Bradley Smoker PLC-5 user manual Programming a Fault Routine, Avoiding Multiple Watchdog Faults

15-6Preparing Fault Routines

Programming a Fault Routine

Avoiding Multiple Watchdog Faults

If you encounter a memory loss fault or watchdog major fault, it may be because multiple watchdog faults occurred while the controller was busy servicing a ladder-related major fault. The memory loss fault occurs when the fault queue, which stores a maximum of six faults, becomes full and cannot store the next fault.

Before calling a service representative when you encounter either a memory loss fault or multiple watchdog faults, check:

If You Encounter	Then
watchdog error and	Extend the watchdog timer so that the real run-time error is not
a fault bit	masked.
	Check your major fault bits. Ignore the watchdog faults and use
	any remaining fault bits to help indicate the source of the
	controller fault.
memory loss fault	1.Power down then power up the controller.
	2.Reload the program.
	3.Set the watchdog timer to a value = 10 current setting
	4.Run the program again.

If you continue to encounter the memory loss fault, call your local Rockwell Automation representative.

To prepare your fault-routine program, first examine the major fault information recorded by the PLC-5 controller and then decide whether to do the following before the PLC-5 controller automatically goes to fault mode:

•set an alarm

•clear the fault

•execute the appropriate fault routine through ladder logic

•execute the appropriate ladder logic to recover from a fault

	If the PLC-5 controller detects a fault in the fault routine
IMPORTANT
	(double-fault condition), the PLC-5 controller goes directly
	to fault mode without completing the fault routine.

Publication 1785-UM012D-EN-P - July 2005