COP instruction in RSL500

[Bullzi]

Hi Everyone,
PLC: ML1400 Testing on a SLC 5/04

I am working on a Project were I need to save 28 days worth of float data. So I set up F9 with 28 floats. When the day changes I want to move F9:1 to 26 down one slot. So F9:1 would move to F9:2 and so on all the way to F9:27. The number that was in F9:27 would go away.

I set up a COP instruction with the Source of F9:0 and Destination of F9:1 length of 27. When I trigger the instruction, I get F9:0 coping to F9:1 but then it fills the file with the value of F9:1.

So how can I move everything down one so I can insert the new value at the top. I have done this before in a Logix Controller using a CPS Instruction, But this seems to be kicking my butt in 500.

Any ideas would be greatly appreciated.

 

[Ron Beaufort]

if you definitely want the data to move "forward" (as you said) then take a look at the "ratchet" method ... if you want to save memory and can live with going "backwards" try using the "ripple" method ...

both ideas are covered in the TWO posts which start here:

http://www.plctalk.net/qanda/showthread.php?p=360484&postcount=3

(yes, I know that you're asking for RSLogix500 - not RSLogix5000 - but the ADDRESSING ideas are the same ...

 

[Bullzi]

Thanks Ron!!
I went back and looked at the 5000 program where I had done this before and sure enough I did the "Ratchet" method.
I changed my program and it works perfectly.
Thanks again.

 

[Ron Beaufort]

I went back and looked at the 5000 program where I had done this before

I guess that's a GOOD thing - when you get to the point that you KNOW so much that you just can't remember it all ...

party on ...