About point versions

Each of the four point categories provides two point versions: read-only and writable.

Read-only version

The read-only version of a control point represents a data item that provides information and cannot be changed. Unlike the writable point version, there are no input type properties for read-only points. These four types are: BooleanPoint, NumericPoint, EnumPoint, and StringPoint.

NOTE: As copied directly from the control palette, there is no application for read-only points. However, proxy points based upon read-only points, which are identical except for a non-null proxy extension and manner of creation, are both common and useful.

Writable version

The writable version of a control point represents a data item that can be changed as well as read (usually by the station). These types are: BooleanWritable, NumericWritable, EnumWritable, and StringWritable.

All writable points provide right-click actions. Override actions are evaluated within the priority scheme used by any writable point. In the case of the set action, the point’s Fallback property is modified. BooleanWritable points also offer built-in minimum on/off timers.

An array of 16 InN inputs, each with a different priority level, plus a Fallback property are available to write a writable point’s value. Level 1 is the highest priority, and level 16 is the lowest. By default, the point’s value can also be set with an operator-issued action (right-click action), available at priority levels 8 (override) and 1 (emergency).

The 16 priority levels used by writable points are modeled after corresponding BACnet priority levels.

Priority levels conform to the following conventions, from highest to lowest:

Emergency (Manual Life Safety)—Unlinkable input, but available as action (command).
Automatic Life Safety
User Defined
User Defined
Critical Equipment Control
Minimum On/Off (BooleanWritable)
User Defined
Override (Manual Operator)—Unlinkable input, but available as action (command).
Demand Limiting
User Defined
Temperature Override
Stop Optimization
Start Optimization
Duty Cycling
Outside Air Optimization
Schedule
NOTE: Although priority levels are patterned after BACnet, there is no direct linkage to BACnet priorities, even with BACnet writable proxy points. Priority inputs of all writable points are strictly a station-centric implementation.