hello,

For a long term proces, where we loose power regular,
we store some states of the proces in the data eeprom,
so after a power failure we can take up the task again at the right place.
(And now it's not easy to place battery backup there)

These sets of data are stored double.
Each set of data has a flag (also in data-eeprom).
The flag is set before writing a data set and cleared when done with 
writing.
So we can always determine which of the 2 sets has been completely 
rewritten,
and therefor must contain the correct data.

Unfortunately, we see that if we switch the power on and off frequently
(to simulate the power failure),
that more than 1 position, sometimes in both data sets and even outside 
that region,
are corrupted.

Now my eye was just caught by this erratta:
http://ww1.microchip.com/downloads/en/DeviceDoc/80053b.pdf
saying that after a program eeprom write
(but in my eyes that's exactly the same as a data-eeprom write),
you should be sure to discharge the high voltage program registers,
to prevent spurious writes.

This should also imply, that after a short power failure,
you should discharge these registers.

Is this true ?
Anyone else has seen these kind of weird random writes ?

thanks,
Stef Mientki








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