ProSoft Technology MVI69L-MBTCP - Manual (Page 108)

Reference MVI69L-MBTCP ♦ CompactLogix Platform
User Manual Communication Module
Page 108 of 152 ProSoft Technology, Inc.
January 6, 2014
7.2 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.
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 commands to the Server. The MVI69L-MBTCP module can work as a
Client and as a Server.
The MVI69L-MBTCP 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
Client and Server devices on Modbus networks.
Modbus Client
The MVI69L-MBTCP Modbus Client actively issues Modbus commands to
Modbus servers on the Modbus TCP/IP network, supporting up to 16 commands
for each Client. The Clients have an optimized polling characteristic that polls
servers with communication problems less frequently.
Command List Up to 16 commands per Client, each fully configurable for function,
server IP address, register to/from addressing and word/bit count.
Polling of command list Configurable polling of command list, including continuous and on
change of data, and dynamically user or automatic enabled.
Status Data Error codes available on an individual command basis. In addition, a
server status list is maintained per active Modbus Client.
Modbus Server
The MVI69L-MBTCP Modbus Server driver permits a remote Client to interact
with all data contained in the module. This data can be derived from other
Modbus server devices on the network, through a Client port, or from the
CompactLogix processor.
Service Port MBAP messaging on Service Port 502
Encapsulated messaging on Service Port 2000
Status Data Error codes, counters and port status available