The EIB Protocol

  The EIB Protocol

•  Structure of Data Packet

The information exchange between two devices is achieved by transmission of data packets. Each data packet must be acknowledged. For every medium, the message frame looks similar like in Fig (1)

 

fig(1)

Some media will precede or follow this message by some medium specific sequences, characteristic for its medium access control or error correction mechanisms.

The data packet (see Fig (2) ) contains the following fields:

-          Control field

-          Source address field

-          Destination address field

-          Length

-          LSDU (Link Service Data Unit) -i.e. info to be transferred-

-          Check byte

In the case for example of a failure detection message or any other urgent message, the EIB system allows a transmission priority to be assigned to the transmission of the data packets. Alarm messages may have priority over all other messages sent in normal operation mode. Retransmitted data packets have also higher priority than normal packets.

 

fig(2)

•   Addressing Mode

Management of EIB Bus devices connected to the Installation Bus can be addressed using two modes:

-          Physical addressing (system operation)

-          Group addressing (normal operation)

Every bus device is identified by a unique physical address. Two EIB Bus devices should not have the same physical address. The physical address consists of a zone, line and EIB Bus device number; it corresponds to the device as a whole. The source address field always contains the physical address. The physical address is only used as destination address for initialization, programming and diagnostic operations (connection oriented transmission). This corresponds to a system access mode.