SYSTEM AND METHOD FOR MANAGING SWITCHED HIERARCHICAL CONTROL STATES

An input-output apparatus is provided. The apparatus includes a lower-level layer interface connected to a field device, a higher-layer interface connected to a controller, a maintenance interface connected to a setting apparatus, a switch, and a control device. The switch switches between a first connection and a second connection. The control device, in an engineering mode, permits the switch to transition freely between the first connection and the second connection, and in an operation mode, controls the switch to switch to the first connection and prohibits communication through the maintenance interface. In response to a permission command received through the higher-level layer interface, the control device permits communication through the maintenance interface, and in response to a connection request received through the maintenance interface when the control device permits communication with the maintenance interface, the control device controls the switch to switch from the first connection to the second connection.