Datasheet

ii
7766E–AVR–04/10
ATmega16U4/ATmega32U4
6.10PLL ........................................................................................................................39
7 Power Management and Sleep Modes ................................................. 43
7.1Idle Mode .................................................................................................................44
7.2ADC Noise Reduction Mode ...................................................................................44
7.3Power-down Mode ..................................................................................................44
7.4Power-save Mode ...................................................................................................44
7.5Standby Mode .........................................................................................................45
7.6Extended Standby Mode .........................................................................................45
7.7Power Reduction Register .......................................................................................45
7.8Minimizing Power Consumption ..............................................................................47
8 System Control and Reset .................................................................... 49
8.1Internal Voltage Reference ......................................................................................54
8.2Watchdog Timer ......................................................................................................55
9 Interrupts ................................................................................................ 61
9.1Interrupt Vectors in ATmega16U4/ATmega32U4 ....................................................61
10 I/O-Ports .................................................................................................. 65
10.1Introduction ............................................................................................................65
10.2Ports as General Digital I/O ...................................................................................66
10.3Alternate Port Functions ........................................................................................70
10.4Register Description for I/O-Ports ..........................................................................82
11 External Interrupts ................................................................................. 85
12 Timer/Counter0, Timer/Counter1, and Timer/Counter3 Prescalers ... 89
12.1Internal Clock Source ............................................................................................89
12.2Prescaler Reset .....................................................................................................89
12.3External Clock Source ...........................................................................................89
12.4General Timer/Counter Control Register – GTCCR ..............................................90
13 8-bit Timer/Counter0 with PWM ............................................................ 91
13.1Overview ...............................................................................................................91
13.2Timer/Counter Clock Sources ...............................................................................92
13.3Counter Unit ..........................................................................................................92
13.4Output Compare Unit ............................................................................................93
13.5Compare Match Output Unit ..................................................................................95
13.6Modes of Operation ...............................................................................................96
13.7Timer/Counter Timing Diagrams .........................................................................100