Part 1 of Two-Part Series
Traditionally Ethernet has been used in enterprise applications – we are familiar with its use in our office environments. But the IEEE 802.3 family of standards is constantly evolving. Industrial networks present their own set of challenges, and Ethernet with its components are evolving again to address the needs of the factory floor. Connectivity hardware that can offer low-latency, enhanced electrostatic discharge (ESD) protection while operating in extended temperature environments is invaluable to industrial network implementation. The Marvell 88E1510P/88E1512P/88E1510Q family of PHY (physical layer device) products was designed from the ground up in collaboration with leaders in industrial automation and has been vetted for use in the most demanding industrial applications.
A multitude of communication protocols are used in industrial networks today including EtherNet/IP, EtherCAT, Profinet and SERCOS III. These are independent and proprietary offerings from different vendors. But what they share in common is the goal to deliver real-time Ethernet to industrial automation applications under harsh environmental conditions. The typical elements of an industrial network might include programmable logic controllers (PLCs), motor controllers and drives, sensor networks and human machine interfaces (HMIs). These elements are connected on the Ethernet backbone using a protocol such as EtherCAT or Profinet. The network topology might be hub-spoke (star) or linear. Regardless of network topology, the goal is to provide precise control and synchronized timing information to each of the nodes. If the topology is a long daisy chain, then each node has to perform with the most optimized latency to enable fast request/response cycle times through the system.
Protocols such as EtherCAT have to process the Ethernet packet and insert new data into the frame as it passes through in real-time. For real-time applications, this imposes tight restrictions on the latency through the switch and PHY. With this requirement in mind, we designed the Marvell 88E1510P/1512P/1510Q family of PHY products to address the stringent latency needs of tier-1 industrial customers. The table below shows that the Marvell low-latency PHY operates 30-40 percent faster as compared to non-optimized implementations. While the data shown above is the default configuration, significantly lower latencies are possible with register programming. The sum total of transmit and receive latency was less than 400ns across the entire range, as shown below. The small latency variation observed (from min to max) is due to the presence of synchronization circuits in the transmit path. Typically a FIFO (first in, first out queue) is used in the transmit path to compensate for any PPM (parts-per-million) differences between the transmit circuits and receiving circuits. Depending on packet size and the number of entries in the FIFO, a small variation in latency can be observed. (Note: When the PHY is used for precision-time protocol- (PTP-) based timestamping applications, the presence of the FIFO does not affect the accuracy of the timestamps. The timestamps are taken closest to the wire, eliminating the FIFO uncertainty).
While 100BASE-TX speeds are sufficient for the majority of factory applications today, there is a growing need to support 1000BASE-T. Since the installation of industrial equipment and networks is capital-intensive, it is prudent to use a PHY device that can future-proof network speed requirements up to 1000BASE-T. The Marvell 88E1510P/1512P/1510Q family of PHY products supports 10BASE-T, 100BASE-TX, and 1000BASE-T. The low latency ranges observed in 1000BASE-T mode is shown below.
In an industrial environment, it is difficult to control temperatures on the plant floor, where surrounding equipment may operate at high temperatures and where it can be difficult to provide good ventilation. Industrial motors and robots connected by an Ethernet network often have to weld metals at very high temperatures. This requires the PHY to operate in environments where the ambient temperature remains high throughout the entire duration of operation (for more than several hours). The Marvell 88E1510P/1512P/1510Q family of PHY products was designed to operate in ambient operating temperature ranges of minus -40 0C to 85 0C degrees (or 125 0C maximum junction temperature.)
In addition to high temperature, industrial environments can also lead to accumulation of electric charge within the machinery. To shield against high voltage surges, the Marvell PHY has enhanced ESD protection circuits. We tested the Marvell PHY in the robust testing environments of some of the largest industrial electronics OEMs who approved the device from an ESD perspective.
The Marvell 88E1510P/1512P/1510Q family of PHYs is offered in 48-pin or 56-pin QFN packages. It also offers a variety of host interface options such as RGMII, MII and SGMII. For information on specific features, please review the attached product selector guide.
In conclusion, connectivity hardware that can offer enhanced ESD protection, low-latency and operate under extended temperature ranges is gaining popularity in industrial networks. The Marvell 88E1510P/1512P/1510Q family of PHYs offers these key benefits to implement in any real-time industrial Ethernet network.