Data Sheet

ii
8161D–AVR–10/09
ATmega48PA/88PA/168PA/328P
8.7128 kHz Internal Oscillator ......................................................................................34
8.8External Clock .........................................................................................................34
8.9Clock Output Buffer .................................................................................................35
8.10Timer/Counter Oscillator .......................................................................................35
8.11System Clock Prescaler ........................................................................................35
8.12Register Description ..............................................................................................37
9 Power Management and Sleep Modes ................................................. 39
9.1Sleep Modes ...........................................................................................................39
9.2BOD Disable ............................................................................................................40
9.3Idle Mode .................................................................................................................40
9.4ADC Noise Reduction Mode ...................................................................................40
9.5Power-down Mode ..................................................................................................41
9.6Power-save Mode ...................................................................................................41
9.7Standby Mode .........................................................................................................41
9.8Extended Standby Mode .........................................................................................41
9.9Power Reduction Register .......................................................................................42
9.10Minimizing Power Consumption ............................................................................42
9.11Register Description ..............................................................................................44
10 System Control and Reset .................................................................... 46
10.1Resetting the AVR .................................................................................................46
10.2Reset Sources .......................................................................................................46
10.3Power-on Reset .....................................................................................................47
10.4External Reset .......................................................................................................48
10.5Brown-out Detection ..............................................................................................48
10.6Watchdog System Reset .......................................................................................49
10.7Internal Voltage Reference ....................................................................................49
10.8Watchdog Timer ....................................................................................................50
10.9Register Description ..............................................................................................54
11 Interrupts ................................................................................................ 57
11.1Interrupt Vectors in ATmega48PA .........................................................................57
11.2Interrupt Vectors in ATmega88PA .........................................................................59
11.3Interrupt Vectors in ATmega168PA .......................................................................62
11.4Interrupt Vectors in ATmega328P .........................................................................65
11.5Register Description ..............................................................................................68
12 External Interrupts ................................................................................. 70