An Evaluation of Serial Protocols and Media Alternatives for Vehicle Multiplex

The desire of automotive designers to pro-vide increasing electronic feature content at a time when market pressures are dictating vehicle downsizing, has forced wire harness manufacturers to find ways of doing more, but in less space. Several methods of expanding the functional capability of the vehicle wire harness, while at the same time reducing its bulk, exist; however, Serial Multiplexing shows the most promise of meeting cost and reliability objectives. This paper describes recent evaluation of a serial multiplex system applied to “body electrical” vehicle functions. Data is analyzed over a variety of media that are regarded as possessing the appropriate characteristics for volume production for automobiles. In addition, a variety of line discipline proto-cols are evaluated, and the rationale to be considered when selecting a protocol for a particular application is discussed.