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Old January 18th, 2005, 10:02 PM   #1
elledge
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Question Controllogix

How is programing different for controllogix compared to RSlogix 5? We are getting a new machine at work that is going to have controllogix PLCs. Everything else we have is PLC5. Do I need to know anything new?
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Old January 18th, 2005, 10:33 PM   #2
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YUP! allot!
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Old January 18th, 2005, 10:39 PM   #3
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Try searching around the forum. I'm pretty sure there are lots of talk about their difference. Sorry I can't remember which thread though.
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Old January 19th, 2005, 09:11 AM   #4
akreel
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You can program a ControlLogix in Ladder Diagram, if you want to.
The similarities pretty much end there.

Learning CLX from scratch can be a bit daunting. If your local distributor offers classes or hands-on with Logix5000, you might want to consider it, especially if you can weasel it out of him for free.

AK
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Old January 19th, 2005, 11:03 AM   #5
Ron Beaufort
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Greetings elledge,

first of all ... you won’t like the RSLogix5000 software ... there are enough differences between it and the familiar old RSLogix5 and RSlogix500 packages to drive you crazy - until you get used to it ... then you won’t go crazy anymore ... you’ll just be extremely annoyed from time to time ...

from an operational standpoint one of the biggest differences is the way the CLX handles its scan sequence ... with a PLC-5 all of the inputs (“I:___” addresses) are read from the field ONCE at the very start of the scan ... the values in those bits won’t change (unless you program something really weird) all the way through the processor’s execution of the ladder program ... and then finally the outputs (“O:___” addresses) are written to the field ONCE at the very end of the scan ...

but with the CLX, the Inputs and Outputs are handled “asynchronously” to the processor scan ... that means that the module can update the Input table from the field – and write the Output table to the field – at any point (or at several points) during the processor’s execution of the ladders ...

in most programs this is a very minor consideration ... in others it can have serious repercussions ...

and the new “task” – “program” - “routine” idea takes some getting used to ...

[attachment]

but high on the plus side ... the CLX modules – and even the processors – are designed to be “hot swappable” ... as long as it’s safe in your application, you can plug things in and out of the chassis without having to stop the process ...

suggested plan of attack: grit your teeth and dig in ... this thing isn’t going to just “go away” any time soon ...

and don’t forget to register on the forum ...
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Old January 19th, 2005, 12:19 PM   #6
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Wow, the updating of I/O within a scan hurts my head. Does it have the option to scan conventionally? I wonder why they did that?

Jim
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Old January 19th, 2005, 12:21 PM   #7
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Thanks for the help. The people we bought it from are going to give a little help I'm sure. I just wanted to at least kinda know what they were talking about. Thanks all. Michael
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Old January 19th, 2005, 12:35 PM   #8
Ron Beaufort
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first to jimpad:

Quote:
Does it have the option to scan conventionally?
no ... but the most common “fix” is to have your program store the inputs in a “buffer” before the processor starts to execute the ladders ... then use these “buffered” inputs as conditions for the rungs ... this “buffered” data won’t change status until you “re-store” the inputs at the top of the next scan cycle ...

you can do the same type of “buffer” thing for the outputs – at the end of the ladder file ...

Quote:
I wonder why they did that?
"speed" and "flexibility" are the most common buzzwords being used ...




and then to Michael:

welcome to the forum ...
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Last edited by Ron Beaufort; January 19th, 2005 at 12:39 PM.
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Old January 19th, 2005, 03:49 PM   #9
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Question CLX, good for us?

First of all, I'm relatively fresh in AB world.

We started using Control Logix and Compact Logix, so that caused me to take a 2 day course by the vendor...... Thank God for that!
As you say Ron, the course will help you on your way!

But is the CLX as bad as it sounds??? (Just asking)

From what I can see so far, it is very flexible! But in that it also lies that it is so flexible that you can make your whole project crash, or run GOOD if all "traps" are taken into consideration.

Right now I'm in an exploring phase when it comes to AB, so I'm trying to suck out as much information as possible from experienced users.
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Old January 19th, 2005, 04:07 PM   #10
Ron Beaufort
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Greetings NorthControl,

Quote:
But is the CLX as bad as it sounds???
I wouldn’t say that it’s “bad” ... but it sure is different from what I’m used to ... the biggest thing that most people don’t like seems to be the software ... RSLogix5 and RSLogix500 seem to be more “polished” ... RSLogix5000 seems to be more “clunky” ... I find myself spending WAY too much time just trying to get the data that I want to monitor properly positioned on the screen ... you can’t just “click-click” and open a data table to monitor the ON/OFF status of a series of bits ... you’ve got to scroll – and scroll – and scroll some more – just to get past the “configuration” data and the “fault” data and a lot of other superfluous junk that you’re not really interested in at the moment ... and then you can’t just drag the display windows around on your screen either ... it’s those little things that really turn me off ...

