Priorities
Priority stages
Program blocks, function blocks as well as inputs and outputs exchange commands and requests. Commands must be prioritized by urgency since the various commands can overlap. The commands receive different priority stages to that end.
The following groups of priorities exist:
- Emergency mode with priority stages 1…3
- Protection function with priority stages 4…6
- Manual mode with priority stages 7, 8 and 13
- Automatic mode with priority stages 9…12 and 14…16
- Default value with priority stage 17 (no priority)
Priority stage | Name | Description |
|---|---|---|
|
1 | Prio 1 Emergency, manual |
|
2 | Prio 2 Emergency | S7 process is stopped (e.g. after a full download) |
3 | Prio 3 Emergency | N/A |
4 | Prio 4 Protection | Local exception mode: Frost protection pump on, valve to 100% |
5 | Prio 5 Protection | General exception mode |
6 | Prio 6 Minimum On/Off time | Minimum on/off, e.g. delay, minimum switch-on time or minimum switch-off time. |
7 | Prio 7 Manual, switch | Local room units, buttons, switches or scenes override all manual interventions and automation functions. |
8 | Prio 8 Manual, system operator | Manual operation by system operator (remote) |
9 | Prio 9 | N/A |
10 | Prio 10 | N/A |
11 | Prio 11 | N/A |
12 | Prio 12 | N/A |
13 | Prio 13 Manual, building user | N/A |
14 | Prio 14 | N/A |
15 | Prio 15 | Auto by the program |
16 | Prio 16 | N/A |
17 | Default | No priority |
BACnet objects using this priority mechanism have a priority matrix. The priority matrix includes all 17 priorities. Entries in the priority matrix can arrive from the program via interconnection to an input for an output object or via BACnet.
The command on the output [PrVal] of a BACnet object consists of the entry in the priority matrix with the highest priority stage (lowest number). This value is depicted on output [PrVal] of the output block. The latest command is selected if multiple commands, e.g. enable requests, with the same priority stage are available. As soon as the current command is no longer available, the command with the next lower priority stage is selected.