RSLogix Maths Problem

jaichains · May 17, 2006

Hi

I am programming an Allen-Bradley SLC 5/04 through RSLogix 500. I have 8 user configurable integers (N7:10, N7:11, N7:12, N7:13, N7:14, N7:15, N7:16, N7:17). I want my ladder logic to calculate which is the biggest integer out of them.

One of the one way is where, i compare each integer with each other. But this will be really big and cumbersome. Can someone suggest another method to calculate this in RSLogix 500 using ladder instructions.. Thanks.

Oakley · May 17, 2006

One thought would be to use something like a bubblesort or some other means of sorting your data into another data range set - that would be most useful if you needed the list in sorted order all the time.

bernie_carlton · May 17, 2006

Try:

BST CLR N7:0 NXB MOV 10 N7:1 BND

LBL 1 GEQ N7:[N7:1] N7:0 BST MOV N7:[N7:1] N7:0 NXB MOV N7:1 N7:2 NXB ADD N7:1 1 N7:1 BND

LEQ N7:1 17 JMP 1

This will end up with the largest value in N7:1, the index of the largest value in N7:2. It also uses N7:0 as an index holder. These can always be other locations.

TConnolly · May 17, 2006

Use a for/next loop and indirect addressing.

See the attached. This short routine will leave an indirect address pointer in N7:0 to the largest value and a copy of the largest value in N7:1.

edit: Bernie beat me to it. His solution is pretty much the same thing.

jaichains · May 17, 2006

Dear Alaric, bernie_carlton

Thanks guys for this, it works wonders....Cheers!

jstolaruk · May 17, 2006

jaichains said:
Hi

I am programming an Allen-Bradley SLC 5/04 through RSLogix 500. I have 8 user configurable integers (N7:10, N7:11, N7:12, N7:13, N7:14, N7:15, N7:16, N7:17). I want my ladder logic to calculate which is the biggest integer out of them.

One of the one way is where, i compare each integer with each other. But this will be really big and cumbersome. Can someone suggest another method to calculate this in RSLogix 500 using ladder instructions.. Thanks.

Thats 8 rungs with a total of 15 instructions. Is that really big and cumbersome?

Mickey · May 17, 2006

jstolaruk said:
Thats 8 rungs with a total of 15 instructions. Is that really big and cumbersome?

I'm from Missouri, show me. Please.

jaichains · May 17, 2006

Thts not 15 instruction but 8 factorial instuction which is mega huge.

jstolaruk · May 17, 2006

Mickey said:
I'm from Missouri, show me. Please.

I can only put the ascii code. Assume n7:0 is the final result:

1: MOV N7:10 N7:0
2: GRT N7:11 N7:0 MOV N7:11 N7:0
3: GRT N7:12 N7:0 MOV N7:12 N7:0
4: GRT N7:13 N7:0 MOV N7:13 N7:0
5: GRT N7:14 N7:0 MOV N7:14 N7:0
6: GRT N7:15 N7:0 MOV N7:15 N7:0
7: GRT N7:16 N7:0 MOV N7:16 N7:0
8: GRT N7:17 N7:0 MOV N7:17 N7:0

I like MO, especially around Linn Creek.

jstolaruk · May 17, 2006

jaichains said:
Thts not 15 instruction but 8 factorial instuction which is mega huge.

You said you wanted the biggest integer; not that you wanted it sorted.

Mickey · May 17, 2006

Thanks

scottmurphy · May 17, 2006

On a side note

I just had a situation where I needed to do the same thing, but instead of generating the code, Omron has an instruction called MAX, which you can define the length, starting register, and result register. There is also a MIN instruction.

This does not tell you what register it is in however, but that can easily be accomplished with a lookup table.

The Omron instruction set is huge, and I only use / know what a fraction of them do.

RSLogix Maths Problem

jaichains

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bernie_carlton

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