ORG     0H
        JMP     START
        ORG     03H
        JMP     INTERRUPT
START:
        SETB    IT0
        MOV     IP,#00000001B
        MOV     IE,#10000001B
        MOV     A,#1
MAIN:
        MOV     P1,A
        RL      A
        CALL    DELAY
        JMP     MAIN
DELAY:
        MOV     R7,#1FH
        DJNZ    R7,$
        RET
INTERRUPT:
        CPL     A
        RETI
        END