<div class="htmlview paragraph">Apart from direct economical benefits the main advantage of standardization is a clear definition of the interface between various units in the vehicle, in the SAE different classes for in-vehicle communication have been defined. A Recommended Practice J1850 has been established for class B.</div> <div class="htmlview paragraph">In ISO the Controller Area Network (CAN) has been proposed as a standard for high speed applications.</div> <div class="htmlview paragraph">To indicate levels of standardization often the “Open Systems Interconnection 7-layer model” defined by ISO is quoted. However, the 7-layer model does not cover the various aspects of a single serial communication bus in sufficient detail for standardization.</div> <div class="htmlview paragraph">For in-vehicle communication we can distinguish 8 independent items that can be standardized: <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">data representation</div></li> <li class="list-item"><div class="htmlview paragraph">message attributes</div></li> <li class="list-item"><div class="htmlview paragraph">address /identifier allocation</div></li> <li class="list-item"><div class="htmlview paragraph">bit-rate</div></li> <li class="list-item"><div class="htmlview paragraph">bit coding</div></li> <li class="list-item"><div class="htmlview paragraph">transfer medium</div></li> <li class="list-item"><div class="htmlview paragraph">bus states</div></li> <li class="list-item"><div class="htmlview paragraph">connector</div></li> </ul></div> <div class="htmlview paragraph">Standardization of some of these items may not be necessary.</div> <div class="htmlview paragraph">For the realization of the CAN bus Philips is developing various circuits (IC's)each taking care of one or more of the items mentioned above. Apart from the implementation of the actual serial bus these circuits contain a number of additional functions that simplify the hardware and software design of the modules taking part in the communication in the vehicle.</div>