Collective feedback switching status
After central commands or after the bus/mains voltage returns, a KNX line is generally heavily loaded by telegrams because numerous bus devices transmit the state of their communication objects as status. This effect occurs particularly when using visualisations. Collective feedback of the gateway can be used to keep the telegram load low during initialisation.
The collective feedback summarises the switching states of the groups and single devices in bit-orientated form. Up to four separate 4-byte communication objects according to KNX DPT 27.001 are available for this, depending on the set addressing type. Each of these objects can visualise the switching state of up to 16 groups or single devices.
for Groups 1-16
It is possible to show up to 16 groups or single devices and thus up to 16 different switching states logically in a 4-byte object. Each group or each single device has one bit representing the switching state ("S"-bit) and another one defining the masking ("M" bit). The "S"-bits correspond to the logical non-inverted switching states of the groups or devices and are either "1" (on) or "0" (off). The M-bits are "1" when the corresponding group or the appropriate single device has been created in the project design of the gateway. Similarly, M-bits are "0" when groups or devices are not available. In this case, the corresponding "S"-bits are continuously "0", as there is no switching status.
After a device reset (ETS programming operation, bus or mains voltage return), the gateway transmits all the collective feedback according to the configured addressing type. If only individual switching states change in gateway operation, only the affected collective feedback objects are updated.
The following example object value formats result...
Groups 1 to 4 available: "00 0F 00 0x", x = switching states
-> Group 1 and 2 ON: "00 0F 00 03" / Group 1 and 3 ON: "00 0F 00 05"
Groups 1 to 6 available: "00 3F 00 xx", x = switching states
-> Group 1 and 2 ON: "00 3F 00 03" / Group 1 and 5 ON: "00 3F 00 11"
Groups 1 to 4 and 10 to 12 available: "0E 0F 0x 0x", x = switching states
-> Group 1 and 4 ON: "0E 0F 00 09" / Group 1 and 10 ON: "0E 0F 02 01"
Use of the collective feedback would be possible in appropriate visualisation applications - for example in public buildings such as schools or hospitals - where the switching states of the actuators are displayed centrally and no separate switching status is displayed at the control sections. In such applications the collective feedback can replace the 1-bit individual feedbacks and thereby significantly reduce the bus load.
Activating collective feedback
The "switching status collective feedback" is a global function for each DALI system and can be enabled on the parameter page "DALI system... -> General" be enabled.
- Activate the parameter "Collective feedback".
- Collective feedback is enabled. The collective feedback objects become visible in the ETS. Depending on the configured addressing type, up to 4 objects are displayed for groups and / or single devices.
- Deactivate the parameter.
- Collective feedback is deactivated. No collective feedback objects are available.
Setting the update of collective feedback
In the ETS, it can be defined when the gateway updates the feedback value for the collective feedback. The object value most recently updated by the gateway is then actively reported to the KNX, provided the "Transmit" flag is set on the communication objects.
The parameter "Updating of the object value" is available on the parameter page "DALI system... -> General" available.
- Collective feedback must be enabled.
- Set the parameter to "after each update object 'Switching'/'Central'"
- The gateway updates the feedback values in the collective feedback as soon as a new telegram is received for groups or single devices at the input objects "Switching - Setting" or "Central function... - Switching" for groups or single devices are updated. A new telegram is also then actively transmitted to the KNX each time. The telegram value does not necessarily have to change. Hence, corresponding collective feedbacks are also generated, e.g. in the event of cyclical telegrams to the input objects.
- Set the parameter to "Only if the feedback value changes".
- The gateway only updates the feedback values in the collective feedback objects when the telegram values of the inputs also change. The feedback remains unchanged if telegram values do not change (e. g. in the event of cyclical telegrams to the input objects with the same telegram value). Consequently, no telegram with the same content is then issued repeatedly.
Setting collective feedback after bus/mains voltage return or after programming with the ETS
The states of the collective feedback are transmitted to the KNX after the bus or mains voltage returns or after an ETS programming operation. In these cases, the feedback telegram can be time-delayed, with the delay set globally for all groups and single devices together.
The parameter "Delay after bus/mains voltage return" is available on the parameter page "DALI system... -> General" available.
- Collective feedback must be enabled.
- Activate the parameter.
- The collective feedback objects are transmitted with a delay after bus or mains voltage return or after programming with the ETS. No feedback telegram is transmitted during a running delay, even if a switching state changes during this delay.
- Deactivate the parameter.
- The collective feedback is transmitted immediately after bus or mains voltage return or after programming with the ETS.
Setting the cyclical transmission of the collective feedback
The objects of the collective feedback can also transmit their value cyclically in addition to transmission when updating.
The "Cyclical transmission" parameter is available on the parameter page "DALI system... -> General" available.
- Collective feedback must be enabled.
- Activate the parameter. Configure the desired time for cyclical transmission in the "Cycle time" parameter.
- Cyclical transmission is activated.
- Deactivate the parameter.
- Cyclical transmission is deactivated which means that collective feedback is transmitted to the KNX only if one of the switching states changes.
