Application (layer) protocol data unit. Basically, a BACnet message—that is, a unit of data specified within any of the BACnet link-layer protocols, consisting of protocol control information and possibly application user data.

Building Automation and Control NETworking protocol (ANSI/ASHRAE Standard 135-2004). An open communication protocol standard conceived by a consortium of manufacturers and system users under the auspices of ASHRAE. Data is modeled as a common set of “objects”, which can be accessed using a standard set of “services.” See Bacnet FAQs about the spelling variation “Bacnet.”

Operation mode for a BACnet system or device, where it makes use of a BACnet device for some particular purpose via a service request instance.

Operation mode for a BACnet system or device, where it provides a service to a requesting client.

Or B/Eth. BACnet over Ethernet, one of the original BACnet link-layer types. Since the introduction of BACnet/IP, its usage has become less common.

Or B/IP. BACnet over Ethernet IP. Introduced in “Annex J” of the BACnet standard, it has become the most popular BACnet link-layer protocol (except in lowest-cost devices, where MS/TP is used).

Or MSTP. BACnet link-layer protocol used by lower-cost devices, using master slave / token passing over RS-485 multidrop networks. QNX-based JACEs support direct MS/TP (network) trunks, one per RS-485 port (if licensed for MS/TP). See Bacnet MS/TP licensing.

BACnet/IP Broadcast Management Device. A device that receives and redistributes broadcast-type BACnet messages (Who-Is, I-Am, etc.) to other B/IP devices on its own subnet, and sends broadcast-type messages to BBMDs on other subnets. By having one BBMD on each subnet, a B/IP network can span subnets (between IP routers, which otherwise typically block broadcast type messages). A Niagara station supports operation as a BBMD. See About BBMDs for more details.

BACnet Testing Laboratories, established by BACnet International to support compliance testing and interoperability testing of BACnet products. The BACnet AWS Supervisor and BACnet OWS Supervisor are each BTL-certified. See BACnet AWS and OWS Supervisors.

NiagaraAX can model BACnet objects in a client BACnet device as “Config” objects, where you can see all properties of the object together. For details, see About Bacnet Config objects.

Change-of-Value. BACnet provides services for COV reporting, on both the client and server sides. NiagaraAX supports COV reporting services on both sides.

Or device component. In general NiagaraAX terms, any component representing an external device. Specific to a BacnetNetwork, each BacnetDevice is a container that represents a particular BACnet device. It has several device extensions, one being the Config Device Ext. By default, this Config extension contains a (frozen) Device Object component, which represents the single BACnet Device Object in that device. This component cannot be deleted, but other Config objects can be added and deleted as needed.

On the BACnet server side, a station’s Device Object is represented by the configuration of its single Local Device component under its BacnetNetwork. See Local Device notes.

A BACnet/IP term for a BACnet device that exists on an IP subnet without a BBMD, where the device can “register” with a BBMD on another (remote) subnet as a “foreign device” to explicitly receive BACnet broadcast messages. In no way does it imply any reduced functionality. For more details, see About BBMDs.

Two or more BACnet networks connected by a BACnet router, or essentially “everything on your site that can be accessed via BACnet”, or whatever you can get to with a BACnet request.

The single BacnetNetwork in a station often represents an internetwork, for example if any external BACnet routers exist, or if the BacnetNetwork has multiple ports under its BacnetComm, Network component. If the latter, the station can act as a BACnet router between its local networks.

In a BACnet internetwork, each network must have a unique Network_Number, from 0 to 65534. Each BACnet device must have a Device object with a unique Object_ID, from 0 to 4194302.

For more details, see Internetworks and BACnet/IP.

Master Slave / Token Passing. See BACnet MS/TP.

Or object ID. A BACnet method to identify a particular object within a device, using a combination of its object type and an instance number (unique for that type, within that device). In the case of the single Device Object (type) per BACnet device, it must have a unique instance number across the BACnet internetwork on which it is installed.