ATmega640/1280/1281/2560/2561
15.2.3
EIMSK – External Interrupt Mask Register
Bit
7
6
5
4
3
2
1
0
0x1D (0x3D)
Read/Write
Initial Value
INT7
R/W
0
INT6
R/W
0
INT5
R/W
0
INT4
R/W
0
INT3
R/W
0
INT2
R/W
0
INT1
R/W
0
INT0
R/W
0
EIMSK
• Bits 7:0 – INT7:0: External Interrupt Request 7 - 0 Enable
When an INT7:0 bit is written to one and the I-bit in the Status Register (SREG) is set (one), the
corresponding external pin interrupt is enabled. The Interrupt Sense Control bits in the External
Interrupt Control Registers – EICRA and EICRB – defines whether the external interrupt is acti-
vated on rising or falling edge or level sensed. Activity on any of these pins will trigger an
interrupt request even if the pin is enabled as an output. This provides a way of generating a
software interrupt.
15.2.4
EIFR – External Interrupt Flag Register
Bit
0x1C (0x3C)
7
6
5
INTF5
R/W
0
4
INTF4
R/W
0
3
INTF3
R/W
0
2
INTF2
R/W
0
1
INTF1
R/W
0
0
IINTF0
R/W
0
INTF7
INTF6
R/W
0
EIFR
Read/Write
R/W
Initial Value
0
• Bits 7:0 – INTF7:0: External Interrupt Flags 7 - 0
When an edge or logic change on the INT7:0 pin triggers an interrupt request, INTF7:0 becomes
set (one). If the I-bit in SREG and the corresponding interrupt enable bit, INT7:0 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 INT7:0 are configured as level interrupt. Note that when entering sleep
mode with the INT3:0 interrupts disabled, the input buffers on these pins will be disabled. This
may cause a logic change in internal signals which will set the INTF3:0 flags. See “Digital Input
Enable and Sleep Modes” on page 74 for more information.
15.2.5
PCICR – Pin Change Interrupt Control Register
Bit
(0x68)
7
6
5
–
4
–
3
–
2
PCIE2
R/W
0
1
PCIE1
R/W
0
0
PCIE0
R/W
0
–
–
PCICR
Read/Write
R
0
R
0
R
0
R
0
R
0
Initial Value
• Bit 2 – PCIE2: Pin Change Interrupt Enable 1
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 inter-
rupt. 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 PCINT15:8 pin will cause an inter-
rupt. The corresponding interrupt of Pin Change Interrupt Request is executed from the PCI1
Interrupt Vector. PCINT15:8 pins are enabled individually by the PCMSK1 Register.
• Bit 0 – PCIE0: Pin Change Interrupt Enable 0
115
2549L–AVR–08/07
ATMEL [ ATMEL ]
