Logic Control Proposed spec


Thread Starter

Ron Gage

Hi Folks:

Thanks to some brilliant timing from some others in the list, I thought I would share with you all something I have been working on in the background.

I am trying to (also) develop an Allen Bradley PLC5 emulator under Linux (and contribute it to the Project in general). I currently don't have much for code, but I do have a written out (partial) spec that I was going to use as a guide.
This spec should allow for a decent engine to get built, one that would be highly extensible and/or customizable. To that end, I would like some comments on it. Please keep the flames to yourself though! :) I know there are Modicon
folks in here as well as Seimens/GE/Mitsubishi/whatever. I am not trying to force something on to you folks, I am just going with something I know - the PLC-5. From what I remember, this project was *supposed* to be able to have a pluggable logic engine interface so it *could* emulate a PLC5, a Modicon, or whatever.

On a side note, I thought seriously about building a (software based) Allen Bradley PLC-5 workalike system under Linux (simular to the SoftLogix product currently marketed by AB). By workalike, I mean something that I could talk to
it via RSLogix5/AI/6200 and make it work. Probably emulating a PLC5/80E or something like that (to guarentee that even 6200 would be able to talk to it). I am not sure that this is a good idea as it would be obviously stepping on way
too many toes at AB. Unless some management level person from AB can give me written assurance that this would be welcomed, I don't think I am going to try. The way I see it, this wouldn't be too hard to do though.

Anyhow, please look over my proposal. It is kinda rough in the writing but should be able to give a decent idea of what I am aiming at. Please note that there are a few extensions above and beyond what AB has with the PLC5, notably
an Inverted Output, a One-shot Transition Contact, and a dedicated one-shot register group.

Thanks folks!

Ron Gage - Plant Engineering
General Motors Powertrain Group
(See attached file: OPLE.txt)

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Jocelyn Boily

Hello All,

I am new to this list, so I am really sorry if I am making a comment that has been assessed already.

You have no references to the IEC 61131-3 languages specification I your specs.

The 5 IEC 61131-3 languages, I believe is becoming the global standard for PLC programming and is used referenced somehow by most PLC players. I would think that these specification (one of the 5 languages at least) should be
the basis for this project. There is no real need to reinvent wheels. And also, it could be very potent for the code to be portable (Back and forth) from/to one PLC application on the Linux PLC to/from a commercial PLC device.

I sugjest you take a look at the Links from the http://www.isagraf.com webpage.

The following book seem very interesting:

An introduction of the standard can be seen at the following address:

I am very interested about your comments on the use of this standard.


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Johan Bengtsson

You are absolutely as far as I see. The idea is to make it (eventually) possible to do both 61131-3 and AB and Siemens and ... (fill in your favorite PLC) but I agree some of the languages found in 61131-3 would be among the first to

/Johan Bengtsson

P&L, the Academy of Automation
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