How 10BASE-T1L MAC-PHY simplifies low-power processor Ethernet connectivity
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How 10BASE-T1L MAC-PHY simplifies low-power processor Ethernet connectivity

Posted Date: 2024-01-22

By: Maurice O'Brien, Strategic Marketing Manager, and Volker E. Goller, Systems Applications Engineer

Introduction

This article describes how to leverage the 10BASE-T1L MAC-PHY to connect the growing number of low-power field and edge devices. Additionally, this article will detail when to use MAC-PHY versus 10BASE-T1L PHY and how these systems can meet future Ethernet interconnect manufacturing and building installation requirements.

Background Information

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

Why use 10BASE-T1L MAC-PHY?

In order to achieve remote Ethernet connections with more low-power devices, the 10BASE-T1L MAC-PHY is required. With the 10BASE-T1L MAC-PHY, Ethernet and the processor can be connected together via SPI, offloading the processor. MAC functionality is now integrated directly with the 10BASE-T1L PHY. The 10BASE-T1L MAC-PHY supports a variety of ultra-low-power processors, providing device architects with flexible choices. By optimizing application partitioning, 10BASE-T1L MAC-PHY can leverage Ethernet APL in process automation to enable lower-power field devices and enable Zone 0 intrinsically safe deployments. In smart building applications, 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 condition monitoring.


Figure 1.10BASE-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 optimizes Ethernet traffic on the network. The 10BASE-T1L MAC-PHY with advanced packet filtering capabilities can significantly reduce the overhead of processing broadcast and multicast communications, freeing the processor from this task. Filtering by destination MAC address is key. MAC-PHY can filter up to 16 unicast or multicast MAC addresses instead of just a single MAC address. Additionally, address masking can support two MAC addresses. This provides a great deal of freedom, and filtering can be applied to both device addresses and commonly supported multicast addresses, such as Link Layer Discovery Protocol (LLDP). By providing additional queues for higher priority messages, certain messages can be prioritized, thereby improving latency and increasing robustness. The priority of frames can be identified through the MAC filter table. For example, you can put broadcast messages into a lower priority queue and unicast messages into a higher priority queue to prevent receivers from being overloaded by 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 MAC-PHY also supports IEEE 1588; therefore, process automation requires 802.1AS clock synchronization. MAC-PHY supports sync counter, timestamp of received messages and timestamp of sent messages capture. This significantly reduces the complexity of software design because no additional hardware is required to achieve time synchronization except for the MAC-PHY itself. The MAC generates output waveforms that are timed to synchronized counters and therefore can be used to synchronize external application-level operations. The SPI interface supports the Open Alliance 10BASE-T1x MAC-PHY serial interface. Open Alliance SPI is a new high-efficiency SPI protocol designed specifically for 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 selection of the main processor, and ultra-low-power processors without integrated MAC can be used to achieve lower system power consumption. When upgrading existing equipment to increase Ethernet connectivity, the 10BASE-T1L MAC-PHY provides a way to repurpose existing processors and increase Ethernet connectivity through the SPI port without migrating to larger processing with integrated MAC device.

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


Figure 2. Comparison of the advantages of MAC-PHY and PHY for 10BASE-T1L connectivity

Increased flexibility for future Ethernet interconnection process installations

Meet future Ethernet interconnect manufacturing installation requirements. Ultra-low-power devices and high-performance devices can be deployed simultaneously on the same Ethernet network and comply with the strict maximum power limits required by hazardous area use cases. 10BASE-T1L power switches and 10BASE-T1L field switches require the combination of a robust, low-power 10BASE-T1L PHY with an industrial Ethernet switch to deploy trunk and spur network topologies that provide both power and data on a single twisted pair (Includes hazardous area use cases).

Field device connections require both 10BASE-T1L PHY and 10BASE-T1L MAC-PHY to connect Ethernet 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 the 10BASE-T1L MAC-PHY to connect to the processor through the SPI interface to enable Ethernet connectivity (see Figure 3).

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

The ADIN1110 (Analog Devices' 10BASET1L PHY) interfaces with the host processor via an SPI interface, enabling a lower-power Ethernet connection, consuming only 42 mW. The ADIN1110 supports the Open Alliance 10BASE-T1x MAC-PHY serial interface for full-duplex SPI communication at 25 MHz clock speed. The ADIN1100 (Analog Devices' 10BASE-T1L PHY) interfaces with the host processor via the MII, RMII, or RGMII MAC interface, enabling a low-power Ethernet connection that consumes only 39 mW. The comparison between ADIN1100 10BASE-T1L PHY and ADIN1110 10BASE-T1L MAC-PHY is shown in Figure 1. Both products are based on the core functionality of 10BASE-T1L, a full-duplex, DC-balanced, point-to-point communications solution 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 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 complies with strict maximum energy limits.

Table 1. Comparison of ADIN1100 PHY and ADIN1110 MAC-PHY

Part
device
ADIN1100
ADIN1100
ADIN1110
ADIN1110
10BASE-T1L PHY
10BASE-T1L PHY
10BASE-T1L MAC-PHY
10BASE-T1L MAC-PHY
Interface

interface
MII, RMII, RGMII

MII, RMII and RGMII
SPI

SPI
Integrated MAC

Built-in MAC
No

no
Yes

yes
Supports Intrinsic Safe

Supports intrinsically safe applications
Yes

yes
Yes

yes
Power Consumption

Power consumption
39 mW

39 mW
42 mW

42 mW
Auto-Negotiation Capability

Auto-negotiation capability
Yes

yes
Yes

yes
On-Chip FIFO

On-chip FIFO
No

no
20 kB receive/
8 kB transmit

20 kB receive/
8 kB sent
MAC Filter (16 Entries)

MAC filter (16 entries)
No

no
Yes

yes
Prioritizing of Traffic

Traffic priority
No

no
Yes

yes
IEEE 1588 Timestamp Support

Supports IEEE 1588 timestamps
No

no
Yes

yes
Temperature Range

temperature range

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