Mitsubishi Electric MR-JE-C Series Instruction Manual page 38

3. Modbus/TCP
Response Message
Transaction Protocol
Length Field
Identifier Identifier
16 bits 0000h
Message field
Transaction Identifier
Protocol Identifier
Length Field
Unit Identifier
Function
Byte Count
Data (Note)
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
2B05h Command pulse frequency
2B06h Analog speed command voltage
Analog speed limit voltage
2B07h Analog torque limit voltage
Analog torque command voltage
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 Points
Unit
Function
Identifier
16 bits FFh 03h
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, "03h" is returned.
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.
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.
Data type
I32
I16
I16
Unit
Function
Identifier
0006h FFh 03h
Set any value.
Set "0000h".
Set "0006h".
Set "FFh".
Set "03h".
Set "2B05h", the start address to read.
Set "04h", because the total number of read points from Modbus registers 2B05h to 2B07h is 4.
Byte Count
H
8 bits 8 bits 8 bits
Description
Access No. of Points
ro 2
ro 1
ro 1
Starting Address
H L H
2Bh 05h 00h
Description
3 - 5
Data
L to H
to 8 bits
Continuous Register value
read/write (Read data)
12345678h
No. of Points
L
04h
L
8 bits
1000h
2000h