Fellow Piclisters,

I am experiencing occasional corruption of the Data EEPROM on a PIC16C84.
On three separate occasions, using three different devices, I have found
that the first location (00H) in the 64-byte area has been reset to 00H -
no other locations have been affected.  This problem has only appeared 3
times in hundreds of hours of usage (including hundreds of power on / off
cycles) but is very annoying as the contents of location 00H are critical
to the operation of my code.  I cannot find any trace of bugs in my code
which could cause this behaviour and, in any case, I have followed the
guidelines in the Microchip databook to prevent erroneous EEPROM writes.

My best guess is that some kind of transient hardware event is causing
this problem.  Is there any condition on the pins of the device which has
been known to cause this corruption (e.g. during power on / off)?  I am
reluctant to implement the obvious kludge, i.e. avoid using location 00H.

If anyone has any experience with this problem and/or a solution, I would
be very pleased to hear from them.

Thanks.

- Ian Chapman
ian@chapmip.demon.co.uk