Datasheet

ATmega8A [DATASHEET]

8159E–AVR–02/2013

12. Interrupts

This section describes the specifics of the interrupt handling performed by the ATmega8A. For a general explana-

tion of the AVR interrupt handling, refer to “Reset and Interrupt Handling” on page 12.

12.1 Interrupt Vectors in ATmega8A

Notes: 1. When the BOOTRST Fuse is programmed, the device will jump to the Boot Loader address at reset, see “Boot

Loader Support – Read-While-Write Self-Programming” on page 194.

2. When the IVSEL bit in GICR is set, Interrupt Vectors will be moved to the start of the boot Flash section. The

address of each Interrupt Vector will then be the address in this table added to the start address of the boot Flash

section.

Table 12-2 shows reset and Interrupt Vectors placement for the various combinations of BOOTRST and IVSEL

settings. If the program never enables an interrupt source, the Interrupt Vectors are not used, and regular program

code can be placed at these locations. This is also the case if the Reset Vector is in the Application section while

the Interrupt Vectors are in the boot section or vice versa.

Table 12-1. Reset and Interrupt Vectors

Vector No.

Program

Address

(2)

Source Interrupt Definition

1 0x000

(1)

RESET External Pin, Power-on Reset, Brown-out Reset,

and Watchdog Reset

2 0x001 INT0 External Interrupt Request 0

3 0x002 INT1 External Interrupt Request 1

4 0x003 TIMER2 COMP Timer/Counter2 Compare Match

5 0x004 TIMER2 OVF Timer/Counter2 Overflow

6 0x005 TIMER1 CAPT Timer/Counter1 Capture Event

7 0x006 TIMER1 COMPA Timer/Counter1 Compare Match A

8 0x007 TIMER1 COMPB Timer/Counter1 Compare Match B

9 0x008 TIMER1 OVF Timer/Counter1 Overflow

10 0x009 TIMER0 OVF Timer/Counter0 Overflow

11 0x00A SPI, STC Serial Transfer Complete

12 0x00B USART, RXC USART, Rx Complete

13 0x00C USART, UDRE USART Data Register Empty

14 0x00D USART, TXC USART, Tx Complete

15 0x00E ADC ADC Conversion Complete

16 0x00F EE_RDY EEPROM Ready

17 0x010 ANA_COMP Analog Comparator

18 0x011 TWI Two-wire Serial Interface

19 0x012 SPM_RDY Store Program Memory Ready