51 MCU Experiment Board DS18B20 Temperature Measurement Program

/***********************************************
** Experiment name: 51 single chip microcomputer experimental board temperature measurement (DS18B20)
** Creator: Xie Junyang
** Description: P3.7 port input, output data.
**------------------------------------------------------------------
** CPU: MCS-51
** Language: Assembly
** Fosc=12M The simulation diagram of this experiment ***************************************************/

GE_BIT EQU 30H
SHI_BIT EQU 31H
BAI_BIT
EQU 32H DI_8BIT
EQU 33H GAO_8BIT EQU 34H
DQ EQU P3.7
ORG 0000H
LJMP START
ORG 0020H
START:
MOV SP,#60H
LCALL ZHUANHUAN ;Call the temperature reading subroutine
LCALL CHULI
LCALL DISPLAY ;Call the digital tube display subroutine
LJMP START

;-------------------------------------------------
;This is the DS18B20 reset initialization subroutine
INIT_1820:
SETB DQ
NOP
CLR DQ ;The host sends a reset low pulse with a delay of 537 microseconds
MOV R1,#3
DU_1:
MOV R0,#107
DJNZ R0,$
DJNZ R1,DU_1
SETB DQ ;Then pull up the data line
NOP
NOP
NOP
MOV R0,#25H
DU_2:JNB DQ,DU_3 ;Wait for DS18B20 to respond
DJNZ R0,DU_2
LJMP DU_4 ;Delay
DU_3:SETB F0 ;Set the flag bit, indicating that DS1820 exists
LJMP DU_5
DU_4:CLR F0 ;Clear the flag bit, indicating that DS1820 does not exist
LJMP DU_7
DU_5:MOV R0,#117
DU_6:DJNZ R0,DU_6 ;The timing requires a delay of some time
DU_7:SETB DQ
RET [page]
;-------------------------------------------------
;Write the subroutine of DS18B20 (with specific timing requirements)
WRITE_1820:MOV R2,#8 ;A total of 8 bits of data
CLR C
WR1:CLR DQ
MOV R3,#6
DJNZ R3,$
RRC A
MOV DQ,C
MOV R3,#23
DJNZ R3,$
SETB DQ
NOP
DJNZ R2,WR1
SETB DQ
RET

;-------------------------------------------------
;Program to read DS18B20, read two bytes of temperature data from DS18B20
READ_1820:MOV R4,#2 ;Read the high and low bits of temperature from DS18B20
MOV R1,#DI_8BIT ;Store the low bit in DI_8BIT and the high bit in GAO_8BIT
RE0:MOV R2,#8 ;There are 8 bits of data in total
RE1:CLR C
SETB DQ
NOP
NOP
CLR DQ
NOP
NOP
NOP
SETB DQ
MOV R3,#9
RE2:DJNZ R3,RE2
MOV C,DQ
MOV R3,#23
RE3:DJNZ R3,RE3
RRC A
DJNZ R2,RE1
MOV @R1,A
INC R1
DJNZ R4,RE0
/* DEC R1
MOV A,GAO_8BIT
XCHD A,@R1
XCH A,@R1
MOV GAO_8BIT,A
MOV A,@R1
SWAP A
MOV @R1,A */
RET
;-------------------------------------------------
;Read the converted temperature value
ZHUANHUAN:
//SETB DQ
LCALL INIT_1820 ;Reset DS18B20 first
JB F0,ZH1
RET ;Judge whether DS1820 exists? If DS18B20 does not exist, return to
ZH1: MOV A,#0CCH ;Skip ROM match
LCALL WRITE_1820
MOV A,#44H ;Issue temperature conversion command
LCALL WRITE_1820
LCALL DISPLAY ;Wait for AD conversion to end, 750 microseconds for 12 bits
LCALL INIT_1820 ;Reset before preparing to read temperature
MOV A,#0CCH ;Skip ROM match
LCALL WRITE_1820
MOV A,#0BEH ;Issue temperature read command
LCALL WRITE_1820
LCALL READ_1820
RET
;-------------------------------------------------
;Data processing subroutine
CHULI:
MOV P0,GAO_8BIT
MOV P2,DI_8BIT
MOV A,GAO_8BIT
JB ACC.7,FU
MOV A,DI_8BIT
MOV B,#16
DIV AB

