3. Modbus/TCP
3 - 5
Response Message
Transaction
Identifier
Protocol
Identifier
Length Field
Unit
Identifier
Function
Byte Count
Data
H
L
to
H
L
16 bits
0000h
16 bits
FFh
03h
8 bits
8 bits
8 bits
to
8 bits
8 bits
Message field
Size
Description
Transaction Identifier
16 bits
Transaction Identifier received from the client (controller) is copied and returned.
Protocol Identifier
16 bits
The value "0000h" is returned.
Length Field
16 bits
The byte length from Unit Identifier to Data is returned.
Unit Identifier
8 bits
Unit Identifier received from the client (controller) is copied and returned.
Function
8 bits
When the message was received without errors, "03h" is returned.
Byte Count
16 bits
The Data frame size (in units of bytes) is returned.
A value obtained by multiplying the value set for No. of Points in the Query
Message by 2 is returned.
Data (Note)
16 bits × n Data starting from the start address specified in the Query Message is returned.
Data is read in order of H (higher bits) and L (lower bits).
Data is read in order starting from the start address.
Note. Higher 8 bits of 1-byte data are set to "00h" when this data is returned.
To use the signed 1-byte data as 2-byte data, perform sign extension on the client (controller) side.
(2) Usage example
The following shows a setting example of when Modbus registers 2B05h (Command pulse frequency) to
2B07h (Analog torque limit voltage) are read.
Index
Name
Data type
Access
No. of Points
Continuous
read/write
Register value
(Read data)
2B05h
Command pulse frequency
I32
ro
2
12345678h
2B06h
Analog speed command voltage
Analog speed limit voltage
I16
ro
1
1000h
2B07h
Analog torque limit voltage
Analog torque command voltage
I16
ro
1
2000h
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
Set any value.
Protocol Identifier
Set "0000h".
Length Field
Set "0006h".
Unit Identifier
Set "FFh".
Function
Set "03h".
Starting Address
Set "2B05h", the start address to read.
No. of Points
Set "04h", because the total number of read points from Modbus registers 2B05h to 2B07h is 4.
Содержание MR-JE-C Series
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