Omron V780 Series, User Manual

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7 Modbus/TCP Communications
7 - 2 UHF RFID System V780-series Reader/Writer User’s Manual (Z389)
7-1 Outline
• A V780 Reader/Writer can perform Modbus/TCP-compliant message communications with the host
device (PLC).
• Communications between the host device (PLC) and the V780 Reader/Writer are performed on a cli-
ent-server basis using the TCP/IP protocol. The computer, PLC, or other host device is the client and
the Reader/Writer is the server.
• The message that the host device (PLC) sends to the Reader/Writer is called a command. The mes-
sage that the Reader/Writer returns is called the response.
Precautions for Correct Use
The slave reader/writer (V780-HMD68-ETN-

-S) disconnects the connection when it sends
a communication command directly from the host device (client).
Use the slave reader/writer via the master reader/writer (V780-HMD68-ETN-

).
Additional Information
Modbus/TCP Protocol
The Modbus/TCP protocol is a communications protocol developed for PLCs by Modicon
Inc.(AEG Schneider Automation International S.A.S.). It is an open standard and has been
used for a variety of industrial devices.
A query in Modbus/TCP communications is called a command in this manual.
7-1-1 Modbus/TCP Communications
Host device
(client)
Reader/Writer
(server)
Ethernet Cable
TCP port number: 502
Command
Response
Power Supply Cable