How 10BASE-T1L MAC-PHY Simplifies Low-Power Processor Ethernet Connectivity

Introduction

This article describes how to use 10BASE-T1L MAC-PHY to connect an increasing number of low-power field devices and edge devices. It will also detail when to use MAC-PHY versus 10BASE-T1L PHY and how these systems can meet future Ethernet-connected manufacturing and building installation requirements.

Background Information

As more devices need to be connected to Ethernet, the use cases for single-pair Ethernet 10BASE-T1L (including Ethernet APL) in process, factory, and building automation applications continue to expand. As more connected devices are added, higher-level management systems can use richer data sets, which can significantly improve production efficiency while reducing operating costs and energy consumption. The vision of Ethernet to the field or edge is to connect all sensors and actuators to a converged IT/OT network. There are system engineering challenges in achieving this vision because some of these sensors are limited by power and space. There is a growing market demand for low-power and ultra-low-power microcontrollers with powerful internal storage capabilities for sensor and actuator applications. But most of these processors have the same problem, that is, there is no integrated Ethernet MAC and no support for MII, RMII or RGMII media independent (Ethernet) interfaces. Traditional PHYs cannot connect to these processors.

Why use 10BASE-T1L MAC-PHY?

To enable long-range Ethernet connectivity with more low-power devices, the 10BASE-T1L MAC-PHY is needed. With the 10BASE-T1L MAC-PHY, Ethernet and processors can be connected together via SPI, thereby reducing the burden on the processor. The MAC function is now directly integrated with the 10BASE-T1L PHY. The 10BASE-T1L MAC-PHY supports a variety of ultra-low-power processors, providing flexible options for device architects. By optimizing application partitioning, the 10BASE-T1L MAC-PHY can leverage Ethernet APL in process automation to enable lower-power field devices and achieve intrinsically safe deployment in Zone 0. In smart building applications, the MAC-PHY can connect more lower-power devices to the same Ethernet network. Smart building applications include HVAC systems, fire safety systems, access control, IP cameras, elevator systems, and status monitoring.

Figure 1. The 10BASE-T1L MAC-PHY can significantly reduce device power consumption and complexity through advanced packet filtering.

10BASE-T1L MAC-PHY Advanced Packet Filtering

The 10BASE-T1L PHY with integrated MAC functionality can optimize Ethernet traffic on the network. The 10BASE-T1L MAC-PHY with advanced packet filtering can significantly reduce the overhead of handling broadcast and multicast traffic, freeing the processor from this task. Filtering by destination MAC address is key. The MAC-PHY can filter up to 16 unicast or multicast MAC addresses, not just a single MAC address. In addition, address masks can support two MAC addresses. This provides a lot of freedom, and filtering can be used for device addresses and commonly supported multicast addresses, such as Link Layer Discovery Protocol (LLDP). By providing additional queues for higher priority messages, some messages can be processed first, thereby improving latency and enhancing robustness. The priority of the frame can be identified by the MAC filter table. For example, broadcast messages can be sent to a lower priority queue and unicast messages can be sent to a higher priority queue to prevent the receiver from being overloaded due to broadcast storms or traffic surges. These MAC-PHY filtering features can enhance the device's robustness to network loads. The MAC also collects frame statistics to facilitate monitoring of network traffic and link quality (see Figure 1).

The MAC in the MAC-PHY also supports IEEE 1588; therefore, 802.1AS clock synchronization is required for process automation. The MAC-PHY supports synchronized counters, timestamps for received messages, and timestamp capture for transmitted messages. This greatly reduces the complexity of software design because no additional hardware is required to achieve time synchronization other than the MAC-PHY itself. The MAC can generate output waveforms that are timed to synchronized counters, so they can be used to synchronize external application-level operations. The SPI interface supports the Open Alliance 10BASE-T1x MAC-PHY serial interface. The Open Alliance SPI is a new, efficient SPI protocol designed specifically for the MAC-PHY.

When to use 10BASE-T1L MAC-PHY and 10BASE-T1L PHY?

10BASE-T1L PHY and 10BASE-T1L MAC-PHY each have distinct advantages in different use cases. In power-critical applications, 10BASE-T1L MAC-PHY provides greater flexibility in the choice of host processor, allowing the use of ultra-low-power processors without integrated MAC to achieve lower system power consumption. When upgrading existing equipment to increase Ethernet connectivity, 10BASE-T1L MAC-PHY provides a way to reuse existing processors and increase Ethernet connectivity through the SPI port without migrating to a larger processor with integrated MAC.

