Does anyone know how often the BACNet interface scans point devices for points? Is it controlled by the minimum exception or compression deviation times, by one of the location field values, or by something else?
Two types of input tags are supported by the interface: polled (or scanned) tags and COV tags.
For polled tags, the interface sends data requests to the device at specified time intervals. The interface can send either ReadProperty or ReadPropertyMultiple requests depending on the /RPMCount parameter specified in the interface startup file. The recommended option is ReadPropertyMultiple unless it is not supported by the device, because the interface runs much more efficiently by grouping requests from multiple tags. The /RPMCount parameter specifies the number of properties to be included in a ReadPropertyMultiple request, with a default value of 50. User can increase this value to achieve higher efficiency to the extent allowed by the device. In this mode, you can configure the scan class with Location attribute of the tag. For more information about scan classes, refer here:
For COV tags, the interface subscribes to the device for Change of Value (COV) of the object properties. The device only sends data updates when the change of value has exceeded the specified COVIncrement parameter. Each COV subscription has a defined Lifetime. The interface does not re-send subscription requests until the COV lifetime has expired. The /COV and /COVIncrement parameters are configured at the tag level in the InstrumentTag attribute. If the /COV option exists, the tag will receive data by the COV subscription method, otherwise it is a polled tag. The /COVLifeTime parameter is configured at the interface level in the startup command file. If a tag is using COV, the Location4 attribute will not be used and will be set to zero.
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