ZCL instruction

[ssommers 20]

I'm in the midst of taking an old PLC-2 ladder program and re-writing it for a SLC-500. Most of it is nothing fancy, but the original program used the ZCL instruction quite liberally to allow them to write several complex rungs in different ZCL areas with the same physical output. In a PLC-2, if the first rung with a ZCL is false, the ladder jumps head to the next ZCL, but leaves all the outputs within that area in their last state. I currently am unsure if there are any bits/outputs that get stuck in-state when a particular section is skipped - I'm going through those four ZCL sections today. What would be the equivalent of a ZCL in the SLC-500? Or do I need to reorganize things into subroutines ensuring that I don't have any "stuck" bits? Thanks in advance! Susan ps. The PLC-2 currently in the machine is about 23 yrs old & I expect it to die at any time now. This is a pre-emptive controller upgrade that will be installed as soon as there's a 3-day downtime available.

[TConnolly 13]

Greetings Susan. Anything that is in a ZCL should be programmed in a conditional subroutine in the SLC500. (Just curious, why a SLC500? The SLCs cost quite a bit more than a Compact logix.) Edit to add: You might want to take a look at technote 18983 in ABs knowledge base. Although the technote is in reference to a different platform it does contain an example on how to convert a ZCL to a SLC or MicroLogix platform. Do you by chance happen to have the PLC/2 programming software? I have one PLC/2 still in operation here, about 20-21 years old, and I would like to get a printout of the program. Edited 13 Nov 2007 by Alaric

[ssommers 20]

Thanks for the technote Alaric! I didn't know that the old 100/150 had a ZCL instruction. Why change to a SLC instead of Compactlogix? 90% of our machines have either an old fixed hardware SLC500 or a SLC5/03, so using a SLC5/03 for any re-controls minimizes my spare parts inventory. I have RSLogix 500, but not RSLogix 5000. I'm also the only controls person for 2 plants, so it's necessary to use the KISS principle everywhere I can. PLC-2 software - I was lucky enough to find a printout made by a local vendor in 2006. I'm having major pneumatic problems with this machine, so I ordered an "aftermarket" program & cable from PLC2Software.com on Friday to help debug the machine before I re-control it. It's not here yet, but I'll post a review here after I try it out. Thanks again! Susan

[TConnolly 13]

I know of the program. I'll look forward to that review. Would you be interested in making a PDF print out for me if I sent you my copy of the program? Edited 13 Nov 2007 by Alaric

[BobLfoot 302]

Sue - one thing to consider you can replace the PLC2 Cpu with a 1771-ASB or 1771-ACN15 and conenct this to a ControlLogix CPU with a Remote IO or COntroNet scanenr and still use all you 1771 hardware. Most of which is not going out of date anytime soon.

[ssommers 20]

BobLfoot - That would make sense if the application was larger than it is. It's a grand total of 28 in, 14 out & no analog. I would have spent more on the CLX and the Remote I/O interface than I did on the SLC5/03 & I/O cards. Not to mention that I'd have to buy the RSLogix 5000 program when I've already got RSLogix 500. Don't get me wrong... I'd love to do an upgrade with another 20 yrs lifespan! Replacing the PLC-2 with a CLX would definitely give me that, but money's extremely tight right now. I may be able to get Logix 5000 next year IF anything goes wrong with the one brand new machine that has a CLX on it. Management decided to buy a long-distance support package from the manufacturer instead of buying the program for me to support it on-site. Thanks for the suggestion... I'll keep it in mind for larger projects.

[ssommers 20]

Here's the promised PLC2Software review... It works nicely, but has a few rough spots. Pros: + Went on-line instantly with no config problems! My computer has Windows XP Pro SP2 with a USB serial cable (COM4). + Can edit the ladder, timer, counter, data table, etc. + Nice cross referencing. + Can document a program (although I haven't figured out how to do it yet) Cons: - It's a clunky DOS interface & uses F1-F10 similar to the old T3 terminal's keypad. - Remember that all folder & file names are limited to 8 characters! (Ye olde DOS limitations) - There are no rung numbers in the on-line screen and you can only see about 4 rungs per screen. Keep a printout handy to figure where you're going next. - The print to file function required a whole lot of editing once I opened it in Word to get rid of the double type (must make bold type on some old printers) and the page breaks. - I had to move the help files to C:\GSHELP to get them to work. All in all... It's worth what I paid for it. I found out that the old printout in the cabinet was missing 2 rungs. Those rungs helped me find an intermittent problem that had the scrap rate soaring - a dirty photoeye. And if I'd replaced the PLC without putting those 2 rungs into the new controller, I would have created even more problems. Thanks for all the help!

[fuenmill 0]

Dear ssomers Sparky and every one:

     Now I am in your situation, but now with the urgency of a broken machine. It is very old too. He have the backup ladder program, but not the software to upload it back to the PLC2/20. PLEASE HELP ME. I hears about PLC2-6200 ant TopDoc. Could you please release a free copy?

Thanks