Page 17 - EngineerIt May 2021

AUTOMATION AND CONTROL

How a 10BASE-T1L MAC-PHY

simplifies low power processor

ethernet connectivity

By Maurice O’Brien, Strategic Marketing Manager and Volker E. Goller, Systems Application Engineer

Introduction MAC-PHY is required. With a 10BASE-T1L MAC-PHY, Ethernet connectivity is provided
This article explains how to connect to a processor via SPI, reducing the burden on the processor by removing the need for an
to an increased number of low power integrated MAC. The MAC functionality is now integrated directly with the 10BASE-T1L PHY.
field or edge devices with a 10BASE- A 10BASE-T1L MAC-PHY provides device architects increased flexibility and choice by
T1L MAC-PHY. It will also detail when enabling a variety of ultra-low power processors. By optimising the application partitioning,
to use the MAC-PHY vs. a 10BASE- a 10BASE-T1L MAC-PHY provides lower power field devices for Zone 0 with intrinsically
T1L PHY and how these systems safe deployment through what is referred to in the process industry as Ethernet-APL. Within
meet the requirements of tomorrow’s intelligent building applications, a MAC-PHY will enable more lower power devices to be
Ethernet-connected manufacturing connected to an Ethernet network. Intelligent building applications include HVAC systems,
and building installations. fire safety systems, access control, IP cameras, elevator systems and condition monitoring.

Background 10BASE-T1L MAC-PHY Advanced Packet Filtering
Single-pair Ethernet 10BASE-T1L use The integration of the MAC functionality with a 10BASE-T1L PHY provides new features
cases, including Ethernet-APL, continue to optimise Ethernet traffic on the network. A 10BASE-T1L MAC-PHY with advanced
to expand across process, factory and packet filtering will significantly reduce the overhead of handling broadcast and multicast
building automation applications, driven traffic, while freeing the processor from this task. Filtering by the destination MAC
by the requirement to connect more address is key. Instead of just a single MAC address, a MAC-PHY can support filtering,
devices to Ethernet networks. With using up to 16 unicast or multicast MAC addresses. In addition, address masking is
more devices connected, richer data supported for two MAC addresses. This gives a great degree of freedom, filtering for the
sets are made available to the higher device address as well as commonly supported multicast addresses such as LLDP (Link
level management systems, leading to Layer Discovery Protocol).
significant increases in productivity while By supporting an additional queue for higher priorities, some messages can be
reducing operating costs and energy prioritised and therefore obtain improved latency and robustness. The priority of a frame
consumption. The vision of Ethernet to the can be identified by the MAC filtering table. For example, broadcast messages can be
field or edge is to connect all sensors and fed into a lower priority queue and unicast into the higher priority queue to prevent the
actuators to a converged IT/OT network. receiver from being overloaded by a broadcast storm or traffic surge. These MAC-PHY
To achieve this vision there are system filtering features enable netload robust devices. Frame statistics are also gathered by the
engineering challenges, as some of these MAC to assist in monitoring the network traffic and the quality of the link (see Figure 1).
sensors are limited in power and space. The MAC in the MAC-PHY also supports IEEE 1588, and therefore 802.1AS time
There is a growing market of low power synchronisation as required in process automation. The MAC-PHY provides support for
and ultra-low power microcontrollers with a synchronised counter, time-stamping of received messages and time-stamp capture
significant internal memory capabilities for transmitted messages. This greatly reduces the complexity of the software design,
for sensor and actuator applications. as there is no further hardware support needed to implement time synchronisation
Most of these processors have one thing beyond the MAC-PHY itself. The MAC can generate an output waveform timed to the
in common—with no integrated Ethernet synchronised counter, which may be used to synchronise external application-level
MAC, they don’t support an MII, RMII or operations. The SPI interface supports the open alliance 10BASE-T1x MAC-PHY serial
RGMII media independent (Ethernet) interface. The Open Alliance SPI is a new and very effective SPI protocol designed
interface. A traditional PHY cannot be specifically for use with a MAC-PHY.
connected to these processors.
When to Use a 10BASE-T1L MAC-PHY and a 10BASE-T1L PHY
Why use a 10BASE-T1L MAC-PHY? Both a 10BASE-T1L PHY and a 10BASE-T1L MAC-PHY bring significant advantages in
To enable long range Ethernet different use cases. For power critical applications, a 10BASE-T1L MAC-PHY enables
connectivity to an increased number of lower system power by providing more flexibility on the choice of host processor, to
lower power devices, a 10BASE-T1L include ultra-low power processors that do not have an integrated MAC. When upgrading

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