Microchip Zeros in on Precision Timing Protocol With Gigabit Ethernet Transceivers

Lately, the industrial sector has benefited greatly from new technologies and innovations such as the Industrial Internet-of-Things (IIot). However, with more interconnected devices, challenges have emerged regarding synchronizing a network.

To address this challenge, the IEEE Standards Association released the IEEE-1588 standard in 2008. As the need for this standard grows, Microchip is answering the call by releasing two new Ethernet transceivers that meet the IEEE-1588 standard.

This article will discuss the need for standardization in the industrial sector, the IEEE-1588 standard, and Microchip’s new products.

 

Need for Synchronization

For digital electronics and communications to work appropriately, engineers must properly synchronize them.

To do this, digital electronics employ a clock, a timekeeping mechanism in the form of a square wave with a known and constant frequency. While this works successfully in theory, in practice, there can be some challenges.

 

LANs require synchronization between devices. Image used courtesy of Cisco

 

For example, in a local area network (LAN), it is not uncommon to find multiple clocked devices, each with its own inherent precision, resolution, and stability. This inherent lack of uniformity between devices can result in offsets between synchronous devices and, ultimately, an inability to have a synchronized network.

 

Precision Timing Protocol (PTP) and the IEEE-1588 Standard

In 2008, the IEEE Standards Association released the IEEE-1588 standard to help define synchronization within measurement and control systems in a LAN, focusing on Ethernet systems.

Colloquially known as the precision timing protocol (PTP), the standard is purposefully designed to help synchronize time through a network. More specifically, the goal of the PTP is to help eliminate any offset between two clocks in a system, such that every device in a LAN is fully synchronized. To achieve this, the protocol calls for a Master (Controller) device to be the provider of time, while the Slave (responder) devices are expected to synchronize their time with the Master. 

As shown in the image below, the protocol uses timestamps to determine network latencies and offsets to synchronize the network clocks appropriately. 

 

Master-Slave messaging timestamps for PTP. Image used courtesy of EndRun Technologies

 

As shown, a message is sent from the Master at the time (T1) and is received by the Slave at the time (T2), with the difference (T2-T1). This difference is known as the Master to Slave delay. On the other hand, the Slave to Master delay is defined as the difference between T4, the time at which the Master receives a delay request message, and T3, the time at which the Slave sends the message. 

From here, a one-way delay is calculated as the average of the two delays. Finally, the offset used to synchronize the Slave clock to the Master clock is defined as the difference between the Master to Slave delay and the one-way delay.

 

Microchip’s New Products 

Capitalizing on the IEEE-1588v2 standards for PTP, last week, Microchip released two new Gigabit Ethernet transceivers.

 

System block diagram of the LAN8840. Image used courtesy of Microchip

 

The two devices, the LAN8840 and LAN8841, are designed to facilitate packet prioritization through high-speed time stamping, allowing one to determine and compensate for different network latencies. Both devices are single-port triple-speed Ethernet PHYs and are explicitly meant to synchronize motors, sensors, and actuators. 

The major difference between the two is that LAN8841 is designed to support time-sensitive networks (TSNs) while LAN8840 is optimized for supporting PTP networks.

For more info on these devices, you can learn more from the LAN8840 datasheet and LAN8841datasheet.

 

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Featured image used courtesy of Microchip