On Thu, 13 Apr 2000 19:19:00 +0100, you wrote:

>We recently designed a board with a PIC16C72A on it which ran the chip
>at 500kHz using a ceramic resonator and two 68pF capacitors on OSC1 and
>OSC2.
>
>The board seemed to run perfectly on the bench but we had major problems
>with - we assume - interference crashing and corrupting the processor
>when the board was installed in the machine it was designed for.
>
>After trying everything we could think of we eventually tried modifying
>the code and running the processor at 4MHz with a quartz crystal and two
>22pF capacitors and magically all the problems went away!
>
>My boss is now keen to change all ceramic resonators in our products for
>quartz crystals but I think at worst we probably only need to avoid
>using ceramic resonators with PIC chips.
>
>Can anyone offer any information to help me understand this incident and
>decide what our policy on ceramic resonators should be in the future?
>
>Brian G.
>briang@cix.co.uk
I think it was probably down to the use of a low frequency resonator
rather than a resonator as such - I've found units below 2MHz to be
rather tempramental. Higher freq ones are fine.