MOST

The MOST bus (Media Oriented System Transport) is used to transmit audio, video, voice, and data signals. This makes the bus system particularly well-suited for applications with high data rates, such as those generated by infotainment systems in modern vehicles. It is used by all major automakers. Optical fibers are used as the transmission medium.

A MOST bus system is always configured in a ring topology. A maximum of 64 devices can be active in a MOST network. The network is plug-and-play capable, making it easy to add or remove devices. Since the MOST bus system supports all seven layers of the ISO-OSI data model, this bus system is more accurately classified as a protocol layer.

In the network, a master coordinates operations by regularly transmitting MOST frames into the ring. These frames begin with a preamble that allows the slaves to maintain continuous synchronization. A total bandwidth of 150 MBaud is available for the transmission of streaming data.

In addition, MOST includes a channel for sending control messages. This allows devices and communication to be configured.

Unlike nearly all other bus systems and protocols used in vehicle diagnostics, MOST is not an open ISO standard but is subject to specific licensing terms set by the MOST Cooperation.