A Comparison of TTP/C and FlexRay

With the announcement of BMW and DaimlerChrysler to 15 develop the new time-triggered protocol FlexRay for safety critical “Xby-Wire” applications, the time-triggered technology is moving into the mainstream of the automotive electronics market. This paper compares the established protocol TTP/C with the new protocol FlexRay from BMW and DaimlerChrysler. This comparison is based 20 on the sparse information about FlexRay that is currently in the public domain and is therefore subject to revisions as a more detailed specification becomes available. This paper identifies five failure scenarios that have the potential for a single node failure to result in a system-wide safety-relevant incident. It discusses how TTP/C controls 25 these scenarios, but cannot answer the question how FlexRay handles these failures, because the information about FlexRay that is in the public domain does not address these safety relevant issues. The comparison comes to the conclusion that FlexRay and TTP/C were designed against the same set of automotive requirements, but that 30 there is a difference in goals: The inherent conflict between flexibility and safety is tilted towards flexibility in FlexRay and safety in TTP/C.