82
7530J–AVR–03/12
Atmel ATmega48/88/168 Automotive
Bit 1, 0 – ISC01, ISC00: Interrupt Sense Control 0 Bit 1 and Bit 0
The External Interrupt 0 is activated by the external pin INT0 if the SREG I-flag and the corre-
sponding interrupt mask are set. The level and edges on the external INT0 pin that activate the
interrupt are defined in
Table 11-2. The value on the INT0 pin is sampled before detecting
edges. If edge or toggle interrupt is selected, pulses that last longer than one clock period will
generate an interrupt. Shorter pulses are not guaranteed to generate an interrupt. If low level
interrupt is selected, the low level must be held until the completion of the currently executing
instruction to generate an interrupt.
11.0.2
External Interrupt Mask Register – EIMSK
Bit 7..2 – Res: Reserved Bits
These bits are unused bits in the ATmega48/88/168, and will always read as zero.
Bit 1 – INT1: External Interrupt Request 1 Enable
When the INT1 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), the exter-
nal pin interrupt is enabled. The Interrupt Sense Control1 bits 1/0 (ISC11 and ISC10) in the
External Interrupt Control Register A (EICRA) define whether the external interrupt is activated
on rising and/or falling edge of the INT1 pin or level sensed. Activity on the pin will cause an
interrupt request even if INT1 is configured as an output. The corresponding interrupt of External
Interrupt Request 1 is executed from the INT1 Interrupt Vector.
Table 11-1.
Interrupt 1 Sense Control
ISC11
ISC10
Description
0
The low level of INT1 generates an interrupt request.
0
1
Any logical change on INT1 generates an interrupt request.
1
0
The falling edge of INT1 generates an interrupt request.
1
The rising edge of INT1 generates an interrupt request.
Table 11-2.
Interrupt 0 Sense Control
ISC01
ISC00
Description
0
The low level of INT0 generates an interrupt request.
0
1
Any logical change on INT0 generates an interrupt request.
1
0
The falling edge of INT0 generates an interrupt request.
1
The rising edge of INT0 generates an interrupt request.
Bit
7
6543
210
–
––––
–
INT1
INT0
EIMSK
Read/Write
RRRR
RR
R/W
Initial Value
0
0000
000