Clock synchronization
Distributed communication systems depend on a common and consistent view about time. The clocks of the communication controllers in the network, however, can be influenced by temperature and voltage fluctuations, or production tolerances of the timing source, e.g. an oscillator, which leads to a differing internal time bases. The FlexRay protocol uses a distributed clock synchronization mechanism. In other words, there is no single physical reference clock. On the contrary, each node individually synchronizes itself to the cluster by observing the timing of transmitted sync frames from other nodes. Thus, a virtual reference clock is established using a distributed fault-tolerant clock synchronization algorithm. The deviation to this reference clock is then periodically measured in regard to phase and frequency deviation in order to ensure offset and rate correction respectively. If necessary, the clock gets adjusted accordingly.
