Datasheet

68
2545T–AVR–05/11
ATmega48/88/168
13.2.2 EIMSK – External interrupt mask register
• Bit 7..2 – Res: Reserved bits
These bits are unused bits in the Atmel 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 inter-
rupt 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 inter-
rupt request even if INT0 is configured as an output. The corresponding interrupt of external
interrupt request 0 is executed from the INT0 interrupt vector.
13.2.3 EIFR – External interrupt flag register
• Bit 7..2 – Res: Reserved bits
These bits are unused bits in the ATmega48/88/168, 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 76543210
0x1D (0x3D) ––––––INT1INT0EIMSK
Read/write RRRRRRR/WR/W
Initial value 00000000
Bit 76543210
0x1C (0x3C) ––––––INTF1INTF0EIFR
Read/write RRRRRRR/WR/W
Initial value 00000000