Siemens S7 300 pointer issues (how to trace)

[maico]

Hi All,
I have a system where there are parameters loaded into a DB from a DCS system. When I check the address's I find no locations in the program visible from the DB as I assume pointers are being used within the program. I just want to find out where these parameters are being used or find the pointers that are using this DB.
Where is the best place to start I have read loads of articles on pointers, within the program I have lots of commands like the one below but how do I trace this to the actual DB.

OPN DB [#ActivePhaseDB_Number]

any help would be great.

 

[gclshortt]

http://www.plctalk.net/qanda/showthread.php?t=25032

The above thread may help you out.

Regards,

 

[mk42]

OPN DB [#ActivePhaseDB_Number]

You have to figure out where #ActivePhaseDB_Number is calculated. It probably changes as the program executes.

 

[qamrij]

as suggested you will have to look where the db number is calculated, and if u use the cross reference. You will see where the pointer access the DBs because you will see a question mark near the db symbol. Its not a big help but at least you will be able to start from somewhere.
Using the inderect adressing is very fast and its cool too because you can significantly reduce your cycle time, but the drawback is troubleshooting.

 

[wimpiesplc]

OPN DB [#ActivePhaseDB_Number]

any help would be great.

anything with # indicates a variable declared in the current block.
For instance, if #ActivePhaseDB_Number is an IN variable of the current block, you have to look at the place where this block is called to see what value or parameter is given.

grtz,

Wimpie