Binary Value

A Binary Value is a two-state value that does not map to a physical input or output. It holds a flag, mode or status that lives in software. A device uses it for things like an occupancy override, an enable switch or a fault summary.

Typical uses

• An occupied/unoccupied mode flag
• A software enable for a control loop
• A summary alarm flag
• A manual override switch
• A schedule output that other devices read

Key properties

Property	What it holds
Present_Value	The current state, ACTIVE or INACTIVE. Writable if the object is commandable or the host allows it.
Active_Text	Optional label shown for the ACTIVE state, such as Occupied.
Inactive_Text	Optional label shown for the INACTIVE state, such as Unoccupied.
Priority_Array	Present only when the object is commandable. Holds one command per priority from 1 to 16.
Relinquish_Default	Present only when the object is commandable. The value used when every priority slot is empty.
Alarm_Value	With intrinsic reporting, the state that puts the object into OFFNORMAL.

How it behaves

A Binary Value may be commandable or not. With intrinsic reporting, the standard pairs it with the CHANGE_OF_STATE algorithm: the object goes OFFNORMAL when Present_Value equals the alarm value for the time delay. Clients can subscribe to changes of Present_Value and Status_Flags.

With the CAS BACnet Stack

Enable it with the STACK_OPTION_OBJECT_TYPE_BINARY_VALUE build option and add each object with BACnetStack_AddObject. Present_Value is served through the callback you register with BACnetStack_RegisterCallbackGetPropertyEnumerated and the BACnetStack_RegisterCallbackSetPropertyEnumerated callback. The object becomes commandable once you enable both PriorityArray and RelinquishDefault; the stack then reads the priority array through the BACnetStack_RegisterCallbackGetPropertyBool callback and the BACnetStack_RegisterCallbackGetPropertyEnumerated callback instead of the plain Present_Value read. Arm the alarm with BACnetStack_SetIntrinsicChangeOfStateAlgorithmBool (an alarm value of true means active), after BACnetStack_SetAlarmsAndEventsForObjectEnabled.

Related object types

Binary Input, Binary Output, Multi-state Value, Analog Value

Properties

The properties ASHRAE 135-2024 clause 12.8 defines for this object type.

How to read the table:

• Conformance is what the standard asks of every object of this type: R is required, W is required and writable by a client, O is optional. A digit after the letter marks a condition in the standard that decides when the property is present or writable, such as support for intrinsic reporting.
• Present by default: yes means the stack presents the property as soon as you add the object; no means it is optional and you turn it on with BACnetStack_SetPropertyEnabled. This is the stack’s starting setup, so it can differ from the conformance code.
• Writable is whether a client can write the property by default. Change it with BACnetStack_SetPropertyWritable.
• not in profile means the stack does not offer this property for this object type.
• Value when your callback does not answer: “Held by the stack” means the stack stores and serves the value itself and does not ask your callbacks. Otherwise it is the value the stack answers when your callback declines or is not registered.

Property	Datatype	Conformance	Present by default	Writable	Value when your callback does not answer
Object_Identifier	BACnetObjectIdentifier	R	yes	no	Held by the stack.
Object_Name	CharacterString	R	yes	no	"Object <type>,<instance>", such as "Object 0,1" for Analog Input 1.
Object_Type	BACnetObjectType	R	yes	no	Held by the stack.
Present_Value	BACnetBinaryPV	R1	yes	no (yes while Out_Of_Service is true)	No default: value-not-initialized. Once Priority_Array and Relinquish_Default are enabled, built by the stack from the priority array your callbacks serve.
Description	CharacterString	O	no	no	""
Status_Flags	BACnetStatusFlags	R	yes	no	Built by the stack from your callbacks.
Event_State	BACnetEventState	R	yes	no	0
Reliability	BACnetReliability	O	no	no (yes while Out_Of_Service is true)	0
Out_Of_Service	Boolean	R	yes	no	false
Inactive_Text	CharacterString	O2	no	no	""
Active_Text	CharacterString	O2	no	no	""
Change_Of_State_Time	BACnetDateTime	O3	no	no	No default: the read fails.
Change_Of_State_Count	Unsigned	O3	no	no	0
Time_Of_State_Count_Reset	BACnetDateTime	O3	no	no	No default: the read fails.
Elapsed_Active_Time	Unsigned32	O4	no	no	0
Time_Of_Active_Time_Reset	BACnetDateTime	O4	no	no	No default: the read fails.
Minimum_Off_Time	Unsigned32	O	no	no	0
Minimum_On_Time	Unsigned32	O	no	no	0
Priority_Array	BACnetARRAY[16] of BACnetOptionalBinaryPV	O5	no	no	Built by the stack from your callbacks.
Relinquish_Default	BACnetBinaryPV	O5	no	no	No default: value-not-initialized until a callback or a client write supplies one.
Time_Delay	Unsigned	O6,8	no	no	0
Notification_Class	Unsigned	O6,8	no	no	0
Alarm_Value	BACnetBinaryPV	O6,8	no	no	0
Event_Enable	BACnetEventTransitionBits	O6,8	no	no	An empty bit string.
Acked_Transitions	BACnetEventTransitionBits	O6,8	no	no	An empty bit string.
Notify_Type	BACnetNotifyType	O6,8	no	no	0
Event_Time_Stamps	BACnetARRAY[3] of BACnetTimeStamp	O6,8	no	no	No default: the read fails.
Event_Message_Texts	BACnetARRAY[3] of CharacterString	O8	no	no	""
Event_Message_Texts_Config	BACnetARRAY[3] of CharacterString	O8	no	no	""
Event_Detection_Enable	Boolean	O6,8	no	no	false
Event_Algorithm_Inhibit_Ref	BACnetObjectPropertyReference	O8	no	no	No default: the read fails.
Event_Algorithm_Inhibit	Boolean	O8,9	no	no	false
Time_Delay_Normal	Unsigned	O8	no	no	0
Reliability_Evaluation_Inhibit	Boolean	O10	no	no	false
Property_List	BACnetARRAY[N] of BACnetPropertyIdentifier	R	yes	no	Held by the stack.
Current_Command_Priority	BACnetOptionalUnsigned	O5	no	no	Built by the stack from your callbacks.
Value_Source	BACnetValueSource	O11,13,15	no	no	No default: the read fails.
Value_Source_Array	BACnetARRAY[16] of BACnetValueSource	O12,14	no	no	No default: the read fails.
Last_Command_Time	BACnetTimeStamp	O12,14	no	no	No default: the read fails.
Command_Time_Array	BACnetARRAY[16] of BACnetTimeStamp	O14	no	no	No default: the read fails.
Audit_Level	BACnetAuditLevel	O16	not in profile	not in profile	No default: the read fails.
Auditable_Operations	BACnetAuditOperationFlags	O16	not in profile	not in profile	No default: the read fails.
Audit_Priority_Filter	BACnetOptionalPriorityFilter	O17	not in profile	not in profile	No default: the read fails.
Tags	BACnetARRAY[N] of BACnetNameValue	O	no	no	No default: the read fails.
Profile_Location	CharacterString	O	no	no	""
Profile_Name	CharacterString	O	no	no	""