Hello All,

did you know how to modify (permanent) value on S7-300 using Step 7? can we use Step 7 or I must use TIA portal to do modify(permanent) value?

 i have tried to modify value but no selection for permanent modify, so its change back to actual value when cycle end/start.


FYI: i want to change memory variable (M) & DB variable (DB), this variable is in the end off ladder diagram (output of ladder). can i force them to my desire value? have any suggestion all?


thanks all

Hello,

Please explain a little more.

You want to modify a value, but that variable is also written in program?

Do you want to force a value?

Best regards,

Wizard

Wizard

Hello,

Please explain a little more.

You want to modify a value, but that variable is also written in program?

Do you want to force a value?

Best regards,

Wizard

 sorry  I am so new at siemens, i don't know whether we are be able to force variable that also written by program.My purpose is to force/modify the variable in the end of ladder(output ladder), to keep varibale not change , is it possible?

Hello,

What variable are you talking about?

You want to "force" it for a particularly time?

Why do you want to modify the variable?

What CPU are you using?

Perhaps a screenshot might help.

Best regards,

Wizard

I want to modify it temporary, the programs like this, 

the target is M91.3 & Q6.7 . I want to keep the variables target is true although the input  changed.

Towome

Hi,

you can force only inputs and outpus, so if you want that value in your variable will not be overwritten, you have to change logic. Use a CLR / SET instruction before M9 / Q6

Regards,

Towome

 can we only modifying? no need to be permanent, only need temporary for a moment. iam read from this article that we can do modifying not only in the output/input,

soruce:

https://instrumentationtools.com/forcing-and-modifying-plc-logic/