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Figure 2: Shown is an example of PAM- 3 signaling as employed by BroadR-Reach.
Benefits of Automotive Ethernet
Let’s consider some of the benefits of using automotive Ethernet, while
comparing it to other protocols that see usage in the automotive environment.
Automotive Ethernet provides higher bandwidth data transmissions compared
with LIN ( 19. 2 kb/s), CAN FD (15 Mb/s), FlexRay ( 10 Mb/s), and MOST ( 25,
50, or 150 Mb/s shared). The LIN protocol really only sees usage for very low-bandwidth applications controlling body electronics such as windows or lights.
CAN and/or CAN FD offers a flexible data rate in the 15-Mb/s range but
still is limited to relatively low-bandwidth applications. The same is true
of FlexRay, which does offer the advantage of redundancy with its pair of
parallel data lines. If one line is damaged, the other can take over its function.
Thus, it has applications in safety or mission-critical functions such as steering
or braking control.
Media-Oriented Systems Transport (MOST) is an infotainment standard
with data-rate variants of 25, 50, and 150 Mb/s. The latter is a higher aggregate
bandwidth than the 100 Mb/s of automotive Ethernet. But a key distinction is
that MOST’s 150 Mb/s is shared across the ring-topology network, while each
dedicated automotive Ethernet link provides the full 150-Mb/s bandwidth
Thus, Automotive Ethernet offers higher bandwidth than do most of the
prevalent automotive serial-data standards. Being that it relies on a single
unshielded twisted pair, it also provides a low-cost cabling scheme. Cabling
weight is about 30 percent less than shielded cabling with connectivity cost
savings of about 80 percent.
Automotive Ethernet meets the stringent EMC and EMI requirements as
well as the temperature-grade requirements of the automotive application
space. A final benefit is that all of the software interfaces for the upper layers
of the Ethernet stack are exactly the same as for standard Ethernet. If you’ve
ever worked with Ethernet in the past, you’ll probably already have all of the
software and test tools covered.
BroadR-Reach vs. 100Base-T1
Both BroadR-Reach and 100Base-T1 are explicitly intended for automotive use
and there’s quite a bit of overlap between them. Let’s look a little more closely
at BroadR-Reach applications and also explain the differences between it and
The configuration of a BroadR-Reach link (Figure 3) shows that the protocol
offers full-duplex operation at a data rate of 100 Mb/s over a simple twisted
pair of wires. At both ends of the link are BroadR-Reach PHY chips that send