We have just learned something new on the ADUC845. We had a application where voltage on the ADC input was present while ADUC845 was powering up. This caused the chip to never power up. We scoped the power up sequence to make sure the power was clean and no over shoot. The Chip will not respond to program mode or even start the crystal. The chip acts like a completely dead chip. We found the only way out of this lockup was to turn off the voltage at the ADC pins then recycle power or trigger a reset. Triggering a reset without removing the voltage at the ADC inputs has no effect.
Is this a bug with the chip? Should it not do this? We also tested several chips all behave the same way.