User Manual

Events and COV reporting
COV reporting
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received, the transmitting device tries to send the information again (three
times).
For system limits, see chapter
System Configuration .
If a COV client cannot be contacted, the COV server ceases to send COV
notifications to that client. The transmission of COV notifications to a COV
client is resumed when the COV client re-subscribes.
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.
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
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
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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COV notifications
Connection terminated
Checking the
connection
COV clients and COV
servers
COV mechanism