Hi erveryone!

We have trouble with our ADuC812-Design.
After high temperature testing at 85°C/185°F ambient temperature, 4 of 8 ADuC812 have permanent failures:
- Vref is 2.7V instead 2.5V
- The Software is running correctly, but we are unable to serial download new software
- Maybe the security bits in EEPROM-page 160 are altered: they read as $ff $fe $bf $ff in the failed devices

To Sascha Pypke: What is your trick to erase the chip with all security bits?

What may have caused the failures?

Guenter