5.1 Signature Bytes

All AVR microcontrollers have a three-byte signature code, which identifies the device. This code can be read in both serial and parallel mode, also when the device is locked. The three bytes reside in a separate address space. For the device signature bytes, there are differences between ATmega48PA/88PA/168PA and ATmega48PB/88PB/168PB, see the table below for more detail.