Feature: Interconnections
Industrial SPE moves beyond its automotive legacy
By Dr Michael Hilgner, Senior Technology Architect, Cornelia Eitel, Senior System Architect, both at Belden, and Timo Zipperle, Junior Product Manager, field switches and accessories, Hirschmann Automation
I
IoT and Industry 4.0 applications that rely on high volumes of data and AI-based analytics are made possible through innovations like Single-Pair Ethernet (SPE). The technology helps industrial spaces
achieve flexible, transparent, sensor-to- cloud connectivity whilst eliminating the space, distance, bandwidth and power limitations associated with traditional multi-pair Ethernet, industrial fieldbus and/or sensor systems and cabling.
SPE and its adoption SPE is a physical layer, standardised by IEEE 802.3 through multiple projects for diverse combinations of segment lengths and bandwidths. The first SPE projects, IEEE 802.3bw
on 100Mb/s and IEEE 802.3bp on 1Gb/s, released in 2015 and 2016 respectively, were driven by the automotive industry’s need for space-saving, lightweight, cost- efficient, in-vehicle Ethernet cabling and, thus, it had defined 15m segments with unshielded cables; see Table 1.
Other sectors, such as industrial
automation and transportation, were served by the added 40m segment with IEEE 802.3bp, which uses shielded cables; however, chip manufacturers widely ignored that when specifying SPE transceiver capabilities, as sales volumes were clearly still dominated by automotive demand. In 2019, SPE standard IEEE 802.3cg
for 10Mb/s was released. It includes a “true” industrial segment with shielded cables for distances of up 1,000m, referred to as 10BASE-T1L. For the automotive sector, 10BASE-
T1S uses unshielded cables, with reach of 15m. For comprehensiveness, a third
segment enables multidrop of up to eight devices on a shared cable, with lengths to 25m. 10BASE-T1L, together with IEC TS 60079-47 that defines intrinsic safety protection for hazardous areas, was also the basis for the specification of Ethernet-APL, the process industry’s
26 July/August 2024
www.electronicsworld.co.uk
solution for field devices with Ethernet connectivity in potentially explosive environments. The design and features of early
SPE transceivers clearly favoured automotive in-vehicle applications where the Ethernet network is fully engineered, which means that the transceivers’ configurations are developed by the manufacturer for optimal communication with vehicle peripherals. To reduce costs, plug-and- play features were not implemented. Other sectors suffered from the
absence of the auto-negotiation feature, which is optional in all SPE standards. As its name indicates, the auto- negotiation feature ensures that, among other fundamental coordination tasks, two connected transceivers exchange data with the maximum “negotiated” bandwidth supported by both, even if their individual maximum bandwidth capabilities are different. For non-engineered applications, this feature is key to widespread adoption,
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