View Full Version : Indirect addressing with S7-300

March 5th, 2004, 03:48 PM
I would like to know if there is and equivalent to the follow AB indirect addressing technique available with S7-300


I use this logic in a shift register (N19). N7:91 is and interger that deterines which step to look at in the shift register. The value of N7:91 will change based on certain criteria, in this case feed speed.

Currently I have to set up three branches with bit for three different feed speeds as shown below.
A DB1.DBX 194.7
A DB1.DBX 195.7
A DB1.DBX 197.7
FP "OS3"

I would like to use indirect addressing similar to AB style.
Or can I copy different DBs into the logic.

The reason for this is that the shift register location is enter through a display so the the machine can be adjusted in the field without changing the program.

Thank for the help.

March 5th, 2004, 04:19 PM
Yes, you can. It won't be quite as clean, however. You will also need to massage the form a bit.
I have attached a relatively simple indirect addressing example. It's just an interpolator between two points, the points determined by another variable. It is a Step7 source file, which is nothing more than a text file. Take a look and see if it helps. The 'P#' lines are pointer designators.
There is a much more involved and powerful way to do this but I've never needed to use that. The Step7 help has a pretty good description of indirect addressing, if you can find it. I'm using non-area crossing pointers, which should work for you.

I hope this helps.