PLC5 slot addressing

ScottSparrow

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Join Date
May 2017
Location
Emsworth
Posts
3
Hi all,

I am currently working on a project to convert three PLC5's to CLX using the Rockwell migration tools.

I was wondering if it were possible to determine the slot addressing used in each of the PLC5 racks (there are 12 racks in total) using photo's and/or the .rsp file?

The site is one of those where it can't be shutdown very easily, so I am trying to avoid having to shutdown the site to check the dip swithes on the chassis or ASB modules

Having read various posts on this forum I am aware that the details listed in the "I/O Configuration" are information/documentaion only and may not reflect the real configuration.

Due to commissioning constraints my plan is to swap out one chassis at a time, so there will be times when the CLX CPU will be controlling both CLX IO and PLC RIO.

I have photographs which I could upload if this is sufficient to determine the slot addressing?

Any help is greatly appreciated.....

P.S I am a long time listener/reader first time poster.
 
It looks as though the Chassis configuration has been indicated using the labels (see attached photo) above the chassis?

In the example rack shown below I think it's set for 1 slot addressing.

There are 32-point digital input modules and they have been paired with the 16-point digital outputs.

PLC1 Chassis 0.jpg
 
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I agree that you're going to want to look at the actual I/O image while observing the indicators on the modules themselves to help verify that your assumptions are correct.

The paired 32-point modules are typical of "1-slot" addressing.

"1-slot" addressing means that each physical slot is allocated one logical "Group", which has 16 bits of Input data and 16 bits of Output data.

Putting a 32-bit Input module into Rack 01, Group 0 means that it will use up Word 0 and Word 1 of the Input data table. That makes Word 1 of the Input data table unavailable to a module located in the adjacent slot.

But that's OK; the next slot is occupied by a 32-bit Output module, which will use Word 0 and Word 1 of the Output data table.

Check the BTR and BTW instructions for the analog modules in Rack 0, and you'll probably find the ones for the Analog Output module are addressed to "Group 5, Slot 0".

The labels on this chassis, of course, also bolster the conclusion that it's set up for 1-Slot addressing.

Other chassis out along the RIO chain might be set up differently.

Stock up on graph paper, practice counting in Octal, and good luck !
 
Another thing about converting PLC5 to watch for is the scaling of analog I/O.

On the PLC5 the scaling is programmed to, and stored on, the I/O card itself - not in the PLC program. If you go online with each card RSLogix 5 analog card and open the properties. RSL5 will popup that it won't read the scaling, but it always has for me - then I take a screenshot of each card's settings.
 
Thank you all for taking the time to reply, your comments have given me confidence that I am understanding the PLC5 configuration.

There seems to be a slight terminology difference with the BTR/BTW instruction parameters between RSL5 and Studio5000

RSL5: Rack, Group, Module
Studio: Rack, Group, Slot

If we took the BTR/BTW for the AO module. As Ron correctly suggested this is configured:

RSL5: Rack 0, Group 5, Module 0
Studio: Rack 0, Group 5, Slot 0

What I am struggling with is why the Module/Slot is always 0 and when would it be different?
 
The 1771 I/O platform was developed in the PLC-2/3 era, when 8-point discrete modules were the standard. A "Group" was actually two slots, named "0" and "1". In the modern era, this is called "2-Slot Addressing".

When you use 1-Slot addressing, a "Group" is just one physical slot, even though there's both a logical "Slot 0" and a logical "Slot 1".

When you are using analog modules in 1-Slot addressed chassis, the Block Transfer is always addressed to Slot 0.

If you were using 2-Slot adressing, you could put two analog modules next to one another and perform BTR/BTW instructions both to Slot 0 and Slot 1 of the same two-physical-slot Group.

One mental trick I use when working with 1771 gear is to always call out the Rack numbers as two digits: "Rack 01" instead of "Rack 1", to remind myself there's something nonstandard about the numbering system I'm using.

I also call out I/O bit numbers as digits instead of conventional numbers: when I'm describing "I:02/11", I call it "Eye, colon, zero-two slash one one" instead of "two slash eleven".

That's to remind myself that I'm dealing with bit 11 (octal), which is the tenth bit, not the eleventh bit, of the 16-bit data Word.
 
Slot Addressing

Cheers to all,

As I recall, using a 32 point module yields that your addressing is a half slot addressing, in this case:

A physical 16 slot addressing rack will become 4 logical racks.

The main point is :whenever you use a 32 point card, you should configure your rack as a half slot addressing.

Hagos
 
here's a snapshot from the Help file that might be helpful ...

many (most?) people think that the old PLC-5 platform is "long gone" - but there are TONS of that stuff out there - still chugging faithfully along - and I still get plenty of requests for training classes on those systems ... so don't count them out just yet ...
.

addressing_help.PNG
 
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Hagos,

Thank you for your contribution. Many systems that use "1/2 Slot" addressing also use 32 point modules for the highest physical density available in the 1771 platform. So it is possible that a system with 32-point modules is, or should, be configured for 2-Slot addressing.

But three other clues are present:

The installation of the 32-point modules in Input/Output pairs suggests that the chassis is configured for 1-Slot addressing.

The installation of decals showing two "logical racks" in a single 16-slot chassis also suggests that the chassis is configured for 1-Slot addressing.

The Block Transfers to the only Analog Output module in Rack 0 are addressed to Group 5, which is where the Analog Output module would be if the chassis were configured for 1-Slot addressing.

I consider those three clues, taken together, to be conclusive.
 
Above, in the first paragraph where it reads "configured for 2-Slot addressing", it should read "configured for 1/2-Slot addressing". 32-point modules are sometimes used in 1/2-Slot Addressing systems. Hat-tip to Ron Beaufort for noticing my typo.

It is almost certain that the chassis that was shown in that photo and subsequently discussed is configured for 1-slot addressing. The labels, the paired In/Out modules, and the address of the Analog Output module all point that direction.

That doesn't guarantee that every 1771 chassis in the system is configured that way, but it's conclusive for the one that was pictured.
 
Three things that haven’t been mentioned yet about PLC-5 addressing:
1. Know the difference between a chassis and a rack. A chassis is a physical device to hold the modules. One chassis can actually be two racks, depending on the addressing scheme.

2. I believe a separate chassis can be an extension of another physical chassis (1/4 rack or 1/2 rack). Someone will correct me if I’m wrong.

3. Certain VFD’s can be addressed as a 1/4 rack for I/O purposes.
 
It's been several years since that thread was started; I can't say why it was resurrected today. Zombies can be unpredictable.

You're absolutely correct that "chassis" and "rack" are not synonyms in the PLC2/3/5 I/O world. Confusing as heck, but it helps keep the amateurs out.

Yes, separate physical chassis can be parts of the same logical "rack" of memory. This is especially common when using FLEX I/O with 2, 4, or 6 modules, but also applies to good old PLC-5 1771 I/O.

The good old 1336, 1336+/+II ,1305, etc could be 1/4 Racks (or more !) of data on an A-B Universal Remote IO network. Modern PowerFlex can be too, but it can get tricky.
 

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