;****************************************************************************** ;* Software License Agreement * ;* The software supplied herewith by Microchip Technology Incorporated * ;* (the "Company") is intended and supplied to you, the Company's * ;* customer, for use solely and exclusively on Microchip products. * ;* * ;* The software is owned by the Company and/or its supplier, and is * ;* protected under applicable copyright laws. All rights are reserved. * ;* Any use in violation of the foregoing restrictions may subject the * ;* user to criminal sanctions under applicable laws, as well as to * ;* civil liability for the breach of the terms and conditions of this * ;* license. * ;* * ;* THIS SOFTWARE IS PROVIDED IN AN "AS IS" CONDITION. NO WARRANTIES, * ;* WHETHER EXPRESS, IMPLIED OR STATU-TORY, INCLUDING, BUT NOT LIMITED * ;* TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A * ;* PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. THE COMPANY SHALL NOT, * ;* IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL OR * ;* CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER. * ;* * ;****************************************************************************** ;***** Timer Module * ;* This module provides the main timing for the system. At the roll over of * ;* TMR0, the routine determines if the PWM is greater or less than 50%. It * ;* then generates the shorter period. It then decrements the skip flags for * ;* the command, keypress, autosequence, and ADC state machines. After the * ;* the skip timer updates, it returns, releasing the system to the other state* ;* machines. On average, the system has a minimum of 1/2 of the period to run* ;* the other state machines. The duty cycle is controlled via the dutycycle * ;* variable. * ;* Timer State machine design * ;* Not a true state machine, rather is a timer system with a PWM pulse * ;* generator as part of the execution path. * ;* * ;* Timing algorithm * ;* * ;* Wait for TMR0 roll over * ;* switch (duty cycle) * ;* { * ;* case 0%: output low * ;* return * ;* * ;* case 100%: output high * ;* return * ;* * ;* case 1-50%: generate high output pulse * ;* return * ;* * ;* case 50-100%: generate low output pulse * ;* return * ;* } * ;* * ;* if (key_skip_timer-- == 0) * ;* { * ;* do_key = true * ;* key_skip_timer = 10 * ;* } * ;* * ;* if (cmd_skip_timer-- == 0) * ;* { * ;* do_cmd = true * ;* cmd_skip_timer = 10 * ;* } * ;* * ;* if (auto_skip_timer-- == 0) * ;* { * ;* do_auto = true * ;* auto_skip_timer = 100 * ;* } * ;* * ;* if (adc_skip_timer-- == 0) * ;* { * ;* do_adc = true * ;* adc_skip_timer = 100 * ;* } * ;* * ;* State Machine Variable List. * ;* NAME DIRECTION RANGE SOURCE/DESTINATION * ;* dutycycle input 0-7F various * ;* tstats.dokey output 0-1 key state machine * ;* tstats.docmd output 0-1 command state machine * ;* tstats.doasq output 0-1 autosequence state mc * ;* tstats.doadc output 0-1 ADC state machine * ;* GPIO.PWM output 0-1 PWM output * ;* TMR0 input 0-FF Hardware Timer * ;* key_skip_timer local 00-0A key sm skip timer * ;* cmd_skip_timer local 00-05 command sm skip timer * ;* asq_skip_timer local 00-64 autosq skip timer * ;* adc_skip_timer local 00-64 ADC skip timer * ;****************************************************************************** Timer btfss INTCON,T0IF ; wait for timer roll over goto Timer bcf INTCON,T0IF ; at roll over, clear flag and start PWM btfsc dutycycle,7 ; duty cycle is 00 > DC > 7F goto pwm_error ; if out of range, then error dc_good movlw 0x7F ; test for 7F duty cycle, if yes (always on) xorwf dutycycle,w btfsc STATUS,Z goto alwayson movf dutycycle,w ; test for 00 duty cycle, if yes (always off) btfsc STATUS,Z goto alwaysoff btfsc dutycycle,6 ; test for > 50% duty cycle (mostly on) goto mostlyon goto mostlyoff ; if not then only option is < 50% (mostly off) pwm_error bsf estats,pwm_err ; duty cycle out of range error clrf dutycycle ; goto 0% for safety return ;****************************************************************************** ;***** 4 PWM CONDITIONS ;********************** PWM CYCLE IS LESS THAN 50% OR MOSTLY OFF ;***** mostlyoff ; duty cycle < 50% so generate high side of pulse bsf CMCON,0 movwf timer1 bsf GPIO,pwm ; set the output to start high side pulse wait1 goto $+1 ; delay 5 cycles goto $+1 nop decfsz timer1,f ; count the delay goto wait1 ; if not zero then delay again bcf GPIO,pwm ; if zero then clear the output to end pulse goto endtimer ; goto the skip timer updates ;********************** PWM CYCLE IS GREATER THAN 50% OR MOSTLY ON ;***** mostlyon ; duty cycle > 50% so generate the low side of pulse bsf CMCON,0 sublw 0x80 ; subract dutycyle from 80 to find low time movwf timer1 bcf GPIO,pwm ; clear the output to start low pulse wait2 goto $+1 ; delay 5 counts goto $+1 nop decfsz timer1,f ; count the delay goto wait2 ; if not zero then delay again bsf GPIO,pwm ; if zero then set the output to end the pulse goto endtimer ; goto the skip timer updates ;********************** PWM CYCLE IS 0% OR ALWAYS OFF ;***** alwaysoff ; duty cycle = 0%, so output is always low bcf GPIO,pwm bsf GPIO,mosfet bcf CMCON,0 goto endtimer ;********************** PWM CYCLE IS 100% OR ALWAYS ON ;***** alwayson ; duty cycle = 100%, so output is always high bsf GPIO,pwm bcf CMCON,0 ;***** ;***************************************************** ;***** END OF TIMER STATE MACHINE, UPDATING THE SKIP TIMERS FOR ALL OTHER STATE MACHINES ;***** endtimer ; update the skip timers decfsz key_skip_timer,f ; decrement key state machine skip timer goto next_skip_1 bsf tstats,dokey ; if zero do key task and reset timer movlw .10 movwf key_skip_timer next_skip_1 decfsz cmd_skip_timer,f ; decrement skip timer goto next_skip_2 bsf tstats,docmd ; if zero do key task movlw .10 movwf cmd_skip_timer ; and reset skip timer next_skip_2 decfsz asq_skip_timer,f ; decrement skip timer goto next_skip_3 bsf tstats,doasq movlw .100 movwf asq_skip_timer return next_skip_3 decfsz adc_skip_timer,f return bsf tstats,doadc movlw .100 movwf adc_skip_timer return