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 ATmega48P/88P/168P and ATmega48PB/88PB/168PB, see the table below for more detail.
| Part | Signature Bytes Address | ||
|---|---|---|---|
| 0x000 | 0x001 | 0x002 | |
| ATmega48P/PV | 0x1E | 0x92 | 0x0A |
| ATmega48PB | 0x1E | 0x92 | 0x10 |
| ATmega88P/PV | 0x1E | 0x93 | 0x0F |
| ATmega88PB | 0x1E | 0x93 | 0x16 |
| ATmega168P/PV | 0x1E | 0x94 | 0x0B |
| ATmega168PB | 0x1E | 0x94 | 0x15 |