Adam stambler wrote:
> Hi, I was wondering if anyone could provide some oscillator guidance.  I am
> trying to run a 16f690 off a 20 mgherz ceramic resonator with built in
> capacitors.
>
> I think i have all my my programming correct, but when I go to turn it on,
> it does not work.  The oscillator does not start up.  However, if I try to
> measure the voltage with my multimeter and touch the Clock input pin, the
> PIC starts to work.  There is about 2.3V on the clock output and input pin
> .
>
> Right now i have a 1 mega Ohm resistor across the input and output leads of
> the resonator like the datasheet said for it to have. I am running the
> resonator in HS mode.
>
> My guess is that my programming is correct but there is not enough drive to
> get the oscillator going.  Unfortunately, I have no idea about how to fix
> the problem.  This is my first oscillator circuit which I am using for a
> school project.
>
> Anyone have any ideas?
>
> Thanks,
> Adam Stambler
>   
I have never been able to get reliable startups with the 20M seramic 
resonators. The fastest reliable speed
for me was 16M. And I love these critters dearly.

I believe the phase-shifting caps do not quite match the Microchip 
oscillator. Drop back to a lower speed
or tinker with cap values. Incidentally, the ones by Murata may run at a 
slightly faster rate.

--Bob
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