Another good use for a storage scope.  Write a piece
of code that outputs a square wave, and let it run
over a period of time and see what happens on the
output.  Thats if you have a storage scope I suppose.


--- Russell McMahon <apptech@paradise.net.nz> wrote:

> > Yes, but given the numbers I see on the frequency
> counter, the
> > oscillator may well be jumping far outside it's
> specs in the short 
> > term.
> > I wish I could sample it for 1S and see how
> jittery it really is. 
> > I'm
> > using a 1S gate time and consecutive readings
> might be <300Hz apart, 
> > or
> > they may be >3KHz apart.  I realize this is
> "within spec", but it's 
> > not
> > what I expected to see.
> 
> >> Now, if this is "normal", I have no idea, but
> is't clearly withing
> >> the specs in the data sheet, not ?
> 
> 
> If you have a second PIC with a crystal oscillator
> you could read the 
> clock using a timer over any desired consecutive
> periods.
> 
> If your counter is OK it sounds as though you have
> semi random 
> variation - maybe not jumping but wandering widely.
> It's conceivable 
> that it may be being affected by eg mains hum. Can
> you try this as far 
> from mains wiring etc as possible. Counter can be at
> the far end of 
> it's probe leads.
> 
> I have seen low quality crystals which exhibited
> similar 
> characteristics - although not of course of such
> magnitude.
> 
> 
>         RM 
> 
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