Can you be more specific about your question ?
The 1756-DHRIO will be in RIO Scanner mode, and will communicate the I/O data from its attached networks to the ControlLogix over EtherNet/IP.
This is a normal network architecture to connect a small number of Remote I/O devices to a ControlLogix Redundancy controller.
The amount of I/O data and what parameters in the AC drives are represented by that I/O data can vary; it can be as simple as Command+Reference / Status + Feedback, or multiple parameters can be read and written from the drive using a feature called "DataLinks".
Is this a system that you are implementing, or one that you are troubleshooting ?
Is there a good reason that the RIO network was maintained instead of migrating those AC drives to use 1203-EN1 network interfaces directly to the EtherNet/IP network ?