8.8External Clock .........................................................................................................36
8.9Clock Output Buffer .................................................................................................36
8.10Timer/Counter Oscillator ........................................................................................37
8.11System Clock Prescaler ........................................................................................37
8.12Register Description ..............................................................................................38
9
Power Management and Sleep Modes ................................................. 40
9.1Sleep Modes ............................................................................................................40
9.2Idle Mode .................................................................................................................40
9.3ADC Noise Reduction Mode ....................................................................................41
9.4Power-down Mode ...................................................................................................41
9.5Power-save Mode ....................................................................................................41
9.6Standby Mode .........................................................................................................42
9.7Power Reduction Register .......................................................................................42
9.8Minimizing Power Consumption ..............................................................................42
9.9Register 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
11.1Overview ................................................................................................................57
11.2Interrupt Vectors in ATmega48 ..............................................................................57
11.3Interrupt Vectors in ATmega88 ..............................................................................59
11.4Interrupt Vectors in ATmega168 ............................................................................62
11.5Register Description ..............................................................................................65
12 External Interrupts ................................................................................. 67
12.1Pin Change Interrupt Timing ..................................................................................67
12.2Register Description ..............................................................................................68
ii
ATmega48/88/168
2545M–AVR–09/07
ATMEL [ ATMEL ]
