Bacnet Tuning Policy (Default Policy) (bacnet-BacnetTuningPolicy)

This component defines a tuning policy for the BacnetNetwork. It includes standard tuning policy properties and additional properties related to client-side usage of the BACnet Subscribe_COV service. For an explanation of driver tuning policies, refer to the Niagara Drivers Guide.

Figure 60. Default Policy properties

One way to access these properties by expanding BacnetNetwork > Tuning Policies and double-clicking Default Policy.

Property	Value	Description
Min Write Time	time (defaults to 0)	Specifies the minimum amount of time allowed between writes to writable proxy points, especially ones that have one or more linked inputs. This provides a way to throttle rapidly changing values so that only the last value is written. The default value (0) disables this rule causing all value changes to attempt to write.
Max Write Time	time (defaults to 0)	Specifies the maximum amount of time to wait before rewriting the value, in case nothing else has triggered a write, to writable proxy points. Any write action resets this timer. The default (0) disables this rule resulting in no timed rewrites.
Write on Start	`true` (default) or `false`	Determines a writable proxy point’s behavior when the station starts. `true` initiates a write when the station first reaches a steady state. `false` prevents a write when the station first reaches a steady state. NOTE: Consider setting to `false` except for critical proxy points, otherwise large networks may experience write-queue-overflow exceptions.
Write on Up	`true` (default) or `false`	Determines a writable proxy point’s behavior when the point and its parent device transition from down to up. `true` initiates a write when a transition from down to up occurs. `false` prevents a write when a transition from down to up occurs.
Write on Enabled	`true` (default) or `false`	Determines a writable proxy point’s behavior when the point’s status transitions from disabled to normal (enabled). `true` initiates a write when the transition occurs. `false` prevents a write when the transition occurs.
Stale Time	hours minutes seconds (defaults to zero)	Defines the period of time without a successful read (indicated by a read status of {ok}) after which a point’s value is considered to be too old to be meaningful (stale). A non-zero value causes the point to become stale (status stale) if the configured time elapses without a successful read, indicated by Read Status {ok}. The default value (zero) disables the stale timer causing points to become stale immediately when unsubscribed.
Poll Frequency	drop-down list (defaults to `Normal`)	References the On Demand Poll Scheduler rates under the NiagaraNetwork’s History Policies container slot. Configures how often this type of poll occurs.
Use Cov	`true` or `false` If the device was discovered, and the station database determined that the device indicates support for server-side COV, this property defaults to `true`. Otherwise, it defaults to `false` indicating that no proxy points under the device use COV.	Enables (`true`) and disables (`false`) a device’s support for COV (change of value) as a way to monitor proxy point values. Assuming the device supports subscription to the COV service, `true` triggers the driver to attempt the necessary updates (proxy subscriptions) to the value of each point using the BACnet COV subscription to the device. If the subscription attempt succeeds, the `Read Status` property of the point’s BacnetProxyExt displays COV. If the subscription attempt fails, the driver uses normal polling and the `Read Status` property shows Polled. When `true`, individual proxy points under the device may use COV subscriptions, depending on their assigned tuning policy. When `false`, the driver ignores any proxy subscription updates.
Use Confirmed Cov	`true` (default) or `false`	Controls device updates. If enabled (`true`), and the assigned proxy points are under a BacnetDevice that supports confirmed COV notifications, the driver attempts any necessary updates (proxy subscriptions) using BACnet confirmed COV subscriptions to the device. If disabled (`false`), the driver requests unconfirmed COV notifications.
Cov Subscription Lifetime	time range (defaults to 15 minutes)	Indicates the lifetime, in minutes, for which the software subscribes for COV notifications, then (if necessary) periodically subscribes again. A value of zero (0) configures an indefinite period of time, although this is not guaranteed to persist across resets of the server device.
Use Cov Property	`true` or `false` (default)	Indicates if the system uses COV Property notification services (`true`) to receive data about points in this device for which COV Property is supported.
Use Confirmed Cov Property	`true` (default) or `false`	Indicates if the software requests confirmed (`true`) or unconfirmed (`false`) COV notifications on a COV property request.
Cov Property Increment	number to two decimal places	Defines an increment for a COV property to apply to the sending of COV notifications. This property applies to numeric COV values only.
Cov Property Subscription Lifetime	number of minutes (defaults to 15)	Configures the lifetime, in minutes, for which the software subscribes to the COV property for COV notifications. Zero (0) configures an indefinite period of time, although it is not guaranteed to persist across resets of the server device.
Accept Unsolicited Cov	`true` or `false` (default)	Allows (`true`) or prohibits (`false`) COV notifications to update a point that is being polled. `false` prevents the unsolicited updates.

Bacnet Tuning Policy (Default Policy) (bacnet-BacnetTuningPolicy)

Figure 60. Default Policy properties

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