Pin Change Enable
Mask [n = 7:0]
Each PCINT[7:0] bit
selects whether pin change interrupt is enabled on the corresponding I/O pin. If
PCINT[7:0] is set and the PCIE0 bit in PCICR is set, pin change interrupt is enabled
on the corresponding I/O pin. If PCINT[7:0] is cleared, pin change interrupt on the
corresponding I/O pin is disabled.