Stl Programming

Dear sir,

I am familiar with ladder logic programs but finds difficulty in understanding STL programs, kindly suggest me some good sites to learn please

Sundarajan,

two questions:

1. What kind of PLC are you talking about? I suspect it's Siemens S5 or S7.
2. If the possibility exists, have you thought about letting the software translate it for you? If I thought right at 1. it's a definite go!
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   Kind regards,

Mitsubishi has a pretty good chapter in there fx programming manual on stl programming.

STL can mean two things;

STatement List (mnemonic instructions)
or STep Ladder (Mitsubishi's own sequence instructions)

You will have to be more precise with your question

I AM TALKING OF SIEMENS S5 PLC, SOFTWARE LETS TO DO THE CONVERSION FROM LADDER TO STL BUT NOT ALL, LIKE WHEN YOU WRITE A BLOCK FIRST IN STL THEN TRY TO CONVERT TO LADDER, IT SAYS CONVERSION NOT POSSIBLE.

MY INTENTION OF POSTING THIS REPLY ONLY TO UNDERSTAND PLC STL PROGRAMMING, BECAUSE WHILE TROUBLE SHOOTING ON LINE PLC LADDER LOGIC SOFTWARE SHOWS WHICH INPUT IS ABSENT TO DISABLE ONE PARTICULAR OUTPUT BY HIGHLIGHTING THE ELEMNT WHEN INPUT IS PRESENT,

WHEN I TROUBLE SHOOT THE STL PROGRAM ON LINE IN BLOCK STATUS WITH STEP-5 SOFTWARE I FIND IT DIFFICULT TO UNDERSTAND WHEATHER INPUT IS PRESENT OR NOT.

HELP ME REGARDING THIS

A I 0.0     U E 0.0

S F 0.0     S M 0.0

A I 0.1     U E 0.1 focus-line   1 or 0 RLO or VKE (german)     

R F 0.0     R M 0.0

NOP 0

*** 

Step5 needs some case some NOP 0 operation for Ladder or FUP views,
if it missing, it can't show that rung (Netzwerk).
1'st do some circuits by Ladder (KOP) or FUP and change it to STL using F5 or (shift F5). Now you can see it how many NOP 0 rows there are and where. Try do some S/R, R/S, Timer and Counter circuits.

In on-line you can see the RLO result of locig Operation (VKE) as far yuor focus is, focus moves by arrow keys (or page down/up).

Somtimes if you see a lot of logic in STL you can break it up with a BLD255 instruction and it will turn to Ladder. This is a bit tricky but With care many STL prgrams will convert.

Lenny

Here comes 'Select Case' STL list from the book 'Programming the S5-135U with STEP5' by Hans Berger, 1st edition, 1987.
This is typical case when it is impossible to view by Ladder or Fub.

As Seppo has pointed out some things are just ment to be STL. We make that sort of stuff funcition blocks with parameters and do little or no "Logic" in them. Mostly math stuff or word logic or mutipal compairs that return bits.

But if you see somthing like:

A I0.0
S F0.0
A I0.1
R F0.0

As in Seppo's first example. You can insert the BLD255 (see Berger)
as below and it will return ladder.

A I0.0
S F0.0
Bld255
A I0.1
R F0.0

Returns

---------| |--------------------------(S)

And

---------| |--------------------------(R)

this only works in the newer packages for all blocks. In the older software it would only work in OB's and PB's. As I said it is a bit tricky because you need to find each "Logical Conclusion" then insert the BLD255. You know right away if you did it wrong because it won't convert.

There is no substatute for well structured code. The Siemens programming software is so powerfull it' a shame so many programmers don't use it to it's full potental. It's funny to see the differance between code written in Europe and here in the US. We find many folks here that just dispise Siemens and refuse to learn how to structure a program. Then we run across a machine from across the pond and 9 times out of 10 the code is so well written that it can be serviced even if the comments and symbols are missing.

Lenny

THANKS EVERY ONE FOR THE INFORMATION I WILL GIVE IT A TRY

THANKS

G.SUNDARARAJAN

Supplementtary and system operations

Dear, I just want to reminde you, but I am sure that you know allready, that some of STEP 5 PROGRAMMING OPERATIONS can be programmed only in STL these operations are Supplementary operations and System Operations these operations you can put only in Function Blocks. For more details you can reffer to your PLC manual.
Thank you.