57
8025I–AVR–02/09
ATmega48P/88P/168P/328P
9. Interrupts
This section describes the specifics of the interrupt handling as performed in
ATmega48P/88P/168P/328P. For a general explanation of the AVR interrupt handling, refer to
”Reset and Interrupt Handling” on page 14.
The interrupt vectors in ATmega48P, ATmega88P, ATmega168P, and ATmega328P are gener-
ally the same, with the following differences:
• Each Interrupt Vector occupies two instruction words in ATmega168P and ATmega328P, and
one instruction word in ATmega48P and ATmega88P.
• ATmega48P does not have a separate Boot Loader Section. In ATmega88P, ATmega168P,
and ATmega328P, the Reset Vector is affected by the BOOTRST fuse, and the Interrupt Vector
start address is affected by the IVSEL bit in MCUCR.
9.1 Interrupt Vectors in ATmega48P
Table 9-1. Reset and Interrupt Vectors in ATmega48P
Vector No. Program Address Source Interrupt Definition
1 0x000 RESET
External Pin, Power-on Reset, Brown-out Reset and Watchdog System Reset
2 0x001 INT0 External Interrupt Request 0
3 0x002 INT1 External Interrupt Request 1
4 0x003 PCINT0 Pin Change Interrupt Request 0
5 0x004 PCINT1 Pin Change Interrupt Request 1
6 0x005 PCINT2 Pin Change Interrupt Request 2
7 0x006 WDT Watchdog Time-out Interrupt
8 0x007 TIMER2 COMPA Timer/Counter2 Compare Match A
9 0x008 TIMER2 COMPB Timer/Counter2 Compare Match B
10 0x009 TIMER2 OVF Timer/Counter2 Overflow
11 0x00A TIMER1 CAPT Timer/Counter1 Capture Event
12 0x00B TIMER1 COMPA Timer/Counter1 Compare Match A
13 0x00C TIMER1 COMPB Timer/Coutner1 Compare Match B
14 0x00D TIMER1 OVF Timer/Counter1 Overflow
15 0x00E TIMER0 COMPA Timer/Counter0 Compare Match A
16 0x00F TIMER0 COMPB Timer/Counter0 Compare Match B
17 0x010 TIMER0 OVF Timer/Counter0 Overflow
18 0x011 SPI, STC SPI Serial Transfer Complete
19 0x012 USART, RX USART Rx Complete
20 0x013 USART, UDRE USART, Data Register Empty
21 0x014 USART, TX USART, Tx Complete
22 0x015 ADC ADC Conversion Complete
23 0x016 EE READY EEPROM Ready
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