Micrologix fault reset

gosenbach

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Join Date
Jul 2006
Location
Everett
Posts
102
I am trying to reset a fault through programming. I have a Micrologix 1200 and I am programming through RS Logix 500. I have been combing through the help files and been serching though posts here and have so far not found anything specific enough to really help me out. There are references to resetting the S:1/15 bit. However, I have not found a way to actually do this. I have tried a rung with a OTU and a RES, neither work. I tried both a MOV and MVM, however I get an error that says that I can not set that to the word level.

I also would like to set the bit S:1/9 to automatically clear faults on startup but when I add a rung with that bit as a cail, I also end up with an error. I figured there is maybe a check box somewhere to turn that on that I do not know about?

There is also reference to a "user fault routine" that runs when there is a fault. How do I go about setting one of those up?

Thanks everyone!

Greg
 
S:1/15 is the First Pass bit. It is set for the first scan of the logic only and then is turned back off by the system. You don't do anything to it. You can use its status (XIC XIO) to trigger actions on that first pass.

Setting S:1/9 is done offline in the 'Processor Status' area. (Though I think you mean S:1/8). Use the 'Errors' tab.

The user fault routine is set up in a ladder file. Place the number of that file into S:29 in that same 'Errors' tab.

After setting these the way you want download the modified program.
 
Oops. I should have typed in S:1/13, not S:1/15

"Non-user - a fault caused by various conditions that cease ladder program execution. The user-fault routine is not run when this fault occurs.
Non-recoverable - a fault caused by the user that cannot be recovered from. The user-fault routine is run when this fault occurs. However, the fault cannot be cleared.
Recoverable - a fault caused by the user that can be recovered from in the user-fault routine by resetting major error halted bit (S:1/13). The user-fault routine is run when this fault occurs."

I can not figure out what method should be used to set that bit to 0. Nothing I have tried so far has worked. Or is it that the word S:1 can only be written to from the defined user fault routine and not from within the main ladder? I'll have to try that today.

Thanks for clueing me into how to set the user fault routine!

Greg
 
An OTU was the first thing I tried. Perhaps it was because it was just in a regular part of the ladder and it ceased to run once it faulted and I just need to put the OTU in the selected fault routine instead. I'll give that a shot!

Thanks!

Greg
 
It should be placed as the last rung in file 2 because file 2 is the only file that is always scanned without having to be called by a JSR. And it should be the last rung because that bit would be set at the end of the program scan and placing it there would immediately unlatch it. If you are calling other program files with unconditional JSR instructions, then you could place it in the very last rung of the program.
 
What knid of faults are you getting that you have to reset? Might be better to prevent faults if possible than to work around them. Just a thought...
 
Generally I just want to make sure that if there is a fault in the field, the end user (who may not be able to talk to the PLC with a laptop to reset it) can get the fault reset.

My current project I was having some overruns but as you said, that is currently being prevented via programming. Mainly I want to get something in there 'just in case' anything else goes wrong.
 
investigate this bit - the Help button should get you started ...

override.JPG


note that this will not FIX a fault ... it just tells the processor to reset a fault and then "try again" the next time it powers up ... if the "thing" that caused the fault in the first place is still there, then you'll just get another shutdown ...

think of it as a circuit breaker with an automatic reset ... once the breaker "cools down" it resets and tries again ... but if the short is still there - oops! ...

there is no absolutely foolproof way to make sure that the customer (without the software, etc.) will always be able to recover from a faulted condition ...

if you're interested in writing a "fault handling" routine, start by telling us what you'd like to have happen whenever the processor runs into a fault condition ... how "foolproof" that approach will turn out to be depends on how much imagination you put into foretelling the things that might make the processor fault ...
 
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