Rockwell Automation 2711E PanelBuilder 1400e Modbus Communications - Manual (Page 68)

Chapter
9
Publication 2711E-6.12 – August 1997
Troubleshooting for Modbus
Applications
This section describes how to diagnose and solve Modbus
communication problems. To help solve PanelBuilder software
problems, refer to your PanelBuilder 1400e Configuration Software
for Windows User Manual.
Refer to the Modbus equipment documentation for Modbus-specific
troubleshooting information.
PanelView terminals on a Modbus network may communicate with
controllers or other devices made by manufacturers other than
Allen-Bradley. You may have to obtain integration and support
services in whole or in part from the controller or device
manufacturer. Contact your local Allen-Bradley office for
information on services available from Global Technical Support or
Allen-Bradley authorized system integrators.
Consult the following table to identify the communications problems
over the Modbus network.
Problem Cause What to do:
Remote station has not replied within specified
ti
out io
The station is not responding. Cycle power to the station.
timeout period.
Electrical noise interference or a faulty
cable. Check all cables and connections. Have the
system evaluated for noise susceptibility. If
the problem persists, contact the controller
or device manufacturer.
The slave controller sent more data than it
should have. This usually indicates a faulty
controller. Consult the documentation for the controller
or device being used. If the problem
persists, contact the controller or device
manufacturer.
Remote station Exception Response — illegal
function The controller could not perform the
specified command. Consult the documentation for the controller
or device being used. Check for the
availability of the requested function.
Contact the controller or device
manufacturer to determine what functions
the controller or device supports.
Remote station Exception Response — illegal
data address The tag address referenced by your
application is invalid. Edit the tag address.
The specified tag address has not been
allocated in the controller. Allocate more registers in the controller, or
change the tag address used in the
application.
Remote station Exception Response — illegal
data value The value referenced in the data field is not
allowable in the addressed slave location. Enter a value within the specified range, or
allocate more registers in the controller to
modify the range to include the value you
entered.
Modbus Communication
Errors