If your using an '874, how about feeding the 4x PWM into 4x RC network
and measuring the DC level?

The DC level would be proportional to the mark / space ratio, and as
long as you pick the RC values wisely bearing in mind the PWM frequency.

Just a thought


Regards, Kevin

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@mitvma.mit.edu] On Behalf Of Jinx
> Sent: 11 April 2002 10:20
> To: PICLIST@mitvma.mit.edu
> Subject: Re: [PIC] Interrupt on change
>
>
> > Another IOC question: what happens if a pin on portb
> changes while i'm
> > busy with the interrupt handler from a previous pin change?
> I'm using
> > four timed PWM modulated signals which could come very
> close together,
> > so the chance of collosion is quite high
>
> It might be better if you connect your signals to four
> general pins and OR the four signals together into b0 and use
> the INT function. When an INT occurs, poll the signal pins to
> find out which one caused it. If signals really do come that
> close (ie closer than you can process them in an ISR) then
> there'll have to be some sort of flagging or logging so that
> events can be processed at a time when you know it can be
> done without interruption
>
> --
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