MOV 35H,A ;Shift the high four bits of DI_8BIT right by four bits and store them in 35H (temperature value)
MOV A,B ;Multiply the low four bits of TEMPER_L by 10/16 to get the decimal point.
MOV B,#10
MUL AB
MOV B,#16
DIV AB
MOV 36H,A ;Store the decimal point in 36H
MOV A,GAO_8BIT ;Store the high eight digits in TEMPER_H, weight 16
MOV B,#16
MUL AB
ADD A,35H ;Store the integer part of the temperature value in 35H
MOV B,#10
DIV AB
MOV GE_BIT,B ;Store the ones digit in 30H
MOV B,#10 ;
DIV AB ;
MOV SHI_BIT,B ;Store the tens digit in 31H
MOV B,#10 ;
DIV AB ;
MOV BAI_BIT,B ;Store the hundreds digit in 32H
MOV A,GAO_8BIT
MOV 37H,#10H ;
JB ACC.7,EXIT
MOV 37H,#00H
SJMP EXIT
FU:
MOV A,DI_8BIT
CPL A
ADD A,#1
MOV B,#16
DIV AB
MOV 35H,A ; Shift the high 4 bits of DI_8BIT right by 4 bits and store them in 35H (temperature value)
MOV A,B ; Multiply the low 4 bits of TEMPER_L by 10/16 to get the decimal place.
MOV B,#10
MUL AB
MOV B,#16
DIV AB
// MOV 36H,A ; Store the decimal place in 36H
// MOV A,GAO_8BIT ;Store the high 8 digits in TEMPER_H, weight 16
MOV B,#16
MUL AB
ADD A,35H ;Store the integer part of the temperature value in 35H
MOV B,#10
DIV AB
MOV GE_BIT,B ;Store the ones digit in 30H
MOV B,#10 ;
DIV AB ;
MOV SHI_BIT,B ;Store the tens digit in 31H
MOV B,#10 ;
DIV AB ;
MOV BAI_BIT,B ;Store the hundreds digit in 32H
MOV A,GAO_8BIT
MOV 37H,#10H ;
JB ACC.7,EXIT
MOV 37H,#00H
SJMP EXIT
EXIT:RET [page]
;-------------------------------------------------
;Note: This ds18b20 temperature measurement experiment was conducted on the 51hei microcontroller experiment board http://www.51hei.com. The test was OK. The following is the data display subroutine
CL0:INC A
AJMP CL1
CHULI:MOV A,DI_8BIT
MOV B,#16
DIV AB
JB B.3,CL0
CL1:MOV 35H,A ;Shift the high four bits of DI_8BIT right by four bits and store them in 35H (temperature value)
MOV A,B ;Multiply the low four bits of TEMPER_L by 10/16 to get the first decimal place.
MOV B,#10
MUL AB
MOV B,#16
DIV AB
MOV 36H,A ;Store the last decimal digit in 36H
MOV A,GAO_8BIT ;Store the high 8 digits in TEMPER_H, weight 16
MOV B,#16
MUL AB
ADD A,35H ;Store the integer part of the temperature value in 35H
MOV B,#10
DIV AB
MOV GE_BIT,B ;Store the ones digit in 30H
MOV B,#10 ;
DIV AB ;
MOV SHI_BIT,B ;Store the tens digit in 31H
MOV B,#10 ;
DIV AB ;
MOV BAI_BIT,B ;Store the hundreds digit in 32H
MOV A,GAO_8BIT
MOV 37H,#10H ;
JB ACC.7,EXIT
MOV 37H,#00H
EXIT: RET */

DISPLAY:MOV DPTR,#TABLE
MOV R0,#4
XUN:MOV R1,#250 ;Display 1000 times
HUAN:MOV A,#10 //Display '-'
MOVC A,@A+DPTR
MOV P1,A
CLR P3.0
LCALL DELAY1MS
SETB P3.0

MOV A,#10 //Display '-'
MOVC A,@A+DPTR
MOV P1,A
CLR P3.1
LCALL DELAY1MS
SETB P3.1

MOV A,BAI_BIT //Display temperature in hundreds digit
MOVC A,@A+DPTR
MOV P1,A
CLR P3.2
LCALL DELAY1MS
SETB P3.2
MOV A,SHI_BIT //Display temperature in tens digit
MOVC A,@A+DPTR
MOV P1,A
CLR P3.3
LCALL DELAY1MS
SETB P3.3
MOV A,GE_BIT //Display temperature units
MOVC A,@A+DPTR
MOV P1,A
CLR P3.4
LCALL DELAY1MS
SETB P3.4

MOV A,#11 //Display \'C\'
MOVC A,@A+DPTR
MOV P1,A
CLR P3.5
LCALL DELAY1MS
SETB P3.5

MOV A,#10 //Display '-'
MOVC A,@A+DPTR
MOV P1,A
CLR P3.6
LCALL DELAY1MS
SETB P3.6

/* MOV A,#10 //Display '-'
MOVC A,@A+DPTR
MOV P1,A
CLR P3.7
LCALL DELAY1MS
SETB P3.7 */
DJNZ R1,HUAN ;250 endless loops
DJNZ R0,XUN ;4 endless loops of 250 times
RET

DELAY10MS:MOV R7,#1 //Delay 10MS subroutine
L1:NOP
DJNZ R7,L1
DELAY1MS:RET

TABLE:DB 3FH ;0
DB 06H ;1
DB 5BH ;2
DB 4FH ;3
DB 66H ;4
DB 6DH ;5
DB 7DH ;6
DB 07H ; 7 DB 7FH
;8
DB 6FH ;9
DB 01000000B ;-
DB 39H ;C
END