The Sample Application
MVI56E-MNETC ♦ ControlLogix Platform
Setup Guide
Modbus TCP/IP Multi Client Enhanced Communication Module
Page 18 of 72
ProSoft Technology, Inc.
April 18, 2011
3.1
About the MODBUS TCP/IP Protocol
MODBUS is a widely used protocol originally developed by Modicon in 1978.
Since that time, the protocol has been adopted as a standard throughout the
automation industry.
The original MODBUS specification uses a serial connection to communicate
commands and data between Client and server devices on a network. Later
enhancements to the protocol allow communication over Ethernet networks using
TCP/IP as a "wrapper" for the MODBUS protocol. This protocol is known as
MODBUS TCP/IP.
MODBUS TCP/IP is a Client/server protocol. The Client establishes a connection
to the remote server. When the connection is established, the Client sends the
MODBUS TCP/IP commands to the server. The MVI56E-MNETC module works
both as a Client and as a server.
Aside from the benefits of Ethernet versus serial communications (including
performance, distance, and flexibility) for industrial networks, the MODBUS
TCP/IP protocol allows for remote administration and control of devices over a
TCP/IP network. The efficiency, scalability, and low cost of a MODBUS TCP/IP
network make this an ideal solution for industrial applications.
The MVI56E-MNETC module acts as an input/output module between devices
on a MODBUS TCP/IP network and the Rockwell Automation backplane. The
module uses an internal database to pass data and commands between the
processor and the Client and server devices on the MODBUS TCP/IP network.
