Control Logix remote I/O rack on PLC-5?

We got into a discussion at work the other day and someone said that they thought you could use a Control Logix rack with an RIO adapter card as a remote rack on a PLC-5 system.

Has anyone done this? We haven't started switching over to Control Logix systems yet, but we have a need for a good amount of I/O in a compact area that includes 120VAC in and out, analog out, contacts, TTL signals, and thermocouple inputs. Right now we're running a lot of wires through a boom connector and we're looking for a better option.

Also, does anyone know if there are PWM driver cards for Control Logix? I know some of the Micrologix controllers have them but I don't need another PLC.

I have Flexlogix IO on a PLC5, using Controlnet. Don't know about any RIO, though!

I looked at Flex a bit, but I don't see any listing for 5vdc TTL inputs, and I have the potential to use 32 inputs of TTL from our data aquisition systems. If I did put in a rack or block I/O modules, I'd like to be able to hook all the signals I am currently passing through the boom to it to reduce wiring.

It appears that the 1756-DHRIO may only run in scanner mode. So a connection to a PLC-5 would have the PLC running in adapter mode (slave), probably not what you are looking for.

http://www.ab.com/en/epub/catalogs/12762/2181376/2416247/360807/1837522/tab7.html