57
ATmega16M1/32M1/64M1 [DATASHEET]
8209E–AVR–11/2012
12.2.3
EIFR – External Interrupt Flag Register
Bit 7:4 – Res: Reserved
These bits are reserved and will always read as zero.
Bit 3:0 – INTF[3:0]: External Interrupt Flag 3:0
When an edge or logic change on the INT3:0 pin triggers an interrupt request, INTF3:0 becomes set (one). If the I-
bit in SREG and the corresponding interrupt enable bit INT3:0 in EIMSK, are set (one), the MCU will jump to the
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. These flags are always cleared when INT3:0 are configured as a level interrupt.
12.2.4
PCICR – Pin Change Interrupt Control Register
Bit 7:4 - Res: Reserved
These bits are reserved and will always read as zero.
Bit 3 - PCIE3: Pin Change Interrupt Enable 3
When the PCIE3 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), pin change interrupt 3 is
enabled. Any change on any enabled PCINT26:24 pin will cause an interrupt. The corresponding interrupt of Pin
Change Interrupt Request is executed from the PCI3 Interrupt Vector. PCINT26:24 pins are enabled individually by
the PCMSK3 Register.
Bit 2 - PCIE2: Pin Change Interrupt Enable 2
When the PCIE2 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), pin change interrupt 2 is
enabled. Any change on any enabled PCINT23:16 pin will cause an interrupt. The corresponding interrupt of Pin
Change Interrupt Request is executed from the PCI2 Interrupt Vector. PCINT23:16 pins are enabled individually by
the PCMSK2 Register.
Bit 1 - PCIE1: Pin Change Interrupt Enable 1
When the PCIE1 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), pin change interrupt 1 is
enabled. Any change on any enabled PCINT14:8 pin will cause an interrupt. The corresponding interrupt of Pin
Change Interrupt Request is executed from the PCI1 Interrupt Vector. PCINT14:8 pins are enabled individually by
the PCMSK1 Register.
Bit 0 - PCIE0: Pin Change Interrupt Enable 0
When the PCIE0 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), pin change interrupt 0 is
enabled. Any change on any enabled PCINT7:0 pin will cause an interrupt. The corresponding interrupt of Pin
Change Interrupt Request is executed from the PCI0 Interrupt Vector. PCINT7:0 pins are enabled individually by
the PCMSK0 Register.
Bit
7
6
543
21
0
–
INTF3
INTF2
INTF1
INTF0
EIFR
Read/write
R
R/W
Initial value
0
Bit
7
65
43
2
1
0
–
PCIE3
PCIE2
PCIE1
PCIE0
PCICR
Read/write
RRR
RR
R/W
Initial value
0