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Old May 16th, 2007, 03:45 AM   #1
userxyz
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Is SCL almost = ST (structure text) ?

I have learned ST @ school a little bit, but never used it in real life...

Does anyone has a tutorial or manual how to program SCL or ST in PLC's... ?

And when is it used mostly instead of STL, LAD, FBD, GRAPH... ?

I know that simotion can be programmed in ST, why is that ?
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Old May 16th, 2007, 04:02 AM   #2
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SCL is exactly the same as IEC1131-3 Structured Text.

Use SCL for manipulating large arrays of data.
Or for complex math.
Or for manipulating Strings.
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Old May 16th, 2007, 04:06 AM   #3
dchartier
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Hello Combo;



Manuals:http://support.automation.siemens.co...odeid0=4000024
(You should know how to look in the Siemens website by now, shouldn't you? I'll let you look for ST [Siemens calls it STL]).

SCL is closer to PASCAL programming, and much easier to understand by a user. We used it to program math functions that required much processing (harder to do in LAD/FBD, almost inscrutable in STL).


Hope this helps,
Daniel Chartier
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Old May 16th, 2007, 04:13 AM   #4
L D[AR2,P#0.0]
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Quote:
Originally Posted by JesperMP
Use SCL for manipulating large arrays of data.
Multi-dimensional arrays in particular.
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Old May 16th, 2007, 05:43 AM   #5
userxyz
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I

I still feel myself als a basic beginner if I reed this, I never worked with arrays and the math that I'm using is something from the childgarden
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Old May 16th, 2007, 05:44 AM   #6
userxyz
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But

But, I've red 2 versions now,

one telling me it's the same SCL = ST

other one SCL = Pascal
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Old May 16th, 2007, 07:15 AM   #7
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SCL conforms exactly to IEC1131-3 ST.
SCL is "similar" but not the same as Pascal.

One wonders which brainhead at Siemens decided to call it SCL, when it really really is ST.
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Old May 16th, 2007, 08:11 AM   #8
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Simply put?

STL is like:

A I 0.0
AN M20.0
= Q 0.1

SCL is like:

If I0.0 and NOT M20.0 then
Q 0.1 = true
else Q 0.1 = false

Note that I have no experience in SCL, only seen a few source-files so above syntax might not be 100% correct.
But it should give you an idea of how the 2 differ.
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Old May 16th, 2007, 09:00 AM   #9
Ken M
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Jesper,
Quote:
One wonders which brainhead at Siemens decided to call it SCL, when it really really is ST
I think it's all down to politics! You have to ask which came first, SCL or ST? I think Siemens had a very early language they implemented in some of their non-PLC controllers which they called SCL. This was before IEC61131-3, so when the IEC Working Party decided to call this language ST, Siemens decided to stick with their name for it, SCL. The same thing happened with Graph 5 which existed before the IEC defined SFC. When S7 was launched, the equivalent language was somehow named S7 Graph (why not Graph 7? who knows)and Siemens stuck with their name for the product despite the IEC saying it should be SFC. And what about good old IL (in IEC terms) which Siemens insists on calling by their own name, STL, because that's what it was called before 61131-3.

I'm sure if Siemens had their way in the IEC working party we would all be talking about SCL and STL rather than ST and IL!

Regards

Ken
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Old May 16th, 2007, 09:24 AM   #10
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Aha, I didnt know that Siemens SCL and GRAPH preceeded IEC ST and SFC.

But I think that it is a good thing that Siemens STL has a different name from IEC IL. These two are not the same.
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Old May 16th, 2007, 09:53 AM   #11
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Hello guys;

Just for the anecdotal value of the thing...
Quote:
named S7 Graph (why not Graph 7? who knows
Grafcet is the original name of SFC programming, developed by the french AFCET in the early 90s, well before IEC61131-3. Since 7 is "sept" in fFrench, pronounced "set", Siemens probably wanted to avoid any confusion (or liability) for their implementation.
Regards,
Daniel Chartier

Last edited by dchartier; May 16th, 2007 at 09:58 AM.
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