8.8Clock Output Buffer .................................................................................................35
8.9System Clock Prescaler ..........................................................................................35
8.10PLL ........................................................................................................................36
8.11Register Description ..............................................................................................37
9
Power Management and Sleep Modes ................................................. 42
9.1Overview ..................................................................................................................42
9.2Sleep Modes ............................................................................................................42
9.3Idle Mode .................................................................................................................42
9.4Power-down Mode ...................................................................................................43
9.5Power-save Mode ....................................................................................................43
9.6Standby Mode .........................................................................................................43
9.7Extended Standby Mode .........................................................................................43
9.8Power Reduction Register .......................................................................................43
9.9Minimizing Power Consumption ..............................................................................44
9.10Register Description ..............................................................................................45
10 System Control and Reset .................................................................... 47
10.1Resetting the AVR .................................................................................................47
10.2Reset Sources .......................................................................................................47
10.3Internal Voltage Reference ....................................................................................51
10.4Watchdog Timer ....................................................................................................51
10.5Register Description ..............................................................................................55
11 Interrupts ................................................................................................ 64
11.1Overview ................................................................................................................64
11.2Interrupt Vectors in ATmega8U2/16U2/32U2 ........................................................64
11.3Register Description ..............................................................................................65
12 I/O-Ports .................................................................................................. 67
12.1Overview ................................................................................................................67
12.2Ports as General Digital I/O ...................................................................................68
12.3Alternate Port Functions ........................................................................................72
12.4Register Description for I/O-Ports ..........................................................................82
13 External Interrupts ................................................................................. 84
13.1Overview ................................................................................................................84
13.2Register Description ..............................................................................................84
14 Timer/Counter0 and Timer/Counter1 Prescalers ................................ 88
ii
ATmega8U2/16U2/32U2
7799D–AVR–11/10
ATMEL [ ATMEL ]
