdr shift enable preamble all 1s break all 0s transmitter control logic shift register tc sctie tcie scte m ensci loops te ptf5/txd txinv internal bus 4 pre- scaler scp1 scp0 scr1 scr2 scr0 baud divider 16 transmitter cpu interrupt request serial communications in terface modu le (sci) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 162 freescale semiconductor 13.3.2.1 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). 13.3.2.2 character transmission during an sci transmission, the transmit shift register shifts a character out to the ptf5/txd pin. the sci data register (scdr) is the write-only buffer between t he internal data bus and the transmit shift register. to initiate an sci transmission: 1. enable the sci by writing a 1 to the enable sci bit (ensci) in sci control register 1 (scc1). 2. enable the transmitter by writing a 1 to the tr ansmitter 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 logi c automatically loads the tran smit shift register with a preamble of 1s. after the preamble shifts out, cont rol logic transfers the s cdr data into the transmit shift register. a 0 start bit automatically goes into the least significant bit (lsb) position of the transmit shift register. a 1 stop bit goes into the most significant bit (msb) position. the sci transmitter empty bit, scte, in scs1 beco mes set when the scdr transfers a byte to the transmit shift register. the scte bi t 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 ptf5/txd pin goes to the idle condition, logic 1. if at any time software clears th e ensci bit in sci control register 1 (scc1), the transmitter and receiver relinquish control of the port e pins. 13.3.2.3 break characters writing a 1 to the send break bit, sbk, in scc2 loads t he transmit shift register with a break character. a break character contains all 0s and has no start, st op, or parity bit. break character length depends on the m bit in scc1. as long as sbk is at 1, transmitte r logic continuously loads br eak characters into the transmit shift register. after software clears the sbk bi t, the shift register finish es 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 ni ne 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 functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 163 13.3.2.4 idle characters an idle character contains all 1s and has no start, st op, 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 tr ansmission, the ptf5/txd pin becom es 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 a break sequence is followed immedi ately by an idle character, this sci design exhibits a condition in wh ich the break character length is reduced by one half bit time. in this instance, the break sequence will consist of a valid start bit, eight or ni ne data bits (as defined by the m bit in scc1) of logic 0 and one half data bit length of logic 0 in the stop bit position followed immediately by the idle char acter. to ensure a break character of the proper length is transmitted, always queue up a byte of data to be transmitted while the final break sequence is in progress. when queueing an idle character, return the te bit to 1 before the stop bit of the current character shifts out to the ptf5/txd pin. setting te after the stop bit appears on ptf5/txd causes da ta previously written to the scdr to be lost. a good time to toggle the te bit is when the scte bit becomes set and just before writing the next byte to the scdr. 13.3.2.5 inversion of transmitted output the transmit inversion bit (txinv) in sci control regi ster 1 (scc1) reverses the polarity of transmitted data. all transmitted values, including idle, break, start, and stop bits, are inverted when txinv is at 1. see 13.7.1 sci control register 1 . 13.3.2.6 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. 13.3.3 receiver figure 13-6 shows the structure of the sci receiver. serial communications in terface modu le (sci) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 164 freescale semiconductor figure 13-6. sci receiver block diagram 13.3.3.1 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-bi t 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). all 1s all 0s m wake ilty pen pty bkf rpf h876543210l 11-bit receive shift register stop start data recovery or orie nf neie fe feie pe peie scrie scrf ilie idle wakeup logic parity checking msb error cpu interrupt request cpu interrupt request sci data register r8 orie neie feie peie scrie ilie rwu scrf idle or nf fe pe ptf4/rxd internal bus pre- scaler baud divider 4 16 scp1 scp0 scr1 scr2 scr0 f op functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 165 13.3.3.2 character reception during an sci reception, the receive shift register shi fts characters in from th e ptf4/rxd pin. the sci data register (scdr) is the read-onl y buffer between the internal data bus and the receive shift register. after a complete character shifts into the receive sh ift 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 the received byte can be read. if th e sci receive interrupt enable bit, scrie, in scc2 is also set, the scrf bit generates a receiver cpu interrupt request. 13.3.3.3 data sampling the receiver samples the ptf4/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 these times (see figure 13-7 ): after every start bit after the receiver detects a data bit change from 1 to 0 (after the majority of data bit samples at rt8, rt9, and rt10 return a valid 1 and the majority of the next rt8, rt9, and rt10 samples return a valid 0) figure 13-7. receiver data sampling to locate the start bit, data recovery logic does an asynchronous search for a 0 preceded by three 1s. when the falling edge of a possible start bit oc curs, 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 13-1 summarizes the results of the start bit verification samples. 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 ptf4/rxd serial communications in terface modu le (sci) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 166 freescale semiconductor if start bit verification is not successful, the rt cl ock 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 13-2 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 1s following a successful start bit verification, the noi se 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 13-3 summarizes the results of the stop bit samples. table 13-1. start bit verification 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 table 13-2. 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 13-3. 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 functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 167 13.3.3.4 framing errors if the data recovery logic does not detect a 1 where t he stop bit should be in an incoming character, it sets the framing error bit, fe, in scs1. t he 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. 13.3.3.5 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. depending on the state of the wake bit in scc1, eith er of two conditions on the ptf4/rxd pin can bring the receiver out of the standby state: address mark ? an address mark is a 1 in the most significant bit position of a received character. when the wake bit is set, an address mark wakes th e receiver from the standby state by clearing the rwu bit. the address mark also sets the sc i 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 cl ear, an idle character on the ptf4/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 1s as idle character bits after the start bit or after the stop bit. note clearing the wake bit after the ptf4/r xd pin has been idle can cause the receiver to wake up immediately. 13.3.3.6 receiver interrupts these 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 1s shifted in from the ptf4/rxd pin. the idle line interrupt enable bit, ilie, in scc2 enables the idle bit to generate cpu interrupt requests. 13.3.3.7 error interrupts these receiver error flags in scs1 can generate cpu interrupt requests: receiver overrun (or) ? the or bit indicates t hat the receive shift register shifted in a new character before the previous c haracter was read from the scdr. the previous character remains in the scdr, and the new character is lost. th e overrun interrupt enable bit, orie, in scc3 enables or to generate sci error cpu interrupt requests. serial communications in terface modu le (sci) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 168 freescale semiconductor noise flag (nf) ? the nf bit is set when t he 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 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 s cc3 enables pe to generate sci error cpu interrupt requests. 13.4 wait mode the wait and stop instructions put the mcu in low power-consumption standby modes. 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 enabl ed 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. 13.5 sci during br eak module interrupts the system integration module (sim) controls whethe r status bits in other modules can be cleared during interrupts generated by the break module. the bcfe bi t 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 in terrupt, write a 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 0 to the bcfe bit. with bcfe at 0 (its default state), software can read and write i/o registers during the brea k state without affecting status bits. some status bits have a 2-step read/write clearing procedure. if so ftware 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 0. after the break, doing the second step clears the status bit. 13.6 i/o signals port f shares two of its pins with the sci module. the two sci input/output (i/o) pins are: ptf5/txd ? transmit data ptf4/rxd ? receive data 13.6.1 ptf5/txd (transmit data) the ptf5/txd pin is the serial data output from th e sci transmitter. the sci shares the ptf5/txd pin with port f. when the sci is enabled, the ptf5/txd pin is an output regardless of the state of the ddrf5 bit in data direction register f (ddrf). i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 169 13.6.2 ptf4/rxd (receive data) the ptf4/rxd pin is the serial data input to the sci receiver. the sci shares the ptf4/rxd pin with port f. when the sci is enabled, the ptf4/rxd pin is an input regardless of the state of the ddrf4 bit in data direction register f (ddrf). 13.7 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) 13.7.1 sci cont rol register 1 sci control register 1 (scc1): 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 ptf4/rxd pin is disconnected from the sci, and the transmitter output goes into the rece iver input. both the trans mitter and the receiver must be enabled to use loop mode. reset clears the loops bit. 1 = loop mode enabled 0 = normal operation enabled address: $0038 bit 7654321bit 0 read: loops ensci txinv m wake ilty pen pty write: reset:00000000 figure 13-8. sci control register 1 (scc1) serial communications in terface modu le (sci) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 170 freescale semiconductor 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 ? transmi t 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 tran smitted 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 13-4 . 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 wa kes up the sci: a 1 (address mark) in the most significant bit (msb) position of a received character or an idle condition on the ptf4/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 1s as idle character bits. the counting begins either after the start bit or after the stop bi t. if the count begins after the start bit, then a string of 1s preceding the stop bit may cause false recognit ion 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 13-4 . when enabled, the parity function inserts a parity bit in the most significant bit position. see figure 13-4 . 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 13-4 . 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. i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 171 13.7.2 sci cont rol register 2 sci control register 2 (scc2): enables these 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 gener ate sci transmitter cpu interrupt requests. setting the sctie bit in scc3 enables scte 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 table 13-4. 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 address: $0039 bit 7654321bit 0 read: sctie tcie scrie ilie te re rwu sbk write: reset:00000000 figure 13-9. sci control register 2 (scc2) serial communications in terface modu le (sci) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 172 freescale semiconductor scrie ? sci receive interrupt enable bit this read/write bit enables the scrf bit to generate sci receiver cpu interrupt requests. setting the scrie bit in scc3 enables the scrf bit to generat e 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 1s from the transmit shift register to the ptf5/txd pin. if so ftware clears the te bit, the transmitter completes any transmission in progress before the ptf5/txd returns to the idle condition (logic 1). clearing and then setting te during a transmission queues an idle characte r 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. clea ring 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 allowe d 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 i nput 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/writ e bit transmits a break character followed by a 1. the 1 after the break character guarantees recogni tion of a valid start bit. if sbk remains set, the transmitter continuously transmits break c haracters with no 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 a fter setting the scte bit. toggling sbk too early causes the sci to send a break character instead of a preamble. i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 173 13.7.3 sci cont rol register 3 sci control register 3 (scc3): stores the ninth sci data bit received and the ninth sci data bit to be transmitted enables sci receiver full (scrf) enables sci transmitter empty (scte) enables the following 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 re ad-only ninth bit (bit 8) of the received character. r8 is received at the same time that the scdr receives the other eight bits. when the sci is receiving 8-bit characters, r8 is a co py 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 regi ster at the same time that the scdr is loaded into the transmit shift register. rese t has no effect on the t8 bit. 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 r equests 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 receiver cpu interrupt requests generated by the parity error bit, pe. see 13.7.4 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 address: $003a bit 7654321bit 0 read: r8 t8 00 orie neie feie peie write: r r r reset:uu000000 r = reserved u = unaffected figure 13-10. sci control register 3 (scc3) serial communications in terface modu le (sci) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 174 freescale semiconductor 13.7.4 sci status register 1 sci status register 1 (scs1) contai ns 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 tr ansfers 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 reques t. in normal operation, clear the scte bit by reading scs1 with scte set and then wr iting to scdr. reset sets the scte bit. 1 = scdr data transferred to transmit shift register 0 = scdr data not transferred to transmit shift register tc ? transmission complete bit this read-only bit is set when the scte bit is se t 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 cleared automatically when data, preamble, or break is queued and ready to be sent. there may be up to 1.5 transmitter clocks of latency be tween queueing data, preamble, and break and the transmission actually starti ng. 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 address: $003b bit 7654321bit 0 read: scte tc scrf idle or nf fe pe write:rrrrrrrr reset:11000000 r= reserved figure 13-11. sci status register 1 (scs1) i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 175 idle ? receiver idle bit this clearable, read-only bit is set when 10 or 11 consecutive 1s appear on the receiver input. idle generates an sci error 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 id le 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 id le 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 da ta 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 ove rrun to occur between reads of sc s1 and scdr in the flag-clearing sequence. figure 13-12 shows the normal flag-clearing sequence and an example of an overrun caused by a delayed flag-clearin g 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. figure 13-12. flag clearing sequence 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 serial communications in terface modu le (sci) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 176 freescale semiconductor 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 ptf4/rxd pin. nf generates an nf 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 fe ? receiver framing error bit this clearable, read-only bit is set when a 0 is accepted as the stop bit. fe generates an sci error cpu interrupt request if the feie bit in scc3 also is se t. 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 pe ? receiver parity error bit this clearable, read-only bit is set when the sci detects a parity error in incoming data. pe generates a pe 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 13.7.5 sci status register 2 sci status register 2 (scs2) contai ns flags to signal these conditions: break character detected incoming data bkf ? break flag this clearable, read-only bit is set when the sci detects a break character on the ptf4/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 be come set again only after logic 1s again appear on the ptf4/rxd pin followed by another br eak character. reset clears the bkf bit. 1 = break character detected 0 = no break character detected address: $003c bit 7654321bit 0 read:000000bkfrpf write:rrrrrrrr reset:00000000 r= reserved figure 13-13. sci status register 2 (scs2) i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 177 rpf ?reception-in-progress flag 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 st op mode can show whether a reception is in progress. 1 = reception in progress 0 = no reception in progress 13.7.6 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:r0/t0 ? receiv e/transmit data bits reading address $003d accesses the read-only receiv ed data bits, r7:r0. writing to address $003d writes the data to be transmitted, t7:t0. reset has no effect on the sci data register. 