Single Pair Ethernet and ASi-5 – when and where does which technology make sense?

The SPE technology is being developed by different associations for a variety of applications.

Each association has a different focus of work and partners or members from different industries. The following three associations are particularly important in this respect:

• Single Pair Ethernet System Alliance

It is an association of companies committed to the dissemination and development of Single Pair Ethernet solutions. Members work together to raise awareness of the advantages of Single Pair Ethernet in various applications and to promote the diffusion of SPE solutions. The activities of the SPE System Alliance focus on the entire future SPE ecosystem and not on a specific connector system or product.

• Single Pair Ethernet Industrial Partner Network

Founded by seven technology leaders in 2019, the SPE Industrial Partner Network consists of more than 50 member companies. It is an alliance of equal companies pushing Single Pair Ethernet technology as the foundation for rapid growth of the IIoT. The goal of the network is to establish SPE as a new Ethernet technology on the market in the sense of a comprehensive ecosystem with all necessary components.

• Single Pair Ethernet Consortium (SPEC)

The SPEC is a manufacturer-neutral organization for technology leaders and users in the field of building automation technology. One of the consortium's goals is to accelerate the introduction of Single Pair Ethernet in building automation technology and to push the implementation of flexible, cost-effective and reliable network solutions. The production of case studies, white papers, and reference architectures, as well as collaborative partnerships with other SPE initiatives and organizations, are also among the SPEC's goals.

Different connector types and standard sections

All associations use different connector types and standard sections that are optimized according to the requirements of the respective industry and application and are often not compatible with each other. A standardization guideline applicable to all that would ensure compatibility of the various devices and systems does not yet exist. Although there are efforts to promote standardization of connectors for SPE solutions, but so far, there is still no solution.

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.

The number of smart components in the field is increasing exponentially in the age of Industry 4.0. Cybersecurity and network security are therefore becoming increasingly important. What security measures are required for SPE and which for ASi-5? The most important difference between the two technologies in this context is the ASi Gateway, which ensures a logic break between ASi-5 and TCP/IP and represents an additional “security door”. This break in communication isolates many network nodes and thus closes security gaps. Those who are responsible for network security can thus concentrate on significantly fewer devices and check them more carefully.

Another advantage: if you want to change the field bus protocol for ASi-5, you only need to replace the corresponding gateway. All ASi modules, sensors, and actuators can remain unchanged. With SPE, on the other hand, you have to secure not only a node (the gateway) but also all sensors and actuators against possible TCP/IP attacks. And if you change the field bus protocol, you often have to replace all sensors and actuators as well – unless they support the new protocol.

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.