This MAY be an even better idea than you realise.

There will be some extra noise on Vcc right at the PIC even with good
decoupling and this will have the result of inducing some noise into
your oscillator. As a consequence you can expect some random jitter
on the clock - this in turn will decrease its spectral purity and
DECREASE the magnitude of harmonics, instead spreading the noise onto
other frequencies. The end result MAY be to reduce your EMC peak
emissions slightly.

HP design systems where the clock is deliberately "spread" this way
for just this reason. Presumably adding varicaps returned to Vcc to
the PIC clock lines may help this effect :-)


regards


        Russell McMahon

-----Original Message-----
From: Ernie Murphy <ernie@SURFREE.COM>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Sunday, June 13, 1999 1:43 AM
Subject: Osc cap return


With the PICs I've been using, Vcc not RTN is nearest the oscilator
pins. I
don't know if this is true the the whole PIC line, but may well be.

So when I have to ground my osc caps (actually I use a resonator,
same
thing applies), I could either go the long way around to the real
ground
pin, or "Ground" these caps to Vcc. Guess what I do? Nail em right to
Vcc.

Vcc is an AC short to ground (what do you think all those bypass caps
do?),
and is a fine return point for the caps. My application is an
accurate
timer, so I implicitly test start-up time. I've tested these things
from
-60 to +150¡C and they start up and start pronto every time.