13.7.7 sci baud rate register the baud rate register (scbr) selects the baud rate for both the receiver and the transmitter. scp1 and scp0 ? sc i baud rate prescaler bits these read/write bits select the baud rate prescaler divisor as shown in table 13-5 . reset clears scp1 and scp0. address: $003d bit 7654321bit 0 read:r7r6r5r4r3r2r1r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset figure 13-14. sci data register (scdr) address: $003e bit 7654321bit 0 read: 0 0 scp1 scp0 0 scr2 scr1 scr0 write: r r r reset:00000000 r = reserved figure 13-15. sci baud rate register (scbr) table 13-5. sci baud rate prescaling scp1:scp0 prescaler divisor (pd) 00 1 01 3 10 4 11 13 serial communications in terface modu le (sci) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 178 freescale semiconductor scr2?scr0 ? sci baud rate select bits these read/write bits select the sci baud rate divisor as shown in table 13-6 . reset clears scr2?scr0. use this formula to calculate the sci baud rate: where: f op = internal operating frequency pd = prescaler divisor bd = baud rate divisor table 13-7 shows the sci baud rates that can be generated with a 4.9152-mhz crystal with the cgm set for an f op of 7.3728 mhz and the cgm set for an f op of 4.9152 mhz. table 13-6. sci baud rate selection scr2:scr1:scr0 baud rate divisor (bd) 000 1 001 2 010 4 011 8 100 16 101 32 110 64 111 128 baud rate f op 64 pd bd ------------------------------------ = i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 179 table 13-7. sci baud rate selection examples scp1:scp0 prescaler divisor (pd) scr2:scr1:scr0 baud rate divisor (bd) baud rate (f op = 7.3728 mhz) baud rate (f op = 4.9152 mhz) 00 1 000 1 115,200 76,800 00 1 001 2 57,600 38,400 00 1 010 4 28,800 19,200 00 1 011 8 14,400 9600 00 1 100 16 7200 4800 00 1 101 32 3600 2400 00 1 110 64 1800 1200 00 1 111 128 900 600 01 3 000 1 38,400 25,600 01 3 001 2 19,200 12,800 01 3 010 4 9600 6400 01 3 011 8 4800 3200 01 3 100 16 2400 1600 01 3 101 32 1200 800 01 3 110 64 600 400 01 3 111 128 300 200 10 4 000 1 28,800 19,200 10 4 001 2 14,400 9600 10 4 010 4 7200 4800 10 4 011 8 3600 2400 10 4 100 16 1800 1200 10 4 101 32 900 600 10 4 110 64 450 300 10 4 111 128 225 150 11 13 000 1 8861.5 5907.7 11 13 001 2 4430.7 2953.8 11 13 010 4 2215.4 1476.9 11 13 011 8 1107.7 738.5 11 13 100 16 553.8 369.2 11 13 101 32 276.9 184.6 11 13 110 64 138.5 92.3 11 13 111 128 69.2 46.2 serial communications in terface modu le (sci) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 180 freescale semiconductor mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 181 chapter 14 system integration module (sim) 14.1 introduction this section describes the system integration module (sim). together with the central processor unit (cpu), the sim controls all micr ocontroller unit (mcu) activities. a block diagram of the sim is shown in figure 14-1 . the sim is a system state controller that coordinat es cpu and exception timing. the sim is responsible for: bus clock generation and control for cpu and peripherals: ? wait/reset/break entry and recovery ? internal clock control master reset control, including power-on reset (por) and computer operating properly (cop) timeout interrupt control: ? acknowledge timing ? arbitration control timing ? vector address generation cpu enable/disable timing modular architecture expandable to 128 interrupt sources table 14-1 shows the internal signal names used in this section. table 14-1. signal name conventions signal name description cgmxclk buffered version of osc1 from clock generator module (cgm) cgmvclk phase-locked loop (pll) circuit output cgmout pll-based or osc1-based clock output from cgm module (bus clock = cgmout divided by two) 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) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 182 freescale semiconductor figure 14-1. sim block diagram 14.2 sim bus clock control and generation the bus clock generator provides system clock signa ls for the cpu and peripherals on the mcu. the system clocks are generated from an incoming clock, cgmout, as shown in figure 14-2 . this clock can come from either an external oscillator or from the on-chip phase-locked loop (pll) circuit. see chapter 4 clock generator module (cgm) . 14.2.1 bus timing in user mode , the internal bus frequency is either the crys tal oscillator output (cgmxclk) divided by four or the pll output (cgmvclk) divided by four. see chapter 4 clock generator module (cgm) . 14.2.2 clock startup fr om por or lvi reset when the power-on reset (por) module or the low-voltage inhibit (lvi) module generates a reset, the clocks to the cpu and peripherals are inactive and held in an inactive phase until after the 4096 cgmxclk cycle por timeout has completed. the rst pin is driven low by the sim during this entire period. the internal bus (ibus) clocks start upon completion of the timeout. wait clock control clock generators por control reset pin control sim reset status register interrupt control and priority decode module wait cpu wait (from cpu) simoscen (to cgm) 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 cgmxclk (from cgm) 2 reset and system initialization mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 183 figure 14-2. cgm clock signals 14.2.3 clocks in wait 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 s ee if the module is active or inactive in wait mode. some modules can be programmed to be active in wait mode. 14.3 reset and s ystem initialization the mcu has these reset sources: power-on reset module (por) external reset pin (rst ) computer operating properly (cop) module low-voltage inhibit (lvi) module 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 register s 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 14.4 sim counter ), but an external reset does not. each of the resets sets a corresponding bit in the sim reset status register (srsr). see 14.7.2 sim reset status register . 14.3.1 external pin reset 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 cgmxclk cycles, assuming that neither the por nor the lvi was the source of the reset. see table 14-2 for details. figure 14-3 shows the relative timing. pll osc1 cgmxclk 2 bus clock generators sim cgm sim counter ptc2 monitor mode clock select circuit cgmvclk bcs 2 a b s* cgmout *when s = 1, cgmout = b user mode system integration module (sim) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 184 freescale semiconductor figure 14-3. external reset timing 14.3.2 active resets from internal sources all internal reset sources actively pull the rst pin low for 32 cgmxclk cycles to allow resetting of external peripherals. the internal reset signal (irst) continues to be asserted fo r an additional 32 cycles (see figure 14-5 ). an internal reset can be caused by an i llegal address, illegal opcode, cop timeout, lvi, or por. (see figure 14-4 .) figure 14-4. sources of internal reset note for lvi or por resets, the sim c ycles through 4096 cgmxclk cycles during which the sim forces the rst pin low. the internal reset signal then follows the sequence from the falling edge of rst , as shown in figure 14-5 . figure 14-5. internal reset timing the cop reset is asynchronous to the bus clock. the active reset feature allows the part to issue a reset to peripherals and other chips within a system built around the mcu. table 14-2. pin bit set timing reset type number of cycles required to set pin por/lvi 4163 (4096 + 64 + 3) all others 67 (64 + 3) rst iab pc vect h vect l cgmout illegal address rst illegal opcode rst coprst lvi por internal reset irst rst rst pulled low by mcu iab 32 cycles 32 cycles vector high cgmxclk reset and system initialization mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 185 14.3.2.1 power-on reset (por) when power is first applied to the mcu, the power- on reset (por) module 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 cgmxclk cycles. sixty-four cgmxclk cycles later, the cpu and memories are released from reset to allow the reset vector sequence to occur. figure 14-6. por recovery 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 hel d inactive for 4096 cgmxclk cycles to allow stabilization of the oscillator. the rst pin is driven low during the oscillator stabilization time. the por bit of the sim reset status register (srs r) is set and all other bits in the register are cleared. 14.3.2.2 computer operating properly (cop) reset an input to the sim is reserved for the cop reset signal. the overflow of th e 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?4 of the sim counter. the sim counter output, which occurs at least every 2 13 ?2 4 cgmxclk 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 irq pin is held at v hi while the mcu is in monitor mode. the cop module can be disabled only through combin ational logic conditioned with the high voltage porrst osc1 cgmxclk cgmout rst iab 4096 cycles 32 cycles 32 cycles $fffe $ffff system integration module (sim) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 186 freescale semiconductor signal on the rst or the irq pin. this prevents the cop from becoming disabled as a result of external noise. during a break state, v hi on the rst pin disables the cop module. 14.3.2.3 illegal opcode reset the sim decodes signals from the cpu to detect illegal instructions. an illegal instruction sets the ilop bit in the sim reset status register (srsr) and causes a reset. because the mc68hc908mr32 has stop mode disabled, execution of t he stop instruction will cause an illegal opcode reset. 14.3.2.4 illegal address reset an opcode fetch from addresses other than flash or ram addresses generates an illegal address reset (unimplemented locations within memory map). the si m verifies that the cpu is fetching an opcode prior to asserting the ilad bit in the sim reset status register (srsr) and resetting the mcu. a data fetch from an unmapped address does not generate a reset. 14.3.2.5 forced monitor mode entry reset (menrst) the menrst module monitors the reset vector fetches and will assert an in ternal reset if it detects that the reset vectors are erased ($ff). when the mcu comes out of reset, it is forced into monitor mode. 14.3.2.6 low-voltage inhibit (lvi) reset the low-voltage inhibit (lvi) module asserts its output to the sim when the v dd voltage falls to the v lvrx voltage and remains at or below that level for at least nine cons ecutive cpu cycles (see 19.5 dc electrical characteristics ). 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 40 96 cgmxclk cycles. sixty-four cgmxclk 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. 14.4 sim counter the sim counter is used by the power-on reset (por) module 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 (cop) module. 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. 14.4.1 sim counter du ring power-on reset the power-on reset (por) module detects power applie d to the mcu. at power-on, the por circuit asserts the signal porrst. once the sim is initialized, it enables the clock generation (cgm) module to drive the bus clock state machine. 14.4.2 sim counter and reset states external reset has no effect on the sim counter. the sim counter is free-running after all reset states. for counter control and internal reset recovery sequences, see 14.3.2 active resets from internal sources . exception control mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 187 14.5 exception control normal, sequential program execution can be changed in three different ways: 1. interrupts: a. maskable hardware cpu interrupts b. non-maskable software interrupt instruction (swi) 2. reset 3. break interrupts 14.5.1 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 return-from-interrupt (rti) instruction recovers the cpu register contents from the stack so that normal processing can resume. figure 14-7 shows interrupt entry timing. figure 14-9 shows interrupt recovery timing. figure 14-7 . interrupt entry 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 14-8 . module idb r/w interrupt dummy sp sp ? 1 sp ? 2 sp ? 3 sp ? 4 vect h vect l iab dummy pc ? 1[7:0] pc ? 1[15:8] x a ccr v data h v data l opcode i bit start addr system integration module (sim) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 188 freescale semiconductor figure 14-8. interrupt processing no no yes as many interrupts as exist on chip swi instruction? rti instruction? fetch next instruction unstack cpu registers stack cpu registers set i bit load pc with interrupt vector execute instruction yes no yes no no yes i bit set? from reset break or swi i bit set? interrupt? yes interrupt? exception control mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 189 figure 14-9. interrupt recovery 14.5.1.1 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 14-10 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 load-accumulator-from- memory (lda) instruction is executed. figure 14-10 . 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. module idb r/w interrupt sp ? 4 sp ? 3 sp ? 2 sp ? 1 sp pc pc + 1 iab ccr a x pc ? 1[7:0] pc ? 1[15:8] opcode operand i bit cli lda int1 pulh rti int2 background routine #$ff pshh int1 interrupt service routine pulh rti pshh int2 interrupt service routine system integration module (sim) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 190 freescale semiconductor 14.5.1.2 software interrupt (swi) instruction the software interrupt (swi) instruction is a non-maska ble instruction that causes an interrupt regardless of the state of the interrupt mask (i bit) in the condition code register. 14.5.2 reset all reset sources always have equal and highest priority and cannot be arbitrated. 14.6 low-power mode executing the wait instruction puts the mcu in a low power-consumption mode for standby situations. the sim holds the cpu in a non-clocked state. wait clears the interrupt mask (i) in the condition code register, allowing interrupts to occur. 14.6.1 wait mode in wait mode, the cpu clocks are inactive while the peripheral clocks continue to run. figure 14-11 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 wa it instruction during which the interrupt occurred. refer to the wait mode subsection of each module to s ee if the module is active or inactive in wait mode. some modules can be programmed to be active in wait mode. wait mode can also be exited by a reset. if the cop di sable bit, copd, in the configuration register is logic 0, then the computer operating properly module (cop) is enabled and remains active in wait mode. figure 14-11. wait mode entry timing figure 14-12 and figure 14-13 show the timing for wait recovery. figure 14-12. wait recovery from interrupt 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 sim registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 191 figure 14-13. wait recovery from internal reset 14.6.2 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 outputs (cgmout and cgmxclk) in stop mode, stopping the cpu and peripherals. stop recovery time is hard wired at the normal delay of 4096 cgmxclk cycles. it is important to note that when using the pwm generator, its outputs will stop toggling when stop mode is entered. the pwm module must be disabled before entering stop mode to prevent external inverter failure. 14.7 sim registers this subsection describes the sim registers. 14.7.1 sim break st atus register the sim break status register (sbsr) contains a flag to indicate that a break caused an exit from wait mode. sbsw ? sim break stop/wait this status bit is useful in applications requiring a return to wait mode after exiting from a break interrupt. clear sbsw by writing a logic 0 to it. reset clears sbsw. 1 = wait mode was exited by break interrupt. 0 = wait mode was not exited by break interrupt. address: $fe00 bit 7654321bit 0 read: rrrrrr sbsw r write: note (1) reset: 0 r= reserved note 1. writing a logic 0 clears sbsw. figure 14-14. sim break status register (sbsr) iab idb rst $a6 $a6 $6e0b rst vct h rst vct l $a6 cgmxclk 32 cycles 32 cycles system integration module (sim) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 192 freescale semiconductor sbsw can be read within the break state swi routine. the user can modify t he return address on the stack by subtracting one from it. 14.7.2 sim reset status register the sim reset status register (srsr) contains six flags that show the source of the last reset. 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 (o pcode fetches only ) 1 = last reset caused by an opcode fetch from an illegal address 0 = por or read of srsr menrst ? forced monitor mode entry reset bit 1 = last reset caused by the menrst circuit 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 menrst lvi 0 write:rrrrrrrr reset:10000000 r= reserved figure 14-15. sim reset status register (srsr) sim registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 193 14.7.3 sim break flag control register the sim break 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 bi ts by accessing status r egisters while the mcu is in a break state. to clear status bits duri ng the break state, the bcfe bit must be set. 1 = status bits cl earable during break 0 = status bits not clearable during break address: $fe03 bit 7654321bit 0 read: bcferrrrrrr write: reset: 0 r= reserved figure 14-16. sim break flag control register (sbfcr) system integration module (sim) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 194 freescale semiconductor mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 195 chapter 15 serial peripheral interface module (spi) 15.1 introduction the serial peripheral interface (spi) module allows full-duplex, synchronous, serial communications with peripheral devices. 15.2 features features of the spi module include: 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 with central processor unit (cpu) service: ? 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 i 2 c (inter-integrated circuit) compatibility 15.3 pin name conventions the generic names of the spi input/output (i/o) pins are: ss , slave select spsck, spi serial clock mosi, master out/slave in miso, master in/slave out spi pins are shared by parallel i/o ports or have alte rnate functions. the full name of an spi pin reflects the name of the shared port pin or the name of an alternate pin function. the generic pin names appear in the text that follows. table 15-1 shows the full names of the spi i/o pins. table 15-1. pin name conventions generic pin names: miso mosi spsck ss full pin names: ptf3/miso ptf2/mosi ptf0/spsck ptf1/ss mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 196 freescale semiconductor serial peripheral in terface module (spi) figure 15-1. block diagram highlighting spi block and pins clock generator module system integration module serial communications interface module serial peripheral interface module (2) timer interface module a low-voltage inhibit module power-on reset module computer operating properly module arithmetic/logic unit cpu registers m68hc08 cpu control and status registers ? 112 bytes user flash ? 32,256 bytes user ram ? 768 bytes monitor rom ? 240 bytes user flash vector space ? 