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Topology and Structures

Topology and structures in KNX-Programming

The KNX bus is hierarchically structured. The smallest installation unit is the line.
Up to 64 bus participants can be connected to each line. A line can consist of a maximum of 4 line segments.

Up to 15 lines can be combined into one area via line couplers.

What happens if more than
64 participants are on a line

If more than 64 participants are connected to one line or the line lengths are exceeded, it is possible to connect more participants to another line via line amplifiers or to allow longer line routes.


Benefits of a clear topology

This setup makes a KNX system manageable for commissioning, diagnostics and maintenance.

Starting with one or a few lines during the initial installation, incremental expansion is easily possible with new requirements. Provided that on initial installation the above guidelines were followed.


Physical address – the house number
of the KNX participants

The physical address uniquely identifies all bus participants. The physical address is
only displayed in three digits and may occur only once in the project.

This unique address allows the participants to be specifically addressed and programmed. The prerequisite for this is that the application program is loaded into the devices.

The physical address will be used after
commissioning for further purposes:

• For diagnosis

• For troubleshooting

• For changing the system by programming

The group address and its representation

In a project, participants communicate with each other via the group addresses. Group addresses can be represented in two ways:

• Two digits (main and subgroups)

• Three digits (main, middle and subgroups)

The group address and its link

The next step is to create the links. Links can be imagined as the connection terminals in the junction box in a conventional installation.

The corresponding communication objects (functions) of the actuators and sensors are stored in a group address. Each bus participant has different objects.


Communication takes place – communication objects

The communication object determines which data is sent on the bus and how big this data is. The smallest data type is the bit, and I’m not talking about the German beer.

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