86
7799D–AVR–11/10
ATmega8U2/16U2/32U2
13.2.3
EIMSK – External Interrupt Mask Register
Bits 7:0 – INT[7:0]: External Interrupt Request 7:0 Enable
When an INT[7:0] 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.
13.2.4
EIFR – External Interrupt Flag Register
Bits 7:0 – INTF[7:0]: External Interrupt Flags 7:0
When an edge or logic change on the INT[7:0] pin triggers an interrupt request, INTF[7:0]
becomes set (one). If the I-bit in SREG and the corresponding interrupt enable bit, INT[7:0] 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 INT[7:0] are configured as level interrupt. Note that when
entering sleep mode with the INT[3:0] interrupts disabled, the input buffers on these pins will be
disabled. This may cause a logic change in internal signals which will set the INTF[3:0] flags.
13.2.5
PCICR – Pin Change Interrupt Control Register
Bit 1:0 – PCIE[1:0]: Pin Change Interrupt Enable 1:0
When the PCIE1/0 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), Pin
Change interrupt 1/0 is enabled. Any change on any enabled PCINT[12:8]/[7:0] pin will cause an
interrupt. The corresponding interrupt of Pin Change Interrupt Request is executed from the
PCI1/0 Interrupt Vector. PCINT[12:8]/[7:0] pins are enabled individually by the PCMSK1/0
Register.
13.2.6
PCIFR – Pin Change Interrupt Flag Register
Bit
76543210
INT7
INT6
INT5
INT4
INT3
INT2
INT1
IINT0
EIMSK
Read/Write
R/W
Initial Value
0
Bit
76543210
INTF7
INTF6
INTF5
INTF4
INTF3
INTF2
INTF1
INTF0
EIFR
Read/Write
R/W
Initial Value
0
Bit
76543210
-
–
PCIE1
PCIE0
PCICR
Read/Write
R
R/W
Initial Value
0
Bit
76543210
-
–
PCIF1
PCIF0
PCIFR
Read/Write
R
R/W
Initial Value
0