Rockwell Automation 1761 MicroLogix 1000 Programmable Controllers - Manual (Page 274)

Preface MicroLogix 1000 Programmable Controllers User Manual
14–6
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 when cycling power to the controller by setting
either one or both of the following status bits in the status file:
•
Fault Override at Powerup bit (S:1/8)
•
Run Always bit (S:1/12)
Clearing a fault using the Run Always bit (S:1/12) causes the controller to
immediately enter the REM Run mode. Make sure you fully understand the
use of this bit before incorporating it into your program. Refer to page B–6
for more information.
Refer to appendix B for more information on status bits.
Note 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 is FF00 to FF0F.
Manually Clearing Faults Using the Fault Routine
The occurrence of recoverable or non-recoverable user faults causes file 3 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 REM
Run mode.
The subroutine does not execute for non-user faults. The user-fault routine is
discussed in chapter 4.