PLC5 to Controllogix communication over RIO?

I have an installation with a PLC5 system controlling a test cell, and I want to add a Controllogix rack with high speed analog I/O cards to do high speed pressure controls. I want to be able to request pressures with the PLC5 from the Panelview (1400e) in a "manual" mode, then accept commands through the high speed analog cards in "automatic" mode.

Can I use the existing RIO network in the test cell to communicate commands and status bits back and forth between the two processors? The other installations I have done with this sort of setup used all digital I/O between the two controllers, and switching relays to swap the pressure command outputs.

With the existing Remote I/O system, the PLC-5 is the Scanner and the PanelView 1400e (and, I assume, remote I/O racks of some sort) are Adapters.

The standard 1756-DHRIO module cannot be an Adapter on RIO, only a scanner. To use it to interface with the PLC-5, you would need an available PLC-5 channel that can be placed in Adapter mode and dedicated to this purpose.

You could also do DH+ messaging (or Ethernet or serial) between the ControlLogix and the PLC-5, but of course this is generally slower and less predictable.

The new 1756-RIO module can be configured as an Adapter. You could put it in the ControlLogix chassis, add it to the PLC-5 scanlist, and use both discrete and block-transfer features to transfer data between the controllers.

The new 1756-RIO module can be configured as an Adapter. You could put it in the ControlLogix chassis, add it to the PLC-5 scanlist, and use both discrete and block-transfer features to transfer data between the controllers.

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Just to clarify this statement: You MUST have ControlLogix Processor in ControlLogix chassis with RIO module to act as an Adapter for PLC5 processor.
1756-RIO does not work without a ControlLogix controller

The CLX chassis will have a processor in it, that is what will be running the pressure control. The PLC5 would run the rest of the test cell as it has, and just communicate commands/status bits to and from the CLX processor.

It sounds like the 1756-RIO module might do what I need. I want to tie into the existing RIO structure in the cell and use that to communicate between processors instead of adding a separate dedicated communication link if at all possible.