SLC Remote I/O - newby help please!

stevendt

Member
Join Date
May 2009
Location
Aberdeen
Posts
54
Hi,

I have an SLC 5/04 (541) in a 10-Slot rack with the following hardware installed :-
1746-BAS in Slot 1
3150-MCM (Prosoft Modbus) in Slot 2
1746-IB16 in slot 4
(Slot 5&6 spare - reserved for 1746-IB16)
1756-OW16 in slot 7
(Slot 8&9 spare - reserved for 1746-OW16)
I am just about to install a 1746-SN in slot 3

I want to have a remote 7-slot chassis hold 2x1746-IB16, 1x1746-OW16 and 3x1746-NI4, as well as the 1746-ASB.

I have not used Remote I/O before and am trying to digest the manuals for the SN and ASB modules. It's starting to make some sense, but I have a few of questions that I'd appreciate some help with please....

1. Hopefully, there are no glaring issues with the proposed configuration above?

2. The distance between the racks will be ~100m, I'm expecting to run the link as fast as I can - 230K, I take it that will be OK in terms of distance?

3. I know that the link can only run at the speed of the slowest device, with just the processor and the remote rack, that should not be a problem, but if I add a PV-300, does that change the maximum speed that's possible?

4. I'm a bit confused about the configuring the 1746-SN - particularly with the analogue modules in the remote rack. (The processor is Series B Rev 3, OS401 Ser C FRN 8). From what I've read so far, the discrete modules appear to be fairly straight forward, but the analogue modules appear more complex.

I'd appreciate a few pointers on the roles of G Files, M files, block transfer commands etc. in the context of how I get the analogue data to the processor.

Is there any preferred order for the discrete and analogue modules in the remote rack? Does placing them one way or another help reading/writing to them more efficient?

In the G file configuration, do I create one group for all modules, e.g., something like Group 0, 3/4 Rack, for 6 modules - I'm assuming the ASB in slot 0 of the remote rack, so would potentially have 6 I/O modules. Does the number of "primary devices" include those that will be accessed by both discrete transfers and block transfers?

I think that the analogue modules need block transfers to work?

Thanks a lot for any help - I am busy RTFM'ing, but it's proving quite difficult to get my head around the concepts

regards
Dave
 
stevendt said:
Hi,

I have an SLC 5/04 (541) in a 10-Slot rack with the following hardware installed :-
1746-BAS in Slot 1
3150-MCM (Prosoft Modbus) in Slot 2
1746-IB16 in slot 4
(Slot 5&6 spare - reserved for 1746-IB16)
1756-OW16 in slot 7
(Slot 8&9 spare - reserved for 1746-OW16)
I am just about to install a 1746-SN in slot 3

I want to have a remote 7-slot chassis hold 2x1746-IB16, 1x1746-OW16 and 3x1746-NI4, as well as the 1746-ASB.

I have not used Remote I/O before and am trying to digest the manuals for the SN and ASB modules. It's starting to make some sense, but I have a few of questions that I'd appreciate some help with please....

1. Hopefully, there are no glaring issues with the proposed configuration above?

Looks fine from here...check power supply loading any time you add cards, but I see nothing wrong or illegal about the configuration.

stevendt said:
2. The distance between the racks will be ~100m, I'm expecting to run the link as fast as I can - 230K, I take it that will be OK in terms of distance?

I wanna say you can go to 10,000 feet with 57.6k and 5000' @ 230.4k? been awhile for me with new RIO installations. So again, you are fine.

stevendt said:
3. I know that the link can only run at the speed of the slowest device, with just the processor and the remote rack, that should not be a problem, but if I add a PV-300, does that change the maximum speed that's possible?

Not sure the 300 is available in a RIO model. RIO network is deterministic, regular, and will either work or it won't. You can BTR/BTW over the RIO link, but the bandwidth for that is already accounted for, so I don't think it will affect the throughput of other devices. Adding a panelview to RIO is going to generate groans from the forum too, because it can be one of the more baffling things to set up and get to work. However, once over the learning curve, RIO does at least force you to be organized with your HMI tagging.

