Writing to BACnet Properties

The driver uses WriteProperty and WritePropertyMultiple services for writing to BACnet properties.

The priority level when writing to commandable properties (Present Value for Analog Output, Analog Value, Binary Output, Binary Value, Multi-state Output, Multi-state Value objects) is controlled by the WritePriority setting in the Citect.ini file and the Device object WritePriority custom property.

At start up the write priority level will be set to the value specified in the WritePriority ini setting or set to 16 (lowest priority) if not specified.

If you require a write to be performed with a specified priority, you will need to change the write priority via the value of the tag with the WritePriority address (before performing a write to a commandable property). After the write has completed, the write priority will be set back to the priority specified in the ini setting, or to the default if an ini setting is not specified.

The Device object WriteNULL custom property is used to write NULL property values. When the value of the tag with that address is set to 1, writing property value 0 will be substituted by a NULL value.

It is also possible to change the value which specifies writing a NULL from 0 to any REAL value by using the WriteNULLValue custom device property. In that case when the WriteNULL is set to 1, you can use WriteNULLValue to change the write NULL value. The value of the WriteNULLValue property will be reset back to 0 after the write is completed.

Note: The Raw and Eng Scale values in the tag configuration should be the same for the WriteNULLValue property to work correctly.

Writing to BACnet properties which have CharacterString data type currently supports only ANSI X3.4 character set.

See Also

Reading BACnet Properties