What B-GENERAL Is
A BACnet device profile is a standardized capability level: a checklist of things a device must be able to do before it can wear the label. B-GENERAL (BACnet General) is defined in Annex L of ANSI/ASHRAE 135-2024 (clause L.8) as the catch-all profile for a device that does not match any of the named profiles but still needs a standardized profile claim.
The checklist items are BACnet Interoperability Building Blocks (BIBBs). B-GENERAL requires only the ability to serve its object values and be discovered; beyond that, a B-GENERAL device declares its actual capabilities in its PICS (Protocol Implementation Conformance Statement) rather than inheriting them from the profile. It is never combined with a named profile except a Miscellaneous one.
Where It’s Used
B-GENERAL fits a device whose function does not map cleanly onto a controller, operator interface, or the other named families.
- Specialty devices. A metering, sensing, or purpose-built device that exposes BACnet objects but is not a controller in the usual sense.
- Novel equipment. A device with a capability mix the named profiles do not describe, which still wants a standardized profile line for specifications.
- Minimal-participation devices. A device that mainly needs to be discovered and read, declaring anything more in its PICS.
Required Services
The table below is the exhaustive service set required by the B-GENERAL BIBBs. Initiates means the device sends the request or notification; Executes means the device receives and acts on it (responding, for confirmed services). BIBB codes encode the same split: a -A BIBB is the initiating side, a -B BIBB the executing side. A - means the profile does not require that direction; a device may still support it.
| Capability area | Service | Required by BIBB | Initiates | Executes |
|---|---|---|---|---|
| Data sharing | ReadProperty | DS-RP-B | - | Yes |
| Device and network management | Who-Is ¹ | DM-DDB-B | - | Yes |
| Device and network management | I-Am ¹ | DM-DDB-B | Yes | - |
| Device and network management | Who-Has ¹ | DM-DOB-B | - | Yes |
| Device and network management | I-Have ¹ | DM-DOB-B | Yes | - |
Because the profile is a floor, most B-GENERAL devices support far more than this. The value of the profile is the guaranteed minimum: any B-GENERAL device can be read and discovered.
¹ The dynamic-binding rows (DM-DDB-B, DM-DOB-B) are waived for a device configured as an MS/TP (Master-Slave/Token-Passing) subordinate, which the master polls directly.
Related Profiles
| Profile | How it differs from B-GENERAL |
|---|---|
| B-SS | Smart Sensor: a named minimal profile for a simple sensing device |
| B-ASC | Application Specific Controller: the profile for a fixed-function controller |
| B-GW | Gateway: a Miscellaneous profile B-GENERAL may be combined with |
What Chipkin Provides
The CAS BACnet Stack implements the ReadProperty and discovery services the B-GENERAL profile requires, and any additional capability a specialty device needs to declare in its PICS. Talk to us about building or integrating a B-GENERAL device on the stack.