Controller for managing switched hierarchical control states

An input-output apparatus which is used in a process control system, the input-output apparatus comprising:

• a lower level interface to which a field device in a plant is connected;
• a second higher level interface to which a controller that is configured to control the field device in the plant is connected;
• a third maintenance interface to which an external setting apparatus is connected;
• a first switch which switches between a first connection of the second higher level interface to the first lower level interface and a second connection of the third maintenance interface to the first lower level interface;
• a control device which controls the first switch;
• and
• a second switch which is controlled by the control device and is disposed between the third maintenance interface and the control device,
• wherein the control device causes the input-output apparatus to enter to one of a first state in which the second higher level interface is connected to the first lower level interface by the first switch and the third maintenance interface is connected to the control device by the second switch, a second state in which the third maintenance interface is connected to the first lower level interface by the first switch and the third maintenance interface is connected to the control device by the second switch, and a third state in which the second higher level interface is connected to the first lower level interface by the first switch but the third maintenance interface is disconnected from the control device by the second switch, and
• wherein the input-output apparatus further comprises:
• an engineering mode for engineering of the process control system allowing the input-output apparatus, when a setting apparatus sends a request for connection to the control device via the third maintenance interface, to transit from the first state to the second state for settings and/or adjustments on the field device and on the input-output apparatus and allowing the input-output apparatus to transit back to the first state when the settings and/or adjustments are completed;
• and
• an operating mode for performing process control of the process control system when the input-output apparatus is in the third state.