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 corresponding 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.