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Verify Communications
MVI56-MCM
♦
ControlLogix Platform
Modbus Communication Module
ProSoft Technology, Inc.
Page 65 of 159
July 24, 2008
"Module Communication Errors" are generated by the MVI56-MCM module, and
are an indication that the communications with the slave device is not occurring
correctly.
Error Code -11 indicates that the module is transmitting a message on the
communications wire. However. it is not receiving a response from the addressed
slave. This is typically an indication of a parameter mismatch (module is set for
9600 baud, slave is set for 19,200, parity is set to none, slave is expecting even,
and so on), wiring problem (jumper on module is not set for correct position, or +
and - lines on RS485 are switched), or the slave device is not set to the correct
address (master command is sending command to slave 1 and the slave device
is setup as device 10).
With a -11 error code, check all of the above parameters, wiring, and settings on
the slave device. Also make sure that you toggle either the
MCM.CONTROL.WarmBoot or ColdBoot bit to make sure that the values you
have entered for within the MCM.CONFIG array are downloaded to the module.
You can also cycle power to the module to perform a reboot and force the
module to read the configuration from the ControlLogix processor.
Error codes of 253 to 255 are typically an indication of noise on RS485 lines.
Make sure that proper RS485 cable is being used, and proper termination
resistors are used on the line. If termination resistors are installed, you may want
to remove them as they are usually on required on cable lengths of more than
1000 feet.
Command List Entry Errors
Code Description
-41
Invalid enable code
-42
Internal address > maximum address
-43
Invalid node address (< 0 or > 255)
-44
Count parameter set to 0
-45
Invalid function code
-46
Invalid swap code
The above error codes indicate that the module has detected an error when
parsing the command.
For all commands that have not been configured (all parameters set to a value of
0) you will receive an error code of -44. To remove this error code, you can
change your MCM.CONFIG.PortX.CmdCount parameter to the number of
commands that are actually configured, and then toggle either the WarmBoot or
ColdBoot bit to download this change to the MVI56-MCM module.