MVI56-MCM ♦ ControlLogix Platform Verify Communications
Modbus Communication Module
Page 66 of 159 ProSoft Technology, Inc.
July 24, 2008
6.2.2 MCM STATUS Data
Status information can also be obtained from the MVI56-MCM module by
checking the MCM.STATUS.PrtXErrs location. Below is a sample.
If your system is working correctly, you will see CmdReq, CmdResp, Requests,
and Responses all incrementing together. If you see that CmdErr is
incrementing, you will need to see what command is in error (using the error
code defined in the previous section) and based on the error code resolve the
issue.
Note: This information is not as detailed as the individual error codes, but they can help to
troubleshoot your application.
Also within the MCM.STATUS location is the parameters for Last Error and
Previous Error, shown below.
This indicates the command index that last generated an error and does not
indicate a command currently in error. In the above example, a value of 2 in
Port1LastErr indicates that the last error was generated by
MCM.Port1MasterCmd[2]. This does not indicate that this command is currently
in error. The value in MCM.STATUS.Port1PreviousErr indicates that before
MasterCmd[2] generated an error, MCM.Port1.MasterCmd[1] posted an error.
6.3 Verify Slave Communications
For verifying the communications to the module as a slave you can monitor the
STATUS tags under the PrtXErrs section.
Below is an example.
The Requests field can be used to determine the number of request messages
sent to the module as a slave, and the Responses section can be used to
determine how many responses field can be used to determine how many times
the module has responded to a request message from the Modbus master.
6.3.1 MVI56-MCM Status Data Definition as a Slave
Refer to MVI56-MCM Status Data Definition (page 119) for complete listing of
Status information.
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