On Thu, 7 Dec 2000 08:34:48 -0500 Olin Lathrop
<olin_piclist@EMBEDINC.COM> writes:
> > I have to say you are probably better served buying the complete
> > oscillator from Digi-key.
> > I just got 10 of them (20 Mhz.) at $2.50 each. No muss, no fuss,
> they
> > just work.
> > Small package, (4 pins in an 8 pin dip), and low power.
>
> That can be a convenience for a low volume product, but will cost at
> least
> double what the crystal and two caps cost.  One good reason for
> having an
> external oscillator is if you are driving multiple devices from the
> same
> clock.
>
> I've never had any problem with having the PIC drive a crystal
> directly
> (except the time I didn't cover the window on a 16C77/JW), and I
> think of
> this as the "easy" solution.
>

        And we're getting ceramic resonators with built-in capacitors for
something like 50 cents each. The cost savings over an external
oscillator or even over a crystal and a couple capacitors is substantial.
Also, there's a substantial savings in board space since the resonator
with capacitors is in a 3 pin SIP (or even smaller when surface mounted).
        muRata has a nice search engine where you can put in a processor number
and it will come back with resonator part numbers that have been
characterised for that processor. It's at
http://www.murata.co.jp/search/ic-e.html .


Harold



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