Two main thing to be aware of: Remote I/O with its own scanner is not updated synchronously with the local hardware or SLC scan, so it can introduce a latency that is both variable and larger than what you would see on local I/O. If a few milliseconds of variation in the lag time picking up inputs or turning on outputs is going to break your project, don't use RIO.

The other main thing is the BTR/BTW for analog (further down your list)

stevendt said:
4. I'm a bit confused about the configuring the 1746-SN - particularly with the analogue modules in the remote rack. (The processor is Series B Rev 3, OS401 Ser C FRN 8). From what I've read so far, the discrete modules appear to be fairly straight forward, but the analogue modules appear more complex.

Can you test to see if your OS/FRN supports the BTR/BTW instructions?

This was added to the SLC firmware many years ago but there are still a lot of SLC out in the wild with old firmware that don't support the instructions.

With the old firmware, performing BTR/BTW with normal logic instructions can be a gigantic PITA, especially if you need to extend or deviate from the simple examples A/B provides.

If at all possible, upgrade firmware to get the new instructions. It is easy to do, and cheaper than the hours you will spend reading about how to replicate the explicit messages by manipulating the M0/M1 files.

stevendt said:
I'd appreciate a few pointers on the roles of G Files, M files, block transfer commands etc. in the context of how I get the analogue data to the processor.

Is there any preferred order for the discrete and analogue modules in the remote rack?

I think it would be best for you to use the forum advanced search to find posts by Ron Beaufort that include the words "1747-SN" or "SLC analog RIO" His explanations are thorough and professional, and last bu not least, accurate. I tend to shoot from the lip and then make a lot of retractions...your situation calls for rtfm, while taking notes to get all the details organized. Ron's experience and advice given here over the years will give you a better real world example to follow along with and compare with yours too.

stevendt said:
Does placing them one way or another help reading/writing to them more efficient?

If you mean the order of the cards? Probably not, although the case could be made that the distance the electron travels is finite and measurable and must come into play. I tend to try to keep the smart modules closer to the CPU/ASB, since smart cards have a lot more electrons to diddle with across the backplane than dumb cards. I have no evidence that it has ever made any measurable performance difference. Base you card layout on isolating mixed voltages more than anything else.

stevendt said:
In the G file configuration, do I create one group for all modules, e.g., something like Group 0, 3/4 Rack, for 6 modules - I'm assuming the ASB in slot 0 of the remote rack, so would potentially have 6 I/O modules.

Yes, each logical group is one input 'word' and one output 'word' where a 'word' is 16 bits, so with 16 point cards you can fit two per group with single slot addressing...3/4 logical rack = 6 single slots. This needs to match the dipswitch settings assigned to the 1747-ASB module.

stevendt said:
Does the number of "primary devices" include those that will be accessed by both discrete transfers and block transfers?

Not sure on this one...I will have to look after I get my RSLogix licenses working on this new machine.

stevendt said:
I think that the analogue modules need block transfers to work?

Yes, and like I said, with the really old firmware it's a biotch, with the right firmware, it isn't really bad at all.
 
Last edited:
Hi!

thanks a lot for the reply and the great pointers!

Sounds like the basic premis is fine.

"Adding a panelview to RIO is going to generate groans from the forum too"

It does sound like PV on RIO is storing up trouble then? The PV would be close to the processor rack, so it sounds like I'd be better adding the PV on the SLC DH+ port, rather than on the remote I/O link. That is workable, so I will go that way.

The timing is not going to be critical, a few ms here or there won't matter, so I think I'm OK there.

My OS/FRN does support BTR/BTW - once I learn how to use it of course :) - so again I'm OK there.


"I think it would be best for you to use the forum advanced search to find posts by Ron Beaufort that include the words "1747-SN" or "SLC analog RIO" His explanations are thorough and professional, and last bu not least, accurate."

Thanks - I will certainly do that - that's my job for tomorrow!

I am doing the RTFM bit, but it's heavy going :) As you say, some real world examples will certainly help.


"If you mean the order of the cards? Probably not"
Yes, that's what I meant - without thinking about those pesky little electrons, it "felt" better to have the analogues next to the ASB, but I wanted to make sure that there was no optimum way of placing them in the rack to help configuration/transfer rates, so thanks for the info.

regards
Dave
 

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