46 bytes irq module power pta ddra ddrb ptb ddrc ptc ptd ddre pte ptf ddrf internal bus osc1 osc2 cgmxfc rst irq v ss v dd v ddad pta7?pta0 pte7/tch3a pte6/tch2a pte5/tch1a pte4/tch0a pte3/tclka pte2/tch1b (1) pte1/tch0b (1) pte0/tclkb (1) ptf5/txd ptf4/rxd ptf3/miso (1) ptf2/mosi (1) ptf1/ss (1) ptf0/spsck (1) timer interface module b pulse-width modulator module ptb7/atd7 ptb6/atd6 ptb5/atd5 ptb4/atd4 ptb3/atd3 ptb2/atd2 ptb1/atd1 ptb0/atd0 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1/atd9(1) ptc0/atd8 ptd6/is3 ptd5/is2 ptd4/is1 ptd3/fault4 ptd2/fault3 ptd1/fault2 ptd0/fault1 pwm6?pwm1 analog-to-digital converter module v ssad v dda v ssa (3) pwmgnd v refl (3) v refh notes: 1. these pins are not available in the 56-pin sdip package. 2. this module is not available in the 56-pin sdip package. 3. in the 56-pin sdip package, these pins are bonded together. single break module functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 197 15.4 functional description figure 15-2 shows the structure of the spi module and figure 15-3 shows the locations and contents of the spi i/o registers. the spi module allows full-duplex, synchronous, se rial communication between the microcontroller unit (mcu) and peripheral devices, incl uding other mcus. software can poll the spi status flags or spi operation can be interrupt-driven. all spi interrupts can be serviced by the cpu. figure 15-2. spi module block diagram transmitter cpu interrupt request 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 spe spwom sprf spte ovrf m s pin control logic receive data register sptie spe internal bus (from sim) modfen errie control modf spmstr mosi miso spsck ss serial peripheral in terface module (spi) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 198 freescale semiconductor 15.4.1 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 t he slave spi. disable the slave spi before disabling the master spi. see 15.12.1 spi control register . only a master spi module can initiate transmissions. software begins the transmission from a master spi module by writing to the spi 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 15-4 . figure 15-4. full-duplex master-slave connections the spr1 and spr0 bits control the baud rate generator and determine the speed of the shift register. see 15.12.2 spi status and control register . through the spsck pin, the baud-rate generator of the master also controls the shift register of the slave peripheral. as the byte shifts out on the mosi pin of the master, another byte shifts in from the slave on the master?s miso pin. the transmission ends when the receiver full bit, sprf, becomes set. at the same time that sprf becomes set, the byte from the slave transfers to the receive data register. in normal operation, addr. register name bit 7 6 5 4 3 2 1 bit 0 $0044 spi control register (spcr) see page 211. read: sprie r spmstr cpol cpha spwom spe sptie write: reset:00101000 $0045 spi status and control register (spscr) see page 212. read: sprf errie ovrf modf spte modfen spr1 spr0 write: r r r r reset:00001000 $0046 spi data register (spdr) see page 214. read: r7 r6 r5 r4 r3 r2 r1 r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: unaffected by reset r= reserved figure 15-3. spi i/o register summary shift register shift register baud rate generator master mcu slave mcu v dd mosi mosi miso miso spsck spsck ss ss transmission formats mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 199 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. 15.4.2 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 15.6.2 mode fault error . in a slave spi module, data enters the shift register und er 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 condit ion, slave software then must read the receive data register before another full byte enters the shift register. the maximum frequency of the spsck fo r an spi configured as a slave is the bus clock speed (which is twice as fast as the fastest master spsck clock t hat can be generated). th e 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 tr ansmit data register at l east 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 e dge of spsck starts a transmission. when cpha is clear, the falling edge of ss starts a transmission. see 15.5 transmission formats . note if the write to the data register is late , the spi transmits the data already in the shift register from the previous transmission. spsck must be in the proper idle state before the slave is enabled to prevent spsck from appearing as a clock edge. 15.5 transmission formats during an spi transmission, data is simultaneously tr ansmitted (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. 15.5.1 clock phase and polarity controls software can select any of four combinations of se rial clock (spsck) phase a nd 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 signi ficant effect on the transmission format. serial peripheral in terface module (spi) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 200 freescale semiconductor the clock phase (cpha) control bit selects one of tw o 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 periphera l 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). 15.5.2 transmission format when cpha = 0 figure 15-5 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 slav e. 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 reconf igured as general-purpose i/o not affecting the spi. (see 15.6.2 mode fault error .) when cpha = 0, the first spsck edge is the msb capture strobe. therefore, the slave must begin driving its data before th e first spsck edge, and a falling edge on the ss pin is used to start the slave data transmission. the slave?s ss pin must be toggled back to high and then low again between each byte transmitted as shown in figure 15-6 . figure 15-5. transmission format (cpha = 0) figure 15-6. cpha/ss timing 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 transmission formats mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 201 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 th e transmit data register and transferred to the shift register after the current transmission. 15.5.3 transmission format when cpha = 1 figure 15-7 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 slav e. 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 15.6.2 mode fault error . when cpha = 1, the master begins driving its mosi pin on the first spsck edge. therefore, the slave uses the first sps ck 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. 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. figure 15-7. transmission format (cpha = 1) 15.5.4 transmission initiation latency when the spi is configured as a master (spmstr = 1), writing to the spdr st arts a transmission. cpha has no effect on the delay to the start of the transmiss ion, 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. 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 serial peripheral in terface module (spi) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 202 freescale semiconductor when cpha = 1, the first spsck cycl e 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 15-8 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 caus es the variation in the in itiation delay shown in figure 15-8 . 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. figure 15-8. transmission start delay (master) 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 error conditions mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 203 15.6 error conditions these 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. 15.6.1 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. 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. modf and ovrf can generate a receiver/error cpu interrupt request. see figure 15-11 . 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 in terrupt is not, watch for an overflow condition. figure 15-9 shows how it is possible to mi ss an overflow. the first part of figure 15-9 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 ca n be set in between the time that spscr and spdr are read. figure 15-9. missed read of overflow condition 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 in terface module (spi) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 204 freescale semiconductor in this case, an overflow can easily be missed. 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 15-10 illustrates this process. g enerally, to avoid this second spscr read, enable the ovrf interrupt to the cpu by setting the errie bit. figure 15-10. clearing sprf when ovrf interrupt is not enabled 15.6.2 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 sele cts 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. modf and ovrf can generate a receiver/error cpu interrupt request. see figure 15-11 . it is not possible to enable modf or 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 error conditions mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 205 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 (modfe n) set, the mode fault flag (modf) is set if ss goes to logic 0. a mode fault in a master spi causes these 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. 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 transmi ssion continues until the spsck returns to its idle level following the shift of the last data bit. see 15.5 transmission formats . note setting the modf flag does not clear the spmstr bit. reading spmstr when modf = 1 will indicate a mode fault error occurred in either master mode or slave mode. 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 late r 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 bi t or reset the spi in any way. software can abort the spi transmission by clear ing 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 procedure must occur with no modf condition existing or else the flag is not cleared. serial peripheral in terface module (spi) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 206 freescale semiconductor 15.7 interrupts four spi status flags can be enabled to gen erate cpu interrupt requests as shown in table 15-2 . 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, provided that the spi is enabled (spe = 1). (see figure 15-11 .) figure 15-11. spi interrupt request generation 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. these 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 can generate either an spi receiver/error or cpu interrupt. spi transmitter empty (spte) ? the spte bit becom es set every time a by te transfers from the transmit data register to the shift register. if the spi transmit interrupt enable bit, sptie, is also set, spte can generate either an spte or cpu interrupt request. table 15-2. 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 overflow spi receiver/err or interrupt request (errie = 1) modf mode fault spi receiver/err or interrupt request (errie = 1) spte sptie sprf sprie errie modf ovrf spe spi transmitter cpu interrupt request spi receiver/error cpu interrupt request resetting the spi mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 207 15.8 resetting the spi any system reset completely resets the spi. partia l resets occur whenever th e spi enable bit (spe) is low. whenever spe is low: the spte flag is set. any transmission currently in progress is aborted. 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 defaul ted back to being general-purpose i/o. these items are reset only by a system reset: all control bits in the spcr all control bits in the spscr (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 betw een transmissions without having to set all control bits again when spe is set back high for t he 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 wa s configured as a master with the modfen bit set. 15.9 queuing tr ansmission 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 transm itted 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 da ta register only when the spte bit is high. figure 15-12 shows the timing associated wi th doing back-to-back transmissi ons with the spi (spsck has cpha:cpol = 1:0). for a slave, 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 sh ift 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 emptie s into the shift register. this allows the user to queue up a 16-bit value to send. for an already active sl ave, 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. serial peripheral in terface module (spi) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 208 freescale semiconductor figure 15-12. sprf/spte cpu interrupt timing 15.10 low-power mode the wait instruction puts the mcu in a low power-consumption standby 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 occu rs, enable the ovrf bit to generate cpu interrupt requests by setting the error interrupt enable bit (errie). see 15.7 interrupts . since the spte bit cannot be cleared during a break wi th the bcfe bit cleared, a write to the transmit data register in break mode does not initiate a transm ission nor is this data transferred into the shift register. therefore, a write to the spdr in br eak mode with the bcfe bit cleared has no effect. 15.11 i/o signals the spi module has five i/o pins and shares four of them with a parallel i/o port. the pins are: miso ? data received mosi ? data transmitted spsck ? serial clock ss ? slave select 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 msbbit 6 bit 5 bit 4 bit 2 bit 1 lsbmsbbit 6 bit 5 bit 4 bit 3 bit 2 bit 1 lsbmsbbit 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 i/o signals mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 209 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 becom es 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 . 15.11.1 miso (mas ter in/slave out) miso is one of the two spi module pins that transmits se rial 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 w hen 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 mi so pin regardless of the st ate of the data direction register of the shared i/o port. 15.11.2 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 mo si pin regardless of the st ate of the data direction register of the shared i/o port. 15.11.3 spsck (serial clock) the serial clock synchronizes data transmission between master and sl ave devices. in a master mcu, the spsck pin is the clock output. in a slave mcu, the spsck pin is the cl ock input. in full-duplex operation, the master and slave mcus exchange a byte of data in eight serial clock cycles. when enabled, the spi contro ls data direction of the spsck pin regardless of the state of the data direction register of the shared i/o port. 15.11.4 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 15.5 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 15-13 . figure 15-13. cpha/ss timing byte 1 byte 3 miso/mosi byte 2 master ss slave ss cpha = 0 slave ss cpha = 1 serial peripheral in terface module (spi) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 210 freescale semiconductor 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 15.12.2 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 conjunc tion with the modf flag to prevent multiple masters from driving mosi and spsck. (see 15.6.2 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 15-3 . 15.11.5 v ss (clock ground) v ss is the ground return for the serial clock pin, spsck, and the ground for the port output buffers. to reduce the ground return path loop and minimize r adio frequency (rf) emissions, connect the ground pin of the slave to the v ss pin of the master. 15.12 i/o registers three registers control and monitor spi operation: spi control register, spcr spi status and control register, spscr spi data register, spdr 15.12.1 spi control register the spi control register (spcr): enables spi module interrupt requests selects cpu interrupt requests or dma service 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 table 15-3. spi configuration spe spmstr modfen spi configuration state of ss logic 0 x (1) 1. x = don?t care 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 i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 211 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 sh ift 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 ? cloc k polarity bit this read/write bit determines the logic stat e of the spsck pin betw een transmissions. see figure 15-5 and figure 15-7 . to transmit data between spi modules, the spi modules must have identical cpol values. reset cl ears the cpol bit. cpha ? clock phase bit this read/write bit controls the timing relationship between the serial clock and spi data. see figure 15-5 and figure 15-7 . to transmit data between spi modules, the spi modules must have identical cpha bits. when cpha = 0, the ss pin of the slave spi module must be set to logic 1 between bytes. see figure 15-13 . reset sets the cpha bit. 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 th e shift register from the data register. therefore, the slave data register must be loaded with the desired transmit data before the falling edge of ss . any data written after the falling edge is stored in the dat a register and transferred to the shift register at the current transmission. when cpha = 1 for a slave, the first edge of the spsck indicates the beginning of the transmission. the same applies when ss is high for a slave. the miso pin is held in a high-impedance state, and the incoming spsck is ignored. in certain cases, it may also cause the modf flag to be set. see 15.6.2 mode fault error . a logic 1 on the ss pin does not in any way affect the state of the spi state machine. spwom ? spi wired-or mode bit this read/write bit disables the pullup devices on pins spsck, mos i, and miso so that those pins become open-drain outputs. 1 = wired-or spsck, mosi, and miso pins 0 = normal push-pull spsc k, mosi, and miso pins address: $0044 bit 7654321bit 0 read: sprie r spmstr cpol cpha spwom spe sptie write: reset:00101000 r= reserved figure 15-14. spi control register (spcr) serial peripheral in terface module (spi) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 212 freescale semiconductor spe ? spi enable bit this read/write bit enabl es the spi module. clearing spe causes a partial reset of the spi. see 15.8 resetting the spi . reset clears the spe bit. 1 = spi module enabled 0 = spi module disabled sptie? spi transmit interrupt enable bit 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 15.12.2 spi status and control register the spi status and control register (spscr) contains flags to si gnal 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 c ontains 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 tr ansfers 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 (dmas = 0), 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 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. address: $0045 bit 7654321bit 0 read: sprf errie ovrf modf spte modfen spr1 spr0 write:r rrr reset:00001000 r=reserved figure 15-15. spi status and control register (spscr) i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 213 ovrf ? overflow bit this clearable, read-only flag is set if software does not read the byte in the receive data register before the next full byte enters the shift register. in an ov erflow 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 t he 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 or an spte dma service 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. for an idle master of idle slave that has no data loaded into its transmit buffer, the spte will be set again within two bus cycles since t he transmit buffer empties into the shift register. this allows the user to queue up a 16-bit value to send. for an already ac tive slave, the load of the shift register cannot occur until the transmission is completed. this impl ies that a back-to-back write to the transmit data register is not possible. the spte i ndicates when the next write can occur. 