John Wrote..

> I have a PWM input to a PIC16c84 chip.  When I look at the PWM signal
> from the device, not connected to PIC, it has a nice 0 to 5V signal.
> When I connect to PIC it has a 4.5 to 5V signal. This causes a problem
> because the pic always recognizes it as a high signal.  I am guessing
> that the inherent capacitance on the input to the chip does not have
> enough time to fully discharge.
>
> Does anyone know or can direct me to a source to solve this problem
>
I would doubt that input capacitance has anything to do this
observed result. I would suspect a poor or no common 0volts
connection between the two devices. That or the PIC pin is
configured as an output.

If all else fails try a suitable pull down resistor , this will depend on
the output capacity of the driving device but 10K is a good place to
start.



_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

www.psych.auckland.ac.nz

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