Sorry, my description of my problem wasn't exactly accurate.  I tried the
circuit with my full program instead of just a turn on LED test.

It turns out, that while the oscillator starts to work when I touch the
multimeter probe to the clock in pin, it only goes through a few
instructions and seems to stop.  Then as I watch the voltage on the Clock in
pin, it starts at 2.2, but then starts to oscillate downward going from 2.2to
1.6 to 2.2 to .7 to 2.2 and then eventually to zero where it stays.  All the
while, the clock out pin is at 2.4 V.


Jim, you suggested adding discrete capacitors between OSC and ground.  Yet,
this resonator is supposed to have built in capacitors.  Is it common to
need to add capacitors to a resonator that is supposed to have them?

I will try out the capacitors once I get out of this class.  Thanks for the
help so far.

Adam

On 12/8/06, Adam stambler <adasta@gmail.com> 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
>
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