Dan,

Using electrolytic cap on MCLR pin is wrong you may have starting problem or
more.
I designed  a board for Harley Davidson (extremely noisy averment)
based on pic I used 39pf cap on MCLR pin it works fine tested under noise
and
125 Degree C then increased up to 150 still worked fine.After all
experiments I
realized that any microchip tool you buy worth it and the  PIC is one of the
best MCU.

Andre Abelian




> >
> > I'd add a mod here. First, (.1uf)*(4700) only gives a .00047 sec
> > RC time constant, which may not hold the MCLR line low long enough
> > for reset. You need a much bigger cap, say 22 uF, which gives .1 sec
> > time constant. Don't increase R by too much, as leakage can be a
> > factor.
> >
> > Secondly, I've found, much to my chagrin (meaning $$$ wasted),
> > that you don't want to tie a capacitor straight onto MCLR on a PIC,
> > as this can damage the chip and lead to very large leakage
> > currents into the MCLR line (order of 100s of uA). Use at least
> > 100 ohms between the cap and MCLR.
> >
> > More info about this particular problem is in the Piclinks
> > page *PIC ERRATA* section on my website -
> >
> > http://www.sni.net/~oricom/piclinks.htm
> >
> > - Dan Michaels
> > Oricom Technologies
> > http://www.sni.net/~oricom
>
> jim@jpes.com
>