Actions in SF in ST - what is R action?

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1 year 3 months ago - 1 year 3 months ago #254 by Sergey Romanov
I am looking in to this document in help

Behavior of the action qualifiers for SFC elements

I cannot understand how do I pass R qualifier? For instance I have 2 actions in step, first is N and second is R.

1. Does the order affect how it works?
2. How action N will know that action R is true or false? Action R have to return something or simply exists?

The confusion is that if R have a priority over all other AQ, then if I add it, no other AG assigned to the same step will be executed. SO why? I could simply not to add any other actions to the step.

Or let me for a question differently.

If there a condition when step is active, and action with AQ R does not block other actions?
Last edit: 1 year 3 months ago by Sergey Romanov. Reason: Explain little bit better where confusion is.

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  • Walter Zögernitz
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1 year 3 months ago #270 by Walter Zögernitz
Replied by Walter Zögernitz on topic Actions in SF in ST - what is R action?
Hello Sergey,


Sometimes SFC elements are a little tricky :-)
"N" in the action block means, that the action variable "A0" will be set to true as long as the step in the left of the action block is true. There is no saving behavior.
"S" means, that the action variable is set to true as long as it will be resettet by "R" in an following action block.

To your questions:
1) yes, the order effects the behavior of the value of the action variable
2) R can be interpreted as an MOVE module, which has "FALSE" on its input, action variable on its output and is controled by the step on its EN-input. It will do a "write operation" only as long as the step on the left will be true.


kind regards
Walter

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1 year 3 months ago #273 by Sergey Romanov
Thank you very much for answer. Although I need a clarification. In the documentation it say

The action qualifier R has always priority. The combination of R with a different action qualifier (e.g. N) results in the behavior for action_ACB.Q as depicted in the following illustrations

So it sounds that R has a priority and order does not matter. If it is TRUE it will block all other action above and below.

Back to my question.

How can I add R action and it is false? Can you give me example of the action code that would make sense to associate with step with R qualifier and situation when step is active, but this action does not block other actions?

I learn best by looking at code.

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  • Walter Zögernitz
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1 year 3 months ago #274 by Walter Zögernitz
Replied by Walter Zögernitz on topic Actions in SF in ST - what is R action?
Hello Sergey,


The behavior of action variables controlled by cycle steps is a little different to any other boolean operations.
Every active action block (and only this one) does its own modification on their common variable "A0".
It is not possible to draw an replacement circiut in FBD which does exact the same as these steps combined with the action blocks.

Please see my attached sample.
As long as "S0" is active the action block on the right will set "A0" permanently* to "TRUE" (saving behavior)
As long as "S1" is active the action block on the right will set "A0" only for this step to "TRUE" (non saving behavior)
As long as "S2" is active the action block on the right will set "A0" permanently* to "FALSE" (saving behavior)
As long as "S3" is active the action block on the right will set "A0" only for this step to "TRUE" (non saving behavior)


*... until it will be (re-)setted by a another action block


The (boolean) line between the cycle step and "its" action block only shows, that this step is active. It can turn the action variable "A0" to false.
Please explain your question a litte more in detail: "How can I add R action and it is false?"
Attachments:

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1 year 3 months ago #275 by Sergey Romanov
I see, I have almost got it.

By the " will set "A0" permanently* to "TRUE"" You mean
A0.Q
or
A0.S
? I guess
A0.Q

By reading your answer and reading this page again I've understood that if action is active it can still be executed even if step tat it is assigned too is not active any more.

Now it all make sense. I was thinking within one step and it did not make sense for me to turn action on and off in the same step.

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1 year 3 months ago #276 by MartinDubGK
Hi All im newbie here. Good art! Thx! Thx!

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