Rockwell Automation 1756-L7x GuardLogix 5570 Controllers - Manual (Page 121)

Rockwell Automation Publication 1756-UM022A-EN-P - November 2012 121
Monitor Status and Handle Faults Chapter 9
Developing a Fault Routine If a fault condition occurs that is severe enough for the controller to shut down,
the controller generates a major fault and stops the execution of logic.
Depending on your application, you may not want all safety faults to shut down
your entire system. In those situations, you can use a fault routine to clear a
specific fault and let the standard control portion of your system continue to
operate or configure some outputs to remain ON.
The controller supports two levels for handling major faults:
• Program Fault Routine
• Controller Fault Handler
Both routines can use the GSV and SSV instructions as described on page 122 .
Program Fault Routine
Each program can have its own fault routine. The controller executes the
program’s fault routine when an instruction fault occurs. If the program’s fault
routine does not clear the fault, or if a program fault routine does not exist, the
controller proceeds to execute the controller fault handler, if one exists.
Controller Fault Handler
The controller fault handler is an optional component that executes when the
program fault routine could not clear the fault or does not exist.
You can create only one program for the controller fault handler. After you create
that program, you must configure a routine as the main routine.
The Logix5000 Controllers Major and Minor Faults Programming Manual,
publication
1756-PM014 , provides details on creating and testing a fault routine.
ATTENTION: You must provide proof to your certifying agency that allowing
a portion of the system to continue to operate maintains safe operation.