Verify Communication MVI56E-MCMR ♦ ControlLogix Platform
User Manual Modbus Communication Module with Reduced Data Block
Page 112 of 223 ProSoft Technology, Inc.
Transferring the Command Error List to the Processor
You can transfer the command error list to the processor from the module
database. To place the table in the database, set the Command Error Pointer
(MCMR.PORT1.CMDERRPTR) parameter to the database location desired.
In the sample ladder, the MCMR.PORT1.CMDERRPTR tag is set to a value of
1100. This will cause the error value of command 0 to be placed at database
address 1100. Each command error value occupies one database word. The
error value for command 1 will be in location 1101 and the remaining values in
consecutive database locations.
To transfer this table to the processor, refer to Command Error Codes (page
108). Make sure that the Command Error table is in the database area covered
by the Read Data (MCMR.MODDEF.READSTARTREG and
MCMR.MODDEF.READREGCNT).
3.1.3 MCM Status Data
Status information can also be obtained from the MVI56E-MCMR module by
checking the MCMR.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, determine what command is causing the error (using the error
code defined in the previous section (page 108)) and correct the issue causing
the error.
Note: This information is not as detailed as the individual error codes, but they can help to
troubleshoot your application.
Also within the MCMR.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 0 in
PORT1LASTERR indicates that the last error was generated by MODBUS PORT 1
COMMAND 0. This does not indicate that this command is currently in error. The
value in MCMR.STATUS.PORT1PREVIOUSERR indicates that before MASTER
COMMAND 0 generated an error, MODBUS PORT 1 COMMAND 1 posted an error.
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