S7-300 address help

Hi all

I am new to Siemens so please be patient!

I have a problem with a S7-300, and I have traced the issue to DB100.DBX6.0 "main motor db". locked_all. Please see pics.

Now I am trying to find how this bit is turned on/off but I do not know how to find it in the program. I have tried cross reference table and the symbol table. I have included the data block info screen as well.

Any help would be appreciated.

Regards, Bob

There seems to be a bit of poor programming there. But let's look at what you need to do.

On Simatic Manager, check the type of DB for DB100 (it is likely that it is instance DB). If the DB is an instance DB, you'll have to find which FB block calls it. I believe this is possible to see from the code structure on the Step7 editor.

Open the FB that uses DB100 as an instance DB.
Go through the local variable list (the display section on top and find that variable there. Click on it. Then press Ctrl+Alt+F (for forwards) and the cursor will jump to where that variable is used. Ctrl+Alt+B will jump backwards through the code.

This, although annoying, is not really a problem if the functionality of the PLC was used as intended, which seems not to be the case here, but we'll have to see what that DB is.

If the DB is global, click on top of the variable to select it, then press Ctrl+Alt+Q and a pop up will open with all the locations where it is used. There will be a tickbox mentioning overlapping memory areas that you should tick as well to see all accesses to this variable.

Thanks for a quick reply!

I have added two more photos. When I press CTRL+ALT+F I get an error saying online connection cannot be established (I am not on site currently so cannot go online)

Once I accept that error I get a Var table pop up...?

The photos I have loaded are the screens I believe I need to open?

Ups... Sorry, I think it's Ctrl+Shift+F.

Ok found the problem, I compared the original program with the version on the PLC and there is a line of code missing!

Thanks for your assistance...