Jason and the group,

Ditto on this and all of the other previous responses, I concur.

But ...

You have not explained exactly what type of crystal you are using (data
book calls for parallel cut crystal on page 49), nor have you explained
exactly how it is hooked up.

It also appears from a cursory perusal of that same page that the
oscillator "mode" needs to be pre-programmed by setting bits FOSC0 and
FOSC1 to correspond to HS mode in order to operate at that speed.

Not knowing much about PIC's, I cannot offer more, but it appears that
there are ample design questions that may not have been properly
addressed, and you may need to start by handing the engineer a datasheet
opened to page 49 or thereabouts.

It is very common to damage or break a crystal. It is even more common
to attempt to make the wrong one work in an improperly designed circuit.

JaMi Smith 

* * *
 
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]] 
Sent: Tuesday, April 23, 2002 5:37 AM
To: [log in to unmask]
Subject: Re: [TN] 20 Mhz crystal start-up woes

Jason

Are you using ultrasonic cleaning? This is a sure way of buggering up
quartz crystals.

Brian

Jason wrote:
>
> 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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