SMC Networks HECR Series - Page 33

MODBUS communication function
5-11 HECR
5.8.4 Function code：17H Reading/writing multiple registers
Register content of assigned points of assigned address is read. Write the register data from the
specified address with specified points simultaneously.
◼ Request message <Normal> (Master to Slave)
Start
Slave Address
Function
Data
LRC
End
[:]
XX
XX
[1]
[7]
XX
XX
[CR]
[LF]
Read Address
Quantity to Read
Write Address
Quantity to Write
Hi
Lo
Hi
Lo
Hi
Lo
Hi
Lo
XX
XX
XX
XX
XX
XX
XX
XX
XX
XX
XX
XX
XX
XX
XX
XX
Byte Count
Write Data1
Write Data n
Hi
Lo
Hi
Lo
XX
XX
XX
XX
XX
XX
XX
XX
XX
XX
◼ Response message <Normal> (Slave to Master)
Start
Slave Address
Function
Data
LRC
End
[:]
XX
XX
[1]
[7]
XX
XX
[CR]
[LF]
Byte Count
Read Data1
Read Data n
Hi
Lo
Hi
Lo
XX
XX
XX
XX
XX
XX
XX
XX
XX
XX
◼ Communication example
1) Slave Address (=Unit number): No 1
2) Read three consecutive data from register 0040H, and write two consecutive data from register 0051h.
(Command to read the internal sensor temperature, external sensor temperature and average temperature
and change the target temperature to <30.0
o
C>, offset temperature to <0.50
o
C >)
Request message
Response message
Code
Contents
Code
Contents
01
Slave Address
01
Slave Address
17
Function
17
Function
0040
Head address of specified register
06
Quantity of byte to read
0003
Quantity of register to read
09E1
Information of 0040H (Internal sensor temperature)
0051
Head address of specified register
FC22
Information of 0041H
(External sensor temperature)
0002
Quantity of register to write
FC22
Information of 0042H (Average temperature)
04
Quantity of byte to read
BE
LRC
0BB8
Information written to 0051H
(Target temperature)
0032
Information written to 0052H
(Offset temperature)
59
LRC
This product
(Request): 01170040000300510002040BB8003259 [CR][LF]
(Response): 01170609E1FC22FC22BE [CR][LF]
Your system
Data is sent and
received in ASCII
code.