Hi!

I have a problem with PWM-generation with the PCA (Programmable Counter Array) in P87C51FA-4B MCU. The PWM-generation already works, but I can´t force the output pin for PWM-Signal to 0. I ever can detect a short 1-phase.

This is because the constraint for the compare-function is compre-value (CAPLn) greather or equal than timer-value. So I ever get a short 1 also when I use FF as compare-value.

For my application I need a clean 0-level. My idea was:

mov A,myValue ; load compare-value
jz f1_aus ; is compare-vlaue = 0?
mov CAPH0,A ; to PCA-Array (8Bit PWM)
mov CAPM0,#%01000010 ; turn 8-Bit PWM on
ljmp f1_end ; jump over switch PWM off
f1_aus:
mov CAPM0,#%00000000 ; switch 8-Bit PWM off
CLR P1.3 ; set PWM-pin to 0
f1_end:

I have tryed many other combinations, but without any success. I need a example for my problem. Is someone here, who have one?

Thanks in advance,
Daniel

PS: In the PCA Cookbook I can´t find a solution for my problem.