ATmega328P datasheet(72/448 Pages) ATMEL

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8161D–AVR–10/09

ATmega48PA/88PA/168PA/328P

12.2.2

EIMSK – External Interrupt Mask Register

• Bit 7..2 – Res: Reserved Bits

These bits are unused bits in the ATmega48PA/88PA/168PA/328P, 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.

• Bit 0 – INT0: External Interrupt Request 0 Enable

When the INT0 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 Control0 bits 1/0 (ISC01 and ISC00) in the

External Interrupt Control Register A (EICRA) define whether the external interrupt is activated

on rising and/or falling edge of the INT0 pin or level sensed. Activity on the pin will cause an

interrupt request even if INT0 is configured as an output. The corresponding interrupt of External

Interrupt Request 0 is executed from the INT0 Interrupt Vector.

12.2.3

EIFR – External Interrupt Flag Register

• Bit 7..2 – Res: Reserved Bits

These bits are unused bits in the ATmega48PA/88PA/168PA/328P, and will always read as

zero.

• Bit 1 – INTF1: External Interrupt Flag 1

When an edge or logic change on the INT1 pin triggers an interrupt request, INTF1 becomes set

(one). If the I-bit in SREG and the INT1 bit in EIMSK are set (one), the MCU will jump to the cor-

responding Interrupt Vector. The flag is cleared when the interrupt routine is executed.

Alternatively, the flag can be cleared by writing a logical one to it. This flag is always cleared

when INT1 is configured as a level interrupt.

• Bit 0 – INTF0: External Interrupt Flag 0

When an edge or logic change on the INT0 pin triggers an interrupt request, INTF0 becomes set

(one). If the I-bit in SREG and the INT0 bit in EIMSK are set (one), the MCU will jump to the cor-

responding Interrupt Vector. The flag is cleared when the interrupt routine is executed.

Alternatively, the flag can be cleared by writing a logical one to it. This flag is always cleared

when INT0 is configured as a level interrupt.

Bit

76543

210

0x1D (0x3D)

–––––

–

INT1

INT0

EIMSK

Read/Write

RRRR

R/W

Initial Value

00000

000

Bit

76543

210

0x1C (0x3C)

–––––

–

INTF1

INTF0

EIFR

Read/Write

RRRR

R/W

Initial Value

00000

000

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