Modbus Tcp; Header Format; Setting Of Unit Id; List Of Modbus Functions Supported - Toshiba TOSVERT VF-AS3 Instruction Manual

3. Modbus TCP

3.1. Header format

Byte Description
0 Transaction
1 identifier
2
Protocol
3 identifier
4
Length of data
5
6 Unit ID (Destination identifier)
7 Modbus request function code Chose from Function code described in Section 3.3.

3.2. Setting of Unit ID

The Unit ID (destination identifier) is used to access inverter Modbus TCP server.
When you use the Unit ID other than 0, please set the Unit ID to parameter [C670].
Unit ID
0 or value of [C670]
255
Note: Detection of time out error in Modbus TCP is done only when using the I/O scanner service.

3.3. List of Modbus functions supported

Function code
03 (0x03)
06 (0x06)
16 (0x10)
23 (0x17)
43 (0x2B)
high order Same transaction ID is returned from Modbus TCP server.
Fixed at 0 if it is not required.
low order
high order
This identifier always equals 0.
low order
high order Number of bytes after the Unit ID (Byte 6). The value of the high
order should be "0", because the frame length is always less
low order
than 256 bytes.
Chose from Unit ID described in Section 3.2.
Modbus TCP server
Inverter (VF-AS3)
I/O Scanner
Function name
Read Holding Register
Write Single Register
Write Multiple Registers
Read/Write Multiple Registers
Read Device Identification
Comments
Inverter parameter
Device identification of inverter
Please refer to "3.7.1 Outline of IO
scanning service"
Description
Read N output words
Write one output word
Write N output words
Read/Write N words
(For I/O Scanning)
Identification
26
E6582125
Accessible data
Size of data
63 words max.
1 word
63 words max.
8 / 8 words max.
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