David Cary wrote:
>
> Dear David VanHorn,
>
> David VanHorn <dvanhorn@CEDAR.NET> on 2001-04-29 11:25:19 PM wondered what the
> problem could be:
> > The discharge time is arbitrarily doubling due to an apparent change in the
> > low logic threshold.
> ...
> > This is all happening on an MPLAB ICE, so I'm calling uChip tomorrow.
> ...
> > Should all be factored out, as long as the thresholds don't change between
> > measurements.
> > That's the problem I'm hitting.
> > The low threshold appears to go absurdly low, practically to zero on occasion.


That does sound bizarre, David, have you checked the
+5v rail as *maybe* you are getting some sort of
charge-pump effect where the constant charge/discharge
of the sense cap is affecting the main Vdd that the
PIC uses to determine threshold voltages for input
pins?? Time to put the scope probe on the +5v
rail and the sense cap to see what voltages you are
really getting there. :o)
-Roman

PS. also re my previous post, try making just ONE
sense pin on it's own port. Each port has it's
own internal power rail with it's own thresholds
(obviously).

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