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-p urpose i/o. when the spi is enabled as a slave, the ss pin is not available as a general-pu rpose i/o regardless of the value of modfen. see 15.11.4 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 15.6.2 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 15-4 . spr1 and spr0 have no effect in slave mode. reset clears spr1 and spr0. serial peripheral in terface module (spi) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 214 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 15.12.3 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 dat a 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 c ontain different values. see figure 15-2 . r7:r0/t7:t0 ? receive/ transmit data bits note do not use read-modify-write instructio ns on the spi data register since the register read is not the same as the register written. table 15-4. spi master baud rate selection spr1:spr0 baud rate divisor (bd) 00 2 01 8 10 32 11 128 address: $0046 bit 7654321bit 0 read:r7r6r5r4r3r2r1r0 write: t7 t6 t5 t4 t3 t2 t1 t0 reset: indeterminate after reset figure 15-16. spi data register (spdr) baud rate cgmout 2bd -------------------------- = mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 215 chapter 16 timer interface a (tima) 16.1 introduction this section describes the timer in terface module a (tima). the tima is a 4-channel timer that provides: timing reference with input capture output compare pulse-width modulator functions figure 16-2 is a block diagram of the tima. 16.2 features features of the tima include: four 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 modulator (pwm) signal generation programmable tima clock input: ? 7-frequency internal bus clock prescaler selection ? external tima clock input (4-mhz maximum frequency) free-running or modulo up-count operation toggle any channel pin on overflow tima counter stop and reset bits mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 216 freescale semiconductor timer interface a (tima) figure 16-1. block diagram highlighting tima block and pins clock generator module system integration module serial communications interface module serial peripheral interface module (2) timer interface module a low-voltage inhibit module power-on reset module computer operating properly module arithmetic/logic unit cpu registers m68hc08 cpu control and status registers ? 112 bytes user flash ? 32,256 bytes user ram ? 768 bytes monitor rom ? 240 bytes user flash vector space ? 46 bytes irq module power pta ddra ddrb ptb ddrc ptc ptd ddre pte ptf ddrf internal bus osc1 osc2 cgmxfc rst irq v ss v dd v ddad pta7?pta0 pte7/tch3a pte6/tch2a pte5/tch1a pte4/tch0a pte3/tclka pte2/tch1b (1) pte1/tch0b (1) pte0/tclkb (1) ptf5/txd ptf4/rxd ptf3/miso (1) ptf2/mosi (1) ptf1/ss (1 ) ptf0/spsck (1) timer interface module b pulse-width modulator module ptb7/atd7 ptb6/atd6 ptb5/atd5 ptb4/atd4 ptb3/atd3 ptb2/atd2 ptb1/atd1 ptb0/atd0 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1/atd9(1) ptc0/atd8 ptd6/is3 ptd5/is2 ptd4/is1 ptd3/fault4 ptd2/fault3 ptd1/fault2 ptd0/fault1 pwm6?pwm1 analog-to-digital converter module v ssad v dda v ssa (3) pwmgnd v refl (3) v refh notes: 1. these pins are not available in the 56-pin sdip package. 2. this module is not available in the 56-pin sdip package. 3. in the 56-pin sdip package, these pins are bonded together. single break module features mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 217 figure 16-2. tima block diagram pte3/tclka prescaler prescaler select tclk internal 16-bit comparator ps2 ps1 ps0 16-bit comparator 16-bit latch tch0h:tch0l ms0a els0b els0a pte4 tof toie inter- channel 0 tmodh:tmodl trst tstop tov0 ch0ie ch0f ch0max ms0b 16-bit counter bus clock pte4/tch0a pte5/tch1a pte6/tch2a pte7/tch3a logic rupt logic inter- rupt logic 16-bit comparator 16-bit latch tch1h:tch1l ms1a els1b els1a pte5 channel 1 tov1 ch1ie ch1f ch1max logic inter- rupt logic 16-bit comparator 16-bit latch tch2h:tch2l ms2a els2b els2a pte6 channel 2 tov2 ch2ie ch2f ch2max ms2b logic inter- rupt logic 16-bit comparator 16-bit latch tch3h:tch3l els3b els3a pte7 channel 3 tov3 ch3ie ch3f ch3max logic inter- rupt logic ms3a timer interface a (tima) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 218 freescale semiconductor addr. register name bit 7 6 5 4 3 2 1 bit 0 $000e tima status/control register (tasc) see page 226. read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst r reset: 0 0 1 0 0 0 0 0 $000f tima counter register high (tacnth) see page 227. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: r r r r r r r r reset: 0 0 0 0 0 0 0 0 $0010 tima counter register low (tacntl) see page 227. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: r r r r r r r r reset: 0 0 0 0 0 0 0 0 $0011 tima counter modulo register high (tamodh) see page 228. read: bit 15 14 13 12 11 10 9 bit 8 write: reset: 1 1 1 1 1 1 1 1 $0012 tima counter modulo register low (tamodl) see page 228. read: bit 7 6 5 4 3 2 1 bit 0 write: reset: 1 1 1 1 1 1 1 1 $0013 tima channel 0 status/control register (tasc0) see page 229. read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset: 0 0 0 0 0 0 0 0 $0014 tima channel 0 register high (tach0h) see page 232. read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $0015 tima channel 0 register low (tach0l) see page 232. read: bit 7 6 5 4 3 2 1 bit 0 write: reset: indeterminate after reset $0016 tima channel 1 status/control register (tasc1) see page 229. read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 r reset: 0 0 0 0 0 0 0 0 $0017 tima channel 1 register high (tach1h) see page 232. read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $0018 tima channel 1 register low (tach1l) see page 232. read: bit 7 6 5 4 3 2 1 bit 0 write: reset: indeterminate after reset $0019 tima channel 2 status/control register (tasc2) see page 229. read: ch2f ch2ie ms2b ms2a els2b els2a tov2 ch2max write: 0 reset: 0 0 0 0 0 0 0 0 r = reserved figure 16-3. tim i/o register summary functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 219 16.3 functional description figure 16-2 shows the tima structure. the central component of the tima is the 16-bit tima counter that can operate as a free-running counter or a modulo up-counter. the tima counter provides the timing reference for the input capture and output compare functions. the tima counter modulo registers, tamodh?tamodl, control the modulo value of the tima counter. software can read the tima counter value at any time without affecting the counting sequence. the four tima channels are programmable independently as input capture or output compare channels. 16.3.1 tima counter prescaler the tima clock source can be one of the seven pres caler outputs or the tima clock pin, pte3/tclka. the prescaler generates seven clock rates from the inte rnal bus clock. the prescaler select bits, ps[2:0], in the tima status and control register select the tima clock source. 16.3.2 input capture an input capture function has three basic parts: 1. edge select logic 2. input capture latch 3. 16-bit counter two 8-bit registers, which make up the 16-bit input capture register, are used to latch the value of the free-running counter after the corresponding input captur e edge detector senses a defined transition. the polarity of the active edge is programmable. the le vel transition which triggers the counter transfer is defined by the corresponding input edge bits (elsxb and elsxa in tasc0?tasc3 control registers with $001a tima channel 2 register high (tach2h) see page 232. read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $001b tima channel 2 register low (tach2l) see page 232. read: bit 7 6 5 4 3 2 1 bit 0 write: reset: indeterminate after reset $001c tima channel 3 status/control register (tasc3) see page 229. read: ch3f ch3ie 0 ms3a els3b els3a tov3 ch3max write: 0 r reset: 0 0 0 0 0 0 0 0 $001d tima channel 3 register high (tach3h) see page 232. read: bit 15 14 13 12 11 10 9 bit 8 write: reset: indeterminate after reset $001e tima channel 3 register low (tach3l) see page 232. read: bit 7 6 5 4 3 2 1 bit 0 write: reset: indeterminate after reset addr. register name bit 7 6 5 4 3 2 1 bit 0 r = reserved figure 16-3. tim i/o register summary (continued) timer interface a (tima) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 220 freescale semiconductor x referring to the active channel number). when an ac tive edge occurs on the pin of an input capture channel, the tima latches the contents of the ti ma counter into the tima channel registers, tachxh?tachxl. input captures can generate tima cpu interrupt requests. software can determine that an input capture event has occurred by enabling i nput capture interrupts or by polling the status flag bit. the free-running counter contents are transferred to the tima channel status and control register (tachxh?tachxl, see 16.7.5 tima channel registers ) on each proper signal transition regardless of whether the tima channel flag (ch0f?ch3f in tasc0?tasc 3 registers) is set or clear. when the status flag is set, a cpu interrupt is generated if enabled. the value of the count latched or ?captured? is the time of the event. because this value is stored in the input capture register two bus cycles after the actual event occurs, user software can respond to this event at a later time and determine the actual time of the event. however, this must be done prior to another input capture on the same pin; otherwise, the previous time value will be lost. by recording the times for successive edges on an incoming signal, software can determine the period and/or pulse width of the signal. to measure a perio d, two successive edges of the same polarity are captured. to measure a pulse width, two alternate polarity edges are captured. software should track the overflows at the 16-bit module counter to extend its range. another use for the input capture function is to establis h a time reference. in this case, an input capture function is used in conjuncti on with an output compare function. for example, to activate an output signal a specified number of clock cycles after detecting an input event (edge), use the input capture function to record the time at which the edge occurred. a number corresponding to the desired delay is added to this captured value and stored to an output compare register (see 16.7.5 tima channel registers ). because both input captures and output compares are referenced to the same 16-bit modulo counter, the delay can be cont rolled to the resolution of the counter independent of software latencies. reset does not affect the contents of the input capture channel registers. 16.3.3 output compare with the output compare function, the tima can gener ate 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 tima can set, clear, or toggle the channel pin. output compares can generate tima cpu interrupt requests. 16.3.3.1 unbuffered output compare any output compare channel can generate unbuffer ed output compare pulses as described in 16.3.3 output compare . the pulses are unbuffered because changing t he output compare value requires writing the new value over the old value currently in the tima channel registers. an unsynchronized write to the tima channel regist ers 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 tima over flow interrupt routine to write a new, smaller output compare value may cause the compare to be missed. the tima may pass the new value before it is written. functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 221 use this method 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 rout ine has until the end of the counter overflow period to write the new value. when changing to a larger output compare value, enable tima overflow interrupts and write the new value in the tima overflow interrupt routine. the tima overflow interrupt occurs at the end of the current counter overflow period. writing a larg er 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. 16.3.3.2 buffered output compare channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the pte4/tch0a pin. the tima channel registers of the linked pair alternately control the output. setting the ms0b bit in tima channel 0 status and control register (tasc0) links channel 0 and channel 1. the output compare value in the tima channel 0 registers initially controls the output on the pte4/tch0a pin. writing to the tima channel 1 registers enables the tima channel 1 registers to synchronously control the output after the tima overflows. at each subsequent overflow, the tima channel registers (0 or 1) that control the output are the ones written to last. tasc0 controls and monitors the buffered output compare function, and tima channel 1 status and control register (tasc1) is unused. while the ms0b bit is set, the channel 1 pin, pte5 /tch1a, is available as a general-purpose i/o pin. channels 2 and 3 can be linked to form a buffered output compare channel whose output appears on the pte6/tch2a pin. the tima channel registers of the linked pair alternately control the output. setting the ms2b bit in tima channel 2 status and control register (tasc2) links channel 2 and channel 3. the output compare value in the tima channel 2 registers initially controls the output on the pte6/tch2a pin. writing to the tima channel 3 registers enables the tima channel 3 registers to synchronously control the output after the tima overflows. at each subsequent overflow, the tima channel registers (2 or 3) that control the output are the ones written to last. tasc2 controls and monitors the buffered output compare function, and tima channel 3 status and control register (tasc3) is unused. while the ms2b bit is set, the channel 3 pin, pte7 /tch3a, 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. 16.3.4 pulse-widt h modulation (pwm) by using the toggle-on-overflow feature with an output compare channel, the tima can generate a pwm signal. the value in the tima counter modulo regi sters determines the period of the pwm signal. the channel pin toggles when the counter reaches the value in the tima counter modulo registers. the time between overflows is the period of the pwm signal. as figure 16-4 shows, the output compare value in the tima channel registers determines the pulse width of the pwm signal. the time between overflow and out put compare is the pulse width. program the tima timer interface a (tima) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 222 freescale semiconductor to clear the channel pin on output compare if the polarity of the pwm pulse is 1 (elsxa = 0). program the tima to set the pin if the polarity of the pwm pulse is 0 (elsxa = 1). the value in the tima 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 $00ff (255) to the tima counter modulo registers produces a pwm period of 256 times the internal bus clock period if the prescaler select value is $000 (see 16.7.1 tima status and control register ). the value in the tima channel registers determines the pulse width of the pwm output. the pulse width of an 8-bit pwm signal is variable in 256 incremen ts. writing $0080 (128) to the tima channel registers produces a duty cycle of 128/256 or 50 percent. figure 16-4. pwm period and pulse width 16.3.4.1 unbuffered pwm signal generation any output compare channel can generate unbuffered pwm pulses as described in 16.3.4 pulse-width modulation (pwm) . the pulses are unbuffered because changing the pulse width requires writing the new pulse width value over the value currently in the tima channel registers. an unsynchronized write to the tima channel regi sters 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 tima overflow interrupt routine to write a new, smaller pulse width value may cause the compare to be missed. the tima may pass the new value before it is written to the tima channel registers. use this method to synchronize unbuffered chan ges 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 ti ma overflow interrupts and write the new value in the tima overflow interrupt routine. the tima ov erflow 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 percent tchx period pulse width overflow overflow overflow output compare output compare output compare tchx polarity = 1 (elsxa = 0) polarity = 0 (elsxa = 1) functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 223 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. 16.3.4.2 buffered pwm signal generation channels 0 and 1 can be linked to form a buffered pwm channel whose output appears on the pte4/tch0a pin. the tima channel registers of the lin ked pair alternately control the pulse width of the output. setting the ms0b bit in tima channel 0 status and control register (tasc0) links channel 0 and channel 1. the tima channel 0 registers initially cont rol the pulse width on the pte4/tch0a pin. writing to the tima channel 1 registers enables the tima cha nnel 1 registers to synchronously control the pulse width at the beginning of the next pwm period. at each subsequent overflow, the tima channel registers (0 or 1) that control the pulse width are the ones wri tten to last. tasc0 controls and monitors the buffered pwm function, and tima channel 1 status and control register (tasc1) is unused. while the ms0b bit is set, the channel 1 pin, pte5/tch1a, is available as a general-purpose i/o pin. channels 2 and 3 can be linked to form a buffered pwm channel whose output appears on the pte6/tch2a pin. the tima channel registers of the lin ked pair alternately control the pulse width of the output. setting the ms2b bit in tima channel 2 status and control register (tasc2) links channel 2 and channel 3. the tima channel 2 registers initially cont rol the pulse width on the pte6/tch2a pin. writing to the tima channel 3 registers enables the tima cha nnel 3 registers to synchronously control the pulse width at the beginning of the next pwm period. at each subsequent overflow, the tima channel registers (2 or 3) that control the pulse width are written to last. tasc2 controls and monitors the buffered pwm function, and tima channel 3 status and control regi ster (tasc3) is unused. while the ms2b bit is set, the channel 3 pin, pte7/tch3a, 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 regist ers. 