2. MODBUS/TCP PROTOCOL
2 - 5
Query Message
Transaction
Identifier
Protocol
Identifier
Length Field
Unit
Identifier
Function
Starting Address
No. of Points
H L H L
16
bits 0000h 0006h FFh 03h 2Bh 05h 00h 04h
Set the following values to each Query Message.
Message field
Description
Transaction Identifier
(Transaction identifier)
Set any value.
Protocol Identifier
(Protocol identifier)
Set "0000h".
Length Field (Message length)
Set "0006h".
Unit Identifier (Unit identifier)
Set "FFh".
Function (Function field)
Set "03h".
Starting Address (Start address)
Set "2B05h", the start address to read.
No. of Points
(Number of read points)
Set "04h", because the total number of read points from Modbus registers 2B05h to 2B07h is 4.
Response Message
Transaction
Identifier
Protocol
Identifier
Length Field
Unit
Identifier
Function Byte
Count
Data
H L H L H L H L
16
bits
0000h
000Bh
FFh
03h
08h
56h 78h 12h 34h 10h 00h 20h 00h
The following shows the information in each Response Message.
Message field
Description
Transaction Identifier
(Transaction identifier)
Transaction Identifier received from the client (controller) is copied and returned.
Protocol Identifier
(Protocol identifier)
The value "0000h" is returned.
Length Field (Message length)
The byte length from Unit Identifier to Data is returned.
Unit Identifier (Unit identifier)
Unit Identifier received from the client (controller) is copied and returned.
Function (Function field)
When the message was received without errors, "03h" is returned.
Byte Count (Byte count)
The value "08h" is returned. This means that data of 8 frames is returned.
Data (Read data)
Data starting from the start address is returned.
Lower-bit value of the register 2B05h: "5678h"
Higher-bit value of the register 2B05h: "1234h"
Value of the register 2B06h: "1000h"
Value of the register 2B07h: "2000h"
Summary of Contents for MELSERVO-JE MR-JE-C
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