Challenging Math Problem with MicroLogix

Archie · Oct 10, 2011

I was working on a project and ran into a problem that seemed very simple at first, but became quite a challenge to implement in RSLogix 500. Although I did come up with solution, it seemed like a lot of ladder code, so I wanted to see how others would do this.

I have a long integer (L9:0) that needs to be broken into 2 integers (N7:0, N7:1). The divisor is 10,000. Some examples:

L9:0= 78200
result:
N7:0= 7
N7:1= 8200

L9:0= -553333
result:
N7:0= -55
N7:1= -3333

L9:0= 649999
result:
N7:0= 64
N7:1= 9999

Lancie1 · Oct 10, 2011

Archie,

I never knew how to braek a double integer into two singles. Please post your method. Even if it is a lot of ladder, at least you have something that will do the job. Right now, I have zilch, and I need to do that for a project.

Steve Bailey · Oct 10, 2011

Would this work?

MUL L9:0 x 1 to get the 32-bit result into S:13 and S:14
DDV by 10000 gets unrounded quotient into S:13, remainder in S:14
MOV S:13 to N7:0
MOV S:14 to N7:1

cjd1965 · Oct 10, 2011

Sounds like a modbus thing.

TConnolly · Oct 10, 2011

DDV is not available on MLX processors, however IIR if you DIV L9:0 by 10,000 and make the destination register S:13 then you can get the result and remainder in S:14. I believe this is detailed in the instruction set reference manual.

edit: I confirmed that from the manual. See under the DIV instruction.

If the Sources are single
words and the Destination is directly addressed to S:13 (math register),
then the quotient is stored in S:14 and the remainder is stored in S:13.

OZEE · Oct 10, 2011

I just found exactly the same answer, Alaric. I thought there was a modulus command, but it's not available in 500.

dcooper33 · Oct 10, 2011

Archie,

Here's a method in RSLogix 500. It's a little clunky, don't know if it's any better than what you had, but here it is:

View attachment LARGE NUMBER DIVIDE.zip

Cheers,
Dustin

EDIT: I didn't have a micrologix handy to try this on, so I had to use a SLC 5/04, which didn't have the "L" register DINT, so I had to use Float, but the principle is the same

Archie · Oct 10, 2011

This was the way I ended up doing it. I should have mentioned it was a 1400, so I was able to use the CPT instruction. I ran into issues because the divisions rounded and not truncated, so I had to do a compare to see if it rounded a positive or rounded a negative

Lancie1 · Oct 10, 2011

Thanks, guys. Archie, Did you mean to have one more MOV at the end to move L9:29 to N7:1?

Sergei Troizky · Oct 11, 2011

Here you are.
You can move L:29 to N, but not the L:28 as it can exceed 16-bit values.

Archie · Oct 11, 2011

Thanks for the various solutions. I knew I had to be just over thinking this.

ndzied1 · Oct 11, 2011

Archie said:
L9:0= -553333
result:
N7:0= -55
N7:1= -3333

Just wondering what you are using this for. Someone mentioned Modbus but that doesn't make sense to me. If it is for a display, then my guess would be that only the 55 in the example above would be negative and not both parts so it seems they are being put back together on the other side....?

Archie · Oct 12, 2011

ndzied1 said:
Just wondering what you are using this for. Someone mentioned Modbus but that doesn't make sense to me.

The MicroLogix is communicating to an Automation Direct servo drive over Modbus. The position commands are stored in 2 registers. One is the number of pulses and the other is the number of revolutions. There are 10,000 pulses per revolution.

vikas1947 · Oct 12, 2011

may be the solution

in this program when i enter 123 so by the help of these tools i can dis attache one's ,ten's ,and hundred's. value in different places

and i think by doing some more operation we can complete this task i will tried on long integer but it fails i dont know why i will try it again.

chavak · Oct 12, 2011

Never tried this, not at my workstation right now,

But just wondering, if convert to string -> split -> convert back to integer ?

Challenging Math Problem with MicroLogix

Archie

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Lancie1

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Steve Bailey

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cjd1965

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TConnolly

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OZEE

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Archie

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