byteflight~A new protocol for safety-critical applications 2000-05-0220

The permanently increasing number of convenience and safety functions leads to higher complexity of in-car electronics and the rapidly growing amount of sensors, actuators and electronic control units places higher demands on high- speed data communication protocols. Safety-critical systems need deterministic protocols with fault-tolerant behavior. The need for on-board diagnosis calls for flexible use of bandwidth and an ever-increasing number of functions necessitates a flexible means of extending the system.

None of the communication solutions available on the market until now (like CAN or TTP) have been able to fulfill all these demands. To solve these problems, BMW together with several semiconductor companies has developed a new protocol for safety-critical applications in automotive vehicles.

The byteflight protocol combines the advantages of the familiar synchronous and asynchronous protocols and guarantees high data integrity at a data rate of 10 Mbps and an information update rate of 250 μs. Additional characteristics are collision-free bus access, guaranteed latency for a certain number of high- priority messages, high flexibility, easy system extension, dynamic use of bandwidth and low system costs.

In order to reduce EMI, a physical layer solution using optical transmission was developed. In a star net configuration with an intelligent star coupler, communication is bidirectional on a single plastic optical fiber. The transceiver chip, the light-emitting diode and the photodiode are integrated into the optical connector.

Silicon for byteflight controllers, an intelligent star coupler and physical layer transceiver as well as several development tools are available. The first application in high-volume automobile production will start within the next year and will include passive-safety and body functions.