How DBD works?

Hello everybody,

I am checking a logic programmed in Step 7 and I have seen that some DBD's are used inside a FB. The values of these DBD are moved to local variables inside this FB, but I can't see anywhere what is the value which is being moved from DBD to local variable.

Could you tell me what this value is? These DBD's are not written in any other part of the program.

Find enclosed a picture of one example

Thank you

Hello ismael;

In Siemens S7 programming, a DBD is a database dword that points to a value inside a DB.

There must be an instruction earlier in your program that opens a specific DB, so the program will know where to search for that particular address. Please review the networks preceding the one in your screenshot to determine which DB this DBD is located in.

In case of doubt, print out the function you are working with (as a pdf file) and post it here on the forum, so we camn help you determine the logic for this DBD address.

Hope this helps,

Daniel Chartier

Find enclosed the cross reference screen with this variable. As you can see this value is only read. It may be possible that this value is introduced through HMI screen and that's the reason I can not find where it's written?

Thank you

I can not find any pointer or call to this DBD. There are many DBDs like this in this FB. I will keep searching, but I doubt I find anything.

Anyway, thank you for your help.

Best regards

ismaelillo

I can not find any pointer or call to this DBD. There are many DBDs like this in this FB. I will keep searching, but I doubt I find anything.

Anyway, thank you for your help.

Best regards

 You did not understand, what others are suggesting you to do. Read the suggestions again.

ismaelillo

I have not a great knowledge about indirect calls, but in the FB call I can not find any reference to the DBDs

 Don't look for DBD references. There was a question, if there is a OPEN DB command somewhere, did you look for that?