ControlLogix fault routines

[alan_505]

Does anyone have any real world examples of using the ControlLogix fault routines?
I can’t seem to find anything on the Rockwell website.

 

[Operaghost]

What are you looking for? Code, or situations where they were used?

OG

 

[alan_505]

Code, we have processor that occasionally has a watchdog fault and want to be able to use a fault routine to reset the fault and put the processor back into run mode.

 

[Operaghost]

It is tricky sometimes to deal with faults from a watchdog timer. These are usually, but not always occurring because you are caught in a loop. I'm sure I'm not saying anything there that you didn't know. But here is the catch...

If you setup a fault routine to capture and clear the fault, when it is done it returns you back to the same location you were in before the fault occurred. Again, that is usually back into that same endless loop. If that's the case, it will just fault again milliseconds later since you are still stuck in the loop.

Rockwell made it so that if a watchdog fault does occur, you can clear it via the fault routine. Once. Not twice. So if the controller returns back into the same loop, we will get a hard fault the second time the watchdog timer expires.

Now, if it isn't a loop and is instead just an excessively long scan, then when it returns after clearing the fault, it hopefully will finish the scan and complete that task. Once that task completes, then if another watchdog fault occurs, it will run the fault routine again. So the task successfully completing resets the "counter" if you will.

I'll post an example of some logic I use here shortly.

OG

 

[Operaghost]

Here is an example of a simple fault routine in the Logix. I used an emulator as my controller and I was using v28. The included file is the .L5K

After opening it, look at the Controller Fault Handler for the fault logic. There is a UDT used for the fault information. The MainTask just has some logic to cause a Watchdog fault.

OG

 

[alan_505]

Thank you I will download and have a play with an offline processor, when it happens on our system we sometimes have to stop or delay the starting of the PanelView sub routine, so I am thinking that we may have an issue with the PanelView, but it only happens once every few months.

 

[5618]

Here’s an example of logging faults from a system I inherited. I have done fault routines in MicroLogix, but haven’t done my own in ControlLogix. I haven’t yet looked at the previous example posted.