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GFK-0825F Chapter 6 Diagnostics and Fault Clearing 6-5
6
Display and Clear Faults from a PLC
A PLC places faults from a Field Control station in the I/O and PLC Fault Tables.
Series 90 PLC: I/O Fault Table
The content of the I/O fault display depends on the revision level of the PLC's Bus Controller
module, and the type of programmer software being used. With a Bus Controller that is version
4.6 or later, when a fault occurs on a Field Control station, the I/O Fault Table shows the station ID
and the rack and slot within the station where the fault has occurred:
14#0.4
Serial Bus Address
Rack
Slot
If the Bus Controller is only a rev. 3 version, it cannot transfer to the PLC the detailed fault
information provided by a Bus Interface Unit. Instead, a rev. 3 Bus Controller reports any fault
from a remote station as a
GENA
fault. To clear the fault table, press the Clear (F9) key.
You must clear the I/O Fault Table from the programming software for the fault to be
cleared in the PLC CPU and for the associated fault contact to be cleared.
Clearing faults
with a Hand-held Monitor alone does not remove them from the Fault Table, or cause any
associated
-[FAULT]-
contacts to stop passing power flow.
Clearing the I/O Fault Table at the PLC causes the Bus Controller to send a Clear All
Circuit Faults background message to all blocks on the bus. Faults can be cleared from the
Fault Table either from the fault table display or by the application program.
Clearing the fault table removes the faults it contains; it does not clear fault conditions in
the system. If the condition that caused a fault still exists and is detected, the fault will be
reported again.
Note:
If faults are cleared from the PLC before the BIU has received outputs from the
PLC, some faults such as Loss of Module or Extra Module are lost.
Series 90 PLC: PLC Fault Table
The PLC Fault Table shows the station ID and the location in the station where the fault occurred:
14#0.4
Serial Bus Address
Rack
Slot
Pressing the Clear key from this display clears the entire PLC Fault Table. If there are
no
faults in
the I/O Fault Table, then pressing Clear will also clear Bus Interface Unit faults.
Series Five or Series Six PLC
If the host CPU is a Series Five or Series Six PLC, faults from a Field Control station are displayed
in the Genius Fault Table. Faults from Field Control stations are identified as GENA faults. The
GENA is the component within the Bus Interface Unit that handles the Genius bus interface.
Pressing the Clear Faults key clears all faults currently in the fault table. This sets the fault count to
zero, and sends a Clear command to the Bus Interface Unit.