PM_MASK
reg16 &= ~(PM_MASK << (bit * 2));
reg16 = (reg16 >> (bit * 2)) & PM_MASK;
reg16 = (reg16 >> (bit * 2)) & PM_MASK;
pm &= ~(PM_MASK << (pin * 2));
reg &= ~(PM_MASK << (pin * 2));
#define PM_PIN_MASK(pin) (PM_MASK << ((pin) * 2))
reg = (reg >> (bit * 2)) & PM_MASK;
reg = (reg >> (bit * 2)) & PM_MASK;