Indirect addressing with S7-300

devittjl

Member
Join Date
Mar 2004
Location
Puget sound area, WA
Posts
4
Hello,
I would like to know if there is and equivalent to the follow AB indirect addressing technique available with S7-300

N19:[N7:91]/15

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 "FEEDHISPEED"
A DB1.DBX 194.7
O
A "FEEDMDSPEED"
A DB1.DBX 195.7
O
A "FEEDLOSPEED"
A DB1.DBX 197.7
)
FP "OS3"
S "R1_LOAD_SIGNAL"

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.
 
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.
Keith
 

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