The role of the group table, address table & association table is:
- to convert multicast telegrams into load adaption (e.g. closing/opening a relay)
- to convert user actions (e.g. push button manipulation) or physical events (e.g. movement detection)
into multicast telegrams
For more information, see the 'Device Configuration' section here
Multicast telegram from the bus
Before a KNX device processes the payload of a telegram it checks whether it addressed by that telegram. If the device is not addressed by the telegram then it will not process the telegram any further.
If the destination address of the multicast telegram, which is a Group Address, is indeed in the group table, then the device will look up which Group Object is associated with that Group Address, the device will do this via the address table and the association table.
The destination address of a received multicast telegram could be associated with more than one Object, in that case all associated Objects will be effected by that telegram.
Multicast telegram to the bus
In order to set up the the destination address of the telegram, the device will look up which Group Address is associated with the Group Object that relates to the user action (e.g. manipulated rocker) or the physical event (e.g. detected movement), the device will do this via the association table and the group table. The payload of the telegram will be set accordingly.
Multiple associations - Sending Group Address
The user action or physical event could be associated with more than one Group Address, in that case however only the first assigned Group Address will be used, i.e. only one telegram will be sent using the first assigned Group Address.
The first assigned Group Address is called the 'Sending Group Address'.
For more information, see also the 'Runtime telegrams - GroupValueWrite: to the bus' here.