MS      EQU (50)
CYCLES  EQU (1000*MS)
TIME    EQU (10000H - CYCLES)

ORG 0
        MOV R7, #20
        CALL INIT_TIMER

        SJMP $

ORG 0BH
        MOV TH0, #HIGH(TIME)
        MOV TL0, #LOW(TIME)

        DJNZ R7, CON
        MOV R7, #20

        CPL P1.0
CON:
        RETI

;-------------------------------------------------------
INIT_TIMER:
    CLR TR0
    ANL TMOD, #11110000B
    ORL TMOD, #1

    MOV TH0, #HIGH(TIME)
    MOV TL0, #LOW(TIME)
    CLR TF0

    SETB ET0
    SETB EA
    SETB TR0

    RET

END