ProSoft Technology MVI56E-MCM/MCMXT - Manual (Page 71)

MVI56E-MCM ♦ ControlLogix Platform Verify Communication
Modbus Communication Module User Manual
ProSoft Technology, Inc. Page 71 of 199
June 18, 2014
Error Code 2 means that the module is trying to read an address in the device
that the Slave does not recognize as a valid address. This is typically caused by
the Slave device skipping some registers. If you have a Slave device that has
address 40001 to 40005, and 40007 to 40010, you cannot issue a read
command for addresses 40001 to 40010 (function code 3, DevAddress 0, Count
10) because address 40006 is not a valid address for this Slave.
Instead, try reading just one register, and see if the error code goes away. You
can also try adjusting your DevAddress -1, as some devices have a 1 offset.
An Error Code of 3 is common on Modbus Write Commands (Function Codes
5,6,15, or 16). Typically, this is because you are trying to write to a parameter
that is configured as read only in the Slave device, or the range of the data you
are writing does not match the valid range for that device.
Refer to the documentation for your Slave device, or contact ProSoft Technical
Support for more help with these types of error codes.
Module Communication Error Codes
Code Description
-1 CTS modem control line not set before transmit
-2 Timeout while transmitting message
-11 Timeout waiting for response after request
253 Incorrect Slave address in response
254 Incorrect function code in response
255 Invalid CRC/LRC value in response
"Module Communication Errors" are generated by the MVI56E-MCM module,
and indicate communication errors with the Slave device.
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 error is typically caused by one or more of the following conditions.
 Parameter mismatch, for example the 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, for example the port jumper on the module is set incorrectly,
or + and - lines on RS485 are switched)
 The Slave device is not set to the correct address, for example the Master is
sending a command to Slave 1 and the Slave device is configured 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 cycle power to the module, or toggle
the MCM.CONTROL.W
ARM B OOT or C OLD B OOT bit to transfer the values in the
MCM.CONFIG array to the module.
Error codes of 253 to 255 typically indicate noise on RS485 lines. Make sure that
you are using the proper RS485 cable, with termination resistors installed
properly on the line. If termination resistors are installed, try removing them as
they are usually only required on cable lengths of more than 1000 feet.