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COUNTER A S3F80JB
12-6
PROGRAMMING TIP — To generate 38 kHz, 1/3duty signal through P3.1
This example sets Counter A to the repeat mode, sets the oscillation frequency as the Counter A clock source,
and CADATAH and CADATAL to make a 38 kHz, 1/3 Duty carrier frequency. The program parameters are:
17.59 us
37.9 kHz 1/3 duty
8.795 us
— Counter A is used in repeat mode
— Oscillation frequency is 4 MHz (0.25 µs)
— CADATAH = 8.795 µs / 0.25 µs = 35.18, CADATAL = 17.59 µs / 0.25 µs = 70.36
— Set P3.1 C-MOS push-pull output and CAOF mode.
— 44 pin package
ORG 0100H ; Reset address
START: DI
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LD CADATAL,#(70-2) ; Set 17.5 ms
LD CADATAH,#(35-2) ; Set 8.75 ms
;
LD P3CON,#11110010B ; Set P3 to C-MOS push-pull output.
; Set P3.1 to REM output
;
LD CACON,#00000110B ; Clock Source → Fosc
; Disable Counter A interrupt.
; Select repeat mode for Counter A.
; Start Counter A operation.
; Set Counter A Output Flip-flop(CAOF) high.
;
LD P3,#80H ; Set P3.7(Carrier On/Off) to high.
; This command generates 38 kHz, 1/3duty pulse signal
; through P3.1
;
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