Page 79 - Basic Course

KNX BASIC COURSE

2 Internal structure of a Bus Coupling Unit

+ ‐ (Flash)ROM: System software PEI
RAM: Current values
EEPROM: Application program,
addresses, objects, parameters

Red Black RAM

(Flash)ROM

TRC
µP

EEPROM

µC

KNX

+ ‐

Figure 2: Internal structure of a bus coupling unit

There are two types of KNX bus coupling units:

A BCU with program memory (microcontroller and a transceiver suitable for the
connected medium) and with PEI to the AM.
A BCU without program memory (only a medium specific transceiver with digital
interface to the application microcontroller)

In the different types of a memory of the microcontroller, the following data is stored:

The system software: the different standardised KNX system software profiles (also
referred to as “system stack”) are identified by their “mask version” or “device
descriptor type 0”. A mask cannot be changed. The mask version consists of 2 bytes
where:

 The first digit y refers to the corresponding medium – 0 for TP, 1 for PL110, 2 for
RF and 5 for KNXnet/IP. Not all software profiles are available on all before-said
media.

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KNX Bus Devices Bus devices_E1213a 5/16