BACnet/IP
BACnet/IP protocol allows communication between the components
of a building automation and control system (for example, HVAC, lighting
control, security systems and related equipment).
The BACnet/IP protocol defines a number of services that are used to communicate between devices and the objects that are acted upon by those services.
| Term | Definition |
|---|---|
| APDU | Application protocol data unit, that data portion of a BACnet message. |
| Confirmed message | A message for which the device expects an answer. |
| COV, COV increment | Change of value, sets the amount by which a value has to change in order for the meter to send a subscription notification. |
| Device | A BACnet device is a unit that is designed to understand and use BACnet protocol (for example, a BACnet-enabled meter or software program). It contains information about the device and device data in objects and object properties. Your meter is a BACnet device. |
| Object | Represents the device and device data. Each object has a type (for example, analog input or binary input) and has a number of properties. |
| Present value | The current value of an object. |
| Property | The smallest piece of information in BACnet communications, it consists of a name, data type and value. |
| Service | Messages from one BACnet device to another. |
| Subscription | A relationship between a BACnet client and the meter, so that when the present value property of an object changes on the meter, a notification is sent to the client. |
| Subscription notification | The message the meter sends to indicate a COV event has occurred. |
| Unconfirmed message | A message for which the device does not expect an answer. |
| BACnet Broadcast Management Device (BBMD) | A BACnet/IP device (or software application) residing on a BACnet/IP subnet that forwards BACnet broadcast messages from devices on its subnet to peer BBMDs and registered foreign devices on other subnets. |
| Foreign device | A BACnet/IP device (or software application) that resides on a remote IP subnet and registers with a BBMD to facilitate the sending and receiving of broadcast messages to/from devices accessible by the BBMD. |