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. 16.3.4.3 pwm initialization to ensure correct operation when generating unbuffered or buffered pwm signals, use this initialization procedure: 1. in the tima status and control register (tasc): a. stop the tima counter by setting the tima stop bit, tstop. b. reset the tima counter and prescaler by setting the tima reset bit, trst. 2. in the tima counter modulo registers (tamodh?tamodl), write the value for the required pwm period. 3. in the tima channel x registers (tachxh?tachxl), write the value for the required pulse width. timer interface a (tima) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 224 freescale semiconductor 4. in tima 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 se lect bits, msxb?msxa. (see table 16-2 .) b. write 1 to the toggle-on-overflow bit, tovx. c. write 1:0 (polarity 1 ? to clear output on compare) or 1:1 (polarity 0 ? 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 16-2 .) note in pwm signal generation, do not program the pwm channel to toggle on output compare. toggling on output compare prevents reliable 0 percent 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 tima status control register (tasc), clear the tima stop bit, tstop. setting ms0b links channels 0 and 1 and configures them for buffered pwm operation. the tima channel 0 registers (tach0h?tach0l) initially control the buffered pwm output. tima status control register 0 (tasc0) controls and monitors the pwm si gnal from the linked channels. ms0b takes priority over ms0a. setting ms2b links channels 2 and 3 and configures them for buffered pwm operation. the tima channel 2 registers (tach2h?tach2l) initially control the buffered pwm output. tima status control register 2 (tasc2) controls and monitors the pwm si gnal from the linked channels. ms2b takes priority over ms2a. clearing the toggle-on-overflow bit, tovx, inhibits output toggles on tima overflows. subsequent output compares try to force the output to a state it is alr eady in and have no effect. the result is a 0 percent duty cycle output. setting the channel x maximum duty cycle bit (c hxmax) and setting the tovx bit generates a 100 percent duty cycle output. (see 16.7.4 tima channel status and control registers .) 16.4 interrupts these tima sources can generate interrupt requests: tima overflow flag (tof) ? the timer overflow flag (tof) bit is set when the tima counter reaches the modulo value programm ed in the tima counter modulo registers. the tima overflow interrupt enable bit, toie, enables tima overflow interrupt requests. tof and toie are in the tima status and control registers. tima channel flags (ch3f?ch0f) ? the chxf bit is set when an input capture or output compare occurs on channel x. channel x tima cpu inte rrupt requests are controlled by the channel x interrupt enable bit, chxie. 16.5 wait mode the wait instruction puts the mcu in low power-consumption standby mode. i/o signals mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 225 the tima remains active after the execution of a wait instruction. in wait mode, the tima registers are not accessible by the cpu. any enabled cpu interrupt request from the tima can bring the mcu out of wait mode. if tima functions are not required during wait mode , reduce power consumption by stopping the tima before executing the wait instruction. 16.6 i/o signals port e shares five of its pins with the tima: pte3/tclka is an external clock input to the tima prescaler. the four tima channel i/o pins are pte4/tch0a, pte5/tch1a, pte6/tch2a, and pte7/tch3a. 16.6.1 tima clock pin (pte3/tclka) pte3/tclka is an external clock input that can be the clock source for the tima counter instead of the prescaled internal bus clock. select the pte3/tclka input by writing logic 1s to the three prescaler select bits, ps[2:0]. see 16.7.1 tima status and control register . the maximum tclk frequency is the least: 4 mhz or bus frequency 2. pte3/tclka is available as a general-purpose i/o pi n when not used as the tima clock input. when the pte3/tclka pin is the tima clock input, it is an input regardless of the state of the ddre3 bit in data direction register e. 16.6.2 tima chan nel i/o pins (pte4/ tch0a?pte7/tch3a) each channel i/o pin is programmable independently as an input capture pin or an output compare pin. pte2/tch0 and pte4/tch2 can be configured as buffered output compare or buffered pwm pins. 16.7 i/o registers these input/output (i/o) registers control and monitor tima operation: tima status and control register (tasc) tima control registers (tacnth?tacntl) tima counter modulo registers (tamodh?tamodl) tima channel status and control registers (tasc0, tasc1, tasc2, and tasc3) tima channel registers (tach0h?tach0l, tach1h?tach1l, tach2h?tach2l, and tach3h?tach3l) 16.7.1 tima status and control register the tima status and control register: enables tima overflow interrupts flags tima overflows stops the tima counter resets the tima counter prescales the tima counter clock timer interface a (tima) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 226 freescale semiconductor tof ? tima overflow flag this read/write flag is set when the tima counter reaches the modulo value programmed in the tima counter modulo registers. clear tof by reading t he tima status and control register when tof is set and then writing a logic 0 to tof. if another tima overflow occurs befor e 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. re set clears the tof bit. writing a logic 1 to tof has no effect. 1 = tima counter has reached modulo value. 0 = tima counter has not reached modulo value. toie ? tima overflow interrupt enable bit this read/write bit enables tima overflow interrupts when the tof bit becomes set. reset clears the toie bit. 1 = tima overflow interrupts enabled 0 = tima overflow interrupts disabled tstop ? tima stop bit this read/write bit stops the tima counter. countin g resumes when tstop is cleared. reset sets the tstop bit, stopping the tima counter until software clears the tstop bit. 1 = tima counter stopped 0 = tima counter active note do not set the tstop bit before entering wait mode if the tima is required to exit wait mode. also when the tstop bit is set and the timer is configured for input capture operation, i nput captures are inhibited until the tstop bit is cleared. trst ? tima reset bit setting this write-only bit resets the tima counter and the tima prescaler. setting trst has no effect on any other registers. counting resumes from $0000. trst is cleared automatically after the tima counter is reset and always reads as logic 0. reset clears the trst bit. 1 = prescaler and tima counter cleared 0 = no effect note setting the tstop and trst bits simultaneously stops the tima counter at a value of $0000. address: $000e bit 7654321bit 0 read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst r reset:00100000 r= reserved figure 16-5. tima status and control register (tasc) i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 227 ps[2:0] ? prescaler select bits these read/write bits select either the pte3/tclka pin or one of the seven prescaler outputs as the input to the tima counter as table 16-1 shows. reset clears the ps[2:0] bits. 16.7.2 tima c ounter registers the two read-only tima counter registers contain the high and low bytes of the value in the tima counter. reading the high byte (tacnth) latches the contents of the low byte (tacntl) into a buffer. subsequent reads of tacnth do not affect the latched tacntl value until tacntl is read. reset clears the tima counter registers. setting the tima reset bit (trst) also clears the tima counter registers. note if tacnth is read during a break interrupt, be sure to unlatch tacntl by reading tacntl before exiting the break interrupt. otherwise, tacntl retains the value latched during the break. table 16-1. prescaler selection ps[2:0] tima clock source 000 internal bus clock 1 001 internal bus clock 2 010 internal bus clock 4 011 internal bus clock 8 100 internal bus clock 16 101 internal bus clock 32 110 internal bus clock 64 111 pte3/tclka register name and address: tacnth ? $000f bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write:rrrrrrrr reset:00000000 register name and address: tacntl ? $0010 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write:rrrrrrrr reset:00000000 r= reserved figure 16-6. tima counter registers (tacnth and tacntl) timer interface a (tima) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 228 freescale semiconductor 16.7.3 tima counter modulo registers the read/write tima modulo registers contain the modulo value for the tima counter. when the tima counter reaches the modulo value, the overflow flag (tof) becomes set, and the tima counter resumes counting from $0000 at the next timer clock. writing to the high byte (tamodh) inhibits the tof bit and overflow interrupts until the low byte (tamodl) is wr itten. reset sets the tima counter modulo registers. note reset the tima counter before writing to the tima counter modulo registers. 16.7.4 tima channel stat us and control registers each of the tima 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 tima overflow selects 0 percent and 100 percent pwm duty cycle selects buffered or unbuffered output compare/pwm operation register name and address: tamodh ? $0011 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset:11111111 register name and address: tamodl ? $0012 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset:11111111 figure 16-7. tima counter modulo registers (tamodh and tamodl) i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 229 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 com pare channel, chxf is set when the value in the tima counter registers matches the value in the tima channel x registers. when chxie = 1, clear chxf by reading tima channel x status and control register with chxf set, and then writing a 0 to chxf. if another interrupt request occurs before the clearing sequence is complete, then writing 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 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 tima cpu interrupts on channel x. reset clears the chxie bit. 1 = channel x cpu interrupt requests enabled 0 = channel x cpu interrupt requests disabled register name and address: tasc0 ? $0013 bit 7654321bit 0 read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 register name and address: tasc1 ? $0016 bit 7654321bit 0 read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 r reset:00000000 register name and address: tasc2 ? $0019 bit 7654321bit 0 read: ch2f ch2ie ms2b ms2a els2b els2a tov2 ch2max write: 0 reset:00000000 register name and address: tasc3 ? $001c bit 7654321bit 0 read: ch3f ch3ie 0 ms3a els3b els3a tov3 ch3max write: 0 r reset:00000000 r= reserved figure 16-8. tima channel status and control registers (tasc0?tasc3) timer interface a (tima) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 230 freescale semiconductor msxb ? mode select bit b this read/write bit selects buffered output compare/pwm operation. msxb exists only in the tima channel 0 and tima channel 2 status and control registers. setting ms0b disables the channel 1 status and control register and reverts tch1a pin to general-purpose i/o. setting ms2b disables the channel 3 status and control register and reverts tch3a pin 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:a 00, this read/write bit selects either input capture operation or unbuffered output compare/pwm operation. see table 16-2 . 1 = unbuffered output compare/pwm operation 0 = input capture operation when elsxb:a = 00, this read/write bit selects the initial output level of the tchxa pin once pwm, input capture, or output compare operation is enabled. see table 16-2 . 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 tima status and control register (tasc). 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 port e, and pin ptex/tchxa is available as a general-purpose i/o pin. however, channel x is at a state determined by these bits and becomes transparent to the respective pin when pwm, input capture, or output compare mode is enabled. table 16-2 shows how elsxb and elsxa work. re set clears the elsxb and elsxa bits. note before enabling a tima channel register for input capture operation, make sure that the ptex/tachx pin is stable for at least two bus clocks. i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 231 tovx ? toggle-on-overflow bit when channel x is an output compare channel, this read/write bit controls the behavior of the channel x output when the tima 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 tima counter overflow. 0 = channel x pin does not toggle on tima counter overflow. note when tovx is set, a tima 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 is 1 and clear output on compare is selected, setting the chxmax bit forces the duty cycle of buffered and unbuffered pwm signals to 100 percent. as figure 16-9 shows, chxmax bit takes effect in the cycle after it is set or cleared. the output stays at 100 percent duty cycle level until the cycle after chxmax is cleared. figure 16-9. chxmax latency table 16-2. mode, edge, and level selection msxb:msxa elsxb:elsxa mode configuration x0 00 output preset pin under port control; initialize timer output level high x1 00 pin under port control; initialize timer 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 00 output compare or pwm software compare only 01 01 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 output overflow ptex/tchx period chxmax overflow overflow overflow overflow compare output compare output compare output compare tovx timer interface a (tima) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 232 freescale semiconductor 16.7.5 tima c hannel registers these read/write registers contain the captured tima counter value of the input capture function or the output compare value of the output compare function. the state of the tima channel registers after reset is unknown. in input capture mode (msxb:msxa = 0:0), reading the high byte of the tima channel x registers (tachxh) inhibits input captures un til the low byte (tachxl) is read. in output compare mode (msxb:msxa 0:0), writing to the high byte of the tima channel x registers (tachxh) inhibits output compares unt il the low byte (tachxl) is written. register name and address: tach0h ? $0014 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address: tach0l ? $0015 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset register name and address: tach1h ? $0017 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address: tach1l ? $0018 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset register name and address: tach2h ? $001a bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset figure 16-10. tima channel registers (tach0h/l?tach3h/l) i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 233 register name and address: tach2l ? $001b bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset register name and address: tach3h ? $001d bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address: tach3l ? $001e bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset figure 16-10. tima channel registers (tach0h/l?tach3h/l) (continued) timer interface a (tima) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 234 freescale semiconductor mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 235 chapter 17 timer interface b (timb) 17.1 introduction this section describes the timer interface module b (t imb). the timb is a 2-channel timer that provides: timing reference with input capture output compare pulse-width modulation functions figure 17-2 is a block diagram of the timb. note the timb module is not available in the 56-pin shrink dual in-line package (sdip). 17.2 features features of the timb 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 timb clock input: ? 7-frequency internal bus clock prescaler selection ? external timb clock input (4-mhz maximum frequency) free-running or modulo up-count operation toggle any channel pin on overflow timb counter stop and reset bits 17.3 functional description figure 17-2 shows the timb structure. the central component of the timb is the 16-bit timb counter that can operate as a free-running counter or a modulo up-counter. the timb counter provides the timing reference for the input capture and output compare functions. the timb counter modulo registers, tbmodh?tbmodl, control the modulo value of the timb counter. software can read the timb counter value at any time without affecting the counting sequence. the two timb channels are programmable independently as input capture or output compare channels. note the timb module is not avai lable in the 56-pin sdip. mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 236 freescale semiconductor timer interface b (timb) figure 17-1. block diagram highlighting timb block and pins clock generator module system integration module serial communications interface module serial peripheral interface module (2) timer interface module a low-voltage inhibit module power-on reset module computer operating properly module arithmetic/logic unit cpu registers m68hc08 cpu control and status registers ? 112 bytes user flash ? 32,256 bytes user ram ? 768 bytes monitor rom ? 240 bytes user flash vector space ? 46 bytes irq module power pta ddra ddrb ptb ddrc ptc ptd ddre pte ptf ddrf internal bus osc1 osc2 cgmxfc rst irq v ss v dd v ddad pta7?pta0 pte7/tch3a pte6/tch2a pte5/tch1a pte4/tch0a pte3/tclka pte2/tch1b (1) pte1/tch0b (1) pte0/tclkb (1) ptf5/txd ptf4/rxd ptf3/miso (1) ptf2/mosi (1) ptf1/ss (1) ptf0/spsck (1 ) timer interface module b pulse-width modulator module ptb7/atd7 ptb6/atd6 ptb5/atd5 ptb4/atd4 ptb3/atd3 ptb2/atd2 ptb1/atd1 ptb0/atd0 ptc6 ptc5 ptc4 ptc3 ptc2 ptc1/atd9(1) ptc0/atd8 ptd6/is3 ptd5/is2 ptd4/is1 ptd3/fault4 ptd2/fault3 ptd1/fault2 ptd0/fault1 pwm6?pwm1 analog-to-digital converter module v ssad v dda v ssa (3) pwmgnd v refl (3) v refh notes: 1. these pins are not available in the 56-pin sdip package. 2. this module is not available in the 56-pin sdip package. 3. in the 56-pin sdip package, these pins are bonded together. single break module functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 237 figure 17-2. timb block diagram addr. register name bit 7 6 5 4 3 2 1 bit 0 $0051 timb status/control register (tbsc) see page 244. read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst r reset: 0 0 1 0 0 0 0 0 $0052 timb counter register high (tbcnth) see page 246. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: r r r r r r r r reset: 0 0 0 0 0 0 0 0 $0053 timb counter register low (tbcntl) see page 246. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: r r r r r r r r reset: 0 0 0 0 0 0 0 0 $0054 timb counter modulo register high (tbmodh) see page 246. