The Header

The Header has the following functions:

• Synchronisation
  Because the Header is only transmitted from the LIN Master and that is the only thing that determines the bus pulse frequency, all devices must first be synchronised through a central transmission. This function is done by the Header. Each Header begins with a synchronisation sequence which in turn consists of three parts. Synchronisation break, synchronisation limit and synchronisation field then signal the beginning of a new transmission and synchronise all the connected LIN Slaves.
• Message address
  Not until all devices are running synchronously is the bus message given a message address. In addition, an identifier is transmitted which contains the address (among other things). Based on this address the connected LIN Slaves can filter out the messages which are relevant for them. The identifier also indicates how many data fields should be included in the Header. This number can be between 0 and 8. And finally, a short checksum follows which detects any transmission errors.

The following picture shows a complete Header: