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Grundlagen FlexRay BasicsV 1.1 17
Unterminiertes Kabelende
Figure 2.8 Open termination [FREPLS06]
All terminating resistors in a branch are parallel. The resulting resistance R DCLoad has to be
between 40 and 55Ω. The usage of a choke is allowed, too. Depending on the topology, there
are different setups for bus termination and the placement of the resistors. The resulting
resistance has to be in the defined range for R DCLoad .
2.4 Physical topology
The physical topology describes the structural setup of the network. Figure 2.9 shows the
most basic passive connection between two nodes, called Point-to-Point or Peer-to-Peer. The
maximum length of the cable lBus is 24m. Both ends have to be terminated with resistors.
Figure 2.9 Point-to-Point connection [FREPLS06]
There are two additional passive bus topologies, the linear passive bus (Figure 2.10), and the
passive star (Figure 2.11). The linear passive bus extends the Point-to-Point connection by
additional nodes. The number of nodes is defined between 4 and 22.
The maximum bus length lBus = lStub n + lSpliceDistance n,m + lStub m = 24m must not be
exceeded. Typically, the stub lines lStub 2 or lStub 3 connecting to the main bus are only a few
centimeters long, and do not contain additional stub lines.
Bäurle 12.10.2012