About Remote I/O configuration

Remote I/O (RIO) is based on the concept of logically representing a physical, remote rack of I/O modules. A physical rack is represented by words of data, referred to as discrete data, that directly reflect the state of the I/O modules in the rack.

Each word of input data has a corresponding word of output data, and these data pairs are referred to as module groups. For a full rack, there are eight words of discrete input data and eight words of discrete output data (that is, eight module groups). RIO protocol allows the sub-division of racks into quarter-sized units. Therefore, it is possible to access 1/4-, 1/2-, 3/4-, and full-rack configurations.

RIO employs a master/slave network structure. The PLC (RIO scanner) acts as the network master and controls all communication. The terminal (RIO adapter) acts as the slave receiving or returning data as directed by the master. Terminals (RIO adapters) on an RIO network cannot communicate directly with each other; they can only communicate through the PLC (RIO scanner).