This section explains how a Communication Adapter relays information between its I/O base and a programmable controller.

A token frame is passed from node to node in a rotating address sequence. The node currently holding the token has the sole right to transmit. All other nodes monitor the network and extract messages addressed to them.

When a Communication Adapter at an input base module acquires the token, it transmits its message to the programmable controller node. The message data describes the current states of the signals at the base's field input terminals.

The controller reads the message and steers its contents into the data registers defined for that adapter's address in the controller's Peer Cop table.

When the programmable controller acquires the token, it transmits its messages to the Communication Adapters. Messages are sent to the node addresses defined in the controller's Peer Cop table, with the message contents taken from the data registers defined in the table.

Each Communication Adapter at an Output base module uses its received message to control the field devices connected to the base's output terminals.