On Wed, 3 Dec 1997 11:58:31 +0000, you wrote:

>I've a PCB layout that will benefit greatly if I could (reliably) hook the
>watch-crytal's capacitors to +V instead of Gnd.
I've alway said they screwd up the pinout on the 18 pin devices - you
always need a gnd near the osc pins, and  MCLR is often tied to Vdd,
but they put them the wrong way round!
>If there's a sufficiently large cap. across the battery, this should be
>equivalent, I think.
As long as the cap has low impedance at the required frequency (size
isn't everything!) - shouldn't be a problem at 32KKz - the usual 100nF
ceramic ought to be OK.
My main worry would be Vcc switching noise from the PIC or elsewhere
affecting the oscillator - noise from the PIC shouldn't be too bad as
it would be synchronous, but may be an issue if there were other
clocks (e.g. using the watch xtal on the Timer 1 osc on a '74)
>Has anyone tried this?
Sorry, no - I'm always very nervous about using watch crystals - they
can be  somewhat tempramental! 

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