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Grundlagen FlexRay BasicsV 1.1 28
As a security measure, the Action Offset Point (APO) in each slot has been introduced (see
Figure 2.24). With the help of the APO, it is possible to compensate slight timing differences
between ECUs, and to compensate for bus delay, without interfering with the global
synchronization process.
Figure 2.24 Action Point and Action Point Offset [VeSc11]
The APO is derived from the actual Action Point (AP) of the sender. The received frame can
be shifted in between the start and the end of a slot. This guarantees, that all ECUs receive a
message in the correct slot.
Figure 2.25 Static Segment Frame [FRPS05]
While transmitting and receiving, the Bus Driver has to switch between these two modes,
because the FlexRay bus is used bi-directional. Therefore, for activating the Bus Driver after
the Action Pont, a Transmission Start Sequence (TSS) is used. The length of the TSS varies
between 3 and 15 bit, depending on the number of Bus Drivers connected to the channel,
Bäurle 12.10.2012