I wrote:
> > Does anyone know the maximum rise and fall times that are safe to
> > use for the INT pin on a PIC17C756A running at 16MHz?
> >
> > The "fall time" from the encoder signal I am using for my interrupt
> > on the INT pin is about 200ns and seems to work well, but I suspect
> > now that the interrupt is being missed intermittently.
> >
> > I found a value of 25ns as the "min INT pin high low time"
> > in DS30289A-page248 but don't know if this is the value I am
> > looking for.

Then Bob Ammerman wrote:
> This is how long the pin must remain in the high or low state for
> the interrupt to be certain to be detected.
Oh, I was thinking they were edge triggered interrupts, but it sounds
like they are level triggered interrupts.

I seem to have solved my problem anyway.  My PortB is already busy,
so I just cleaned up my INT and T0CKL input signal edges to about 20ns
with an external schmitt trigger.

It seems like the INT and/or TOCKL interrupt inputs don't work 100%
with slow inputs.  I didn't work out exactly what was going wrong,
but cleaning up the edges of the signals made the PIC code run like
I expected it..

I'll be more careful with my interrupt signal edges in the future.

Simon

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