Standby Mode..................................................................................................... 37
Power Reduction Register.................................................................................. 37
Minimizing Power Consumption ......................................................................... 38
System Control and Reset................................................................ 40
Internal Voltage Reference................................................................................. 45
Watchdog Timer ................................................................................................. 46
Interrupts............................................................................................ 51
Interrupt Vectors in ATmega48........................................................................... 51
Interrupt Vectors in ATmega88........................................................................... 53
Interrupt Vectors in ATmega168......................................................................... 57
I/O-Ports.............................................................................................. 62
Introduction......................................................................................................... 62
Ports as General Digital I/O................................................................................ 63
Alternate Port Functions ..................................................................................... 67
Register Description for I/O Ports....................................................................... 79
External Interrupts............................................................................. 80
8-bit Timer/Counter0 with PWM........................................................ 85
Overview............................................................................................................. 85
Timer/Counter Clock Sources............................................................................. 86
Counter Unit........................................................................................................ 86
Output Compare Unit.......................................................................................... 87
Compare Match Output Unit............................................................................... 89
Modes of Operation ............................................................................................ 90
Timer/Counter Timing Diagrams......................................................................... 94
8-bit Timer/Counter Register Description ........................................................... 95
Timer/Counter0 and Timer/Counter1 Prescalers.......................... 102
16-bit Timer/Counter1 with PWM.................................................... 104
Overview........................................................................................................... 104
Accessing 16-bit Registers ............................................................................... 106
Timer/Counter Clock Sources........................................................................... 110
Counter Unit...................................................................................................... 110
Input Capture Unit............................................................................................. 111
Output Compare Units...................................................................................... 113
Compare Match Output Unit............................................................................. 114
Modes of Operation .......................................................................................... 115
Timer/Counter Timing Diagrams....................................................................... 123
16-bit Timer/Counter Register Description ....................................................... 125
8-bit Timer/Counter2 with PWM and Asynchronous Operation.. 132
ii
ATmega48/88/168
2545D–AVR–07/04
ATMEL [ ATMEL ]
