START:
LOOP:  SETB P2.0
       JNB 2.0,SUBONE
       SETB P2.1
       JB 2.1,SUBTWO
       SETB 2.2
       JB 2.2,SUBTHREE
       SEB 2.3
       JB 2.3,SUBFOUR
       SJMP LOOP

SUBONE:
       RET
SUBTWO:
       RET
SUBTHREE:
       RET
SUBFOUR:
       RET
       END