A.MOV DPTR,#3F98H B.MOV R0,#0FEH C.MOV 50H,#0FC3DH D.INC R0
A.INC DPTR B.MOV R0,#0FEH C.DEC A D.PUSH A
A.MOV P0,#0FFH B.CLR P1.0 C.CPL A D.POP PSW