ProSoft Technology MVI56E-MNETCR - Manual (Page 97)

MVI56E-MNETCR ♦ ControlLogix Platform Reference
Modbus TCP/IP Multi Client Enhanced Communications Module for Remote Chassis User Manual
ProSoft Technology, Inc. Page 97 of 159
June 14, 2011
5.2 Functional Overview
5.2.1 About the MODBUS/TCP 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.
MODBUS/TCP 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 commands to the server. The MVI56E-MNETCR module
simulates up to 30 clients.
Aside from the benefits of Ethernet versus serial communications (including
performance, distance, and flexibility) for industrial networks, the MODBUS/TCP
protocol allows for remote administration and control of devices over an Internet
connection. It is important to note that not all Internet protocols are implemented
in the module, for example, HTTP and SMTP protocols are not available.
Nevertheless, the efficiency, scalability, and low cost of a MODBUS/TCP network
make this an ideal solution for industrial applications.
The MVI56E-MNETCR module acts as an input/output module between devices
on a MODBUS/TCP network and the Rockwell Automation backplane. The
module uses an internal database to pass data and commands between the
processor and the server devices on the MODBUS/TCP network.