3
Parameter
MODBUS Hold Register Address (16-bit)
Real-time Temperature Value
0000H,float standard: A, B, C, D
Slave Address (Address)
002FH,unsigned integer representation, Default:123
Baud Rate
0030H, the default slave address is 9600, it is saved as 96
when saving, and so on (all to be divided by 100)
Keep the register list
Notes
Access to other addresses is not allowed.
Temperature, float representation IEEE754, single format, 32 bit
s e[8] f[23]
s e7 e6 e5 e4 e3 e2 e1 e0 f22 f21 f20 f19 f18 f17 f16 f15 f14 f12 f11 f10 f9 f8 f7 f6 f5 f4 f3 f2
f1 f0
Splitting into 4 bytes for Modbus encoding
A: [ s e7 e6 e5 e4 e3 e2 e1]
B: [e0 f22 f21 f20 f19 f18 f17 f16]
C: [f15 f14 f12 f11 f10 f9 f8]
D: [f7 f6 f5 f4 f3 f2 f1 f0]
Most masters do use the A, B, C, D representation
.
MODBUS RTU Instruction
Supported MODBUS function codes: 0x03, 0x06
Example of 03H function code: Read the temperature measurement data of the sensor with slave
address 123.
Host Query Command
Slave Address
7BH
Slave Address
Function
03H
Function code
Byte Count
04H
4 bytes in length
Data Hi
42H
The temperature at this time is: 92.5589 °C
Data Lo
B9H
The temperature at this time is: 92.5589 °C
Data Hi
1EH
The temperature at this time is: 92.5589 °C
Data Lo
33H
The temperature at this time is: 92.5589 °C
CRC Check Lo
ADH
CRC check code is 8 bits low
CRC Check Hi
DCH
CRC check code is 8 bits high
Slave Address
7BH
Slave Address
Function
03H
Function code
Starting Address Hi
00H
Start register address is 8 bits high
Starting Address Lo
00H
Start register address is 8 bits low
No. of Registers Hi
00H
The upper 8 bits of the number of registers
No. of Registers Lo
02H
The lower 8 bits of the number of registers
CRC Check Lo
CFH
CRC check code low 8 bits
CRC Check Hi
91H
CRC check code high 8 bits
Response
Example of 06H function code: Modify the baud rate (this example is modified to 57600bps).
