FieldServer FS-8704-06 - Manual (Page 28)

FS-8704-06 BACnet IP Driver Manual Page 28 of 57
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Appendix A.7.3. Using Intrinsic Reporting for a Multistate Value
To use Intrinsic Reporting for a Multistate value, it is necessary to classify each of the states as Normal, Alarm or
Trouble. This is done by adding another column to the Offset_Table, called Table_User_Value. Each state is then
classified by inserting one of the following values in its row:
0 = normal
1 = alarm
2 = fault
//set up a look up table
Offset_Table
Offset_Table_Name , Table_String , Table_Index_Value , Table_User_Value
FIRE_ALRM_TEXT , SYSTEM READY , 1 , 0
FIRE_ALRM_TEXT , ALARM , 2 , 1
FIRE_ALRM_TEXT , MAINTENANCE , 3 , 2
FIRE_ALRM_TEXT , OFF-LINE , 4 , 2
FIRE_ALRM_TEXT , IN SERVICE , 5 , 0
FIRE_ALRM_TEXT , OTHER , 6 , 2
Note: The state value (Table_Index_Value) is an enumerated value between 1 and 16. Zero is not a valid value, but
since many client side configurations will wake up with values of zero, the BACnet server will treat a value of zero
as a normal value (i.e. not as an alarm or fault value)
Appendix A.8. COV and Intrinsic Reporting
The COV (Change of Value) and Intrinsic Reporting services are two distinct ways in which point values can be
reported to a client workstation as they change, i.e. in an event-driven opposed to a polling method. This can
increase performance dramatically compared to polling method alone. It also reduces network traffic significantly.
The services are suited to different purposes:

COV is suited to value updates. On analog points the sensitivity can be set using the COV_Increment property.
Only changes larger than the COV_Increment value will be reported.

Intrinsic Reporting is used for alarming. It is implemented via Notification_Class objects, which can receive
subscriptions from client workstations that add themselves to the RecipientList property of a
Notification_Class
object. Notifications are done using ConfirmedEventNotification or
UnconfirmedEventNotification. Intrinsic Reporting also allows for alarms to be acknowledged and for all
subscribed client workstations to be notified of alarm acknowledgements (using EventNotifications of type
ACK_NOTIFICATION).
Appendix A.8.1. Notes on COV configuration:
 No special configuration entries are needed to enable COVs. The service is enabled by default for all protocols
except MSTP. Most client workstations will automatically subscribe to all points once they discover that the
FieldServer supports COV services. This only applies to BACnet Objects - Property subscribes are not
supported by the FieldServer. COV only works for BACnet Map Descriptors with length set to 1. If length is not
specified, then it defaults to 1, so this is only a problem where length has been specified as greater than 1.