Applications - CAN System Engineering - page 256

Fig. 5.1 Bus protocols and their bandwidth
The controller area network (CAN) bus protocol is currently applied in two dif-
ferent variants which correspond to class B and class C of the SAE logic.
Figure 5.1 shows typical bus protocols for automotive applications which are ei-
ther already in use or in development. They are ranked according to their bandwidth.
Simple functions can be covered by the Local Interconnect Network (LIN) bus
which allows for a data transmission of up to 20 kbit/s. The low-speed CAN bus can
operate with a data rate of 5 kbit/s and up to125 kbit/s and in a network of up to 32
nodes. The strengths of the low-speed CAN are fault tolerance and the possibility to
transmit over a single wire connection.
Due to the ever-increasing data rates and the ongoing trends towards higher
functional integration along with a decreasing cost advantage of the low-speed
CAN versus the high-speed CAN (Class C), low-speed CAN will soon go out of
use. There is a trend visible that, in future vehicle architectures, the cost-effective
LIN will be used for rather elementary functions. More demanding functions will
be realized using the high-speed CAN and/or FlexRay, especially for time-critical
or safety-critical applications. Media Oriented Systems Transport (MOST) will be
used for multimedia applications in the infotainment and entertainment domain. In a
broader perspective, Ethernet will play a significant role for system interconnection
and can replace some of the traditional bus protocols. First applications for vehicle
flash and diagnostic access are already in the market.
The electronic system architectures which we find today in modern cars will
not change suddenly. Different bus protocols will be used even in the coming years
since a radical change of the architecture would create huge costs and high quality
risks. Even if the goal of the system architect remains to establish a more homoge-