pointers/indexing in S7 for guy coming from Allen-Bradley

[buhnen]

Right before starting to think about what kind of indirect adressing suits best my needs, I'd like to ask for your advice on finding the best how to structure my code...

The case is next: If I have to, for instance, count the number of hours my motors are on, I'll create a code for it and put it into an FB. Then after I'll create as many DB's as motors I want to control. In each DB I will store (among other data), a variable containing the number of hours. The FB will call to all those associated DB's by means of a loop instruction with indirect addressing.
This is how I've been doing in Allen-Bradley (multiinstancing)....my question is: is this way I've just described above the most efficient one in Siemens in order to take best advantage of the use of the CPU's memory for a S7-300?

 

[L D[AR2P#0.0]]

Which CPU will you be using 315/7/9 ?

No need for indirect addressing with what you have shown so far. Create an instance for each motor.

 

[buhnen]

I'll be using a 315, I think. My main concern was about whether I'm running a project with , let's say 50 or even more motors, it would be convinient or not to handle such amount of DB's ... I mean, the FB making 50 calls to each of them.

...In any event, as far as I've got to know the size limit per DB is 80kb so I'll work out the calculations for my project and look up into the technical documentation of the CPU's more info about this subject.

 

[Nick B]

You don't need 50 DB's. Using multi Instance (use search function) you can do it with one.