PL_INTR_EVENT
u_short st = inpw(PLC(PB,PL_INTR_EVENT)) ;
u_short st = inpw(PLC(PA,PL_INTR_EVENT)) ;
(void)inpw(PLC(p,PL_INTR_EVENT)) ; /* clear interrupt event reg */
(void)inpw(PLC(np,PL_INTR_EVENT)) ;