Reference MVI56E-MNETC/MNETCXT ♦ ControlLogix Platform
User Manual Modbus TCP/IP Client Enhanced Communication Module - Client/Server
Page 130 of 172 ProSoft Technology, Inc.
September 20, 2018
Server Driver
The server driver allows the MVI56E-MNETC/MNETCXT module to respond to
data read and write commands issued by Clients on the Modbus TCP/IP
network. The following illustration describes the flow of data into and out of the
module.
1 The server driver receives the configuration information from the
configuration file on the Personality Module (compact flash card), and the
module initializes the server.
2 A host device, such as a Modicon PLC or an HMI application, issues a read
or write command to the module’s node address. The server driver validates
the message before accepting it into the module. If the message is
considered invalid, an error response is returned to the originating Client
node.
3 After the module accepts the command, the module processes the data
contained in the command.
o If the command is a read command, the data is read out of the database
and a response message is built.
o If the command is a write command, the data is written directly into the
database and a response message is built.
o If the command is a write command and the pass-through feature is
utilized, the write message is transferred to the processor ladder logic and
is not written directly into the module’s database, unless it is returned as a
change in the output image that overwrites data in the WriteData area as
a result of such ladder logic processing.
4 After the data processing has been completed in Step 3, a response is issued
to the originating Client node.
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