Staging

A Staging object turns one number into a pattern of on and off outputs. You define stages, each with a limit and a set of states for a group of binary objects. As the value rises and falls, the object moves between stages and writes the matching states to the binary objects it controls.

Typical uses

• Stage chillers on as load rises
• Switch banks of lights by light level
• Bring boiler stages on and off with demand
• Stage fans or pumps by pressure
• Drive several relays from one setpoint

Key properties

Property	What it holds
Present_Value	The number that selects the stage. A write is held between Min_Pres_Value and Max_Pres_Value.
Present_Stage	The index of the active stage. It is not available until the object has chosen a stage after a restart or a change of the stage table.
Stages	The stage table. Each stage has a limit, a deadband and the on or off state for every target.
Target_References	The Binary Output, Binary Value or Binary Lighting Output objects the stages control.
Priority_For_Writing	The priority used when writing to the targets.

How it behaves

The object has no priority array, and the standard applies no event algorithm to it. COV notifications go out when Present_Value changes by COV_Increment, when Present_Stage changes, or on any change to Status_Flags.

With the CAS BACnet Stack

Enable it with the STACK_OPTION_OBJECT_TYPE_STAGING build option. It is on in the full target; in the embedded target, define it yourself (see Configuring a build). CASBACnetStackDLL.h has no function dedicated to this type, so create it with BACnetStack_AddObject. The stack serves the object identifier, object type, property list and status flags itself; your callbacks serve every other property, matched to its datatype. Call BACnetStack_UpdateValue whenever the value you serve changes, so COV, trend logs and alarms see it.

Related object types

Binary Output, Binary Value, Binary Lighting Output

Properties

The properties ASHRAE 135-2024 clause 12.62 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	Real	W	yes	yes	No default: value-not-initialized.
Present_Stage	Unsigned	R	yes	no	0
Stages	BACnetARRAY[N] of BACnetStageLimitValue	R1	yes	no	No default: the read fails.
Stage_Names	BACnetARRAY[N] of CharacterString	O1	no	no	""
Status_Flags	BACnetStatusFlags	R	yes	no	Built by the stack from your callbacks.
Event_State	BACnetEventState	R	yes	no	0
Reliability	BACnetReliability	R	yes	no	0
Out_Of_Service	Boolean	R	yes	no	false
Description	CharacterString	O	no	no	""
Units	BACnetEngineeringUnits	R	yes	no	95 (no units)
Target_References	BACnetARRAY[N] of BACnetDeviceObjectReference	R2	yes	no	No default: the read fails.
Priority_For_Writing	Unsigned(1..16)	R	yes	no	0
Default_Present_Value	Real	O	no	no	0.0
Min_Pres_Value	Real	R	yes	no	0.0
Max_Pres_Value	Real	R	yes	no	0.0
COV_Increment	Real	O3	no	no	0.0
Notification_Class	Unsigned	O4,5	no	no	0
Event_Enable	BACnetEventTransitionBits	O4,5	no	no	An empty bit string.
Acked_Transitions	BACnetEventTransitionBits	O4,5	no	no	An empty bit string.
Notify_Type	BACnetNotifyType	O4,5	no	no	0
Event_Time_Stamps	BACnetARRAY[3] of BACnetTimeStamp	O4,5	no	no	No default: the read fails.
Event_Message_Texts	BACnetARRAY[3] of CharacterString	O5,6	no	no	""
Event_Message_Texts_Config	BACnetARRAY[3] of CharacterString	O5	no	no	""
Event_Detection_Enable	Boolean	O4,5	no	no	false
Reliability_Evaluation_Inhibit	Boolean	O	no	no	false
Property_List	BACnetARRAY[N] of BACnetPropertyIdentifier	R	yes	no	Held by the stack.
Value_Source	BACnetValueSource	O7,8,9	no	no	No default: the read fails.
Audit_Level	BACnetAuditLevel	O10	not in profile	not in profile	No default: the read fails.
Auditable_Operations	BACnetAuditOperationFlags	O10	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	""