Rockwell Automation 1764-xxxx MICROLOGIX 1500 PROGRAMMABLE CONTROLLERS - Manual (Page 128)

Publication 1764-UM001B-EN-P - April 2002
C-4 Troubleshooting Your System
Identifying Controller Faults While a program is executing, a fault may occur within the operating
system or your program. When a fault occurs, you have various
options to determine what the fault is and how to correct it. This
section describes how to clear faults and provides a list of possible
advisory messages with recommended corrective actions.
Automatically Clearing Faults
You can automatically clear a fault by cycling power to the controller
when the Fault Override at Power-up bit (S:1/8) is set in the status file.
You can also configure the controller to clear faults and go to RUN
every time the controller is power cycled. This is a feature that OEMs
can build into their equipment to allow end users to reset the
controller. If the controller faults, it can be reset by simply cycling
power to the machine. To accomplish this, set the following bits in the
status file:
•
S2:1/8 - Fault Override at Power-up
•
S2:1/12 - Mode Behavior
If the fault condition still exists after cycling power, the controller
re-enters the fault mode. For more information on status bits, refer to
the MicroLogix 1200 and MicroLogix 1500 Instruction Set Reference
Manual, publication 1762-RM001.
Manually Clearing Faults Using the Fault Routine
The occurrence of recoverable or non-recoverable user faults can
cause the user fault subroutine to be executed. If the fault is
recoverable, the subroutine can be used to correct the problem and
clear the fault bit S:1/13. The controller then continues in the Run or
test mode.
The subroutine does not execute for non-user faults. Refer to the
MicroLogix 1200 and MicroLogix 1500 Instruction Set Reference
TIP
You can declare your own application-specific major
fault by writing your own unique value to S:6 and
then setting bit S:1/13 to prevent reusing system
defined codes. The recommended values for user
defined faults are FF00 to FF0F.