This section describes datapoint update priorities and consists of the following:
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Normal and Priority Override Values
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You can manually relinquish a default using the CMS Datapoints widget. For example, the following dialog illustrates the priority array for a datapoint with overrides active at priorities 12 and 14. The present value is 70. If you relinquish priority 12 with the Relinquish button for priority 12, the present value becomes 75. If you relinquish the priority 14 with the Relinquish button for priority 12, the present value becomes the normal value which is 70.5. The null values are priority override values that have not been assigned.
Datapoints widget View Overrides dialog
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Example
As described in the first paragraph for this topic, you can use the IAP scheduler service in a SmartServer that has been configured by the CMS Calendar widget to set the occupancy state datapoint for a zone controller based on time of day. In the same SmartServer, you can use the CMS Datapoints widget to manually set the same occupancy state datapoint to occupied for a service event.
To create the schedule and temporarily override the schedule, follow these steps:
Open the CMS Calendar widget.
Create a daily repeating all-day schedule event that sets the normal value for all zone controller occupancy states to automatic. This becomes the default value for the zone controller occupancy state so that occupancy is controlled by occupancy sensors.
Create a Monday through Friday repeating 7:00am to 6:30pm schedule event the sets the priority 16 value for all zone controller occupancy states to occupied. This overrides the default occupancy state specified in step 2 to the occupied state at priority 16 on the specified days during the specified hours. The override is relinquished at 6:30pm on Monday through Friday, returning the occupancy state to automatic.
Open the CMS Datapoints widget and set the occupancy state for the appropriate zone controller to occupied at priority 8. This forces the occupancy state for the specified zone controller to occupied indefinately until the priority 8 value is changed or relinquished, or a higher priority override is specified.
To cancel the override, relinquish the priority 8 override for the occupancy state for the zone controller occupancy state you set in step
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#4.
IAP and BACnet Datapoint Priorities
IAP and BACnet have similar datapoint priority models. Following is a comparison:
Both models support 16 priority overrides, with 1 as the highest priority and 16 as the lowest priority.
The normal value in IAP maps to the relinquish default value in BACnet.
The datapoint priority setting is only sent to BACnet devices; it is not sent to LON or Modbus devices. LON and Modbus devices have no concept of priorities. Instead, whatever was written last to the datapoint is the current value. Many BACnet devices support priority levels, although it is not required.
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Working with BACnet Devices or Using a BACnet Tool
If you are working with BACnet devices, or using a BACnet tool to access LON and Modbus devices connected to a SmartServer
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, then be aware that BACnet supports priorities 1-16
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while the SmartServer supports priorities 1-16 and normal.
If you use the SmartServer to write to a BACnet device, then the SmartServer will write to the BACnet device using the priority that you specify. Since the SmartServer supports normal priority, which is not supported by BACnet,
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when you write at normal priority, the SmartServer will actually send the value at priority 16.
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If you use a BACnet tool to write to a LON or Modbus device within the SmartServer, then it will only use priorities 1 through 16.
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A BACnet tool cannot write to normal priority. If you are using a BACnet tool, then make sure the lowest priority that you use in the SmartServer is priority 16 for schedules and when writing to the LON or Modbus device.
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When using the CMS Calendar
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widget, you may want to only use priority 1-16 for
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scheduling events.