以下是一个0到99度的测温程序，只要把数据处理程序改一下就可以改变测量范围和精度。
#INCLUDE <P16F877A.INC>
CBLOCK 20H
INPUT_HIGH_8 ;high 8 bit,don't allow other P use it but temperature conversion p
INPUT_LOW_8 ;low 8 bit,don't allow other P use it but temperature conversion p
DELAY_TEMP0
DELAY_TEMP1
PASS_TEMP
UNITS_ORDER
TENS_DIGIT
COUNT_16
ENDC
ORG 00H
NOP
GOTO INITIAL
ORG 05H
TABLE
ADDWF PCL,1
DT 0C0H,0F9H,0A4H,0B0H,99H,92H,82H,0F8H,80H,90H,90H,90H,90H ;comment anode
DISPLAY
MOVFW UNITS_ORDER
CALL TABLE
MOVWF PORTC
BCF PORTA,0 ;trigger transistor of NPN than display units_order
CALL DELAY_1MS
BSF PORTA,0 ;close
MOVFW TENS_DIGIT
CALL TABLE
MOVWF PORTC
BCF PORTA,1 ;trigger transistor of NPN than display tens_digit
CALL DELAY_1MS
BSF PORTA,1
RETURN
DELAY_1MS
MOVLW 12H
MOVWF DELAY_TEMP0
MOVLW 12H
MOVWF DELAY_TEMP1
DECFSZ DELAY_TEMP1
GOTO $-1
DECFSZ DELAY_TEMP0
GOTO $-5
RETURN
INITIAL
BANKSEL TRISA
MOVLW 00H
MOVWF TRISA ;porta0..1 to launch LED, porta2 18b20 communICation port
MOVLW B'00000110' ;set porta as digital port
MOVWF ADCON1
MOVLW 00H
MOVWF TRISC ;8 bits led data bus
MOVLW 0FFH ;portb1 as a command key
MOVWF TRISB
MOVLW 00H
MOVWF OPTION_REG ;portb as week pull up
BANKSEL PORTA
CLRF UNITS_ORDER
CLRF TENS_DIGIT
MAIN
CALL DISPLAY ;press key to start the function
BTFSC PORTB,2
GOTO $-2
BTFSS PORTB,2 ;key release?
GOTO $-1
CALL INITIAL_18B20
BTFSS DELAY_TEMP1,1
GOTO MAIN
MOVLW 0CCH ;skip the rom
MOVWF PASS_TEMP
CALL WRITE_18B20
MOVLW 44H ;release the command of conversion
MOVWF PASS_TEMP
CALL WRITE_18B20
MOVLW D'30'
MOVWF COUNT_16
MOVLW D'90' ;delay 900ms for conversion
MOVWF DELAY_TEMP1
MOVLW D'110'
MOVWF DELAY_TEMP0
DECFSZ DELAY_TEMP0
GOTO $-1
DECFSZ DELAY_TEMP1
GOTO $-5
DECFSZ COUNT_16
GOTO $-9
CALL INITIAL_18B20
BTFSS DELAY_TEMP1,1
GOTO MAIN
MOVLW 0CCH
MOVWF PASS_TEMP
CALL WRITE_18B20 ;release the command of reading
MOVLW 0BEH
MOVWF PASS_TEMP
CALL WRITE_18B20
CALL READ_18B20
CALL INITIAL_18B20 ;end the other data to transmit
BTFSS DELAY_TEMP1,1
GOTO MAIN
CALL BCD_CONVERSION
GOTO MAIN
INITIAL_18B20
BCF PORTB,2
BANKSEL TRISA
BCF TRISA,2
BANKSEL PORTA
MOVLW 0BH
MOVWF DELAY_TEMP0
MOVLW 22H
MOVWF COUNT_16
DECFSZ COUNT_16,1
