According to the KNX system specifications, a Group Address has a width of 16 bits (two bytes). The entire Group Address range therefore allows for a maximum of 65536 entries (2^16). The Group Address with the value zero (0) is reserved by the KNX system for broadcast telegrams and can therefore not be used as a GA.
In ETS3 it was not possible to create a GA using the most significant bit #15 (regardless of whether the KNX system itself supported this). ETS4/5 (in contrast to ETS3) now supports the full 16-bit GA range (i.e. also addresses in which bit #15 is used). Such an address is referred to as an "extended group address" or "extended GA". All extended GAs together are called the "extended GA range". Positive consequences of this in ETS4/5 are the use of ~ 65,000 subgroups in the free-level group address style or the use of up to 32 MaGs.
Extended Group Addresses and Devices
Standard Devices (with no plug-in) can use extended GAs in the same way as normal GAs, i.e. a user can link this GA to a GO in the usual manner.
|Power Line Devices|
As laid down in the KNX system specifications, PL devices cannot handle subgroups in a MaG > 15 (in a 3-level GA style) or subgroups > 32767 (in a free-level GA style). In this case, ETS will display an error message and deny the connection process (because ETS3 does not allow the use of extended group addresses, these kinds of situations did not occur in previous ETS versions).
•The explicit creation of such connections is prevented.
•Changes the results of which lead to an address higher than indicated are prevented.
ETS3 plug-ins must be executable in ETS4/5 without modifications. ETS4/5 achieves this by using a "built-in" ETS3 plug-in software compatibility layer which serves as the basis on which all ETS3 plug-ins run. This layer by definition only supports those functions and properties that previously existed in ETS3. Consequently, the free-level group address style is not supported by this compatibility mode and it is tunneled from ETS4/5 via this compatibility layer in ETS3 plug-ins.
Native plug-ins (native = plug-ins or DCAs designed for ETS4/5 only) have access to the new ETS4/5 properties, also including the free-level group address style (i.e. the information that this style is set for the project and which subgroups exist at which levels). The following table shows the effect on ETS3 plug-ins in dependence on the associated project option’s ability to hide certain areas from ETS3 plug-ins, which can be found on the project overview page.
Project Option Details
(From the perspective of an ETS3 plug-in via the compatibility layer, GAs are always displayed in the 3-level group address style.