Controller 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.
1. 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.
2. The input-output apparatus according to claim 1 , wherein the control device sets the second switch to an open state to restrict access, and sets the second switch to a closed state to permit access.