Maximum number of VFD's on a RIO network

Does anybody know if there is an actual limit on the number of drives that can be connected via RIO? I think I've heard there is a theoretical limit (one that won't actually be reached) but I'm not quite sure. I've been reading through the 20-COMM-R manual as we're adding some Powerflex 70 drives and the only mention of any limit or maximum that I can really find is the max cable length. Any help is much appreciated!

What processor are you using? I think it would depend on the processor that determines the maximum number of physical/logical rack that you can have.

AB literature says for 1756-xx RIO:

32 logical rack connections per remote I/O channel

http://www.ab.com/en/epub/catalogs/...ata-Highway-Plus-and-Remote-I-O-Networks.html

If you are using a PLC5, then each I/O channel has a logical limit (32 Racks?) and a physical limit. I forget what the physical limit is. The difference between the two terms come from the fact that you can use 1/4 or 1/2 logical racks for the drives (ie you could have 4 drives per rack). So you might think that you could have 32 x 4 = 128 drives. The physical limit is less than that.

If you are using a controllogix with a 1756-RIO card, I do not know if the same limits exist.

Thanks everyone. We're using 1/4 rack with a PLC5/40E Series F if this makes any difference. I think we will be more than fine.

Edit: I have looked in the PLC5/40E manual and have found "A single remote I/O scanner channel can support up to 32 devices but only 16 rack numbers." So, I'm taking this to mean that I can only have 32 devices on each channel that supports RIO scanner (Channel 1A and 1B) giving me 64 total devices for my particular PLC.