Introduction to Serial Bus Systems in Motor Vehicles

Over the course of time, a number of application domains or areas of use have emerged for serial communication in motor vehicles: These include powertrain, chassis, convenience, sensor/actuator, passive safety, active safety, and infotainment. The tasks to be performed by a serial bus system need to be solved differently based on its specific application domain. No single serial bus system is capable of satisfying all requirements. Many of the solutions developed by car producers and suppliers have gradually disappeared from the scene. Only those serial bus systems that were supported by a majority of car producers right from the start have become established. Special importance was, and continues to be, attached to the various consortiums, each of which promotes a specific bus technology.

Today, there are essentially four bus technologies for implementing serial data exchange between ECUs in motor vehicles: CAN, LIN, FlexRay and MOST. The very robust CAN bus technology is used primarily in the convenience area (Class B) and powertrain (Class C); since 1994 it has existed as an ISO standard. The LIN bus technology represents a standardized communication concept for transmission of non-safety-critical sensor and actuator signals in Class A. FlexRay can fulfill the strictest communication requirements, such as those occurring in very safety-critical, distributed applications in the car. MOST technology is available to automotive OEMs for transmitting audio and video signals in the car. With the exception of CAN, all other bus technologies are based on initiatives by consortiums.