Jason,

I don't know about that particular PIC processor, but many processors have a
programmable oscillator start-up delay (fuse selectable).  This is to allow
the oscillator to stabilize before allowing the processor to run.
Typically, processors that have this feature have two or three settings.
Shortest delay is usually for RC oscillator (yes, people do use these!),
medium delay for ceramic resonator and longest delay is for crystal.  Check
to see if your processor has this option and set the delay to the longest
possible.  Crystals have very high-Q and therefore take a long time to
settle down.

Regards,

Seth Goodman
Goodman Associates, LLC
tel 608.833.9933
fax 608.833.9966


> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Jason
> Sent: Monday, April 22, 2002 11:24 AM
> To: [log in to unmask]
> Subject: [TN] 20 Mhz crystal start-up woes
>
>
> Has anyone had difficulty with crystal start-up.
> Currently we are having problems with a circuit that uses a PIC16C711-
> 201/P, 2 @ 22pF load caps and a 20 Mhz AT crystal. The
> configuration is for
> fundamental operation.
>
> We are using a high temp screen (85 deg C storage before functional check)
> to try and weed out problems but have still found modules not
> functional at
> the production plant.
> Sleepy crystals have been discussed but we have experimented with three
> different manufactures of crystals we have ruled this out.
> One of our action items is to redesign and use 10 Mhz, but right now we
> aren't sure of the root cause of failure so there really isn't a guarantee
> that this plan will work.
>
> What are some specific design parameters that could be measured to arrive
> at the root cause?
>
> Thanks,
> Jason
>
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