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venfree/Wiki/KNX Group Address

KNX Group Address

A KNX group address (GA) is a logical address that links communication objects (COs) of different devices. Whatever is written to a GA is received by all other COs bound to that GA, the publish-subscribe principle of KNX.

Structure and Format

Group addresses are structured in three levels by default: main group (0–31), middle group (0–7), and sub group (0–255). Written as "1/2/5". ETS also supports a 2-level format (main/sub) or a free 16-bit format.

A total of 65,535 group addresses are available per project. Address 0/0/0 is reserved and means "unconnected", COs with this GA do not communicate.

Assignment Scheme and Best Practice

A systematic assignment greatly simplifies maintenance and expansion. The function-based scheme is common: main group by function (1 = lighting, 2 = blinds, 3 = heating), middle group by floor, sub group by room or channel.

Each GA should have exactly one DPT. COs with different DPTs on the same GA write without errors in ETS, but the receiving device misinterprets the data. ETS shows a warning but does not prevent it.

Key Facts

  • Max. 65,535 group addresses per project
  • 0/0/0 is reserved = CO unconnected
  • Multiple COs can be bound to one GA (1:n or n:m)
  • Each GA should have exactly one DPT
  • Structure is convention, not mandated by the KNX standard

Related Articles

KNX Communication Object (CO)
A communication object (CO) is a data point on a KNX device. It has a type (DPT), a direction (send/receive), and is linked to COs on other devices via group addresses.
KNX Data Point Type (DPT)
A data point type (DPT) defines the format and value range of a KNX communication object. Two COs that communicate must share the same DPT, otherwise the receiving device misinterprets the data.
KNX Flags – C, R, W, T, U, I
KNX flags control the behaviour of a communication object on the bus. They define whether a CO can send, receive or respond to telegrams, and whether it requests a value on startup.
KNX Telegram
A KNX telegram is the smallest unit of communication on the bus. It contains sender (physical address), destination address (group address), data value and priority, and is received simultaneously by all devices on the line.

Related Functions

KNX Switch Actuator
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KNX Binary Input & Push Button Interface
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KNX Blind Actuator
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