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The constantly increasing demand for additional functions and convenience in the vehicle calls for the use of ever more wide ranging electronics. Whereas the first Audi A8 model introduced in 1994 required a maximum of only 15 control units for implementation of all vehicle functions, this number will increase five fold in the Audi A8 ´03. Number of control units orking ee of netw Degr The increased use of electronics also required a new approach to data transfer between the individual control units. A first important step towards this was the introduction of the CAN data bus at Audi in the mid 1990s. This system does however have its limitations, particularly with regard to the transmission rates involved in the infotainment sector. The only solution is therefore to employ transmission systems designed to deal with specific requirements. Service and diagnosis functions will also benefit from this development. Contents Page Introduction 4 LIN bus The single wire data bus Introduction . 6 Data transfer . 9 Messages . 11 Diagnosis . 16 MOST bus The optical data bus Introduction 17 Design of control units . 20 Optical fibre . 23 Attenuation in optical bus . 27 Ring configuration of MOST bus . 30 MOST bus system statuses 31 Frames . 33 Operating sequences in MOST bus . 36 Diagnosis . 41 TM Bluetooth The wireless data bus Introduction 44 Operation . 46 Diagnosis . 49 Diagnosis bus . 50 The Self Study Programme contains information on design New Attention features and functions. Note The Self Study Programme is not intended as a Workshop Manual Values given are only intended to help explain the subject matter and relate to the software version applicable at the time of SSP compilation. Use should always be made of the latest technical publications when performing maintenance and repair work. 3 Introduction Topology Adaptive cruise control D