Using global DBs in SCL FB for S7-1200

[DLMUK]

Hi,

I am new to Siemens and SCL. I have a datablock which is a global data block. I want to use some of the values in this DB in a FB block.

When I reference local data in SCL I would do the following

#localData

What I want to do is the following

IF globalData > #localData THEN
#localOutput := 1;

ELSE #localOutput :=0;

END IF;

But when I try and use the global data it lets me input the whole DB within quotation marks but I cannot figure out how to address the specific data value within the DB.

Can anyone help?

Thanks.

 

[BryanG]

Typical reference for a global variable:

"RigDataRetained"."B Total pumped" := 1;

"RigDataRetained".Total_Paint_in_Line := 1;

The easy way is to open the DB, highlight the line of the data, then Copy and Paste.

The quotes are only needed when the you spaces in names.

Of course if we were proper programmers we would never use a Global Variable within an FC/FB, you would pass the variable as an In/Out parameter.

 

[DLMUK]

Thanks - worked perfectly. I was trying this... "Display Values.H1" whereas I should have been doing it as you suggested.

Would you normally do this programming a PLC? To me it seems like it would just create more work/points for potential error?

Of course if we were proper programmers we would never use a Global Variable within an FC/FB, you would pass the variable as an In/Out parameter.

 

[BryanG]

I never said 'I' was a proper programmer!!

There is a whole world of argument about 'proper' technique, but for me, so long as the program makes sense and is simple to follow, then we are probably doing it right.

Just to contradict myself. When I am working in 'C', then I tend to follow, proper technique, even though I do find it tends to make it harder to follow a program sequence. At least if you use Global Variables then it is called the same thing everywhere in the program, where as a passed variable may be called something different in a sub routine.