Grundlagen FlexRay - Institut fÃ¼r Automatisierungs- und ...

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Grundlagen FlexRay BasicsV 1.1 38 2.14 Scheduling and Cycle Multiplexing The scheduling is defined during the network design. By defining static and dynamic slots, a fixed time frame is provided. This enables the unique assignment of frames to the corresponding slots in each channel. The number of slots is constant and cannot be changed after the network design. The flexibility and the usage of the bandwidth is defined during development. Table 2.4 Scheduling example [VeSc11] In Table 2.4, a scheduling for nodes K, L, M, N and O is provided. It is allowed to send different frames in different cycles for the same slot. This is called Cycle Multiplexing. For Cycle Multiplexing, the following information is needed: • Slot-ID in the cycle 0...2047 • Base or Start Cycle 0...63 • Repetition Factor {rep = 2 x with 0 ≤ x ≤ 7} • Channel {A, B, A&B} • Name of the node If we take a look on node M in Table 2.4, we can see that it is assigned slots 2 and 7. In the static segment, node M uses channel A only. Here, it sends three different frames, e.g. frame y, which has a base cycle of 2 and a repetition factor of 4. That means, that frame y is sent in cycle 2 for the first time, and after that every 2+4n (with n = 1..15) cycle. In the dynamic segment, it is acceptable for different nodes to use the same slot. Further, the nodes are allowed to send different frames, and different nodes may use the different channels of a slot. Again, all frames have to provide the information needed for Cycle Multiplexing. If we take a look at slot 7, we can see that node M shares this slot with nodes L and O. In a cycle, it is possible to send different frames from different nodes. It is also possible for Channels A and B to be asynchronous, i.e. for a given point of time, A has a different slot id than B. Bäurle 12.10.2012
Grundlagen FlexRay BasicsV 1.1 39 Literature [Joch07] Jochim, M.: Zeitig steuern In: c’t Magazin für Computertechnik, http://publications.markusjochim.de/2007/FlexRay_Artikel_CT/Zeitig_steuern.pdf H. 2 S. 190-195, 2007 [Göhn10] Göhner, P.: Automatisierungstechnik I. Uni Stuttgart, Skript SS2010, S. 227…229 [Flex11 FlexRay Consortium: www.flexray.com, Stand 02/2011 [FRPS05] FlexRay Consortium: FlexRay Communications System Protocol Specification, Version 2.1 Rev. A, 2005 [FREPLA06] FlexRay Consortium: FlexRay Communications System Electrical Physical Layer Application Notes, Version 2.1 Rev. B, 2006 [FREPLS06] FlexRay Consortium: FlexRay Communications System Electrical Physical Layer Specification, Version 2.1 Rev. B, 2006 [FRRS05] FlexRay Consortium: FlexRay Requirements Specification, Version 2.1, 2005 [LIN11] LIN Consortium: http://www.lin-subbus.org/, Stand 02/2011 [MOST11] MOST Cooperation: http://www.mostcooperation.com/home/index.html, Stand 02/2011 [Vect11] Vector Informatik GmbH: www.vector.com, Stand 02/2011 [VeSc11] Vector Informatik GmbH: Unterlagen zum FlexRay Workshop, In: CANoe/CANalyzer.FlexRay Workshop, 2011 Bäurle 12.10.2012
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