Single Pair Ethernet Is Revolutionizing Industrial Communication

2023 Author : Hannah Pearcy | [email protected] . Last modified: 2023-05-24 11:12

When Robert Metcalfe christened his proprietary network in the Xerox labs in Palo Alto in the 1970s with arm-thick cables running along the ceiling, he most likely had no idea the importance of this LAN network. However, the naming already shows the intention: The term Ethernet goes back to the term ether, coined in the 17th century, an "omnipresent medium" with which the propagation of electromagnetic waves was explained like light.

The "ether declaration" was later discarded, the Ethernet from Xerox, Intel and DEC developed into an open standard that formed the basis for the current IEEE 802.3 standard.

Originally designed for office environments with RJ45 connectors, variants of Ethernet under the generic term Industrial Ethernet are now used in industrial automation for time-critical applications such as high-speed machines.

However, sensors and actuators are difficult to implement here, since office RJ45 connectors and cables are only of limited suitability for the industrial environment. They are usually encapsulated or enclosed for the harsh environmental conditions and therefore require a lot of space. In contrast, high data rates as in the office environment play a rather minor role in industry. Long transmission lengths, simple handling and IP protection classes are important.

These constraints pushed efforts to expand Industrial Ethernet (four twisted pairs are standard) with an additional physical layer, so to speak, “downwards”. Developments from the automotive industry were based on a twisted pair of copper wires: the Single Pair Ethernet, SPE for short. A proposal from Broadcom (BroadR-Reach automotive specification) is specified by the automobile manufacturers.

Single Pair Ethernet: The potential in industry

In industry, the Ethernet with SPE has the potential to close the gap between the control level and the field level, i.e. the sensor / actuator networks. A continuous Ethernet connection down to the lower field level offers technical and economic advantages: SPE cables and connectors are significantly smaller, lighter and easier to install. The low-cost SPE scores especially with compact I / O interfaces.

Transfer rates of 10 Mbit / s (1000 m) to 1 Gbit / s (40 m or 10 m) can currently be achieved. Time-synchronous, deterministic transmission of data, TSN (Time-Sensitive Networking), is also possible. It is also favorable that the sensors (periphery) can be supplied with current / voltage with powers up to 50 W via the same pair of wires (Power over Data Line - PoDL, pronounced “poodle”).

Consistent networking across all levels

SPE thus enables the consistent intelligent, scalable deterministic networking of an application across all levels. Various companies are already developing products (cables, connectors, switches, I / O modules, etc.) that implement current and future SPE standards. In order to ensure the compatibility between the proprietary devices, cables and connectors from the various manufacturers, those involved pushed ahead with international standardization, especially Harting. In addition, the semiconductor industry should be motivated to develop new PHY chipsets. Analog Devices, for example, has now done this with the Chronous series.

Standardization through IEEE, ISO / IEC and TIA

Some time ago, the IEEE802.3 committee commissioned ISO / IEC JTC 1 / SC 25 WG 3 and TIA to propose and standardize connectors. Numerous well-known manufacturers and bodies took part in this selection process.

The IEEE802.3 defines application and transmission channel. ISO / IEC JTC 1 SC25 WG3 describes the transmission requirement and the parameters of the passive cabling structures in industry, buildings, smart homes and data centers. The electrical and mechanical parameters define the IEC SC 48B (plug connector) and the IEC SC 46C (cable). The current version of the document describes possible connectors that can be used on the MDI (Medium Dependent Interface). These SPE connectors are described in the IEC 63171-X series of standards. They differ in terms of mating face, dimensions and mechanical properties.

In the IEEE 802.3cg (SPE 10 Mbit / s, 1000 m) the electrical properties of connectors are explained for the first time under the point MDI. In addition to terminals, connectors according to IEC 63171-1 (LC style) and IEC 63171-6 (T1 industrial style) are named as MDI.

