Liebert FS-8704-02 Appendix A. Advanced Topics, Appendix A.1. BACnet Object Names

FS-8704-02_BacnetEthernet.doc Driver Manual Page 15 of 20

Appendix A. Advanced Topics

Appendix A.1. BACnet Object Names

When an external BACnet Client builds a list of Object Names, the BACnet Server Map Descriptor name determines the BACnet Object Name. If the Map Descriptor length is greater than 1, then the Object Name will be suffixed with the index into the Map Descriptor. For example, if the Map Descriptor name is SMD_AI_01 and the length 3, then the Object Names will be SMD_AI_01[0], SMD_AI_01[1] and SMD_AI_01[2].

Appendix A.2. FieldServer implementation of BACnet priority Arrays

When writing to a BACnet Output Object, a write priority value must be specified. When the FieldServer receives the write value, it will be stored to the Map Descriptor Priority Array Table at the specified priority. The Priority Array Table is then scanned and the value with the highest priority is stored to the Data Array location specified by the Map Descriptor.

When a Write “Relinquished” command is received, the value is removed from the Priority Array Table and the next highest value from the Priority Array Table is stored to the Data Array.

If all values have been “Relinquished” from the Priority Array Table, then the Map Descriptors “Relinquish Default” value will be stored to the Data Array.

Appendix A.3. Accessing Priority Array information from other protocol drivers

The Priority Array table and its “In_Use” (or Not Relinquished) state are stored internally to every Map Descriptor, and cannot be accessed directly. If the following data arrays are specified, however, they will maintain an exact copy of the Priority Array Table for the Map Descriptor. Thus the Priority Array Table can be accessed.

Section Title
Map_Descriptors
Column Title	Function		Legal Values
	Name of Data Array where the Priority Array		Up to 16
DA_Pri_Array	Table will be stored. Location 0 is the
			alphanumeric
	Relinquish Default value and locations 1 to 16
			characters
	the different entries of the Priority Array Table.
DA_Pri_Array_Offset	Starting location in Data Array.	1-65535 (17)
	Name of Data Array that indicates if a
DA_Pri_In_Use	particular Priority Values is in use. Location 0		Up to 16
	indicate if the Relinquish Default has been set		alphanumeric
	and locations 1 to 16 indicate if the index is in		characters
	use (1), or if it has been Relinquished (0).
DA_Pri_In_Use_Offset	Starting location in Data Array.	1-65535 (17)

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