GOTO $-1 ;delay 586us
DECFSZ DELAY_TEMP0,1
GOTO $-5
BANKSEL TRISA
BSF TRISA,2 ;release the bus
BANKSEL PORTA
MOVFW PORTA
MOVLW D'25' ;delay 76us
MOVWF DELAY_TEMP0
DECFSZ DELAY_TEMP0,1
GOTO $-1
BTFSS PORTA,2
GOTO $+3
BCF DELAY_TEMP1,1 ;not respondence
GOTO $+2
BSF DELAY_TEMP1,1
MOVLW D'160' ;delay 480us
MOVWF DELAY_TEMP0
DECFSZ DELAY_TEMP0,1
GOTO $-1
BSF DELAY_TEMP1,1 ;the slave device responded and set the bit of flag
RETURN
WRITE_18B20
MOVLW 08H
MOVWF DELAY_TEMP0
BCF STATUS,C
WR_LOOP1
BCF PORTA,2
BANKSEL TRISA
BCF TRISA,2
BANKSEL PORTA
NOP
NOP
RRF PASS_TEMP,1
BTFSS STATUS,C
GOTO WR_ZERO
BANKSEL TRISA
BSF TRISA,2
BANKSEL PORTA
WR_ZERO
MOVLW D'25' ;delay 75us
MOVWF DELAY_TEMP1
DECFSZ DELAY_TEMP1
GOTO $-1
BANKSEL TRISA
BSF TRISA,2
BANKSEL PORTA
NOP
NOP
DECFSZ DELAY_TEMP0,1
GOTO WR_LOOP1
RETURN
READ_18B20
MOVLW D'16'
MOVWF DELAY_TEMP0
READ_LOOP2
BCF PORTA,2
BANKSEL TRISA
BCF TRISA,2
BANKSEL PORTA
NOP
NOP
NOP
NOP
NOP
BANKSEL TRISA
BSF TRISA,2
BANKSEL PORTA
NOP
NOP
NOP
NOP
BTFSS PORTA,2
GOTO $+3
BSF STATUS,C
GOTO $+2
BCF STATUS,C
RRF INPUT_HIGH_8,1
RRF INPUT_LOW_8,1
MOVLW D'20' ;delay 60us
MOVWF DELAY_TEMP1
DECFSZ DELAY_TEMP1,1
GOTO $-1
DECFSZ DELAY_TEMP0,1
GOTO READ_LOOP2
RETURN
BCD_CONVERSION
MOVLW 08H
MOVWF COUNT_16
MOVLW 0FH
ANDWF INPUT_HIGH_8,1
SWAPF INPUT_HIGH_8,1
MOVLW 0F0H
ANDWF INPUT_LOW_8,1
SWAPF INPUT_LOW_8,1
MOVFW INPUT_LOW_8
ADDWF INPUT_HIGH_8,1 ;save 8bits data in input_high_8
CLRF INPUT_LOW_8
BCF STATUS,C
LOOP_8TIMES
RLF INPUT_HIGH_8,1
RLF INPUT_LOW_8,1
DECFSZ COUNT_16
GOTO $+2
GOTO SEPARATE_2RS
MOVLW INPUT_LOW_8
MOVWF FSR
CALL ADJ_BCD
GOTO LOOP_8TIMES
ADJ_BCD
MOVLW 03H
ADDWF INDF,W
MOVWF TENS_DIGIT
BTFSC TENS_DIGIT,3
MOVWF INDF ;if the low four bits plus 3 is more than 7,
MOVLW 30H ;add 3,if less than 7,do not change it
ADDWF INDF,W ;if the high four bits plus 3 is more than 7,than
MOVWF TENS_DIGIT
BTFSC TENS_DIGIT,7 ;add 3,if less than 7,do not change it
MOVWF INDF
RETURN
SEPARATE_2RS
MOVFW INPUT_LOW_8
MOVWF UNITS_ORDER
MOVWF TENS_DIGIT
MOVLW 0FH
ANDWF UNITS_ORDER,1
MOVLW 0F0H
ANDWF TENS_DIGIT,1
SWAPF TENS_DIGIT,1
RETURN
END
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