ProSoft Technology MVI56E-MCMXT User Manual

MVI56E-MCM ♦ ControlLogix Platform Verify Communication
Modbus Communication Module User Manual
ProSoft Technology, Inc. Page 73 of 209
To know where to look for the error data, you need to know what the individual
error codes are.
The following tables describe the possible error codes for the module:
Standard Modbus Protocol Errors
Code
Description
1
Illegal Function
2
Illegal Data Address
3
Illegal Data Value
4
Failure in Associated Device
5
Acknowledge
6
Busy, Rejected Message
The "Standard Modbus Protocol Errors" are error codes returned by the device
itself. This means that the Slave device understood the command, but replied
with an Exception Response, which indicates that the command could not be
executed. These responses typically do not indicate a problem with port settings
or wiring.
The most common values are Error Code 2 and Error Code 3.
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.

ProSoft Technology MVI56E-MCMXT Specifications

General

Brand	ProSoft Technology
Model	MVI56E-MCMXT
Category	Control Unit
Language	English