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Data exchange in a Flexray cluster is based on the TDMA method: All communication is organized in communication cycles, and each communication cycle is made up of a defined number of time slots exclusively reserved for transmission of messages. Communication in a FlexRay cluster is characterized by a hybrid communication structure.
Each communication cycle comprises a static (synchronous) and a dynamic (asynchronous) communication segment. The static communication segment is provided for deterministic data transmission. Bandwidth in the dynamic communication segment, on the other hand, is available for need-based data transmission.
Each communication cycle exhibits two other time segments. The “symbol window” segment serves to check the operation of the bus guard. During the “Network Idle Time – NIT” segment, the FlexRay nodes compute the correction factors required for synchronization of their local clocks. If necessary, an offset correction is performed at the end of the NIT (rate correction is always performed distributed over the entire communication cycle). No data is transported during the NIT.
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