>> I'd like to operate a normal 4MHz, PIC16C84 with an 32.768kHz crystal
>> (the same one that used in clocks), but I had problems.
>> I have used of course LP config mode, and 100pF capacitors.

>Did the chip work when the scope probe was held against the pins?  If so
>then you will probably need more capacitance (we had the same problem
>with this frequency of crystal).

We found we needed less (22pF each side, as I recall.)  The other thing
you might need is a drive limiting resistor in series with the crystal;
I think (and I might be well wrong here) that a distorted output from the
crystal (i.e. a distorted input to the PIC) indicates overdrive.

The clock oscillator gave more trouble than any other bit of the last
widget we designed..

Dave