Civil Engineering Reference
In-Depth Information
Fig. 2.7
Schematic and application of a single star topology
2.1.6
Network Topologies
In modern cars, different topology concepts are used. In industrial applications, the
linear bus topology is preferred. The different topologies are:
• Single star
• Twin star
• Linear bus
• Hybrid topology
2.1.6.1
Single Star
In the single star topology (Fig.
2.7
), all stabs are connected in the centre of the star.
Only one termination resistor (60 Ω) is used in this single star architecture. The
advantage of this topology is the flexibility and the possible high number of nodes
in a network. The length of each wire can be up to 9 m. The maximum baud rate in
this topology is 500 kbaud. Higher bus rates are not possible. The ringing at the end
of a dominant bit is very long and dominates the maximum baud rate.
2.1.6.2
Twin Star
The twin star topology consists of two single stars, which are connected to each
other (Fig.
2.8
). With this kind of topology, an optimized adaption wiring harness is
possible. The termination resistors are located in the centre of each star. The maxi-
mum baud rate is also 500 kbaud.
2.1.6.3
Linear Bus Topology
The linear bus topology is used in the industrial world and in cars (Fig.
2.9
). For cars, it
is not flexible enough, but it allows baud rates up to 1 Mbaud. In the ISO 11898-2, the
recommended stub length is maximum 30 cm. The total length should be below 40 m.
