Rockwell Automation Publication 1718-UM001A-EN-E - December 2019
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Appendix
A
Troubleshoot Your Module
This chapter describes troubleshooting for RS-485-based bus systems.
Communication errors
WARNING:
Risk of explosion
When work is performed on the remote I/O unit in hazardous areas, there is a
risk of explosion from spark formation.
Before starting any work on the remote I/O unit, familiarize yourself with the
instruction manuals for the components and their relevant certificates.
Table 8 - Communication errors
Error
Remedy
Communication error on the fieldbus
•
Check that the cables are connected.
•
Check that the transmitting and receiving lines are wired correctly and have not been swapped.
•
Check that the nodes are positioned in linear form and without branches. A star-shaped layout is not permitted.
•
Check that the terminator has been activated. The fieldbus must have exactly two terminators per segment, one
at the beginning and one at the end.
•
In the configuration software, check that the selected address is the same as the remote FB I/O device address.
•
In the configuration software, check whether the master read cycle and the
com unit watchdog
are coordinated
with one another.
Communication error on the service bus
•
Check that the cables are connected.
•
Check that the nodes are positioned in linear form and without branches. A star-shaped layout is not permitted.
•
Check that the terminator has been activated. The service bus must have exactly two terminators per segment,
one at the beginning and one at the end.
•
In the configuration software, check that the selected address is the same as the remote FB I/O device address.
•
Check that the correct interface is preset in the configuration software.
Communication error on the service bus after successfully
establishing a connection
•
Check that the service bus is galvanically isolated.
•
If you are using a laptop, operate the laptop using a battery.
•
Check the settings for the baud rate and transfer direction.
A new remote I/O unit will not work on a bus if other remote
FB I/O devices are already operating on the bus
•
Check that the terminators are still on the beginning and end of the bus after expansion.
The software cannot locate the adapter when establishing the
connection
•
Check that the adapter is plugged in correctly.
Communication to the extension backplane is not possible
•
Check that the plug-in jumpers are set correctly.
•
Check that the base backplane and the extension backplane are wired correctly.
Bus-independent deactivation of the I/O modules is not
possible
•
Check that the plug-in jumpers are set correctly.
Multiple I/O modules fail simultaneously
•
Check that the power supply is working properly.
•
Check that the base backplane and the extension backplane are wired correctly.