GE Industrial Solutions AF-300 P11_G11 Ethernet Interface - Manual (Page 9)

About the OPC-G11S-ETN 3
Modbus/TCP Network Overview
Modbus/TCP was invented by Modicon/Group Schneider and is today is one of the most popular protocols
embedded inside the TCP/IP frames of Ethernet.
The Modbus protocol was first published back in the 1970's and has been adopted by users and vendors alike
in the industrial automation world. No changes have been made to the protocol itself but changes have been
made in the way or the rate that messages are sent in order to fulfill the real-time needs of industrial
applications. This has given us Modbus/TCP.
Modbus/TCP basically embeds a Modbus frame into a TCP frame in a simple manner. This is a connection-
oriented transaction, which means every query expects a response.
This query/response technique fits well with the master/slave nature of Modbus, adding to the deterministic
advantage that Switched Ethernet offers industrial users.
For further information:
The Modbus Organization
PO Box 628
Hopkinton, MA 01748-0628
Phone: 508-435-7170
http://www.modbus.org