You mean jumping over some code which is not used? Well, every language allows this. Some compilers will throw warning, but nothing more.

Poor coding is poor coding an has not much to do with a language used.

Hello Jacek, it really isn't obvious, but the second jump (JC AUTO) didn't always execute. It took a while, but I spotted the A Flag1 all on its own.

So the real logic is:
A     Flag1
AN    Flag2
JC   AUTO

This was really hard to find, and in my opinion shouldn't be allowed to happen in the first place.

What does everyone else think?

Brian

hi Brian,

with STL you have to know what you are doing. It is a high-perfomance language, even because of this posibilities. 

It is near to the hardware, and with those languages you have to be careful what you are doing. 

I just remember what my teacher in school said about Assembler-Language:

"Assembler is only doing what you tell it to do. But it is doing it!" (whitout a warning or message)

Assembler is very similar to AWL

regards,

brian.grimshaw

Acknowledging that there are flaws with STL, should we be using it at all?

Allow me to quote our good friend Aret from THIS thread to give you my take on things as I couldn't have said it better myself:

"LAD and FBD are like a bicycle - easy to use, but possibilities are limited. STL then is motorcycle here - powerful, but requires a lot of experience to use all its power"

fritz

"LAD and FBD are like a bicycle - easy to use, but possibilities are limited. STL then is motorcycle here - powerful, but requires a lot of experience to use all its power"

 ... and when you have an accident, it hurts more than with a bicycle.

I was reading the Siemens Programming Styleguide for S7-1200/S7-1500 at the weekend - sad I know

Recommendation: preferential use of SCL
SCL should be selected as programming languages for blocks. SCL offers the best
readability among the programming languages and, at the same time, has no
performance disadvantages as opposed to other SIMATIC PLC programming
languages.

So STL is not the highest performing language after all - that is surprising.

Brian

brian.grimshaw

......

So STL is not the highest performing language after all - that is surprising.

Brian

 Hi Brian!

I can't read out the same from the quote you've posted.

In the case of S7-1x00 PLCs it is normal that Siemens recomends SCL, since if you want to write compatible code with S7-1200, you should not use STL.

BTW, you are comparing apple with pear, since STL and SCl are at different level from machine code's point of view. smiffy could tell us a lot about this.

https://support.industry.siemens.com/tf/ww/en/posts/tia-portal-vs-step7-scl-compiler/143213/?page=0&pageSize=10