Hello all!

Short version:
Is it possible that EEPROM up to 30% of the PIC:s is bad?

Long version:
This week I got my PCBs from the PCB house and programmed the PICs with
my bootloader and the actual software. Everything ok so far, but when
trying 10 PICs, 3 of them didn't work.

My bootloader reads the last EEPROM-byte and if it's 0xFF it goes into
bootloader mode and if it isn't the normal software starts.

I found out that these 3 PICs that didn't work leave in bootloader mode.
I did suspect that the EEPROM byte wasn't cleared the first time the
actual software started but 2 of the 3 PIC's did actually work about 30%
of the time.

One solution for this problem would be to read that EEPROM two or three
times and compare, then there would be (hopefully) only one that didn't
work. Even better is to make the bootloader work some other way.

But the biggest question is still: Should I be worried that the other
EEPROM bytes doesn't "read right" sometime?? It can't be necessary to
always read EEPROM twice to make sure I get the right data! Or are there
most problems with that last byte?

Anyone else recognized something like this?
BTW, I'm using 16F877.

Thanks a lot for your advices!

/Andreas

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