I have encountered a very strange problem with my ATmega103 device.
In my project it gets 4V power supply and uses internal EEPROM. It was
running a simple test program which fills EEPROM with some data
(00,01,02,03...). While it worked, I decided to switch off the power
to see what will happen. Results exceeded expectations. When I powered
it again, EEPROM ceased to work at all! I can read it, but cannot
write to it (EEWE=1 and never becomes 0).
Furthermore, I have found one more serious thing. The device now
cannot be serial programmed. ERASE and WRITE commands doesn't work.
After first ERASE command Flash memory became corrupted and now can't
be written or erased anyway. I tried to change power supply voltage in
4-5V range, but without any result.
My circuit has brown-out detector which resets MCU when Vcc=3,7V.
Does anybody know what has happened and how to revitalize my