Mitsubishi Electric MR-JE-C Series Instruction Manual page 42

3. Modbus/TCP
(2) Usage example
The following shows a setting example for writing "0100h" in the Modbus register 2102h ([Pr. PC02]).
Index Name
2102h PC02
Query Message
Transaction Protocol
Length Field
Identifier Identifier
16 bits 0000h
Set the following values to each Query Message.
Message field
Transaction Identifier
Protocol Identifier
Length Field
Unit Identifier
Function
Starting Address
No. of Registers
Byte Count
Data
Response Message
Transaction Protocol
Length Field
Identifier Identifier
2 × 8 bits 0000h
The following shows the information in each Response Message.
Message field
Transaction Identifier
Protocol Identifier
Length Field
Unit Identifier
Function
Starting Address
No. of Registers
Data type
U32
Unit
Function
Identifier
000Ah FFh 10h
Set any value.
Set "0000h".
Set the byte length from Unit Identifier to Data.
Set "FFh".
Set "10h".
Set "2102h", the start address of the registers to which data is written.
Set "02h", because the total number of write points of the Modbus register 2102h is 2.
Set "04h". This means that data of 4 frames is sent.
Set values in order starting from the start address.
Lower-bit value of the register 2102h: "0100h"
Higher-bit value of the register 2102h: "0000h"
Unit
Function
Identifier
0006h FFh 10h
Size
16 bits Transaction Identifier received from the client (controller) is copied and returned.
16 bits The value "0000h" is returned.
16 bits The byte length from Unit Identifier to Data is returned.
8 bits Unit Identifier received from the client (controller) is copied and returned.
8 bits When the message was received without errors, "10h" is returned.
16 bits The value "2102h", the start address of the holding registers to which the data
was written is returned.
H: "21h"
L: "02h"
16 bits The number of registers to write "02h" is returned.
No. of
Access
Registers
rw 2
Starting No. of
Address Registers
H L H L
21h 02h 00h 02h
Description
Starting Address
H L H
21h 02h 00h
Description
3 - 9
Continuous
Setting value
read/write
00000100h
Data
Byte
Count
H L H
04h 01h 00h 00h
No. of Points
L
02h
L
00h