Pin Change Enable
Mask
Each PCINT[15:8]-bit
selects whether pin change interrupt is enabled on the corresponding I/O pin. If
PCINT[15:8] is set and the PCIE1 bit in PCICR is set, pin change interrupt is
enabled on the corresponding I/O pin. If PCINT[15:8] is cleared, pin change
interrupt on the corresponding I/O pin is disabled.