SMC Networks HECR Series Communications Manual page 30

5.8 Explanation of function codes
5.8.1 Function code：03H Reading multiple registers
Register data of assigned points from assigned address is read.
◼
Request message <Normal> (Master to Slave)
Start Slave Address
[:]
XX XX
◼
Response message<Normal> (Slave to Master)
Start Slave Address
[:]
XX XX
◼
Communication example
1) Slave Address (=Unit number): No.1
2) Read three consecutive data from register 0040H.
(Read internal sensor temperature, external sensor temperature, average temperature.)
Your system
(Request):010300400003B9 [CR][LF]
(Response):01030609E1FC22FC22D0 [CR][LF]
Request message
Code
01 Slave Address
03 Function
0040 Head address of specified register
0003 Quantity of register to read
B9 LRC
HECR
MODBUS communication function
Function
[0] [3]
Read Address
Hi
XX XX XX
Function
[0] [3]
Byte Count
XX XX XX
Contents
Data
Quantity to Read
Lo Hi
XX XX XX
Data
Read Data1
Hi Lo
XX XX XX
Response message
Code
01 Slave Address
03 Function
06 Quantity of bytes to read
Information of 0040H
09E1
(internal sensor temperature)
Information of 0041H
FC22
(external sensor temperature)
Information of 0042H
FC22
(average temperature=external temperature)
D0 LRC
LRC End
XX XX [CR]
Lo
XX XX
LRC End
XX XX [CR]
Read Data n
Hi
Lo
XX
XX XX
This product
Data is sent and
received in ASCII
code.
Contents
[LF]
[LF]
XX
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