respected all,

i started my career as a automation engineer ( industrial process ) recently. I need help from all the experts here and my question is that my most of the work based on making changes or updating the available s7 300 program and i found it logically a long process to do any given task so please let me guide how can i easily read any program logic and get it understand fast. 

Thank you all

Atif Ahmed

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Split from about SIEMENS PLC.

Hello atif;

Many of the answers to this kind of question will depend on which programming software you are using for your S7-300: Simatic Manager (Step 7 v5.x) or Tia Portal (Step 7 Professoonal v1x).

The original thread you posted in gave you many links to basic manuals and tutorials on the S7-300 programming that you could consult if you need to refresh your knowledge on the subject.

Step 7 (both versions) integrates many useful tools to understand an inknown program, such as Cross-references: program structure. used/unused addresses, etc...

If your program is original (not an uploaded version) comments and address symbols provided by the original programmer should help clarify how he/she organized the program. Unfortunately, if this is an uploaded copy you will have no comment or symbols,  so you will have to rebuild them, based for example on the electric plans of the process you want to control.

hi dear,

thanks for ur answer. as per my understanding from ur answer that is if the program is uploaded version then there is no way to understand the logic ?

i am using simatic manager for programming.

thank u

 Hello atif;

@tif84

hi dear,

thanks for ur answer. as per my understanding from ur answer that is if the program is uploaded version then there is no way to understand the logic ?

i am using simatic manager for programming.

thank u

 Not exactly, atif;

This is what I wrote earlier:

"Unfortunately, if this is an uploaded copy you will have no comment or symbols,  so you will have to rebuild them, based for example on the electric plans of the process you want to control."

You can use the code in an uploaded program to understand the controls, but it will be much harder without the programmer's comments and the symbols for variable addresses and function parameters.

Hope this helps,

Daniel Chartier

@tif84

thanks for ur answer. as per my understanding from ur answer that is if the program is uploaded version then there is no way to understand the logic ?

Our dear friend, sometimes you can have all - symbols, comments - and you won't be able to understand the logic as there's no any logic in the logic. 

K_Ohjus

I think that there is no point of translating old code, it is probably a piece of crap and out of date. Just think the process and what that piece of code does. Then rewrite it to match today and change what ever you need. 

Creating from scratch a control software for running industrial process? Brave idea.

Maybe it's just dung scraping from a floor or maybe it's oil refining. If it's the later and you try then the first will fly everywhere.

Jacek

good point, but i think there is a huge problem with program updates. Install S-1500 to replace 300, no code modifications needed. Just replicate old code and all is good!!

You can buy S-300 PLC, but if you do an PLC upgrade to 1500, upgrade the program too, otherwise it is just idiocy. Could be of topic, cos i do not remember what the topic is.

Do not just blindly follow old program, have some self confidence and do modifications, when needed. Oil refining process is pretty simple and it is hardly regulated. Try some nuclear power plant, program changes are not welcome.