For high-performance applications that require a high-performance processor (which may already have an integrated MAC) in a field or edge device, the 10BASE-T1L PHY combined with the MII, RMII, and RGMII interfaces enables rapid development of the 10BASE-T1L PHY. This is achieved by reusing the existing MAC interface driver to add Ethernet connectivity (see Figure 2).

Figure 2. Comparison of MAC-PHY and PHY advantages for implementing 10BASE-T1L connections

Increased flexibility for future Ethernet-connected process installations

Meeting the requirements of future Ethernet-connected manufacturing installations. Ultra-low power devices and high-performance devices can be deployed simultaneously on the same Ethernet network within the strict maximum power limits required by hazardous area use cases. 10BASE-T1L Power Switches and 10BASE-T1L Field Switches require the combination of robust low-power 10BASE-T1L PHYs with industrial Ethernet switches to deploy trunk and branch network topologies that deliver both power and data (including hazardous area use cases) over a single twisted pair.

Field device connectivity requires both 10BASE-T1L PHY and 10BASE-T1L MAC-PHY to enable Ethernet connectivity to various field devices. Higher power field devices, including flow meters, use high-performance processors with integrated MAC and 10BASE-T1L PHY. Lower power field devices, including temperature sensors with built-in ultra-low power processors without integrated MAC, use 10BASE-T1L MAC-PHY to connect to the processor through the SPI interface to achieve Ethernet connectivity (see Figure 3).

Comparison of key features of 10BASE-T1L PHY and 10BASE-T1L MAC-PHY

The ADIN1110 (Analog Devices’ 10BASET1L PHY) connects to a host processor via an SPI interface for lower power Ethernet connectivity, consuming only 42 mW. The ADIN1110 supports the Open Alliance 10BASE-T1x MAC-PHY serial interface for full-duplex SPI communications at a 25 MHz clock speed. The ADIN1100 (Analog Devices’ 10BASE-T1L PHY) connects to a host processor via an MII, RMII, or RGMII MAC interface for low power Ethernet connectivity, consuming only 39 mW. A comparison of the ADIN1100 10BASE-T1L PHY and the ADIN1110 10BASE-T1L MAC-PHY is shown in Figure 1. Both products build on the 10BASE-T1L core functionality of a full-duplex, DC-balanced, point-to-point communication scheme, using PAM 3 modulation at a 7.5 MBd symbol rate and 4B3T encoding. 10BASE-T1L supports two amplitude modes: 2.4 V peak-to-peak for cables up to 1 km long and 1.0 V peak-to-peak for shorter distances. The 1.0 V peak-to-peak amplitude mode means that this new physical layer technology can also be used in explosion-proof system environments and comply with strict maximum energy limits.

Figure 3. Trunk and branch network topology using 10BASE-T1L MAC-PHY and 10BASE-T1L PHY for process automation

summary

The 10 Mb Ethernet physical layer (10BASE-T1L) incorporates power delivery (Engineered Power/PoDL/SPoE) over a single twisted pair up to 1 km, creating new Ethernet-connected devices that can generate more valuable information that is more easily accessible through converged IT/OT Ethernet. In process automation and factory automation applications, this new information can help improve production efficiency and reduce energy consumption. In building automation applications, this new information can help improve energy efficiency, safety, and comfort. Therefore, the 10BASE-T1L MAC-PHY will accelerate the realization of lower power devices.

Learn more about the ADI ChronousTM Industrial Ethernet Solutions portfolio and how it can accelerate transformation to real-world Industrial Ethernet networks.

About Analog Devices

Analog Devices, Inc. (NASDAQ: ADI) is a leading global semiconductor company dedicated to building a bridge between the real world and the digital world to achieve breakthrough innovations in the field of intelligent edge. ADI provides solutions that combine analog, digital and software technologies to promote the continuous development of digital factories, automobiles and digital healthcare, meet the challenges of climate change, and establish reliable connections between people and everything in the world. ADI's revenue in fiscal year 2023 exceeded US$12 billion and it has approximately 26,000 employees worldwide.

About the Author

Maurice O'Brien is a strategic marketing manager for the Industrial Automation Division at Analog Devices. He is responsible for delivering system-level solutions focused on industrial automation. Prior to this, Maurice worked in the Industrial Ethernet field at Analog Devices for 3 years and in power management applications and marketing for 15 years. He holds a bachelor's degree in electronic engineering from the University of Limerick, Ireland.