ProSoft Technology MVI56E-MNETC - Manual (Page 141)

MVI56E-MNETC ♦ ControlLogix Platform Reference
Modbus TCP/IP Client Enhanced Communication Module User Manual
ProSoft Technology, Inc. Page 141 of 183
February 3, 2013
5.3.2 Client Driver
In the Client driver, the MVI56E-MNETC module issues read or write commands
to servers on the Modbus TCP/IP network using up to 30 simulated Clients. The
commands originate either from the module's user-configured Client x Command
List for each Client, or directly from the processor as Event Commands. The
commands from the Client x Command List are executed either via routine
polling or as a result of special Command Control block requests from the
processor. Client status data is returned to the processor in special Client Status
blocks. The following flowchart describes the flow of data into and out of the
module.
1 The Client driver obtains configuration data when the module restarts. This
includes the timeout parameters and the Command List. These values are
used by the driver to determine the types of commands to be issued to
servers on the Modbus TCP/IP network.
2 When configured, the Client driver begins transmitting read and/or write
commands to servers on the network. The data for write commands is
obtained from the module's internal database.
3 Assuming successful processing by the server specified in the command, a
response message is received into the Client driver for processing.
4 Data received from the server is passed into the module's internal database,
if the command was a read command. General module status information is
routinely returned to the processor in the input images.
5 Status data for a specific Client can be requested by the processor and
returned in a special Client Status block.
6 Special functions, such as Event Commands and Command Control options,
can be generated by the processor and sent to the Client driver for action.