STL statement

[Tom749 0]

Hi, Everyone. I have one question about the STL statement. That is what is the main purpose of using the STL statement in Siemens PLC program? My colleague who likes to use the STL statement says to me because of the speed of process and the short of the PLC program. But in my case the STL is to hard to understand when I open the program which was developed by him... He always keeps making the plc program using the STL statement. Why do we use the STL statement? Is there any way to understand and get the information of the STL statement? Thanks for your reply in advance.

[jmsmoreira 0]

As your friend said STL makes the program faster to write. I personally don't like to use it, because when you are online is easier to follow the program if you do it on ladder. However, on the Siemens editor, on the tab View, you can switch between both views (Ladder and STL) without any problem, with the exception of some particular STL statements.

[Moggie 17]

Not all STL can be converted into ladder - This will convert into LAD A M 3.0 S M 3.2 A M 3.1 R M 3.2 NOP 0 This will not convert - A M 3.0 S M 3.2 A M 3.1 R M 3.2 But both work exactly the same!

[AdamF 0]

To add something from myself - many functions in S7 is not possible using FBD or LAD - only STL. For example pointer operation, jump lists and other program control functions. I like writing programs in STL but debugging it in online is not as fast as with FBD or LAD. In other hand i write functions in STL that i will never look into later - i'm sure they work so I call it and use it's input output and have no interest to look or change the code inside.