User Manual

Events and COV reporting
COV reporting
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To ensure that the COV service is maintained over a long period, a maximum time period without COV
reporting can be set in the BACnet Device Info Object via the BACnet property COV Resubscription Interval
[CovRI]. The client must subscribe with SubscribeCOV again before [CovRI] expires.
COV clients and COV servers
The local PXM10 operator unit is not a BACnet client and cannot, therefore, be used as a COV client.
See
PXM10 operator unit: User's guide (CM110397).
COV reporting between COV client and COV server
COV mechanism
BACnet clients use the COV mechanism for continuous monitoring of process variables without putting an
excessive load on the bus through continuous polling. They subscribe to the objects that they are
monitoring. These COV connections must be maintained as long as the object is being monitored.
The BACnet client subscribes to the COV server as a COV client using the BACnet service SubscribeCOV.
The server sends a SimpleAck acknowledgement. Immediately after the acknowledgement, the COV server
transmits an initial ConfirmedCOVNotification. The COV client acknowledges receipt of the value with a
SimpleAck acknowledgement. The COV connection between the COV server and COV client is now
established, and ConfirmedCOVNotifications are sent whenever a trigger for the subscribed COV occurs.
Block A
Block Z
Block B
Block V
Block Q
PXM20
Automation level
COV
Client
COV
Client
COV
Client
COV
Server
COV
Server
Desigo CC
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