Access Zone

An Access Zone object represents a secured area. People enter through entry Access Points and leave through exit Access Points. The zone can count how many are inside and track who they are.

Typical uses

• A laboratory with a maximum head count
• A parking area that counts vehicles in and out
• A ‘who is inside’ list for an evacuation roll call
• A zone that blocks re-entry with the same card

Key properties

Property	What it holds
Occupancy_State	Summarises the zone against its limits, for example below the lower limit or at the upper limit.
Occupancy_Count	How many people the zone currently holds, when counting is enabled.
Occupancy_Upper_Limit	The count at which the zone is considered full.
Credentials_In_Zone	The credentials currently inside. This is the ‘who is in’ list.
Entry_Points	The Access Point objects people use to enter.
Exit_Points	The Access Point objects people use to leave.

How it behaves

Intrinsic reporting is based on Occupancy_State and uses the CHANGE_OF_STATE algorithm, so a client can be notified when the zone moves into a limit state.

With the CAS BACnet Stack

Enable it with the STACK_OPTION_OBJECT_TYPE_ACCESS_ZONE build option and add each object with BACnetStack_AddObject. Property values come from your callbacks. Arm the alarm with BACnetStack_SetAlarmsAndEventsForObjectEnabled and then BACnetStack_SetIntrinsicChangeOfStateAlgorithmEnum; each call adds one occupancy state to Alarm_Values.

Related object types

Access Point, Access Door, Access Credential

Properties

The properties ASHRAE 135-2024 clause 12.32 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.
Description	CharacterString	O	no	no	""
Global_Identifier	Unsigned32	W	yes	yes	0
Occupancy_State	BACnetAccessZoneOccupancyState	R	yes	no	0
Status_Flags	BACnetStatusFlags	R	yes	no	Built by the stack from your callbacks.
Event_State	BACnetEventState	R	yes	no	0
Reliability	BACnetReliability	R1	yes	no (yes while Out_Of_Service is true)	0
Out_Of_Service	Boolean	R	yes	no	false
Occupancy_Count	Unsigned	O1,3,4	yes	no (yes while Out_Of_Service is true)	0
Occupancy_Count_Enable	Boolean	O3,4	yes	no	false
Adjust_Value	Integer	O3,4,5	yes	yes	0
Occupancy_Upper_Limit	Unsigned	O	no	no	0
Occupancy_Lower_Limit	Unsigned	O	no	no	0
Credentials_In_Zone	BACnetLIST of BACnetDeviceObjectReference	O	no	no	No default: the read fails.
Last_Credential_Added	BACnetDeviceObjectReference	O	no	no	A reference to Access Credential instance 4194303 (none).
Last_Credential_Added_Time	BACnetDateTime	O	no	no	No default: the read fails.
Last_Credential_Removed	BACnetDeviceObjectReference	O	no	no	A reference to Access Credential instance 4194303 (none).
Last_Credential_Removed_Time	BACnetDateTime	O	no	no	No default: the read fails.
Passback_Mode	BACnetAccessPassbackMode	O	no	no	0
Passback_Timeout	Unsigned	O2	no	no	0
Entry_Points	BACnetLIST of BACnetDeviceObjectReference	R	yes	no	No default: the read fails.
Exit_Points	BACnetLIST of BACnetDeviceObjectReference	R	yes	no	No default: the read fails.
Time_Delay	Unsigned	O3,7	no	no	0
Notification_Class	Unsigned	O3,7	no	no	0
Alarm_Values	BACnetLIST of BACnetAccessZoneOccupancyState	O3,7	no	no	0
Event_Enable	BACnetEventTransitionBits	O3,7	no	no	An empty bit string.
Acked_Transitions	BACnetEventTransitionBits	O3,7	no	no	An empty bit string.
Notify_Type	BACnetNotifyType	O3,7	no	no	0
Event_Time_Stamps	BACnetARRAY[3] of BACnetTimeStamp	O3,7	no	no	No default: the read fails.
Event_Message_Texts	BACnetARRAY[3] of CharacterString	O7	no	no	""
Event_Message_Texts_Config	BACnetARRAY[3] of CharacterString	O7	no	no	""
Event_Detection_Enable	Boolean	O3,7	no	no	false
Event_Algorithm_Inhibit_Ref	BACnetObjectPropertyReference	O7	no	no	No default: the read fails.
Event_Algorithm_Inhibit	Boolean	O7,8	no	no	false
Time_Delay_Normal	Unsigned	O7	no	no	0
Reliability_Evaluation_Inhibit	Boolean	O	no	no	false
Property_List	BACnetARRAY[N] of BACnetPropertyIdentifier	R	yes	no	Held by the stack.
Audit_Level	BACnetAuditLevel	O9	not in profile	not in profile	No default: the read fails.
Auditable_Operations	BACnetAuditOperationFlags	O9	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	""