RIO General Questions

How can you tell if a RIO system is maxed out on a plc 5?

What are the RIO limits?

I have 3 open slots in the main chassis and 1 RIO adapter going to 4 slc I/O chassis each of these slc chassis it the 13 slot and are fully loaded most with 16 point I/O

Can I have anything larger than 16 point I/O in the slc chassis 32 point on RIO?

The I/O in the slc chassis appears to be octal it is numbered 0-7 10-17 and has octal on the front of the module. Are these special I/O for RIO on slc? I do not see anything like that in the slc I/O manual. Is it some kind of conversion kit i.e. new led cover and sticker? I can’t get the part numbers off the modules because the line is running. Sure would be nice if the put the model # and firmware rev on the front.

Sorry for all these rambling questions I have been reading all the RIO manuals for plc 5 and slc I can find but none teach you the system in great detail. That is my opinion anyway. This RIO stuff is really kicking and stomping me.

The Plc Kid said:

How can you tell if a RIO system is maxed out on a plc 5?

What are the RIO limits?

I have 3 open slots in the main chassis and 1 RIO adapter going to 4 slc I/O chassis each of these slc chassis it the 13 slot and are fully loaded most with 16 point I/O

Can I have anything larger than 16 point I/O in the slc chassis 32 point on RIO?

The I/O in the slc chassis appears to be octal it is numbered 0-7 10-17 and has octal on the front of the module. Are these special I/O for RIO on slc? I do not see anything like that in the slc I/O manual. Is it some kind of conversion kit i.e. new led cover and sticker? I can’t get the part numbers off the modules because the line is running. Sure would be nice if the put the model # and firmware rev on the front.

Sorry for all these rambling questions I have been reading all the RIO manuals for plc 5 and slc I can find but none teach you the system in great detail. That is my opinion anyway. This RIO stuff is really kicking and stomping me.

Click to expand...

Different PLC 5 models allow for a different maximum number of logical racks. Check the manual for your PLC-5. (from memory, so I might be off... a PLC-5/40 can support racks 0-37 octal or 32 racks of I/O)

By RIO adapter, do you mean one of the processor channels is configured for RIO? This is the normal way to do it.

The labels on your SLC style I/O cards are just that, labels. They come in the box so if you install them in a PLC-5 system you can change the default 00-15 to 00-17 so it matches the PLC-5 octal addressing.

If this was a SLC, you could get the model numbers of the cards from RSLogix under "Controller" "IO configuration". But that doesn't work for a PLC-5. You'll have to wait until you can pull the cards. You can check and see if some nice person filled out the "IO configuration" for you, but you can't trust it like you can on a SLC. You can narrow it down by looking at the front. Number of points and type will usually get you close. Firmware revs on digital I/O cards don't usually matter. Some analog cards, it does matter (thinking 1771-IFE series A vs C).

I suggest you look in RSLogix under "Channel configuration" to get an idea how your RIO racks are organized. Important thing to know here is the difference between "chassis" and "rack" in Rockwell's way of thnking. Chassis are hardware. They are that thing you are tempted to call a rack that contains your I/O cards. A rack is a logical grouping of I/O cards that may or may not match up to a physical chassis.

The most important manual for you to read would be the one for the 1747-ASB remote I/O adapter module. It's very dense and there are tons of optional configurations. But it's the key to understanding this kind of system.

Good luck, I expect you will have more questions on this one.

Yeah don't gloss over and miss the point on Chasis vs Rack. A logical rack is actually 8 I/O groups. The chasis - as already explained - is hardware. You need to take time to understand the different addressing methods available to you - ie 1/2 slot, 1 slot, and 2 slot. The thing to keep in mind about the PLC5 is that each I/O group has one 16 bit input word and one 16 bit output word. The difference between the different addressing methods is whether an I/O group is allocated to two slots, 1 slot or 1/2 slot. So for example, with 2 slot addressing you only have 16 bits of input and 16 bits of output to share between two slots. That is why you will see alternating ins and outs throughout the rack. In the PLC5, the addressing method is setup via dip switches (I think on the chasis if memory serves). In the SLC??? I would assume that it defaults to 1 or 2 slot adddressing, but I have never tried that one. It would have to allow 1/2 slot addressing to allow 32 bit cards (ie, two groups per slot - 32 I's and 32 O's).

Check out the manual. This stuff can be confusing.

I was going to wait until after he read the manual to go into slot addressing but here's my take on it.

2 slot - 16 physical slots make one logical rack (8 groups) This is mostly legacy of old systems that originally used 8-point cards. You will see some of those upgraded to 16 point cards, with alternating input and output cards. Some people will actually do this on purpose for new installation, I wouldn't. I see 2 slot fairly often on old systems that I work on especially ones that were converted from PLC-2.

1 slot - 8 physical slots make one logical rack (8 groups) This is needed to support 16-point cards without restrictions. This is by far the most common choice for recent installations (less than 10 years old) that I work on.

1/2 slot - 4 physical slots make one logical rack (8 groups) This is pretty rare in my experience. It is needed to support 32-point cards without restrictions. I've never cared for the 32-point cards in 1771 or 1747 series. ControlLogix is a different story, I've used 1756 series 32-point modules and they were OK.

The point of all this is the PLC-5 has a fixed address space for I/O. It doesn't matter how many points per card you use, the capacity remains the same. You may save in space, cost of power supplies and chassis, but the I/O capacity is not increased by using higher density I/O cards.