BACnet Driver Addressing

The general format for addressing BACnet objects and properties is as follows (Brackets [ ] are used for array items. Braces { } are shown to mark optional components, but must not be used in the actual address string):

ObjectType{:}#{.Property}{[I]}{(P)}

where:

• ObjectType is the BACnet object Default Address, Acronym, or Object Type code, according to the following table. A colon is required to separate the type code from the instance number, but this is optional when using an address or acronym. Vendor-specific objects are only supported through codes (127-1023).
• # is the object instance number
• Property is either the name of the property or its numeric identifier, as defined in ANSI/ASHRAE Standard 135-2012, clauses 12 and 21. If omitted, it is assumed as Present_Value (85), which usually contains the current value assigned to the object. Vendor-specific properties are only supported through identifiers (512-4194303).
• I is the array index, required for properties encoded as such.
• P is the write priority, used to write to commandable properties. Values from 1 to 16 are accepted. If not specified, devices assume it as 16 (the lowest).

(Examples follow the table.)

Object Name	Default Address	Accepted Acronyms	Type Code
Analog Input	AnalogInput	AI	0
Analog Output	AnalogOutput	AO	1
Analog Value	AnalogValue	AV	2
Binary Input	BinaryInput	BI	3
Binary Output	BinaryOutput	BO	4
Binary Value	BinaryValue	BV	5
Calendar	Calendar	CAL	6
Command	Command	COM, CMD	7
Device	Device	DEV	8
Event Enrollment	EventEnrollment	EE	9
File	File	F	10
Group	Group	G	11
Loop	Loop	LP	12
Multi-state Input	MultiStateInput	MSI, MI	13
Multi-state Output	MultiStateOutput	MSO, MO	14
Notification Class	NotificationClass	NC	15
Program	Program	PROG	16
Schedule	Schedule	SCH	17
Averaging	Averaging	AVG	18
Multi-state Value	MultiStateValue	MSV, MV	19
Trend Log	TrendLog	TL	20
Life Safety Point	LifeSafetyPoint	LSP	21
Life Safety Zone	LifeSafetyZone	LSZ	22
Accumulator	Accumulator	ACM	23
Pulse Converter	PulseConverter	PC	24
Event Log	EventLog	EL	25
Global Group	GlobalGroup	GG	26
Trend Log Multiple	TrendLogMultiple	TLM	27
Load Control	LoadControl	LC	28
Structured View	StructuredView	SV	29
Access Door	AccessDoor	ACD	30
Access Credential	AccessCredential	ACC	32
Access Point	AccessPoint	ACP	33
Access Rights	AccessRights	ACR	34
Access User	AccessUser	ACU	35
Access Zone	AccessZone	ACZ	36
Credential Data Input	CredentialDataInput	CDI	37
Network Security	NetworkSecurity	NS	38
BitString Value	BitStringValue	BSV, BS	39
CharacterString Value	CharacterStringValue	CSV, CS	40
Date Pattern Value	DatePatternValue	DPV, DP	41
Date Value	DateValue	DV	42
DateTime Pattern Value	DateTimePatternValue	DTPV, DTP	43
DateTime Value	DateTimeValue	DTV	44
Integer Value	IntegerValue	IV	45
Large Analog Value	LargeAnalogValue	LAV	46
OctetString Value	OctetStringValue	OSV, OS	47
Positive Integer Value	PositiveIntegerValue	UV, PIV	48
Time Pattern Value	TimePatternValue	TPV, TP	49
Time Value	TimeValue	TV	50
Notification Forwarder	NotificationForwarder	NF	51
Alert Enrollment	AlertEnrollment	AE	52
Channel	Channel	CH	53
Lighting Output	LightingOutput	LO	54

For example, to read or write the value of Analog Input 1, any of the following is accepted:

AnalogInput1

AnalogInput:1

AI1

AI1.85

0:1

AnalogInput1.Present_Value

AI1.Present_Value

To retrieve the engineering units of the Accumulator object #3, both of the following can be used:

Accumulator3.Units

ACM3.Units

23:3.117

To write the present value of Analog Value 2 under priority 3:

AnalogValue3.Present_Value(3)

AV2(3)

2:2(3)

If non-null values are currently stored under higher priorities (1 or 2), reading the previous address will return the highest priority value instead. Under such circumstances, a VTScada output widget will not report success in the writing procedure, unless the Read Address of the tag is set to:

AnalogValue3.Priority_Array[3]

The BACnet Driver provides an address selection module to help you write addresses in the correct format:

Object Type

Select the object type from this drop list. All standard BACnet object names are shown, regardless of being supported or present in the connected device.

Instance Number

Any number between 0 and the maximum object identifier (default: 4194303) can be selected, regardless of the range supported by the device.

Property

The property to read or write can be selected from this drop list. By selecting the first option in the list, the address will not specify a property, thus Present_Value will be assumed, even if the object doesn't support it. Properties supported by the selected object (per the BACnet standard) are listed on top, but any existing property can be selected. The support of specific properties, even those defined in the standard, depends on the device.

Array Index

The index of the array item being addressed, for properties encoded as such. BACnet array indexes are 1-based, with index 0 used to access the size of the array.

The driver will not prevent an array index from being specified, regardless of the type of the selected property. If it is not an array, the device will return an error when attempting to read or write it.

Write Priority

Select the priority used to write to commandable properties (typically, the Present_Value property of output and value-storing objects). The BACnet prioritization system uses priority values from 1 (highest) to 16 (lowest) to arbitrate between multiple devices attempting to write to the same property.

The non-null value with the highest priority assigned to it will be returned when attempting to read the property. Therefore, this setting has no effect on the value being read. Items of the read-only property Priority_Array contain the values currently assigned to each priority level. If all priorities are assigned a null value, Present_Value will return the value of the property Relinquish_Default instead. If the first option (Default) is selected, no priority will be specified when attempting to write to the device, which is effectively the same as priority 16. Devices will ignore this setting if the property does not support write priorities.