PROCESSOR 16C74
INCLUDE "P16C74B.INC "
SEC EQU 0X23 ;
MSEC EQU 0x24
TEMP1 EQU 0X22
FLAG2 EQU 0X28
ORG 0x00
GOTO START
ORG 0x04 ; 設定中斷向量
BCF STATUS,RP0
BTFSC INTCON,T0IF ; 判斷TIER0中斷標誌位是否被設置
GOTO TMR0_ISR ; 若是，則去執行TIMER0中斷子程序
RETFIE
START:
CALL PIC_INIT ;去設置端口、TIMER0工作模式
BSF INTCON,GIE
BSF INTCON,T0IE
MAIN_LOOP:
;程序的主體是個無限循環
BTFSC FLAG2,7
CALL DISPLAY
GOTO MAIN_LOOP
PIC_INIT:
CLRF INTCON
BCF INTCON,T0IE
BSF STATUS,RP0
MOVLW B'00000000' ;B’XXXXXXXX’表示單引號中的數是二
MOVWF TRISB
MOVLW B'00000000'
MOVWF TRISC
BCF STATUS,RP0
MOVLW B'11000000' ;B’XXXXXXXX’表示單引號中的數是二
MOVWF PORTB
MOVLW B'11000000'
MOVWF PORTC
BSF STATUS,RP0
MOVLW B'11000100'
MOVWF OPTION_REG ; 對TIMER0工作模式進行設置，32分頻
BCF STATUS,RP0
MOVLW 0X06
MOVWF TMR0
CLRF SEC
CLRF MSEC
CLRF TEMP1
CLRF FLAG2
RETURN
TMR0_ISR:
CLRWDT
BSF FLAG2,7
BCF INTCON,T0IF
MOVLW 0X06
MOVWF TMR0
CLRWDT
INCF TEMP1,1
MOVF TEMP1,0
SUBLW .125 ;125-TEMP
BTFSS STATUS,2
RETFIE
CLRWDT
CLRF TEMP1
INCF MSEC,1
RETFIE
DISPLAY:
MOVF MSEC,0
SUBLW .10
BTFSS STATUS,2
GOTO NEXT_1
CLRWDT
CLRF MSEC
INCF SEC,1
MOVF SEC,0
SUBLW .6
BTFSS STATUS,2
GOTO NEXT_1
CLRF SEC
NEXT_1:
CLRWDT
MOVF MSEC,W
CALL CHAR_CODE
MOVWF PORTC
MOVF SEC,W
CALL CHAR_CODE
MOVWF PORTB
BCF FLAG2,7
RETURN
CHAR_CODE:
ADDWF PCL,1 ;PCL+=W
RETLW B'11000000' ; Code for 0
RETLW B'11111001' ; Code for 1
RETLW B'10100100' ; Code for 2
RETLW B'10110000' ; Code for 3
RETLW B'10011001' ; Code for 4
RETLW B'10010010' ; Code for 5
RETLW B'10000010' ; Code for 6
RETLW B'11111000' ; Code for 7
RETLW B'10000000' ; Code for 8
RETLW B'10010000' ; Code for 9
END