S5 viewing in STL and LAD

PLucas

Member
Join Date
Apr 2002
Location
Gillingham Kent
Posts
1,742
Hi all,

Sitting in my office I have a S5 115U plc for 'playing' with, so I played with it and wrote myself a little bit of test code. Anyway, PB1 segment 1 has the following:

In statement

:C DB10
:***

In ladder

|
|--------------------------( C )-|
|

Now the 'problem' I am having is, if I view this segment online in statement it gets processed no problem, if I then change to view in ladder the block does not get processed! Can anybody explain why this should be the case? I wrote this segment originally in ladder not statement, It is not really a problem because the PLC skips happily along, it's just something I notice while debugging.

Any explanations will be gratefully received.

Paul
 
Basically, anything you write in Ladder can be converted to STL.

However, not everything you write in STL can be converted to Ladder.

This is because of the inherent limitations of Ladder.

It appears that your problem is that the Ladder Code was converted to STL in such a way that it could not be properly re-converted to the original Ladder code.

ANY reasonable and rational sequence of steps that you can imagine can be described in STL. Not so in Ladder. Ladder is limited to the constraints as provided by the developer.

In some PLC's you can not do the following...

Code:
  IN-1
---| |------+---------(    ) Out-1
            |  IN-2
            +---| |---(    ) Out-2

While in others you can not do even this...

Code:
---| |------+-----(    ) Out-1
            |
            +-----(    ) Out-2

You can certainly do all of those in STL!

STL is essentially ASSEMBLY LANGUAGE which is only ONE-Step above Machine-Code.

You can accomplish far more by using STL. However, as many will (or rather, might) point out, STL IS more complicated and might not be understood by all that need to understand.

While I am a proponent for ALL PLC PROGRAMMERS using ALL of the available tools, I recognize that certain situations require that the code be... Not as efficient as it could be (translated, dumbed-down a bit).
 
Last edited:
Terry

Thank you for your input, I am aware of the 'failings' of programming in ladder compared to STL. I was just suprised to see that this segment was not being processed in ladder, but was ok in STL. All the other segments that I programmed in PB1 will process when viewing in either ladder, STL and CSF. As this segment was the only one that would not, I was curious as to the reason why.

This has probably happened to me many times in the past but this is the first time that I have noticed it.

Still we live and learn

Paul
 
Terry Woods said:
While I am a proponent for ALL PLC PROGRAMMERS using ALL of the available tools, I recognize that certain situations require that the code be... Not as efficient as it could be (translated, dumbed-down a bit).

Terry, now and then you can be veeerrry diplomatic! :D (Have your keepers returned???)
 
can anyone help me with my project... because it is very hard for i am just a beginner in PLC...

can anyone gave me a program for "trafic junction operation..."
 
I've got to assume that this is a post intended to push a few people's buttons.

Why else would a brand new member and first time poster, resurrect a 17-month old thread rather than start a new one in order to ask the ultimate beginning student question.

I strongly urge all members to refrain from offering any helpful advice.
 
PLucas, I think the DB open is working and won't display in LADDER. We are assuming, the DB you are calling is created in the PLC and that PB1 is being called from OB1. To prove it, try something like this.
C DB10
L DBW0
L KF+1
+F
T DW0

Then run the CPU and check in the STATUS mode and see if, in the right column, that your DB is called and in the STATUS VARIABLE screen if the DB , DBW0 is incrementing. If a DB is not open, the PLC will crash.

Otarra, do your homework, there are no "Free" rides.
 
OK.. i am succesfully got the exact program thnks for nothing guys.... hope that you?

thanks for nothing guys... hope that all of you will become a Million Dollar man in the future for your being very good in PLC...... but .......wait for me cause ill be one of you someday.......
 
Otarra, since you've broken form and followed up your initial post, if you can come up with a credible explanation of why you posted your question where you did, I'll retract my statement and apologize.

Key questions to be answered include:

1. Why did you not start a new thread?
2. Why did you choose to ask your question by responding to this particular thread?
3. What connection exists between the original question posed in the thread and your question?

Extra credit may be awarded for originality and creativity.
 
Being intimately familiar with one PLC platform is possible. However if a programmer is required to use AB, Tele, Step 7, etc..., it isn't humanly possible to be an expert in all platforms.
 

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