Datasheet

13.2. Clock Sources............................................................................................................................ 47
13.3. Crystal Oscillator........................................................................................................................ 48
13.4. Low-frequency Crystal Oscillator................................................................................................49
13.5. External RC Oscillator................................................................................................................50
13.6. Calibrated Internal RC Oscillator................................................................................................51
13.7. External Clock............................................................................................................................ 51
13.8. Timer/Counter Oscillator.............................................................................................................52
13.9. Register Description...................................................................................................................52
14. Power Management and Sleep Modes................................................................... 54
14.1. Sleep Modes.............................................................................................................................. 54
14.2. Idle Mode....................................................................................................................................55
14.3. ADC Noise Reduction Mode...................................................................................................... 55
14.4. Power-down Mode..................................................................................................................... 55
14.5. Power-save Mode...................................................................................................................... 55
14.6. Standby Mode............................................................................................................................ 56
14.7. Minimizing Power Consumption.................................................................................................56
14.8. Register Description...................................................................................................................57
15. System Control and Reset.......................................................................................59
15.1. Resetting the AVR...................................................................................................................... 59
15.2. Reset Sources............................................................................................................................59
15.3. Internal Voltage Reference.........................................................................................................62
15.4. Watchdog Timer......................................................................................................................... 63
15.5. Timed Sequences for Changing the Configuration of the Watchdog Timer............................... 63
15.6. Register Description...................................................................................................................64
16. Interrupts................................................................................................................. 68
16.1. Interrupt Vectors in ATmega8A.................................................................................................. 68
16.2. Register Description...................................................................................................................73
17. External Interrupts................................................................................................... 76
17.1. Register Description...................................................................................................................76
18. I/O Ports.................................................................................................................. 80
18.1. Overview.................................................................................................................................... 80
18.2. Ports as General Digital I/O........................................................................................................81
18.3. Alternate Port Functions.............................................................................................................84
18.4. Register Description...................................................................................................................93
19. 8-bit Timer/Counter0..............................................................................................104
19.1. Features................................................................................................................................... 104
19.2. Overview.................................................................................................................................. 104
19.3. Timer/Counter Clock Sources.................................................................................................. 105
19.4. Counter Unit............................................................................................................................. 105
19.5. Operation..................................................................................................................................106
19.6. Timer/Counter Timing Diagrams.............................................................................................. 106
19.7. Register Description.................................................................................................................106
AVR 8-Bit Microcontroller
© 2017 Microchip Technology Inc.
Datasheet Complete
40001974A-page 4