Process variables which can be mapped to standard BACnet objects are COV-capable.
I/O function block
Function blocks for Analog, Binary and Multistate Inputs, Outputs and Values are mapped directly to the associated BACnet object types. They are COV-capable and can establish COV connections with all COV clients.
Interface variables of compounds and function blocks whose data type is Analog, Binary, Multistate, Integer, Duration and DateTime are COV-capable and can be mapped to simplified BACnet value objects for operation and monitoring.
A COV is initiated when the value of the process variable [PrVal] of the BACnet object which represents it changes. A COV is also initiated when a status flag [StaFlg] (InAlarm, Fault, Overridden or Out of service) changes, e.g., when a sensor open circuit (fault) occurs or when an I/O value is overwritten manually.
For analog objects, a COV is not initiated for every minor change of [PrVal], but only when the value changes by an amount greater than a predefined increment. This increment is saved in the COV increment [COV] of the analog object, and can be defined in Xworks Plus (XWP) during engineering.