;PROGRAM NAME B11-5.ASM
MS10    EQU     9217    ;APPROXIMATELY 10MS INTERRUPR
INTR_CNT EQU    30H     ;CNT STORIAGE
BUFFER  EQU     31H     ;DISPLAY BUFFER
BINARY  EQU     32H     ;BINARY DATA 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
        MOV     BINARY,#00H ;BINARY DATA FOR DISPLAY
;
$LOOP   MOV     A,BINARY
        ADD     A,#01H
        MOV     BINARY,A
        CJNE    A,#100,$S100;IF A>=100 THEN A=0
        MOV     BINARY,#00H ;CLEAR BINARY DATA
;
$S100   ACALL   CONV    ;CONVERT BINARY TO BCD
;
        ACALL   DELAY
        ACALL   DELAY
        ACALL   DELAY
        SJMP    $LOOP
;
CONV    MOV     A,BINARY
        MOV     B,#10
        DIV     AB      ;A=A/10,B=A MOD 10
        ANL     A,#0FH  ;A=A AND 0FH
        JNZ     $1
        MOV     A,#0FH  ;IF A=00H THEN A=0FH LEADING BLANK
$1      SWAP    A
        ORL     A,B     ;A AS BCD FORM
        MOV     BUFFER,A ;SAVE AT BUFFER
        RET
;
DELAY   MOV     R7,#00H
$1      MOV     R6,#00H
        DJNZ    R6,$
        DJNZ    R7,$1
        RET
;
T0_ISR  SETB    SCOPE
        MOV     TH0,#(65536-MS10) / 256 ;RELOAD TH0
        MOV     TL0,#(65536-MS10) .MOD. 256
        PUSH    A
        PUSH    PSW
;
        MOV     A,BUFFER
        ANL     A,#0FH  ;GET LOW NIBBLE
        SETB    ACC.5   ;BIT5=1
        MOV     P1,A    ;SHOW 1 DIGIT
        MOV     R0,#30H
        DJNZ    R0,$    ;DELAY
;inter-blanking
        CLR     ACC.4
        CLR     ACC.5
        MOV     P1,A    ;ALL DIGIT BLANK
        MOV     R0,#04H
        DJNZ    R0,$    ;DELAY
;
        MOV     A,BUFFER
        ANL     A,#F0H  ;GET HIGH NIBBLE
        SWAP    A       ;SWAP A
        SETB    ACC.4   ;BIT4=1
        MOV     P1,A    ;SHOW ANOTHER DIGIT
        MOV     R0,#30H
        DJNZ    R0,$    ;DELAY
;
        CLR     ACC.4
        CLR     ACC.5
        MOV     P1,A    ;ALL DIGIT BLANK
;
;INTR_CNT+1
        INC     INTR_CNT
        MOV     A,INTR_CNT
        CJNE    A,#100,$T0_END
        MOV     INTR_CNT,#00H
$T0_END POP     PSW
        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
;