Point with writable output using 16-level priority array. Writable points typically are a setpont or actuator command. Haystack writable points are modeled on the BACnet 16-level priority array with a relinquish default which effectively acts as level 17.
The following levels have special behavior:
The priority array provides for contention resolution when many different control applications may be vying for control of a given point. Low level applications like scheduling typically control levels 14, 15, or 16. Then users can override at level 8. But a higher levels like 2 to 7 can be used to trump a user override (for example a demand response energy routine that requires higher priority).
The actual value to write is resolved by starting at level 1 and working down to relinquish default to find the first non-null value. It is possible for all levels to be null, in which case the overall write output is null (which in turn may be auto/null to another system). Anytime a null value is written to a priority level, we say that level has been set to auto or released (this allows the next highest level to take command of the output).
marker |
Marker labels a dict with typing information |
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writeErr |
Error description when writeStatus indicates error condition |
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writeLevel |
Current priority level for writeVal as number between 1 and 17 |
writeStatus |
Current status of a writable point output |
writeVal |
Current desired value to write to output |