Export Table (bacnet-BacnetExportTable)

This frozen slot under BacnetNetwork > Local Device contains all the server (export) descriptors BACnet export folders used to export station objects as BACnet objects. You use different export manager views of this table to export station objects. It has no configuration properties but three important views.

Figure 27. Example of Export Table properties

You access this Property Sheet by expanding Config > Drivers > BacnetNetwork > Local Device, right-clicking Export Table and clicking Views > AX Property Sheet.

Server descriptors

BACnet server descriptors are the components responsible for exporting station objects as BACnet objects. Each descriptor resides under the Export Table in the Nav tree, and corresponds to a particular component, file, or history in the station.

You add, edit, and manage server descriptors using the manager views of the Export Table. Each manager view simplifies selection and enforces object ID instance rules. The driver automatically gives server descriptors names (upon creation) using an <ObjectType>_<InstanceNumber> convention. For example: analogValue_1, trendLog_0, schedule_2, and so on.

NOTE: Generally, it is recommended that you do not change the driver-assigned name of the export descriptor. If you wish to change the name by which the object is known to BACnet clients, do this in the objectName property, which is initialized with the name of the exposed component.

There are three categories of BACnet server descriptors:

Export descriptors (for components, reflecting the station object space)
File descriptors (for files)
Log descriptors (for histories)

In addition, as needed, you can add BACnet export folders to organize BACnet server descriptors.

Export descriptors

BACnet export descriptors include 15 different types to export components, including Boolean, Enum, and Numeric points (read-only and writable), and various Schedule types. You add them using the Bacnet Export Manager view.

Externally, to another BACnet device, the exported BACnet object opens with properties that source from two different areas of the station. For example, each exported component (point or schedule) exports as a BACnet object with properties from the component itself, plus additional properties in its export descriptor.

NOTE: You do not see export (component) descriptors in the Bacnet File Export Manager and Bacnet Niagara Log Export Manager views. These views show other non-component server descriptors.

File descriptors

A BACnet file descriptor exports a file under the station directory as a BACnet file object. You add file descriptors using the Bacnet File Export Manager view of the Export Table.

NOTE: You do not see file descriptors in the Bacnet Export Manager and Bacnet Niagara Log Export Manager views, These views show other server descriptors.

Log descriptors

A BACnet log descriptor exports a history as a BACnet trend log object. There are two log descriptors:

The system creates a BacnetNiagaraHistoryDescriptor when you select and add a standard history using the Bacnet Niagara Log Export Manager view of the Export Table. The resulting exported trend log object is compliant only with the original broken specification for BACnet trend logs, which was superseded and fixed in Addendum B to the 2001 version of the spec.
The system creates a BacnetTrendLogDescriptor when you add a specialized BacnetTrendLogExt extension to a point. The resulting exported trend log object is fully-BACnet compliant with the 2004 version of the BACnet spec.