C-4Troubleshooting 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.

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 are FF00 to FF0F.

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 Manual for information on creating a user fault subroutine.

Fault Messages

Refer to the MicroLogix 1200 and 1500 Instruction Set Reference Manual for the controller fault messages that can occur during operation of the MicroLogix 1500 programmable controllers. Each fault message includes the error code description, the probable cause, and the recommended corrective action.

Basic 32 Loader Control UGC007/0702