The Importance of Automotive Ethernet Standards

The adoption and transformation of Ethernet by original equipment manufacturers (OEMs) and Tier 1 automotive companies began several years ago. Amendments to the Institute of Electrical and Electronics Engineers (IEEE) 802.3 standard for automotive applications include IEEE 802.3bw (100BASE-T1, 100Mbps, copper) and IEEE 802.3bp (1000BASE-T1, 1Gbps, copper).

These revisions are significant because they will incorporate more requirements and features for cars, including the explosive growth of in-vehicle infotainment systems, advanced driver assistance systems, on-board diagnostic systems, and car-to-the-world connectivity technologies (5G, V2X).

The revision mainly addresses the needs of the physical layer (PHY). The PHY interfaces involved include the electrical interface and the network, which are also called the media dependent interface (MDI). A key factor in the automotive-specific PHY specification is MDI signaling, which can both solve electromagnetic interference (EMI)/electromagnetic compatibility (EMC) issues and support the use of unshielded single twisted pair cables in the network. This reduces the weight and cost of wiring, which is an important factor for automobiles.

Reduced weight and lower costs are not the only benefits of connected cars . Ethernet facilitates switched networks that enable higher bandwidth and higher data rates than other shared bus topologies (Controller Area Networks, Local Interconnect Networks, FlexRay, and Media Oriented Systems Transport).

The adoption of a switched network approach in vehicle communication systems will bring many of the same limitations that previous shared bus topologies have, such as reliability, EMI/EMC, compliance with electrical interface specifications, and functional compliance. The last two items mentioned above will affect interoperability with other devices connected to the network. The number of network-connected in-vehicle sensors is increasing, and these sensors may come from different suppliers, and each sensor may use a different PHY (see Figure 1).

Figure 1: Distributed vehicle sensor network

Early on, several automotive industry players realized that a formal collaboration was needed to address EMC/EMI and interoperability issues. The One Pair Ethernet (OPEN) Alliance (OA) Special Interest Group (SIG) was formed in 2011 and now has more than 300 members, including OEMs, suppliers, and technology providers. OA not only guides the development of revisions to the Ethernet standard for automotive, but also develops compliance test specifications for PHYs to ensure threshold functionality and performance of different components from various suppliers, thereby achieving the necessary system integration reliability and ease of integration required by the automotive industry.

The PHY compliance test specifications developed by OA include three main aspects: EMC/EMI performance, functional and IEEE standard electrical compliance, and interoperability between PHYs from different manufacturers. The specific test specifications are:

The above are collectively referred to as 100BASE-T1 PHY interoperability and compliance tests, and these test specifications are developed by OA Technical Committee 1 (TC1). Together, they constitute the main compliance tests that technology vendors must pass, demonstrating the threshold functionality and performance required by the standard. They also give OEMs and suppliers tools to compare PHYs.

TC1 appointed three independent laboratories to provide testing services to the industry, each responsible for a major aspect of the PHY compliance test specification. As a member of the OA, TI participated in the testing. For example, TI's DP83TC811R-Q1 and DP83TC811S-Q1 successfully passed various compliance tests performed by the three laboratories, including interoperability. Interoperability testing evaluates the compatibility of the device under test (DUT) with other link partner (LP) devices in various operating scenarios, where the DUT may act as a master or slave in the system.

The tested features include:

Successful independent interoperability testing, as well as EMI/EMC and PHY functional testing, demonstrates that the DP83TC811R-Q1 and DP83TC811S-Q1 are fully qualified Automotive Electronics Council (AEC) Q-100 PHYs for 100BASE-T1 (IEEE 802.3bw, BroadR-Reach) networks. The devices are fully supported by evaluation modules, input/output buffer information specification (IBIS) models, and software drivers.