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: 1 1 1 1 1 1 1 1 $0055 timb counter modulo register low (tbmodl) see page 246. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: 1 1 1 1 1 1 1 1 r= reserved figure 17-3. timb i/o register summary prescaler prescaler select tclk internal 16-bit comparator ps2 ps1 ps0 16-bit comparator 16-bit latch tch0h:tch0l ms0a els0b els0a pte1 tof toie inter- channel 0 tmodh:tmodl trst tstop tov0 ch0ie ch0f ch0max ms0b 16-bit counter bus clock pte0/tclkb pte1/tch0b pte2/tch1b logic rupt logic inter- rupt logic 16-bit comparator 16-bit latch tch1h:tch1l ms1a els1b els1a pte2 channel 1 tov1 ch1ie ch1f ch1max logic inter- rupt logic timer interface b (timb) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 238 freescale semiconductor 17.3.1 timb counter prescaler the timb clock source can be one of the seven prescaler outputs or the timb clock pin, pte0/tclkb . the prescaler generates seven clock rates from the inte rnal bus clock. the prescaler select bits, ps[2:0], in the timb status and control register select the timb clock source. 17.3.2 input capture an input capture function has three basic parts: 1. edge select logic 2. input capture latch 3. 16-bit counter two 8-bit registers, which make up the 16-bit input capture register, are used to latch the value of the free-running counter after the corresponding input captur e edge detector senses a defined transition. the polarity of the active edge is programmable. the le vel transition which triggers the counter transfer is defined by the corresponding input edge bits (elsxb and elsxa in tbsc0?tbsc1 control registers with x referring to the active channel number). when an ac tive edge occurs on the pin of an input capture channel, the timb latches the contents of the ti mb counter into the timb channel registers, tchxh?tchxl. input captures can generate timb cpu interrupt requests. software can determine that an input capture event has occurred by enabling input capture interrupts or by polling the status flag bit. the free-running counter contents are transferred to the timb channel status and control register (tbchxh?tbchxl, see 17.7.5 timb channel registers ) on each proper signal transition regardless of $0056 timb channel 0 status/control register (tbsc0) see page 247. read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset: 0 0 0 0 0 0 0 0 $0057 timb channel 0 register high (tbch0h) see page 250. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset $0058 timb channel 0 register low (tbch0l) see page 250. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset $0059 timb channel 1 status/control register (tbsc1) see page 247. read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 r reset: 0 0 0 0 0 0 0 0 $005a timb channel 1 register high (tbch1h) see page 250. read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset $005b timb channel 1 register low (tbch1l) see page 250. read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset addr. register name bit 7 6 5 4 3 2 1 bit 0 r= reserved figure 17-3. timb i/o register summary (continued) functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 239 whether the timb channel flag (ch0f?ch1f in tbsc0?tbsc 1 registers) is set or clear. when the status flag is set, a cpu interrupt is generated if enabled. the value of the count latched or ?captured? is the time of the event. because this value is stored in the input capture register two bus cycles after the actual event occurs, user software can respond to this event at a later time and determine the actual time of the event. however, this must be done prior to another input capture on the same pin; otherwise, the previous time value will be lost. by recording the times for successive edges on an incoming signal, software can determine the period and/or pulse width of the signal. to measure a perio d, two successive edges of the same polarity are captured. to measure a pulse width, two alternate polarity edges are captured. software should track the overflows at the 16-bit module counter to extend its range. another use for the input capture function is to establis h a time reference. in this case, an input capture function is used in conjuncti on with an output compare function. for example, to activate an output signal a specified number of clock cycles after detecting an input event (edge), use the input capture function to record the time at which the edge occurred. a number corresponding to the desired delay is added to this captured value and stored to an output compare register (see 17.7.5 timb channel registers ). because both input captures and output compares are refer enced to the same 16-bit modulo counter, the delay can be controlled to the resolution of the counter independent of software latencies. reset does not affect the contents of the input capture channel register (tbchxh?tbchxl). 17.3.3 output compare with the output compare function, the timb can gener ate 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 timb can set, clear, or toggle the channel pin. output compares can generate timb cpu interrupt requests. 17.3.3.1 unbuffered output compare any output compare channel can generate unbuffer ed output compare pulses as described in 17.3.3 output compare . the pulses are unbuffered because changing t he output compare value requires writing the new value over the old value currently in the timb channel registers. an unsynchronized write to the timb channel regist ers 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 timb over flow interrupt routine to write a new, smaller output compare value may cause the compare to be missed. the timb may pass the new value before it is written. use this method 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 rout ine has until the end of the counter overflow period to write the new value. when changing to a larger output compare value, enable timb overflow interrupts and write the new value in the timb overflow interrupt routine. the timb overflow interrupt occurs at the end of the current counter overflow period. writing a larg er 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. timer interface b (timb) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 240 freescale semiconductor 17.3.3.2 buffered output compare channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the pte1/tch0b pin. the timb channel registers of the linked pair alternately control the output. setting the ms0b bit in timb channel 0 status and co ntrol register (tbsc0) links channel 0 and channel 1. the output compare value in the timb channel 0 registers initially controls the output on the pte1/tch0b pin. writing to the timb channel 1 registers enables the timb channel 1 registers to synchronously control the output after the timb overflows. at each subsequent overflow, the timb 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 timb channel 1 status and control register (tbsc1) is unused. while the ms0b bit is set, the channel 1 pin, pte2 /tch1b, 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. 17.3.4 pulse-widt h modulation (pwm) by using the toggle-on-overflow feature with an output compare channel, the timb can generate a pwm signal. the value in the timb counter modulo regi sters determines the period of the pwm signal. the channel pin toggles when the counter reaches the value in the timb counter modulo registers. the time between overflows is the period of the pwm signal. as figure 17-4 shows, the output compare value in the timb channel registers determines the pulse width of the pwm signal. the time between overflow and out put compare is the pulse width. program the timb to clear the channel pin on output compare if the polarity of the pwm pulse is 1 (elsxa = 0). program the timb to set the pin if the polarity of the pwm pulse is 0 (elsxa = 1). figure 17-4. pwm period and pulse width the value in the timb 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 $00ff (255) to the timb counter modulo registers produces a pwm period of 256 times the internal bus clock period if the prescaler select value is $000 (see 17.7.1 timb status and control register ). tchx period pulse width overflow overflow overflow output compare output compare output compare tchx polarity = 1 (elsxa = 0) polarity = 0 (elsxa = 1) functional description mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 241 the value in the timb channel registers determines the pulse width of the pwm output. the pulse width of an 8-bit pwm signal is variable in 256 incremen ts. writing $0080 (128) to the timb channel registers produces a duty cycle of 128/256 or 50 percent. 17.3.4.1 unbuffered pwm signal generation any output compare channel can generate unbuffered pwm pulses as described in 17.3.4 pulse-width modulation (pwm) . the pulses are unbuffered because changing the pulse width requires writing the new pulse width value over the value currently in the timb channel registers. an unsynchronized write to the timb channel regi sters 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 timb overflow interrupt routine to write a new, smaller pulse width value may cause the compare to be missed. the timb may pass the new value before it is written to the timb channel registers. use this method to synchronize unbuffered chan ges 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 ti mb overflow interrupts and write the new value in the timb overflow interrupt routine. the timb ov erflow 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 percent 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. 17.3.4.2 buffered pwm signal generation channels 0 and 1 can be linked to form a buffered pwm channel whose output appears on the pte1/tch0b pin. the timb channel registers of the lin ked pair alternately control the pulse width of the output. setting the ms0b bit in timb channel 0 status and co ntrol register (tbsc0) links channel 0 and channel 1. the timb channel 0 registers initially control the pulse width on the pte1/tch0b pin. writing to the timb channel 1 registers enables the timb channel 1 r egisters to synchronously control the pulse width at the beginning of the next pwm period. at each subsequent overflow, the timb channel registers (0 or 1) that control the pulse width are the ones wri tten to last. tbsc0 controls and monitors the buffered pwm function, and timb channel 1 status and control register (tbsc1) is unused. while the ms0b bit is set, the channel 1 pin, pte2/tch1b, 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 regist ers. user software should track the timer interface b (timb) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 242 freescale semiconductor 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. 17.3.4.3 pwm initialization to ensure correct operation when generating unbuffered or buffered pwm signals, use this initialization procedure: 1. in the timb status and control register (tbsc): a. stop the timb counter by setting the timb stop bit, tstop. b. reset the timb counter and prescaler by setting the timb reset bit, trst. 2. in the timb counter modulo registers (tbmodh?tbmodl), write the value for the required pwm period. 3. in the timb channel x registers (tbchxh?tbchxl), write the value for the required pulse width. 4. in timb channel x status and control register (tbscx): a. write 0:1 (for unbuffered output compare or pwm signals) or 1:0 (for buffered output compare or pwm signals) to the mode se lect bits, msxb?msxa. (see table 17-2 .) b. write 1 to the toggle-on-overflow bit, tovx. c. write 1:0 (polarity 1 ? to clear output on compare) or 1:1 (polarity 0 ? 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 17-2 .) note in pwm signal generation, do not program the pwm channel to toggle on output compare. toggling on output compare prevents reliable 0 percent 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 timb status control register (tbsc), clear the timb stop bit, tstop. setting ms0b links channels 0 and 1 and configures t hem for buffered pwm operation. the timb channel 0 registers (tbch0h?tbch0l) initially control the bu ffered pwm output. timb status control register 0 (tbsc0) controls and monitors the pwm signal from the linked channels. ms0b takes priority over ms0a. clearing the toggle-on-overflow bit, tovx, inhibits output toggles on timb 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 percent duty cycle output. setting the channel x maximum duty cycle bit (c hxmax) and setting the tovx bit generates a 100 percent duty cycle output. (see 17.7.4 timb channel status and control registers .) interrupts mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 243 17.4 interrupts these timb sources can generate interrupt requests: timb overflow flag (tof) ? the timer overflow flag (tof) bit is set when the timb counter reaches the modulo value programm ed in the timb counter modulo registers. the timb overflow interrupt enable bit, toie, enables timb overflow interrupt requests. tof and toie are in the timb status and control registers. timb channel flags (ch1f?ch0f) ? the chxf bit is set when an input capture or output compare occurs on channel x. channel x timb cpu inte rrupt requests are controlled by the channel x interrupt enable bit, chxie. 17.5 wait mode the wait instruction puts the mcu in low-power standby mode. the timb remains active after the execution of a wait instruction. in wait mode, the timb registers are not accessible by the cpu. any enabled cpu interrupt request from the timb can bring the mcu out of wait mode. if timb functions are not required during wait mode , reduce power consumption by stopping the timb before executing the wait instruction. 17.6 i/o signals port e shares three of its pins with the timb: pte0/tclkb is an external clock input to the timb prescaler. the two timb channel i/o pins are pte1/tch0b and pte2/tch1b. 17.6.1 timb clock pin (pte0/tclkb) pte0/tclkb is an external clock input that can be the clock source for the timb counter instead of the prescaled internal bus clock. select the pte0/tclkb input by writing 1s to the three prescaler select bits, ps[2:0]. see 17.7.1 timb status and control register . the maximum tclk frequency is the least: 4 mhz or bus frequency 2. pte0/tclkb is available as a general-purpose i/o pi n or adc channel when not used as the timb clock input. when the pte0/tclkb pin is the timb clock input, it is an input regardless of the state of the ddre0 bit in data direction register e. 17.6.2 timb chan nel i/o pins (pte1/ tch0b?pte2/tch1b) each channel i/o pin is programmable independently as an input capture pin or an output compare pin. pte1/tch0b and pte2/tch1b can be configured as buffered output compare or buffered pwm pins. timer interface b (timb) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 244 freescale semiconductor 17.7 i/o registers these input/output (i/o) registers control and monitor timb operation: timb status and control register (tbsc) timb control registers (tbcnth?tbcntl) timb counter modulo registers (tbmodh?tbmodl) timb channel status and control registers (tbsc0 and tbsc1) timb channel registers (tbch0h?tbch0l and tbch1h?tbch1l) 17.7.1 timb status and control register the timb status and control register: enables timb overflow interrupts flags timb overflows stops the timb counter resets the timb counter prescales the timb counter clock tof ? timb overflow flag this read/write flag is set when the timb counter reaches the modulo value programmed in the timb counter modulo registers. clear tof by reading t he timb status and control register when tof is set and then writing a logic 0 to tof. if another timb overflow occurs befor e 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 th e tof bit. writing a logic 1 to tof has no effect. 1 = timb counter has reached modulo value. 0 = timb counter has not reached modulo value. toie ? timb overflow interrupt enable bit this read/write bit enables timb overflow interrupts when the tof bit becomes set. reset clears the toie bit. 1 = timb overflow interrupts enabled 0 = timb overflow interrupts disabled address: $0051 bit 7654321bit 0 read: tof toie tstop 00 ps2 ps1 ps0 write: 0 trst r reset:00100000 r= reserved figure 17-5. timb status and control register (tbsc) i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 245 tstop ? timb stop bit this read/write bit stops the timb counter. countin g resumes when tstop is cleared. reset sets the tstop bit, stopping the timb counter until software clears the tstop bit. 1 = timb counter stopped 0 = timb counter active note do not set the tstop bit before entering wait mode if the timb is required to exit wait mode. also, when the tstop bit is set and the timer is configured for input capture operation, input captures are inhibited until tstop is cleared. trst ? timb reset bit setting this write-only bit resets the timb counter and the timb prescaler. setting trst has no effect on any other registers. counting resumes from $0000. trst is cleared automatically after the timb counter is reset and always reads as logic 0. reset clears the trst bit. 1 = prescaler and timb counter cleared 0 = no effect note setting the tstop and trst bits simultaneously stops the timb counter at a value of $0000. ps[2:0] ? prescaler select bits these read/write bits select either the pte0/tclkb pin or one of the seven prescaler outputs as the input to the timb counter as table 17-1 shows. reset clears the ps[2:0] bits. table 17-1. prescaler selection ps[2:0] timb clock source 000 internal bus clock 1 001 internal bus clock 2 010 internal bus clock 4 011 internal bus clock 8 100 internal bus clock 16 101 internal bus clock 32 110 internal bus clock 64 111 pte0/tclkb timer interface b (timb) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 246 freescale semiconductor 17.7.2 timb c ounter registers the two read-only timb counter registers contain the high and low bytes of the value in the timb counter. reading the high byte (tbcnth) latches the contents of the low byte (tbcntl) into a buffer. subsequent reads of tbcnth do not affect the latched tbcntl value until tbcntl is read. reset clears the timb counter registers. setting the timb reset bit (trst) also clears the timb counter registers. note if tbcnth is read during a break interrupt, be sure to unlatch tbcntl by reading tbcntl before exiting the break interrupt. otherwise, tbcntl retains the value latched during the break. 