PIC16F84A Microcontroller Chip Attack
It is not always necessary for the power glitches to be outside the specified power supply voltage range. For example, in the same PIC16F84A microcontroller the protection mechanism can be defeated by applying a mere 50 mV glitch after the chip erase operation has started which will cause the failure of PIC16F84A Microcontroller Chip Attack. That causes termination of the program memory erase operation but not the fuse erase.
PIC16F84A Microcontroller Chip Attack
All the above examples of glitch attacks show how powerful such attacks can be unless special countermeasures are implemented. These could be voltage and clock monitor circuits which reset the CPU if the voltage or clock frequency go out of range. Clock-monitoring circuits are normally used in smartcards but very few microcontrollers have them.