Micrologix AB PLC's Watchdog

I am looking for a way to determine when a Micrologix 1100 has faulted. I have found that when there is a watchdog fault that was caused by a firmware problem that I was unaware when it happened. It appears that the enthernet communication was still active but the processor had faulted.

I currently have it hooked to Wonderware.

srussell said:

I am looking for a way to determine when a Micrologix 1100 has faulted. I have found that when there is a watchdog fault that was caused by a firmware problem that I was unaware when it happened. It appears that the enthernet communication was still active but the processor had faulted.

I currently have it hooked to Wonderware.

Click to expand...

I don't have a micrologix here but with the SLCs there's a few bits that will tell you the current state of the preccessor and if comms are active for each channel.
Use a heartbeat to your wonderware and if it becomes inactive, you have just lost processor/comms.
The Status bits for SLC Chan0 are as follows:
Comms active S:33/4
Processor Mode S:1/0- S:1/4
Channel Mode S:33/3
etc.

You'll find what you need under Status.
Good luck.

Thanks for the info.

S:1/0 - 1/4 would be nice to tell if the processor is in any other mode other than run.

S:13 (I think was the one) that gave me a fault indication.

I just figured the processor was inactive when a major fault happened. I had an idea that I could use the real time clock to give me status of the processor and found it was still functioning. This lead me off to find the fault status bit.

once again thank for the response.

srussell said:

I just figured the processor was inactive when a major fault happened.

Click to expand...

The ladder program is halted. The processor continues to do housekeeping chores. Wonderware (or any other suitable app) can read the any value in memory even when the controller is faulted.

Alaric said:

The ladder program is halted. The processor continues to do housekeeping chores. Wonderware (or any other suitable app) can read the any value in memory even when the controller is faulted.

Click to expand...

Is this true of PLC-5, SLC, and ControlLogix Processors?

Aiki202,

For the majority of faulted PLC's the communication links still remain. Mostly because a lot of times you can go online and clear the faults or make online changes so that the faults don't occur again. There are instances where the communication will not work but usually that only happens on catatstrophic hardware faults and not faults do to software.