Poor Man's FAL/COP

[robertmee]

Ran across this code today in RSLogix5000.

First Rung - Isn't this just a straight file copy?

Second Rung - Isn't this just populating an Array with a value of 0 to 16?

 

[rdrast]

Looks like yes and yes, but in #2 it would go to 16.

Probably a copy of a "Generic" assignment from another brand of processor.

 

[robertmee]

Yes 16....posted before I proofread.

 

[ASF]

Rather than completing the whole copy in one scan, it'll just copy one element every second scan - but otherwise, yes, that looks very much like a "poor man's COP instruction" to me!

I suspect rdrast is right...probably code copied and pasted from a less powerful/different brand of processor.

 

[Sergei Troizky]

There may be some reasons for the shown method, though most probably ASF is right.
Unlike copying by a single instruction:
- The pointers may be used somewhere else in the program.
- The array transfer may be terminated/restarted/repointed programmatically before completed.
- Scantime is not increased unnecessarily. Yes, the shown arrays are short, but there may be lots of them in the program.