CCW FDB's - How to set a variable to a constant

[RMore]

I am new to using Functional Block Diagram (FDB) language programming in CCW.

I want to set a variable to a constant if a contact is closed. How do I do this?

Also, where can I find a comprehensive tutorial on using FBD in CCW?

 

[drbitboy]

The Rube-Goldbergs/Heath-Robinsons below work, but there has to be a better way. We should be able to enable the EN/ENO input/output of an instruction block, but in my version of CCW that option only shows up in ladder.

 

[KuulKuum]

Per this linked RA KB you can create a user-defined function block (UDFB) but stated you need CCW 20.01 or later to work.

ID: QA64950 | Access Levels: Everyone
CCW - MOV instruction in FBD language
https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/1137173/loc/en_US#__highlight

 

[5618]

I think this would work for you, adapt as needed for other data types. Make a new user defined function block. I called this SelectReals and wrote the block in ST. Here's the code:

IF Select THEN Output := SelectOn;
ELSE Output := Select Off;
END_IF;

Local varaiables for that are:
Select, BOOL, VarInput
SelectOff, Real, VarInput
SelectOn, Real, VarInput
Output, Real, VarOutput

That function will appear in the select list for an instruction block.

 

[drbitboy]

From RA:

Question
Is it possible to make MOV instruction in FBD language conditional, ...?



Answer
No, it is not possible.

The Rube-Goldbergs/Heath-Robinsons below work, but there has to be a better way.

LOL. The impossible we do right away, the difficult ... wait a minute ...

 

[KuulKuum]

From RA:




LOL. The impossible we do right away, the difficult ... wait a minute ...

Yes, I love the way RA shows pictures of example CCW UDFB for MOV instruction... But displays it in Ladder and NOT FBD

 

[RMore]

Perfect, Thank you.

 

[RMore]

Per this linked RA KB you can create a user-defined function block (UDFB) but stated you need CCW 20.01 or later to work.

ID: QA64950 | Access Levels: Everyone
CCW - MOV instruction in FBD language
https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/1137173/loc/en_US#__highlight

Perfect. Thank You!