Porting AB PLC programs to PC


Thread Starter

robert trask

List persons,

Curious to any comments good or bad in taking RSLogix 5 programs into the RSLogix 5000 software - basically taking existing PLC code and porting it to a PC based platform.

A-B documentation and salesman give the thumb's up. What does the real world have to say?

Feel free to respond to me direct if nervous about A-B list watchers.

Robert Trask, P.E. [email protected]
Three Seas Group
Wilmington, NC USA

Larry Lawver


I'm concerned about the way you phrased your question. RSLogix5 is programming and documentation software for PLC-5 systems from
Allen-Bradley. RSLogix5000 is prog&doc software for ControlLogix (CLX) systems from A-B, a new control architecture not necessarily PC-based.

Both will support a PC-based control platform--- SoftLogix5 and SoftLogix5800, respectively--- but neither package you mentioned is a control solution itself. You should clarify your migration path for this discussion. What platform are you using now, and where do you want
to end up?

Now to your question, if I have it right: Reusing RSLogix5 code in RSLogix5000 to migrate from the PLC-5 to the CLX platform. I have had
pretty good results, but I have heard of problems. I'm looking forward to the submissions to this thread! I have come to the opinion (my own) that migrating to the CLX platform without embracing the producer-consumer architecture produces mediocre results.

This isn't like the progression from the PLC to the PLC-2 to the PLC-5 to the Enhanced PLC-5, where the benefits of upgrading were obvious
and the risks were minimal. In that progression over the last three decades, the master-slave architecture stayed the same and the CPU
continuously improved.

With CLX, a lot of issues that used to be solved in code have been reduced to configuration issues, and producer-consumer architecture is
only a benefit if you move away from the master-slave thinking. While I am enthusiastic about CLX for new designs, I have found myself
recommending PLC-5s and SLC500s to existing customers expanding existing systems.

Ultimately, since PLC-5s and SLC500s are still getting enhanced and are in no danger of obsolescence, a client that just wants to do what these well-established products do might as well continue to buy them. (Again, my own opinion!!!) The benefits of the CLX architecture are not realized by simply reusing code.

Finally, I would be astounded to learn that anyone on the A-List is nervous about us A-B partisans. We play nice and put up with irrational attacks upon our products with a smile. For me, the List provides a valuable opportunity to learn what the world outside my market is experiencing with my products, for the benefit of my own clients. Thus, I hope that everyone responding to your question posts to the List.

Hope this helps!

Larry Lawver
Rexel / Central Florida

Trevor Ousey

I just attended an AB TechEd/ACIG session and you can convert PLC5 to ControlLogix, but there is a good chance it may run slower. Apparently there is a white paper at AB.com (somewhere?) discussing optimising for ControlLogix. At this stage I haven't tried it.

Trevor Ousey

Craig Spinharney

"Ultimately, since PLC-5s and SLC500s are still getting enhanced and are in no danger of obsolescence,"

Enhancements to the PLC-5 have been and are getting to be fewer and farther in between. With cost/performance considerations, the CLX is almost always a better solution to the PLC-5. The SLC500 on the other hand, has had enhancements (very recently too!!). It is still a very viable platform when a MicroLogix is not enough and the migration to CLX is fiscally out of the question.
The migration of code from PLC to CLX is not as clean as I would like it, but the fact that you are going from a structured (data tables) format to a more free-form environment poses problems for any conversion algorithm and a "best guess" is sometimes all that is rendered. But hey, the PLC-2 to PLC-5 conversion required mopping up as well due to communications, BCD, and unsupported command issues. All in all it does a pretty good job and yes, optimization after the fact is often necessary.

Craig Spinharney
Rockwell Automation