I have observed that

(a) PICs like a bypass capacitor directly across their power pins
(b) The reset input is noise-sensitive and any tracks to reset should be
as short as possible. Ensure also that the +5V rail is solid and
noise-free, particularly in the area of the reset pullup.

> ----------
> From:         Wynn Rostek[SMTP:war@PALMNET.NET]
> Reply To:     pic microcontroller discussion list
> Sent:         Friday, December 19, 1997 6:30 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: what are the five dumbest things to check?
>
> At 09:39 AM 12/18/97 -0500, you wrote:
> >Hi All:
> >
> >At the risk of offending the geniuses out there, I have a(nother)
> >completely dumb question.  I have a PIC application that works
> >beautifully on a microchip demonstration board, and won't work on my
> >own.
>
> If it were me I'd look very carefully at the oscillator.  I've seen a
> lot of
> problems there over the years.  The other thing I'd check is to make
> sure
> all "unused" pins are pulled up or down, I've seen floating pins cause
> interrupts and resets on more than a system or two.
>
> Wynn
>