BACnet Device Backup and Restore Procedures
Automation developers should be familiar with the BACnet procedures for device Backup and Restore. Both procedures are defined in detail in Clause 19 of the BACnet standard. These procedures may involve network-visible BACnet objects as well as settings that are not visible over the network.
Backup and Restore procedures use File objects to contain and transfer configuration data. The specific content and format of this data is determined by the developer. The developer must also determine whether stream-based or record-based files will be used.
Services Required for Backup and Restore
The BACnet standard identifies the following services for Backup and Restore procedures:
- Reinitialize Device
- Read Property
- Write Property
- Atomic Read
- Atomic Write
- Create Object (optional)
Backup and Restore Procedure Phases
The Backup and Restore procedures operate in a similar manner, with one additional step required for the Backup procedure.
The standard defines the following phases:
- Procedure Initiation
- Procedure Preparation
- Load Parameters (Backup procedure only)
- Configuration of Files
- Procedure Ending
Procedure Initiation
During the Initiation phase, a Reinitialize Device message is sent from one device to another using the following structure:
Reinitialize Device (STARTBACKUP or RESTORE,
The sending device waits for a response from the receiving device before continuing with either procedure.
Procedure Preparation
The Preparation phase involves receiving an approval or rejection in response to the previous phase. The following result codes indicate whether the procedure can continue:
- Result(+) – Approval
- Result(-) – Rejection
Load Parameters
The Backup procedure includes an additional step referred to as Load Parameters. After an approval result is received, the Configuration_Files property within the Device object is used as part of this phase. These configuration files contain vendor-specific data related to the Backup and Restore procedures.
Configuration of Files
The next phase involves the actual Backup or Restore operation. This is performed using information from the Configuration_Files property together with the Atomic Read and Atomic Write services.
Procedure Ending
The Ending phase for both procedures involves another Reinitialize Device message from the sending device to the receiving device. The standard uses the following structure:
Reinitialize Device (ENDBACKUP or RESTORE,
Both procedures end after approval and receipt of the previous message.
Backup and Restore in Building Automation
In building control applications, many automation devices contain configuration data developed by the manufacturer. Developers should be familiar with the procedures defined by the BACnet standard when an interoperable device Backup and Restore feature is provided by an automation device.
Written by: Scott Cosby