85
2513L–AVR–03/2013
ATmega162/V
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 44. 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.
Extended MCU
Control Register –
EMCUCR
Bit 0 – ISC2: Interrupt Sense Control 2
The asynchronous External Interrupt 2 is activated by the external pin INT2 if the SREG I-bit and
the corresponding interrupt mask in GICR are set. If ISC2 is cleared (zero), a falling edge on
INT2 activates the interrupt. If ISC2 is set (one), a rising edge on INT2 activates the interrupt.
Edges on INT2 are registered asynchronously. Pulses on INT2 wider than the minimum pulse
width given in
Table 45 will generate an interrupt. Shorter pulses are not guaranteed to generate
an interrupt. When changing the ISC2 bit, an interrupt can occur. Therefore, it is recommended
to first disable INT2 by clearing its Interrupt Enable bit in the GICR Register. Then, the ISC2 bit
can be changed. Finally, the INT2 Interrupt Flag should be cleared by writing a logical one to its
Interrupt Flag bit (INTF2) in the GIFR Register before the interrupt is re-enabled.
Table 43. 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 44. 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
765
4321
0
SM0
SRL2
SRL1
SRL0
SRW01
SRW00
SRW11
ISC2
EMCUCR
Read/Write
R/W
Initial Value
000
0000
0
Table 45. Asynchronous External Interrupt Characteristics
Symbol
Parameter
Condition
Min.
Typ.
Max.
Units
tINT
Minimum pulse width for
asynchronous external interrupt
50
ns