Resetting Controllogix Program

jgreenewv

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Join Date
Aug 2002
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New Mexico, USA
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I have a job coming up where the engineer wants a button on the RSView display to force a ControlLogix 1756-L62 to basically reset the processor, as if you had cycled power. I've never heard of anyone setting a system up like this. Is there a tag in the ControlLogix processors that force a reset? Or is this engineer crazy? Thanks in advance.
 
Why would you leave it up to the operator or even manager to know when your supposed to restart the CLX. If there is a problem with the CLX then I think you should go to the front of the processor with the right guy for the job to investigate what the problem is. So I think the engineer is crazy your going to have all types of problems with that, even if you password protect the button.
 
jgreenewv said:
I have a job coming up where the engineer wants a button on the RSView display to force a ControlLogix 1756-L62 to basically reset the processor, as if you had cycled power. I've never heard of anyone setting a system up like this. Is there a tag in the ControlLogix processors that force a reset? Or is this engineer crazy? Thanks in advance.

Is this engineer one of those that firmly believes if the program logic goes haywire, powering down will reset the problem?

I think the guy may have heard about power up routines or fault routines and has assumed that those routines can be used on command to resolve problems.

Ian
 
DBLD99 said:
Why would you leave it up to the operator or even manager to know when your supposed to restart the CLX. If there is a problem with the CLX then I think you should go to the front of the processor with the right guy for the job to investigate what the problem is. So I think the engineer is crazy your going to have all types of problems with that, even if you password protect the button.

Believe me, I agree with you completely. However, this engineer is quite odd in his specifications, and trying to convince him that his way is probably not the best is like o_O so unfortunately, I at least have to attempt to come up with a way to do this. I'm HOPING several people tell me it's impossible, so I don't have to put that option in.
 
curlyandshemp said:
Is this engineer one of those that firmly believes if the program logic goes haywire, powering down will reset the problem?

I think the guy may have heard about power up routines or fault routines and has assumed that those routines can be used on command to resolve problems.

Ian

:confused:

I couldn't even begin to explain this engineer's thinking. He knows NOTHING about controls, so he has a contractor in the same building come up with the controls specs (with the implicit understanding this contractor will get the job) This contractor knows approximately 10% more about controls than the engineer.

On this particular job, we managed to get low bid, so the engineer and his pet contractor are going to be VERY hard to get along with. If something in his specs is impossible to implement, I'm probably going to be required to get the manufacturer to say so.

I would assume, like you, that he is confusing something he read in the specs about fault handling or the like, and thinks you can just set a bit and reset everything. Of course, my thought is that if it's THAT messed up, chances are setting a bit in the processor isn't going to do a lot of good.
 
I don't know of a bit that can do this, but you can donnect the power supply through a NC relay closure that you can open with a PLC output when they push the button...

But like DBLD99 and curlyandshemp, I've got to wonder why??? What's the benefit? Has he explained that yet??
 
OZEE said:
I don't know of a bit that can do this, but you can donnect the power supply through a NC relay closure that you can open with a PLC output when they push the button...

But like DBLD99 and curlyandshemp, I've got to wonder why??? What's the benefit? Has he explained that yet??

I'd thought of the relay also, but nothing like that is shown on the spec drawings. The only explanation we've ever been able to get from him is "because that's what the specifications say".
 
jgreenewv said:
I'd thought of the relay also, but nothing like that is shown on the spec drawings. The only explanation we've ever been able to get from him is "because that's what the specifications say".

You may have to put that to them then. You can state you have never heard of the reset bit, but that does not mean it does not exist. It could be one of those 'hidden' features. If this bit does not exist, then as OZEE stated, you can offer the power down relay.

Ian
 
curlyandshemp said:
You may have to put that to them then. You can state you have never heard of the reset bit, but that does not mean it does not exist. It could be one of those 'hidden' features. If this bit does not exist, then as OZEE stated, you can offer the power down relay.

Ian

That's basically what I am planning. I just wanted to hit up the forum to see if anyone had actually heard of a "reset bit" or anything native to the processor. I'm trying to get all of my information together before we have to meet with him to go over details.
 
I've never heard nor read about any way of forcing a CLX CPU to perform its POST from application code.

I could write you some code that'd cause it to Fault; ask your man if that's any use to him!! o_O
 
No such thing as a soft boot

Between us, here on the Forum:

If I wanted to simulate a restart of a ControlLogix, I would intentionally fault the controller on a watchdog timeout by building a For/Next loop that's longer than the task watchdog. When the controller faulted, the Fault Handler routine would play the role of the Power-Up Handler, resetting the condition that caused the watchdog fault and performing other tasks to get the program ready to run.

Even that mechanism is not the same as a power cycle, because it's not actually running the powerup tests, and it's running the Fault Handler, not the Power-Up Handler.

If your client needs an authoritative letter from Rockwell stating that there is no "soft-boot" function in the ControlLogix, we can set that up with your local office.
 
Thanks to all that responded on this. When we get to that point, I'm going to have our local distributor get a letter from someone at Rockwell saying this is impossible. If the engineer doesn't like that, he'll have to explain to me how to do it.
 
That's a plan, let him do the legwork!

You find, as a PLC programmer, that you are at the bottom of a big funnel, and nothing gets past you if it won't work.

It's nice in some ways...
 
It is not unusual to have logic included in a program to set a machine / process into a known safe or neutral state on power-up or on change into run mode. This can be done in a dedicated power-up routine or by making use of the "first scan" status bit at appropriate points throughout the main program.

If this is the function that your customer perceives as a "reset", then it will be fairly simple to implement.
 

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