;PROGRAM NAME B11-2.ASM
MS10    EQU     9217    ;APPROXIMATELY 10MS INTERRUPR
INTR_CNT EQU    30H     ;CNT STORIAGE
;
SCOPE   REG     P3.3    ;CHECK BY SCOPE
BUZZER  REG     P3.4
LED     REG     P3.7
;
        ORG     0000H
        JMP     START
        ORG     0003H   ;[DISABLE]  EXTERNAL INT0 INTERRUPT
        RETI
        ORG     000BH   ;[ENABLE]  TIMER0 OVERFLOW INTERRUPT
        JMP     T0_ISR
;
        ORG     0013H
        RETI            ;[DISABLE] EXTERNAL INT1 INTERRUPT
        ORG     001BH
        RETI            ;[DISABLE] TIMER1 OVERFLOW INTERRUPT
        ORG     0023H
        RETI            ;[DISABLE] SERIAL INTERRUPT
;
        ORG     30H
START   MOV     R0,#00H
        DJNZ    R0,$    ;DELAY A WHILE
        MOV     SP,#60H
        MOV     P1,#FFH
        MOV     P3,#FFH
        MOV     INTR_CNT,#00H
        CLR     BUZZER  ;P3.4=0,BUZZER OFF
        CLR     LED     ;P3.7=0,LED OFF
;
        CALL    SET_TMR0
$LOOP   SJMP    $LOOP
;
T0_ISR  SETB    SCOPE
        MOV     TH0,#(65536-MS10) / 256 ;RELOAD TH0
        MOV     TL0,#(65536-MS10) .MOD. 256
        PUSH    A
        MOV     A,INTR_CNT
        CJNE    A,#10,$1
$1      JNC     $2
        SETB    BUZZER
        SJMP    $3
$2      CLR     BUZZER
$3      INC     INTR_CNT
        MOV     A,INTR_CNT
        CJNE    A,#100,$T0_END
        MOV     INTR_CNT,#00H
$T0_END POP     A
        CLR     SCOPE
        RETI
;
SET_TMR0
        MOV     A,#01H  ;TIMER MODE 1
        MOV     TMOD,A
        MOV     TH0,#(65536-MS10) / 256 ;RELOAD TH0
        MOV     TL0,#(65536-MS10) .MOD. 256
        CLR     TF0     ;CLEAR TIMER0 FLAG
        SETB    TR0     ;TIMER0 START COUNT
        SETB    ET0     ;ENABLE TIMER0 INTERRUPT
        SETB    EA      ;ENABLE SYSTEM INTERRUPT
        RET
;