The subject matter contained within this SAE Information Report is set forth by the Class A Task Force of the Vehicle Network for Multiplexing and Data Communications (Multiplex) Committee as information the network system designer should consider. The Task Force realizes that the information contained in this report may be somewhat controversial and a consensus throughout the industry does not exist at this time. The Task Force also intends that the analysis set forth in this document is for sharing information and encouraging debate on the benefits of utilizing a multiple network architecture.

Three Classes Multiplex Networks

The Vehicle Network for Multiplexing and Data Communications (Multiplex) Committee has defined three classes of vehicle data communication networks.

Class A

Low-Speed Body Wiring and Control Functions, e.g., Control of Exterior Lamps

Class B

Data Communications, i.e., Sharing of Vehicle Parametric Data

Class C

High-Speed Real Time Control, e.g., High-Speed Link for Distributed Processing

Interrealtionship of Classes A, B, and C

The Class B Network is intended to be a functional superset of the Class A Network. That is, the Class B Bus must be capable of communications that would perform all of the functions of a Class A Bus. This feature protects the use of the same bus for all Class A and Class B functions or an alternate configuration of both buses with a “gateway” device. In a similar manner, the Class C Bus is intended as a functional superset of the Class B Bus.