Step7 search parameter???

Hey folks,

About to modify a fairly large Step 7 program and i have a question concerning locating an object.

A method I have seen to control for example several heaters with device feedack is to use a single common PID control for all heaters. The data necessary for each heater (setpoints, PID values, etc.) is stored in seperate DB's. The PID loop is stored in an FB. An FC for example will call the same PID FB for each instance there ia a heater using a different DB to hold the specific data for the corresponding heater.
Outputs for each heater is routed the same, from the output of the PID FB back through the DB so each heater has its own output.

In the program I have, I connot find the individual outputs that normally would be controlled through the DB in the manner I specify above. There are some other questions I have for this program but I have to start somewhere.

My question, is there a way to include the PQW's in the generation of the crossreference/reference data? Also, is there a way to search through all the programming to find the PQW's?


Thanks folks!
JiNCs

It would be pretty unusual for somebody to be controlling the outputs via the PQW outputs where you cannot address a single output but only in groups of Byte, Word or DWord.

I would expect the controller to be driving single outputs of the form Qx.y which you should be able to find in the Cross-Reference list - unless they are being addressed indirectly, which I wouldn't really expect in this case.

If you right click on an I/O/M address, you can use the goto function and type in the PQW address you require.

or... The PQW addresses may be specified in a DB and not referenced directly - one quick way to track down where the PQW is being written (it has to be outside of the process image) is to remove it from the H/W config and make the plc goe into stop (if your process allows this of course). If OB122 is in the plc, you will have to delete it to ensure the plc stops when it tries to write to the PQW address. You can view the stacks to find the block writting the PQW value.

or... You could post the relevant code for analysis.

To ensure the PQWs are shown in the xref, click on the check boxes in the filter:

Step7 search parameter???: Reply to all

Thanks RMA and L D[AR2,P#0.0].

The filter for the cross reference did the trick. The control I was speaking of actually used a PID. The PQW outputs were located in OB35.

If memory serves, the call for the PID needs to be in a constant scan time location (OB35?) . . . doesn't it? Think I should have known where to look for the PQW's. The program used a coded name for this OB that didn't lend itself to locating the PQW's.



Thnaks again!
JiNCs

Yes, PID must know how often it is executed. So OB35.