ProSoft Technology MVI56E-MCMR - Manual (Page 144)

Reference MVI56E-MCMR ♦ ControlLogix Platform
User Manual Modbus Communication Module with Reduced Data Block
Page 144 of 225 ProSoft Technology, Inc.
May 13, 2014
6.1 About the Modbus 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 Master and Slave devices on a network. Later
enhancements to the protocol allow communication over other types of networks.
Modbus is a Master/Slave protocol. The Master establishes a connection to the
remote Slave. When the connection is established, the Master sends the Modbus
commands to the Slave. The MVI56E-MCMR module can work as a Master and
as a Slave.
The MVI56E-MCMR module also works as an input/output module between itself
and the Rockwell Automation backplane and processor. The module uses an
internal database to pass data and commands between the processor and
Master and Slave devices on Modbus networks.