Page 6 - Serial Data Transmission and KNX Protocol

KNX TUTOR SEMINAR

1.1.4 Classification of Serial Buses
According to their methods of data transmission and bus access:

Figure 2: Classification of Serial buses

Frequency Division Multiplexing (FDM)
The messages to be transmitted modulate the carrier frequencies, either by amplitude or
frequency modulation. One bus line can therefore transmit several channels (different
frequencies) each of which allows data traffic independently of the others.

Time Division Multiplexing (TDM)
Certain time slices are allocated to each message or channel, i.e. the bus devices may
only use the bus one after the other. With TDM therefore, access to the bus must be
controlled in order to prevent simultaneous bus access of several bus devices.
centralised bus allocation (Master/Slave)
decentralised bus allocation (e.g. Token Passing, Flying Master)
combination of both access control methods (e.g. PROFIBUS)
CSMA/CD (Carrier Sense Multiple Access with Collision Detection e.g. Ethernet)
CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance e.g. KNX,CAN)

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