17.7.3 timb counter modulo registers the read/write timb modulo registers contain the modulo value for the timb counter. when the timb counter reaches the modulo value, the overflow flag (tof) becomes set, and the timb counter resumes counting from $0000 at the next timer clock. writing to the high byte (tbmodh) inhibits the tof bit and overflow interrupts until the low byte (tbmodl) is wr itten. reset sets the timb counter modulo registers. note reset the timb counter before writing to the timb counter modulo registers. register name and address: tbcnth ? $0052 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write:rrrrrrrr reset:00000000 register name and address: tbcntl ? $0053 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write:rrrrrrrr reset:00000000 r = reserved figure 17-6. timb counter registers (tbcnth and tbcntl) register name and address: tbmodh ? $0054 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset:11111111 register name and address: tbmodl ? $0055 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset:11111111 figure 17-7. timb counter modulo registers (tbmodh and tbmodl) i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 247 17.7.4 timb channel stat us and control registers each of the timb 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 timb overflow selects 0 percent and 100 percent pwm duty cycle selects buffered or unbuffered output compare/pwm operation chxf ? channel x flag 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 com pare channel, chxf is set when the value in the timb counter registers matches the value in the timb channel x registers. when chxie = 1, clear chxf by reading timb channel x status and control register with chxf set, and then writing a 0 to chxf. if another interrupt request occurs before the clearing sequence is complete, then writing 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 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 timb cpu interrupts on channel x. reset clears the chxie bit. 1 = channel x cpu interrupt requests enabled 0 = channel x cpu interrupt requests disabled register name and address: tbsc0 ? $0056 bit 7654321bit 0 read: ch0f ch0ie ms0b ms0a els0b els0a tov0 ch0max write: 0 reset:00000000 register name and address: tbsc1 ? $0059 bit 7654321bit 0 read: ch1f ch1ie 0 ms1a els1b els1a tov1 ch1max write: 0 r reset:00000000 r= reserved figure 17-8. timb channel status and control registers (tbsc0?tbsc1) timer interface b (timb) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 248 freescale semiconductor msxb ? mode select bit b this read/write bit selects buffered output compare/pwm operation. msxb exists only in the timb channel 0. setting ms0b disables the channel 1 status and control register and reverts tch1b 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:a 00, this read/write bit selects either input capture operation or unbuffered output compare/pwm operation. see table 17-2 . 1 = unbuffered output compare/pwm operation 0 = input capture operation when elsxb:a = 00, this read/write bit selects the initial output level of the tchx pin once pwm, input capture, or output compare operation is enabled. see table 17-2 . 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 timb status and control register (tbsc). 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 port e, and pin ptex/tchxb is available as a general-purpose i/o pin. however, channel x is at a state determined by these bits and becomes transparent to the respective pin when pwm, input capture, or output compare mode is enabled. table 17-2 shows how elsxb and elsxa work. re set clears the elsxb and elsxa bits. note before enabling a timb channel register for input capture operation, make sure that the ptex/tbchx pin is stable for at least two bus clocks. tovx ? toggle-on-overflow bit when channel x is an output compare channel, this read/write bit controls the behavior of the channel x output when the timb 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 timb counter overflow. 0 = channel x pin does not toggle on timb counter overflow. i/o registers mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 249 note when tovx is set, a timb 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 is 1 and clear output on compare is selected, setting the chxmax bit forces the duty cycle of buffered and unbuffered pwm signals to 100 percent. as figure 17-9 shows, chxmax bit takes effect in the cycle after it is set or cleared. the output stays at 100 percent duty cycle level until the cycle after chxmax is cleared. figure 17-9. chxmax latency table 17-2. mode, edge, and level selection msxb:msxa elsxb:elsx a mode configuration x0 00 output preset pin under port control; initialize timer output level high x1 00 pin under port control; initialize timer 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 00 output compare or pwm softare compare only 01 01 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 output overflow ptex/tchx period chxmax overflow overflow overflow overflow compare output compare output compare output compare tovx timer interface b (timb) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 250 freescale semiconductor 17.7.5 timb c hannel registers these read/write registers contain the captured timb counter value of the input capture function or the output compare value of the output compare function. the state of the timb channel registers after reset is unknown. in input capture mode (msxb?msxa = 0:0), reading the high byte of the timb channel x registers (tbchxh) inhibits input captures un til the low byte (tbchxl) is read. in output compare mode (msxb?msxa 0:0), writing to the high byte of the timb channel x registers (tbchxh) inhibits output compares unt il the low byte (tbchxl) is written. register name and address: tbch0h ? $0057 bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address: tbch0l ? $0058 bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset register name and address: tbch1h ? $005a bit 7654321bit 0 read: bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8 write: reset: indeterminate after reset register name and address: tbch1l ? $005b bit 7654321bit 0 read: bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 write: reset: indeterminate after reset figure 17-10. timb channel registers (tbch0h/l?tbch1h/l) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 251 chapter 18 development support 18.1 introduction this section describes the break module, the moni tor read-only memory (mon), and the monitor mode entry methods. 18.2 break module (brk) the break module (brk) can generate a break interrupt that stops normal program flow at a defined address to enter a background program. features include: accessible input/output (i/o) registers during the break interrupt central processor unit (cpu) generated break interrupts software-generated break interrupts computer operating properly (cop ) disabling during break interrupts 18.2.1 functional description when the internal address bus matches the value writt en in the break address registers, the break module issues a breakpoint signal to the cpu. the cpu th en 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). these 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 microcontroller unit (mcu) to normal operation. figure 18-1 shows the structure of the break module. 18.2.1.1 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. development support mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 252 freescale semiconductor figure 18-1. break module block diagram addr.register name bit 7654321bit 0 $fe00 sim break status register (sbsr) see page 255. read: rrrrrrbwr write: reset: 0 $fe03 sim break flag control register (sbfcr) see page 255. read: bcferrrrrrr write: reset: 0 $fe0c break address register high (brkh) see page 254. read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 $fe0d break address register low (brkl) see page 254. read: bit 7654321bit 0 write: reset:00000000 $fe0e break status and control register (brkscr) see page 254. read: brke brka 000000 write: reset:00000000 note: writing a 0 clears bw. = unimplemented r = reserved figure 18-2. i/o register summary iab15?iab8 iab7?iab0 8-bit comparator 8-bit comparator control break address register low break address register high iab15?iab0 break break module (brk) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 253 18.2.1.2 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 in struction, the break inte rrupt begins immediately. 18.2.1.3 tim1 and tim2 during break interrupts a break interrupt stops the timer counters. 18.2.1.4 cop during break interrupts the cop is disabled during a break interrupt when v tst is present on the rst pin. 18.2.2 low-power modes the wait and stop instructions put the mcu in low power- consumption standby modes. 18.2.2.1 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. clear the bw bit by writing logic 0 to it. 18.2.2.2 stop mode the break module is inactive in stop mode. the stop instruction does not affect break module register states. 18.2.3 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) development support mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 254 freescale semiconductor 18.2.3.1 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 addres s 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 18.2.3.2 break address registers the break address registers (brkh and brkl) contai n the high and low bytes of the desired breakpoint address. reset clears the break address registers. address: $fe0e bit 7654321bit 0 read: brke brka 000000 write: reset:00000000 = unimplemented figure 18-3. break status and control register (brkscr) address: $fe0c bit 7654321bit 0 read: bit 15 14 13 12 11 10 9 bit 8 write: reset:00000000 figure 18-4. break address register high (brkh) address: $fe0d bit 7654321bit 0 read: bit 7654321bit 0 write: reset:00000000 figure 18-5. break address register low (brkl) monitor rom (mon) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 255 18.2.3.3 break status register the break status register (sbsr) contains a flag to indicate that a break caus ed an exit from wait mode. the flag is useful in applications requiring a return to wait mode after exiting from a break interrupt. bw ? break wait bit this read/write bit is set when a break interrupt causes an exit from wait mode. clear bw by writing a logic 0 to it. reset clears bw. 1 = break interrupt during wait mode 0 = no break interrupt during wait mode bw can be read within the break interrupt routine. the user can modify the return address on the stack by subtracting 1 from it. 18.2.3.4 break flag control register the break flag control register (sbfcr) contains a bi t 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 bi ts by accessing status r egisters while the mcu is in a break state. to clear status bits duri ng the break state, the bcfe bit must be set. 1 = status bits cl earable during break 0 = status bits not clearable during break 18.3 monitor rom (mon) the monitor rom (mon) allows complete testing of the microcontroller unit (mcu) through a single-wire interface with a host computer. monitor mode entry can be achieved without the use of v tst as long as vector addresses $fffe and $ffff are blank, thus reducing the hardware requirements for in-circuit programming. address: $fe00 bit 7654321bit 0 read: rrrrrrbwr write: reset: 0 figure 18-6. sim break status register (sbsr) address: $fe03 bit 7654321bit 0 read: bcferrrrrrr write: reset: 0 r= reserved figure 18-7. sim break flag control register (sbfcr) development support mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 256 freescale semiconductor features include: normal user-mode pin functionality one pin dedicated to serial communicati on between monitor rom and host computer standard mark/space non-return-to-zero (nrz) communication with host computer 4800 baud?28.8 kbaud communication with host computer execution of code in random-a ccess memory (ram) or rom flash programming 18.3.1 functional description the monitor rom receives and executes commands from a host computer. figure 18-8 shows a sample circuit used to enter monitor mode and communic ate with a host computer via a standard rs-232 interface. simple monitor commands can access any memory address. in monitor mode, the mcu can execute host-computer code in ram while all mcu pins re tain normal operating mode functions. all communication between the host computer and the mcu is through the pta0 pin. a level-shifting and multiplexing interface is required between pta0 and the host computer. pta0 is used in a wired-or configuration and requires a pullup resistor. 18.3.1.1 entering monitor mode there are two methods for entering monitor: the first is the traditional m68hc08 method where v dd + v hi is applied to irq1 and the mode pins are configured appropriately. a second method, intended for in-circuit progra mming applications, will force entry into monitor mode without requiring high voltage on the irq1 pin when the reset vector locations of the flash are erased ($ff). note for both methods, holding the ptc2 pin low when entering monitor mode causes a bypass of a divide-by-two st age at the oscillator. 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 percent duty cycle at maximum bus frequency. table 18-1 is a summary of the differences between user mode and monitor mode. 18.3.1.2 normal monitor mode table 18-2 shows the pin conditions for entering monitor mode. table 18-1. mode differences modes functions cop rest vector high reset vector low break vector high break vector low swi vector high swi vector low user enabled $fffe $ffff $fffc $fffd $fffc $fffd monitor disabled (1) 1. if the high voltage (v dd + v hi ) is removed from the irq1 pin or the rst pin, the sim asserts it s cop enable output. the cop is a mask option enabled or disabled by th e copd bit in the configuration register. $fefe $feff $fefc $fefd $fefc $fefd monitor rom (mon) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 257 figure 18-8. monitor mode circuit + + + + 10 m ? x1 v dd v hi mc145407 mc74hc125 mc68hc908mr16/ rst irq cgmxfc osc1 osc2 v ssa v ss v dd pta0 v dd 10 k ? 0.1 f 0.02 f 10 k ? 6 5 2 4 3 1 db-25 2 3 7 20 18 17 19 16 15 v dd v dd v dd 20 pf 20 pf 10 f 10 f 10 f 10 f 1 2 4 7 14 3 0.1 f 4.9152 mhz 10 k ? ptc2 v dd 10 k ? b a s2 position a ? bus clock = cgmxclk 4 or cgmvclk 4 s2 position b ? bus clock = cgmxclk 2 5 6 pwmgnd v ssad v refl v dda 0.1 f v dda v ddad 0.1 f v ddad v refh 0.1 f v refh ptc3 ptc4 v dd 10 k ? mc68hc908mr32 pta7 v dd 10 k ? a b s3 s1 s2 s3 position a ? parallel communication s3 position b ? serial communication mc68hc908mr32 ? mc68hc908mr16 data sheet, rev. 6.1 258 freescale semiconductor development support table 18-2. monitor mode signal requirements and options irq reset (s1) $fffe /$ffff pll ptc3 ptc4 ptc2 (s2) external clock (1) 1. external clock is derived by a 32.768 khz crystal or a 4.9152/9.8304 mhz off-chip oscillator. cgmout bus frequency cop for serial communication (2) 2. dna = does not apply, x = don?t care comment pta0 pta7 (s3) baud rate (3) (4) 3. pat0 = 1 if serial communication; pta0 = x if parallel communication 4. pta7 = 0 serial, pta7 = 1 parallel communication for security code entry x gnd x x x x x x 0 0 disabled x x 0 no operation until reset goes high v tst v dd or v tst x off100 4.9152 mhz 4.9152 mhz 2.4576 mhz disabled 1 0 9600 ptc3 and ptc2 voltages only required if irq = v tst ; ptc2 determines frequency divider x 1 dna v tst v dd or v tst x off101 9.8304 mhz 4.9152 mhz 2.4576 mhz disabled 1 0 9600 ptc3 and ptc2 voltages only required if irq = v tst ; ptc2 determines frequency divider x 1 dna v dd v dd $ffff blank off x x x 9.8304 mhz 4.9152 mhz 2.4576 mhz disabled 1 0 9600 external frequency always divided by 4 x 1 dna v dd or gnd v tst $ffff blank offxxx x ? ? enabledxx ? enters user mode ? will encounter an illegal address reset v dd or gnd v dd or v tst non-$ff programmed off x x x x ? ? enabled x x ? enters user mode monitor rom (mon) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 259 enter monitor mode by either: executing a software interrupt instruction (swi) or applying a logic 0 and then a logic 1 to the rst pin once out of reset, the mcu waits for the host to send eight security bytes. after receiving the security bytes, the mcu sends a break signal (10 consecutive logi c 0s) to the host computer, indicating that it is ready to receive a command. the break signal also provides a timing reference to allow the host to determine the necessary baud rate. monitor mode uses alternate vectors for reset and swi. the alternate vectors are in the $fe page instead of the $ff page and allow code execution from the inte rnal monitor firmware instead of user code. the computer operating properly (cop) module is disabled in monitor mode as long as v hi is applied to either the irq pin or the rst pin. (see chapter 14 system integration module (sim) for more information on modes of operation.) 18.3.1.3 forced monitor mode if the voltage applied to the irq1 is less than v dd + v hi the mcu will come out of reset in user mode. the menrst module is monitoring the rese t vector fetches and will assert an internal reset if it detects that the reset vectors are erased ($ff). when the mcu comes out of reset, it is forced into monitor mode without requiring high voltage on the irq1 pin. the cop module is disabled in forced monitor mode. any reset other than a por reset will automatically force the mcu to come back to the forced monitor mode. 18.3.1.4 data format communication with the monitor rom is in standard non-return-to-zero (nrz) ma rk/space data format. (see figure 18-9 and figure 18-10 .) figure 18-9. monitor data format figure 18-10. sample monitor waveforms the data transmit and receive rate can be anywher e from 4800 baud to 28.8 kbaud. transmit and receive baud rates must be identical. bit 5 start bit bit 0 bit 1 next stop bit start bit bit 2 bit 3 bit 4 bit 6 bit 7 bit 5 start bit bit 0 bit 1 next stop bit start bit bit 2 bit 3 bit 4 bit 6 bit 7 start bit bit 0 bit 1 next stop bit start bit bit 2 $a5 break bit 3bit 4bit 5bit 6bit 7 development support mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 260 freescale semiconductor 18.3.1.5 echoing as shown in figure 18-11 , the monitor rom immediately echoes each received byte back to the pta0 pin for error checking. figure 18-11. read transaction any result of a command appears after the echo of the last byte of the command. 18.3.1.6 break signal a start bit followed by nine low bits is a break signal. see figure 18-12 . when the monitor receives a break signal, it drives the pta0 pin high for the duration of two bits before echoing the break signal. figure 18-12. break transaction 18.3.1.7 commands the monitor rom uses these commands (see table 18-3 ? table 18-8 ): read, read memory write, write memory iread, indexed read iwrite, indexed write readsp, read stack pointer run, run user program addr. high read read addr. high addr. low addr. low data echo sent to monitor result 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 monitor rom (mon) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 261 table 18-3. read (read memory) command description read byte from memory operand 2-byte address in high-byte:low-byte order data returned returns contents of specified address opcode $4a command sequence table 18-4. 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 18-5. 