At 12:15 AM 12/03/1999 +0800, you wrote:
>Hi,
>
>I have a PIC16LC715 with industrial temp range running off a 32768Hz watch
>crystal in LP mode @ 3V.  I was playing around with it today - spraying
>(the uP only) with
>a freezing spray and I got some interesting behavior at low temperatures.
>

>
We are using ther PIC's at low temperatures (-30 deg.C ) and they are fine.-

I think you have two or three different problems:

1) Moisture. This may form (condensation) when moving from cold to
warm ambient. Correct capacitors may reduce the problem, but it seems mostly
to be a lay-out problem. Try to deposit small waterdrops on your circuit on
and
around the components for the oscillator and you may find which components
are too
close together,

2) Selection of capacitors. We have never been able to get safe operation
with a PIC16C7X
with 15 pF capacitors with large variations in temperature and supply voltage.
Note also, if the powersupply comes from a battery, voltage and available
power may be
different at very low temperatures.

3) Some watch crystals works better than others for PIC's - even
if the specifications looks much the same.
Farnell has a large selection - try a couple and find a good type.


Hope this can help -

Best regards, Hans