but ...

maybe someday they’ll get the software all sorted out and then I know that I’ll learn to love the little beast ... I’ve been keeping one of them all set up in the back bedroom at home ... I fire it up and tinker around with it every chance I get ... it’s basically got a lot of good ideas whose time will eventually come ... I for one hope to be ready ...

and welcome to the forum ...
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Old January 19th, 2005, 04:57 PM   #11
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Question

Thanks for the warm welcome everyone. I don't really understand the reasoning behind a company that has everything PLC5 to buy one machine that is CLX. I read that the software is tag based can someone clarify that for me. Does that me we won't search for B3/01? Would we search for UpIntPE?
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Old January 19th, 2005, 05:10 PM   #12
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Quote:
Originally posted by elledge
Does that me we won't search for B3/01? Would we search for UpIntPE?
Yes.

You create all of the memory tags you intend to use, of whatever type you desire, including user-defined data types. Don't expect to see N7:xx data tables in CLX. There are also controller and program scoped tags. But wait! We haven't told you that the CLX can run multiple programs at once yet!

If you're a total geek, like me, I think you'll enjoy this.

AK
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Old January 19th, 2005, 05:15 PM   #13
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We haven't told you that the CLX can run multiple programs at once yet! You've got please explain!!!
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Old January 19th, 2005, 06:17 PM   #14
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I think Ron is not doing justice to the ControlLogix (CLX) here, or at least not to his usual high standard.

PLC5 is based on a system that was first introduced in the early 80's. Yup...it is now over 25 years old, and still going strong. Stable, capable, with a very large installed based and lots of people familiar with it, the PLC5 system has to be one the most successful automation products of all time.

However it does have significant limitations. The inflexible 1771 IO system, the limited comms options and non-symbolic tag programming are just several that pop to mind. It is simply inevitable for any vendor that intends to stay in business to produce new products. I seem to recall from my time selling AB that customers tend to either be on the phone nagging for when the latest new feature will be released, or the type that grizzle everytime something new comes along that they aren't familiar with. Oh well such is life. At some point in the future the PLC5 system will reach its "used by date". I have no idea when, but one day it will be. At that point most AB users will have made the transition to ControlLogix, and will gladly never look back.

The question of asynchronous IO update is simple. In the PLC/SLC system the processor is the master of the all IO modules which act as simple slaves. By contrast the CLX backplane is like a peer network were all the modules are equals and produce/consume data to each other. This advantage of this is that multiple processors, multiple comms modules and very efficient data models become possible. IO modules are intelligent entitities that produce data according to their own configurations, and thus data is consumed by the CPU's asynchronously to the programs scans. Ron's point about IO data buffering is valid but certainly not the mountain he makes of it. In fact IO buffering has become a standard feature of all my programs. Actaully I even use buffering in my SLC programs these days even when not strictly necessary because it allows me better organisation of my logic.

The are the main developments in CLX over PLC:

1. More powerful system Task/Program/Routine organisation scheme.

2. All data is named and organised by symbolic tags.

3. The ability for the user to create their own data structures called User Defined Tables. Once you start using these you never look back. Huge productivity gains.

4. Far more powerful language sets, now including native on-line editing for Ladder, Function Block, SFC and Structured Text. The SFC language is far more advanced than that found in the PLC 5.

5. I think Ron's "bizzaro" ladder constructs are wonderful. They actually correspond to C langauge constructs quite well and allow logic statements to be compactly associated together, and more information displayed on the screen at a time.

6. Communication are far more open and flexible. The CPU is no longer the center of the comms paths. Comms modules can be added to your hearts content and with some limitations, bridging and routing throughout the whole system is native.

Now I have to temper this rant with the observation that CLX is not perfect. Most users have a list of improvements they are hoping/waiting for; but the reality is that few of them would EVER consider going back to the PLC5 if they had a choice.

And elledge...welcome to PLCS.net. !!!
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Last edited by PhilipW; January 19th, 2005 at 06:52 PM.
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Old January 19th, 2005, 09:39 PM   #15
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Quote:
Originally posted by Ron Beaufort
... with a PLC-5 all of the inputs (“I:___” addresses) are read from the field ONCE at the very start of the scan ... the values in those bits won’t change (unless you program something really weird) all the way through the processor’s execution of the ladder program ... and then finally the outputs (“O:___” addresses) are written to the field ONCE at the very end of the scan ...
Only if it's Local I/O. Remote I/O is asynchronous.
The 1774 (PLC-1) was asynch (all remote I/O)
PLC-2 introduced synchronous I/O, but only for local. remote I/O is asynch.
PLC-3 is asynch (all remote I/O)
PLC-5/250 is asynch ( all remote)
ControlLogix is asynch (even for local I/O).

So...asynchronous I/O scan is nothing new.
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