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 read read echo sent to monitor address high address high address low data return address low write write echo from host address high address high address low address low data data iread iread echo from host data return data development support mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 262 freescale semiconductor a sequence of iread or iwrite commands can acce ss a block of memory sequentially over the full 64-kbyte memory map. table 18-6. iwrite (indexed write) command description write to last address accessed + 1 operand single data byte data returned none opcode $19 command sequence table 18-7. 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 table 18-8. run (run user program) command description executes pulh and rti instructions operand none data returned none opcode $28 command sequence iwrite iwrite echo data data from host readsp readsp echo from host sp return sp high low run run echo from host monitor rom (mon) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 263 18.3.1.8 baud rate with a 4.9152-mhz crystal and the ptc2 pin at lo gic 1 during reset, data is transferred between the monitor and host at 4800 baud. if the ptc2 pin is at logic 0 during reset, the monitor baud rate is 9600. see table 18-9 . 18.3.2 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 bl ank. for security reasons, program locations $fff6?$fffd even if they are not used for vectors. during monitor mode entry, the mcu waits after the powe r-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 wa s not a power-on reset, security remains bypassed and security code entry is not required. (see figure 18-13 .) 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 secu rity 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 char acter until after the host sends the eight security bytes. 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 can be reset (v ia power-pin reset only) and brought up in monitor mode to attempt another entry. after failing the se curity sequence, the flas h mode can also be bulk erased by executing an erase routine that was downloaded into internal ram. the bulk erase operation clears the security code locations so th at all eight security bytes become $ff. table 18-9. monitor baud rate selection vco frequency multiplier (n) 123456 monitor baud rate 4800 9600 14,400 19,200 24,000 28,800 development support mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 264 freescale semiconductor figure 18-13. monitor mode entry timing byte 1 byte 1 echo byte 2 byte 2 echo byte 8 byte 8 echo command command echo pa0 pa7 rst v dd 4096 + 32 cgmxclk cycles 24 bus cycles 256 bus cycles (minimum) 1 3 1 1 2 1 break notes: 2 = data return delay, 2 bit times 3 = wait 1 bit time before sending next byte. 3 from host from mcu 1 = echo delay, 2 bit times mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 265 chapter 19 electrical specifications 19.1 introduction this section contains electrical and timing specifications. 19.2 absolute maximum ratings maximum ratings are the extreme limits to which t he microcontroller unit (mcu) can be exposed without permanently damaging it. note this device is not guaranteed to operate properly at the maximum ratings. for guaranteed operating conditions, refer to 19.5 dc electrical characteristics . note this device contains circuitry to pr otect 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 ). characteristic (1) 1. voltages referenced to v ss . symbol value unit supply voltage v dd ?0.3 to +6.0 v input voltage v in v ss ?0.3 to v dd +0.3 v input high voltage v hi v dd + 4 maximum v maximum current per pin excluding v dd and v ss i 25 ma storage temperature t stg ?55 to +150 c maximum current out of v ss i mvss 100 ma maximum current into v dd i mvdd 100 ma electrical specifications mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 266 freescale semiconductor 19.3 functional operating range 19.4 thermal characteristics characteristic symbol value unit operating temperature range (1) mc68hc908mr24cfu mc68hc908mr24vfu 1. see freescale representative for temperature availability. c = extended temperature range (?40 c to +85 c) v = automotive temperature range (?40 c to +105 c) t a ?40 to 85 ?40 to 105 c operating voltage range v dd 5.0 10% v characteristic symbol value unit thermal resistance, 64-pin qfp ja 76 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 x v dd ) + p i/o = k/(t j + 273 c) w constant (2) 2. k is a 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 x ja w/ c average junction temperature t j t a + (p d x ja ) c maximum junction temperature t jm 125 c dc electrical characteristics mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 267 19.5 dc electrical characteristics characteristic (1) 1. v dd = 5.0 vdc 10%, v ss = 0 vdc, t a = t l to t h , unless otherwise noted. symbol min typ (2) 2. typical values reflect average measur ements at midpoint of voltage range, 25 c only. max unit output high voltage (i load = ?2.0 ma) all i/o pins v oh v dd ?0.8 ??v output low voltage (i load = 1.6 ma) all i/o pins v ol ??0.4v pwm pin output source current (v oh = v dd ?0.8 v) i oh ?7 ? ? ma pwm pin output sink current (v ol = 0.8 v) i ol 20 ? ? ma input high voltage, all ports, irq s, reset , osc1 v ih 0.7 x v dd ? v dd v input low voltage, all ports, irq s, reset , osc1 v il v ss ? 0.3 x v dd v v dd supply current run (3) wait (4) stop (5) 3. run (operating) i dd measured using external square wave clock source (f osc = 8.2 mhz). 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 run i dd ; measured with all modules enabled 4. wait i dd measured using external square wave clock source (f osc = 8.2 mhz); 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 in puts; osc2 capacitance linearly affects wait i dd ; measured with pll and lvi enabled. 5. stop i dd measured with pll and lvi disengaged, ocs1 grounded, no port pins sourcing current. it is measured through combination of v dd , v ddad , and v dda . i dd ? ? ? ? ? ? 30 12 700 ma ma a i/o ports high-impedance leakage current i il ?? 10 a input current (input only pins) i in ?? 1 a capacitance ports (as input or output) c out c in ? ? ? ? 12 8 pf low-voltage inhibit reset (6) 6. the low-voltage inhibit reset is software selectable. refer to chapter 9 low-voltage inhibit (lvi) . v lv r 1 4.0 4.35 4.65 v low-voltage reset/recover hysteresis v lv h 1 40 90 150 mv low-voltage inhibit reset recovery (v rec1 = v lv r 1 + v lv h 1 ) v rec1 4.04 4.5 4.75 v low-voltage inhibit reset v lv r 2 3.85 4.15 4.45 v low-voltage reset/recover hysteresis v lv h 2 150 210 250 mv low-voltage inhibit reset recovery (v rec2 = v lv r 2 + v lv h 2 ) v rec2 4.0 4.4 4.6 v por re-arm voltage (7) 7. maximum is highest vo ltage that por is guaranteed. v por 0?100mv por rise time ramp rate (8) 8. if minimum v dd is not reached before the in ternal por is released, rst must be driven low externally until minimum v dd is reached. r por 0.035 ? ? v/ms por reset voltage (9) 9. maximum is highest vo ltage that por is possible. v porrst 0 700 800 v monitor mode entry voltage (on irq ) v hi v dd + 2.5 ?8.0v electrical specifications mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 268 freescale semiconductor 19.6 flash memory characteristics 19.7 control timing characteristic symbol min typ max unit ram data retention voltage v rdr 1.3 ? ? v flash program bus clock frequency ? 1 ? ? mhz flash read bus clock frequency f read (1) 1. f read is defined as the frequency range for which the flash memory can be read. 0?8 mhz flash page erase time <1 k cycles >1 k cycles t erase 0.9 3.6 1 4 1.1 5.5 ms flash mass erase time t merase 4??ms flash pgm/erase to hven setup time t nvs 10 ? ? s flash high-voltage hold time t nvh 5?? s flash high-voltage hold time (mass erase) t nvhl 100 ? ? s flash program hold time t pgs 5?? s flash program time t prog 30 ? 40 s flash return to read time t rcv (2) 2. t rcv 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 0. 1?? s flash cumulative program hv period t hv (3) 3. t hv is defined as the cumulative high voltage programming time to the same row before next erase. t hv must satisfy this condition: t nvs + t nvh + t pgs + (t prog x 32) t hv maximum. ?? 4ms flash endurance (4) 4. typical endurance was evaluated for this product family . for additional information on how freescale defines typical endurance , please refer to engineering bulletin eb619. ? 10 k 100 k ? cycles flash data retention time (5) 5. typical data retention values are based on intrinsic capability of the technology measured at high temperature and de-rated to 25c using the arrhenius equation. for additional information on how freescale defines typical data retention , please refer to engineering bulletin eb618. ? 15 100 ? years characteristic (1) 1. v dd = 5.0 vdc 10%, v ss = 0 vdc; timing shown with respect to 20% v dd and 70% v dd , unless otherwise noted symbol min max unit frequency of operation (2) crystal option external clock option (3) 2. see 19.8 serial peripheral interface characteristics for more information. 3. no more than 10% duty cycle deviation from 50%. f osc 1 dc (4) 4. some modules may require a minimum frequency greater than dc for proper operation; see appropriate table for this information. 8 32.8 mhz internal operating frequency f op ?8.2mhz reset input pulse width low (5) 5. minimum pulse width reset is guaranteed to be recognized. it is possible for a smaller pulse width to cause a reset. t irl 50 ? ns serial peripheral inte rface characteristics mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 269 19.8 serial peripheral interface characteristics diagram number (1) 1. v dd = 5.0 vdc 10%, all timing is shown with respect to 20% v dd and 70% v dd , unless otherwise noted; assumes 100 pf load on all spi pins characteristic (2) 2. numbers refer to dimensions in figure 19-1 and figure 19-2 . symbol min max unit operating frequency master slave f op(m) f op(s) f op /128 dc f op /2 f op mhz 1 cycle time master slave t cyc(m) t cyc(s) 2 1 128 ? t cyc 2 enable lead time t lead(s) 15 ? ns 3 enable lag time t lag(s) 15 ? ns 4 clock (spck) high time master slave t sckh(m) t sckh(s) 100 50 ? ? ns 5 clock (spck) low time master slave t sckl(m) t sckl(s) 100 50 ? ? ns 6 data setup time (inputs) master slave t su(m) t su(s) 45 5 ? ? ns 7 data hold time (inputs) master slave t h(m) t h(s) 0 15 ? ? ns 8 access time, slave (3) cpha = 0 chpa = 1 3. time to data active from high-impedance state t a(cp0) t a(cp1) 0 0 40 20 ns 9 disable time, slave (4) 4. hold time to high-impedance state t dis(s) ?25ns 10 data valid time after enable edge master slave (5) 5. with 100 pf on all spi pins t v(m) t v(s) ? ? 10 40 ns electrical specifications mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 270 freescale semiconductor figure 19-1. spi master timing note ss pin of master held high msb in ss input spck, cpol = 0 output spck, cpol = 1 output miso input mosi output note 4 5 5 1 4 bits 6?1 lsb in master msb out bits 6?1 master lsb out 10 11 10 11 7 6 note note: this last clock edge is generated inte rnally, but is not seen at the sck pin. ss pin of master held high msb in ss input spck, cpol = 0 output spck, cpol = 1 output miso input mosi output note 4 5 5 1 4 bits 6?1 lsb in master msb out bits 6?1 master lsb out 10 11 10 11 7 6 a) spi master timing (cpha = 0) b) spi master timing (cpha = 1) note: this first clock edge is generated internally, but is not seen at the sck pin. serial peripheral inte rface characteristics mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 271 figure 19-2. spi slave timing note: not defined, but normally msb of character just received slave ss input spck, cpol = 0 input spck, cpol = 1 input miso input mosi output 4 5 5 1 4 msb in bits 6?1 8 6 10 11 11 note slave lsb out 9 3 lsb in 2 7 bits 6?1 msb out note: not defined, but normally lsb of character previ ously transmitted slave ss input spck, cpol = 0 input spck, cpol = 1 input miso input mosi output 4 5 5 1 4 msb in bits 6?1 8 6 10 note slave lsb out 9 3 lsb in 2 7 bits 6?1 msb out 10 a) spi slave timing (cpha = 0) b) spi slave timing (cpha = 1) 11 11 electrical specifications mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 272 freescale semiconductor 19.9 timer interface module characteristics 19.10 clock generation modu le component specifications 19.11 cgm operating conditions characteristic symbol min max unit input capture pulse width t tih, t til 125 ? ns input clock pulse width t tch, t tcl (1/f op ) + 5 ?ns characteristic symbol min typ max notes crystal load capacitance c l ??? consult crystal manufacturing data crystal fixed capacitance c 1 ? 2 * c l ? consult crystal manufacturing data crystal tuning capacitance c 2 ? 2 * c l ? consult crystal manufacturing data feedback bias resistor r b ? 22 m ? ? series resistor r s 0330 k ? 1 m ? not required filter capacitor c f ? c fact * (v dda /f xclk ) ? bypass capacitor c byp ?0.1 f? c byp must provide low ac impedance from f = f xclk /100 to 100*f vclk , so series resistance must be considered characteristic symbol min typ max unit crystal reference frequency f xclk 1?8mhz range nominal multiplier f nom ?4.9152? mhz vco center-of-range frequency f vrs 4.9152 ? 32.8 mhz vco frequency multiplier n 1 ? 15 ? vco center of range multiplier l 1 ? 15 ? vco operating frequency f vclk f vrsmin ? f vrsmax ? cgm acquisition/lock time specifications mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 273 19.12 cgm acquisition/lo ck time specifications description symbol min typ max notes filter capacitor multiply factor c fact ? 0.0154 ? f/sv acquisition mode time factor k acq ? 0.1135 ? v tracking mode time factor k trk ? 0.0174 ? v manual mode time to stable t acq ? (8*v dda )/ (f xclk *k acq) ? if c f chosen correctly manual stable to lock time t al ? (4*v dda )/ (f xclk *k trk ) ? if c f chosen correctly manual acquisition time t lock ? t acq +t al ? tracking mode entry frequency tolerance ? trk 0? 3.6% acquisition mode entry frequency tolerance ? acq 6.3% ? 7.2% lock entry frequency tolerance ? lock 0? 0.9% lock exit frequency tolerance ? unl 0.9% ? 1.8% reference cycles per acquisition mode measurement n acq ?32? reference cycles per tracking mode measurement n trk ?128? automatic mode time to stable t acq n acq /f xclk (8*v dda )/ (f xclk *k acq) ? if c f chosen correctly automatic stable to lock time t al n trk /f xclk (4*v dda )/ (f xclk *k trk ) ? if c f chosen correctly automatic lock time t lock ? t acq +t al ? pll jitter (deviation of average bus frequency over 2 ms) f j 0? (f xclk ) *(0.025%) *(n/4) n = vco freq. mult. electrical specifications mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 274 freescale semiconductor 19.13 analog-to-digital co nverter (adc) characteristics characteristic symbol min typ max unit notes supply voltage v ddad 4.5 ? 5.5 v v ddad should be tied to the same potential as v dd via separate traces input voltages v adin 0? v ddad v v adin <= v ddad resolution b ad 10 ? 10 bits absolute accuracy a ad ?? 4 lsb includes quantization adc internal clock f adic 500 k ? 1.048 m hz t aic = 1/f adic conversion range r ad v ssad ? v ddad v power-up time t adpu 16 ? ? t aic cycles conversion time t adc 16 ? 17 t aic cycles sample time t ads 5? ? t aic cycles monotonicity m ad guaranteed zero inpu t reading z adi 000 ? 003 hex v adin = v ssad full-scale reading f adi 3fc ? 3ff hex v adin = v ddad input capacitance c adi ? ? 30 pf not tested v refh /v refl current i vref ?1.6 ? ma absolute accuracy (8-bit truncation mode) a ad ?? 1 lsb includes quantization quantization error (8-bit truncation mode) ??? + 7/8 ? 1/8 lsb mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 275 chapter 20 ordering information and mechanical specifications 20.1 introduction this section provides ordering information for the mc68hc908mr16 and mc68hc908mr32 along with the dimensions for: 64-lead plastic quad flat pack (qfp) 56-pin shrink dual in-line package (sdip) the following figures show the latest package drawings at the time of th is publication. to make sure that you have the latest package specifications, contact your local freescale sales office. 20.2 order numbers figure 20-1. device numbering system table 20-1. order numbers mc order number (1) 1. fu = quad flat pack b = shrink dual in-line package operating temperature range 68hc908mr16cfu 68hc908mr16vfu ?40 c to +85 c ?40 c to +105 c 68hc908mr16cb 68hc908mr16vb ?40 c to +85 c ?40 c to +105 c 68hc908mr32cfu 68hc908mr32vfu ?40 c to +85 c ?40 c to +105 c 68hc908mr32cb 68hc908mr32vb ?40 c to +85 c ?40 c to +105 c m c 6 8 h c 9 0 8 m r 3 2 x x x family package designator temperature range ordering information and mechanical specifications mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 276 freescale semiconductor 20.3 64-pin plastic quad flat pack (qfp) 56-pin shrink dual in-line package (sdip) mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 277 20.4 56-pin shrink dual in-line package (sdip) ordering information and mechanical specifications mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 278 freescale semiconductor mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 freescale semiconductor 279 appendix a mc68hc908mr16 the information contained in this document pertains to the mc68hc908mr16 with the exception of that shown in figure a-1 . mc68hc908mr16 mc68hc908mr32 mc68hc908mr16 data sheet, rev. 6.1 280 freescale semiconductor $0000 $005f i/o registers ? 96 bytes $0060 $035f ram ? 768 bytes $0360 $7fff unimplemented ? 31,904 bytes $8000 $beff flash ? 16,128 bytes $bf00 $fdff unimplemented ? 16,128 bytes $fe00 sim break status register (sbsr) $fe01 sim reset status register (srsr) $fe02 reserved $fe03 sim break flag control register (sbfcr) $fe04 reserved $fe05 reserved $fe06 reserved $fe07 reserved $fe08 flash control register (flcr) $fe09 unimplemented $fe0a unimplemented $fe0b unimplemented $fe0c sim break address register high (brkh) $fe0d sim break address register low (brkl) $fe0e sim break flag control register (sbfcr) $fe0f lvi status and control register (lviscr) $fe10 $feff monitor rom ? 240 bytes $ff00 $ff7d unimplemented ? 126 bytes $ff7e flash block protect register (flbpr) $ff7f $ffd1 unimplemented ? 83 bytes $ffd2 $ffff vectors ? 46 bytes figure a-1. mc68hc908mr16 memory map 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/pacific: 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 semiconduc tor 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 specifically disclai ms any and all liability, including without limitation consequential or incidental damages. ?typical? parameters that may be provided in freescale semiconductor data shee ts and/or specificati ons can and do vary in different applications and actual perfo rmance may vary over time. all operating parameters, including ?typicals?, 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 officers, employees, subsidiaries, affiliates, 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. 2005. all rights reserved. mc68hc908mr32 rev. 6.1, 07/2005 |
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