IEC 63171: The basic standard for SPE connectors

The proposals for connectors tested by the standardization bodies ISO / IEC at the beginning of 2018 had to meet basic requirements, which are defined in the basic standard SPE connector IEC 63171 "General Requirements and Test". Since January 23, 2020, IEC 63171-6, the first standard for industrial SPE mating faces, has been published and available. However, the standardization work has not yet been completed.

User organizations such as PI (PROFIBUS and PROFINET International) and ODVA are currently evaluating the topic.

The first draft for SPE connectors for industrial and industry-related applications is based on a mating face from Harting (development started in 2014), which was submitted to SC48B in 2016 and published as IEC 61076-3-125 up to CD status (Committee Draft for comments) has been. This was followed by CommScope (IEC 63171-1) and Reichle & De Massari (IEC 63171-2) for M ₁ I ₁ C ₁ E ₁ applications (building cabling).

IEC 61076-3-125 was updated in collaboration with TE Connectivity to IEC 63171-6 for M ₂ I ₂ C ₂ E ₂ and M ₃ I ₃ C ₃ E ₃ applications and will be published on January 23, 2020 as a standard been. For industrial applications, IEC 63171-5 for M ₂ I ₂ C ₂ E ₂ and M ₃ I ₃ C ₃ E ₃ applications is also in the works, based on the connector face from Phoenix Contact (CD status), a publication of the standard is planned for May 2020.

Technical solutions in practice

In practice, it looks like two consortia want to advance technical solutions. On the one hand, these are the "SPE Industrial Partner Network", which, in addition to the founding members Harting, TE Connectivity, Hirose, Würth Elektronik, Leoni, Murrelektronik and Softing IT Networks, now includes another 9 partners that will be announced shortly. On the other hand there is the "SPE Technology Cluster", consisting of Phoenix Contact, Weidmüller, Reichle & De Massari, Telegärtner, Belden, Rosenberger and Fluke Networks.

The SPE Partner Network advocates the T1 Industrial interface defined by ISO / IEC JTC 1 / SC 25 / WG 3 and TIA42 in 2018 according to IEC 63171-6 as a uniform Media Depended Interface (MDI). For the reliable establishment of the entire future SPE ecosystem, standards for transmission protocols, cabling and device components are also shared.

The SPE Technology Cluster supports the plug-in faces of IEC 63171-2 (office environment) and IEC 63171-5 (industrial environment) from Phoenix Contact that have been incorporated into the standardization. They define IP20 and IP65 / 67 plug-in faces for single and four-pair data transmission via SPE with the aim of ensuring a coordinated infrastructure for devices, connectors, cables and measurement technology.

Single pair Ethernet: what's next?

Just like classic Ethernet, single pair Ethernet is not a static technology, it is being consistently developed. The user can look forward to numerous improvements. One thing is certain: SPE opens up a large number of new application options for structured cabling in the automotive industry, in applications in industry and process control, but also in office environments and data centers. Belden [3] gives a time horizon for upcoming developments: The automotive market has been developed by SPE since 2015. The process industry is expected to follow in 2022; transportation 2025; Robotics and factory automation in 2025 and building automation in 2028.

The market for SPE in industry is currently defined by standards, product developments and partnerships. The SPE Partner Network has the first standard. The first general meeting is to take place at the Hanover Fair. Tech Days are planned for the current year.

Weidmüller and Phoenix Contact presented the first prototypes for the PLC (based on IEC 63171-5), which are 0.5 times smaller than the RJ45 (IP20 or IP67, dielectric strength 2.25 kV). Completed series for M8 sensor connections in protection class IP20 are to follow at the Hanover Fair.

This article first appeared on our partner portal Elektronikpraxis.de.

credentials

[1] White paper Single Pair Ethernet from Harting

[2] Whitepaper Single Pair Ethernet from Weidmüller

[3] Whitepaper Single Pair Ethernet from Belden

Article files and article links

Link: This article was first published in the special edition Electromechanics I of ELEKTRONIKPRAXIS (Download PDF).