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Single Pair Ethernet and ASi-5 – When and Where does Which Technology make Sense?

What is Single Pair Ethernet?

Single Pair Ethernet (SPE) enables the transmission of data via Ethernet with just one twisted pair of wires.Transfer rates of 10 MB/s to 1 GB/s are currently possible. In contrast, the previous Ethernet technology used in industrial applications requires two or four cable pairs. The two-wire design of Single Pair Ethernet therefore reduces the cabling weight by almost half compared to conventional categories of Ethernet cables.


Furthermore, SPE is used to standardize power transmission. Through Power over Dataline (PoDL), both power and data with an output of up to 50 W are transported on a cable, which are not compatible with the current Power over Ethernet standard.


The idea to develop SPE technology came from the automotive industry. That's because wiring accounts for a large part of the vehicle's weight. In industrial applications, Ethernet with SPE is intended to close the gap between the control system level and the field level, i.e., the sensor/actuator networks, and to create a consistent Ethernet connection. For this reason, SPE cables and connectors are significantly smaller, lighter, and easier to install than previous industrial Ethernet solutions, and ASi needs no connectors at all.

ASi-5 Eliminates the Need for Connectors

Today, the latest ASi generation is already conveniently and cost-effectively replacing many conventional Ethernet connections in the field. Besides the lower costs of ASi, its greatest advantage is that penetration technology makes it possible to completely eliminate the need for prefabricated cables and connectors.


What's more, ASi-5 is a completely redesigned system that is optimally adapted to the requirements of Industry 4.0. Thanks to the high data size and short cycle times, which are more than sufficient for many Ethernet-based automation solutions, many things that were previously impossible with AS-Interface can now be realized.


For this reason, ASi-5 is already being used to replace conventional Ethernet connections cost-effectively and conveniently. We offer a wide range of solutions for this. Here are three examples:

  • Our ASi-5 Motor Module for SEW MOVIMOT® (BWU4068) enables the same data image as with an optionally available PROFINET interface from the manufacturer.
  • The ASi-5 Motor Modules for Interroll EC5000 AI (BWU4246, BWU4212) offer the same drive control data as the manufacturer's Ethernet-based roller controllers.
  • With our ASi-5 IO-Link Masters (e.g., BWU4067, BWU3819), you can save up to 40% on a medium-sized application with 50 IO-Link devices compared to comparable Ethernet solutions – while achieving the full performance of IO-Link.


More information about ASi-5

Technical Comparison – ASi-5 vs. Single Pair Ethernet


Switch instead of protocol converter

Unlike ASI-5, SPE does not require protocol converters. Through the physical layer of SPE, data is captured in a unified protocol at the information source (sensor) and transmitted via switches – non-smart distributors – to the output location of a network participant (computer). To prevent loss, this data is temporarily stored in the switch.

The ASi-5 gateway, on the other hand, is a smart network participant with an integrated switch. It additionally "translates" the data into ASi-5 ASIC for the higher-level control system. Likewise, the data – together with diagnostic messages – can also be viewed directly on the display or conveniently via remote access.

Fig.: SPE enables communication at all levels with a single protocol. Therefore, no gateway is required and the intermediate "protocol conversion" is no longer necessary.

ASi Cable = Extremely Simple Installation + Efficient Power Distribution

ASi or ASi 5 lets you take advantage of the proven piercing technology. Thanks to ASi piercing technology, modules are simply plugged onto the profile cable without a connector – with maximum contacting reliability. The profile cable is simply taken from the cable reel in the desired length and the modules are then placed exactly where they are needed, down to the millimeter. No unnecessary cable runs are needed, as is inevitable with pre-assembled cables, and no expensive connectors or T-pieces are necessary.

Further advantages include complete freedom of topology and efficient power distribution. The black profile cable transmits 16 A or 20 A, depending on the cable cross-section – thus significantly more power than typical round cable solutions.


More information about ASi cable

Fig.: Four gold-plated needles always penetrate vertically into the profile cable to ensure perfect contacting.

Fig.: With the ASi profile cable, simple branches are easily possible at any point in the system. The topology is therefore freely selectable.

Conclusion: Single Pair Ethernet and ASi-5

What is the conclusion of the comparison between ASi-5 and Single Pair Ethernet? Making a final conclusion is not easy with the information available to date. The following statements can be made, however:

  •  "A lean, lightweight, yet high-performance Ethernet infrastructure was needed to enable the industry to digitize the field level and move towards IIoT." (Source: single-pair-ethernet.com)
  • Single Pair Ethernet has its strengths thanks to high data size, high data volumes, and through the use of a switch instead of a protocol converter.
  • ASi was developed for typical field applications in machines and systems, which is precisely where its strengths lie.
  • ASi-5 replaces conventional Ethernet in many of today's applications, e.g., in drive technology or IO-Link.
  • Both SPE and ASi can complement Ethernet in the field with their lean, lightweight, yet powerful infrastructure.

FAQs about Single Pair Ethernet

Users have a choice: Shielded/unshielded options are available for each SPE standard. However, these cable variants are not necessarily mentioned in the specifications. Depending on the standard, which in turn determines the speed, the cable length can be significantly increased by using a shielded SPE cable. For example, from 15 m (unshielded) to 40 m (shielded) at 1 Gbit/s as defined by 1000BASE-T1 or IEEE 802.3bp.

The SPE System Alliance consortium makes the following statement on its homepage (singlepairethernet.com): "A complete 360° enclosed stainless steel sheath surrounding the entire connector [SPE] provides excellent electromagnetic compatibility (EMC)." It can therefore be assumed that SPE is EMC-resistant in the industrial environment, especially with the connector and cable shielding mentioned above. Due to the current stage of development, no further details are available.

SPE uses the so-called multidrop method, which does not exist in conventional Ethernet. This means that the reach is shorter with SPE, but also that only simple T-pieces without switches are required. Moreover, the cables and connectors are significantly smaller with SPE.

Since PROFINET is an Ethernet-based protocol, it can basically be transmitted via SPE. SPE is just a new physical layer, i.e., new hardware for the transfer of information from protocols such as Ethernet.


The different physical layers are connected via a switch to enable them to communicate with each other.

Due to the current stage of development, no precise details have been published to date. However, it can be assumed that the wiring in such an application scenario is based on the implementation using conventional Ethernet.


It would make sense to connect a switch with 32 ports, each with the data rate of 10 Mbit/s, to a control system via a 1 Gbit/s port. This is the only way to ensure that every port can use the full bandwidth at all times. Most SPE applications in the field could be a combination of switches and point-to-point connections. The point-to-point connections, each limited to 1,000 m in length, would connect the attached sensors to the switch

SPE and ASi-5 both offer a lean, lightweight, yet powerful infrastructure. As a result, they make Ethernet in the field superfluous in many aspects. At the same time, SPE and ASi-5 make it easier for the industry to digitize the field level – and thus take the step towards IIoT.

How is the SPE standard with the data transfer rate 10 Mbit/s defined? How are the rules for connecting participants defined here (e.g., for multidrop)?


The corresponding standard is IEEE 802.3cg. It includes a

  • ShortReach channel (point to multipoint) in a 25-m channel with max. 8 participants and

  •  a classic point-to-point channel with a channel length of up to 1,000 m.

Questions about ASi-5 and Single Pair Ethernet?

We would be happy to assist you.