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PWM GENERATION WITH ST62 AUTO-RELOAD TIMER

Program example

A

.def 0FFh,0FFh,0FFh

;Accumulator

;************** Port Register Set ************************************

PA

.def 0C0h,0FFh,0FFh

;Data Register Port A

PADIR

.def 0C4h,0FFh,0FFh

;Data Direction Reg. Port A

PAOPT

.def 0CCh,0FFh,0FFh

;Option Register Port A

;**************** Timer Register Set *********************************

RC

.def 0D9h,0FFh,0FFh

;reload capture register

CP

.def 0DAh,0FFh,0FFh

;compare Register

MC

.def 0D5h,0FFh,0FFh

;mode control register

SC0

.def 0D6h,0FFh,0FFh

;status control register 0

SC1

.def 0D7h,0FFh,0FFh

;status control register 1

LR

.def 0DBh,0FFh,0FFh

;load register

;********************* ADC Register Set ******************************

ADCC

.def 0D1h,0FFh,0FFh

;adc control register

ADC

.def 0D0h,0FFh,0FFh

;adc result Register

;********************* MAIN *******************************************

;port A must be an IOP3 type (port with analog input mode):

ldi PADIR,000h

ldi PAOPT,001h

;PA0 is the analog input

ldi PA, 001h

;PA1..PA7 are input with pull-up

ldi SC1,00000000b

;PSC divides by 1

ldi CP,080h

;compare register = 128d

;(initial duty = 50%)

ldi RC,000h

;reload register = 0

;(count up from 0 to 255)

ldi MC,11100000b

;auto-reload mode,interrupt disabled

;PWMOUT enabled, start timer with

;duty cycle 50% at start-up

adc_loop

ldi ADCC,030h

;start A/D conversion

wt_eoc

jrr 6,ADCC,wt_eoc

;wait for end-of-conversion

ld A,ADC

;save result into Accumulator

ld CP,A

;copy it into CP register

jp adc_loop

;do it again