FlexRay-FlexRay synchronization with CANoe as gateway
One FlexRay bus provides a global system time on which all ECUs can synchronize. When two FlexRay buses are required, they run normally independently of each other. Even if both buses implement the same schedule, they have an offset to each other and they possibly drift. The synchronous FlexRay time for ECUs on the different buses gets lost.
Moreover, when data must be transferred from one bus to the other, a so-called FlexRay – FlexRay gateway creates a non-negligible delay in terms of multiples of the cluster’s period (in any of the directions), because of the time-triggered bus access. For event-triggered buses (like CAN) the delay only depends (on low bus loads) nearly on the reaction delay (which is much smaller than the message’s cycle period) of the gateway application.
Additionally, due to a normally non-existing synchronization between both FlexRay clusters, they will drift to each other. Therefore, the routing delay may vary during run-time and is in-deterministically.
For details, see Vector Application Note:
AN-IND-1-010 FlexRay-FlexRay synchronization with CANoe as gateway