What the Credential Data Input Object Is
The Credential Data Input object, defined in Clause 12.36 of ANSI/ASHRAE 135-2024, is how a BACnet device represents a physical reader that captures authentication factors: a card reader, keypad, or biometric reader. An authentication factor is the unique digital identifier a credential presents, and Present_Value holds the most recently read factor.
A reader that supports several factor formats that are not interchangeable is modeled as several Credential Data Input objects, one per function (for example, a combined card-and-biometric reader). A reader whose formats are interchangeable, such as one that reads multiple Wiegand formats, is modeled as a single object. Credential Data Input objects may optionally support intrinsic reporting, but only to report fault conditions: they perform the first stage of reliability evaluation and apply no off-normal event algorithm. The Access Point object consumes the factors this object captures.
Where You’ll See It
- Readers at a door. Each card reader, keypad, or biometric reader wired to an access controller is a Credential Data Input object.
- Multi-technology readers. A reader that captures both a card and a fingerprint is two Credential Data Input objects, one per factor.
- Fault reporting. A tamper or communications fault on the reader surfaces through
Reliabilityand the fault-reporting properties.
Required Properties
Clause 12.36 requires every Credential Data Input object to provide these properties. Datatypes are the spec’s names: Unsigned is an integer, BOOLEAN a true/false flag, and the BACnet-prefixed types are structured values defined by the standard.
| Property | Datatype | What it holds |
|---|---|---|
Object_Identifier | BACnetObjectIdentifier | The object’s type and instance number, unique within the device |
Object_Name | CharacterString | The human-readable point name, unique within the device |
Object_Type | BACnetObjectType | Always credential-data-input for this object |
Present_Value | BACnetAuthenticationFactor | The most recently read authentication factor |
Status_Flags | BACnetStatusFlags | Four health flags: in-alarm, fault, overridden, out-of-service |
Reliability | BACnetReliability | Names the reason whenever the fault flag is set |
Out_Of_Service | BOOLEAN | When true, Present_Value is decoupled from the physical reader for testing |
Supported_Formats | BACnetARRAY[N] of BACnetAuthenticationFactorFormat | The authentication-factor formats this reader can capture |
Update_Time | BACnetTimeStamp | When Present_Value was last updated |
Property_List | BACnetARRAY[N] of BACnetPropertyIdentifier | The list of properties this instance actually implements |
Optional Properties
The properties integrators meet most are Supported_Format_Classes and the fault-reporting group. The intrinsic-reporting group here supports fault conditions only, since this object applies no off-normal event algorithm. Audit_Level and Auditable_Operations are the audit-logging controls added in 135-2024.
| Property | Datatype | Group |
|---|---|---|
Description | CharacterString | General |
Supported_Format_Classes | BACnetARRAY[N] of Unsigned | Access model |
Event_Detection_Enable | BOOLEAN | Intrinsic reporting |
Notification_Class | Unsigned | Intrinsic reporting |
Event_Enable | BACnetEventTransitionBits | Intrinsic reporting |
Event_State | BACnetEventState | Intrinsic reporting |
Acked_Transitions | BACnetEventTransitionBits | Intrinsic reporting |
Notify_Type | BACnetNotifyType | Intrinsic reporting |
Event_Time_Stamps | BACnetARRAY[3] of BACnetTimeStamp | Intrinsic reporting |
Event_Message_Texts | BACnetARRAY[3] of CharacterString | Intrinsic reporting |
Event_Message_Texts_Config | BACnetARRAY[3] of CharacterString | Intrinsic reporting |
Reliability_Evaluation_Inhibit | BOOLEAN | Fault detection |
Audit_Level | BACnetAuditLevel | Auditing |
Auditable_Operations | BACnetAuditOperationFlags | Auditing |
Tags | BACnetARRAY[N] of BACnetNameValue | Tagging and profile |
Profile_Location | CharacterString | Tagging and profile |
Profile_Name | CharacterString | Tagging and profile |
Related Objects
- Access Point: the object that consumes the factors this reader captures and performs authentication.
- Access Credential: the credential whose stored factors are matched against a captured factor.
- Access Door: the door the access point unlocks after a successful read.
What Chipkin Provides
The Credential Data Input object, including its authentication-factor capture and format model, is a first-class object type in the CAS BACnet Stack. Talk to us about modeling your device’s points.