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Putting the ‘pro’ into industrial Ethernet protocols

Home Engineering Automation & Control Putting the 'pro' into industrial Ethernet protocols

Darrell Halterman, senior product manager of PACSystems controllers at Emerson’s machine automation solutions business, explains the advantages of using Profinet protocol for PLC, PAC and industrial edge controller applications.

THE Profinet industrial Ethernet communications protocol was purpose-built to deliver interoperability, high-performance communications, high-availability architectures, and advanced diagnostics to help with troubleshooting.

These features help to minimise operational downtime and enable designers to create robust and reliable industrial automation input/output (I/O) networks that are maintainable long-term. These I/O networks are relied upon to enable programmable logic controllers (PLCs), programmable automation controllers (PACs) and industrial edge controllers to perform deterministic control.

Early industrial automation protocols relied upon proprietary media and components, partly to guarantee performance. As industrial networking made the transition towards commercial Ethernet technology, it remained necessary to address the always-on need for automation systems while guaranteeing performance. Here are some of the reasons why Profinet is an ideal fit for industrial I/O networks.


Automation systems for industrial machines and equipment rely on the connection of controllers to hardwired field devices such as sensors and actuators via I/O modules. Controllers also connect with more intelligent and capable I/O devices, such as variable frequency drives (VFDs) and smart pneumatic solenoid manifolds.

These devices often have Ethernet connectivity and can be located in a protected control panel or installed directly on equipment. Using an industrial protocol such as Profinet, designers have the flexibility to choose any combination of best-of-class I/O systems.

They can select panel or field-mountable versions of each device as required to fit the application, and can even source them from different suppliers, with high confidence in their reliability and interoperability.

Uninterrupted communications

In much the same way as consumer-grade home networks, industrial-grade I/O systems can be connected with switches and cables in a star topology. However, the `always-on’ performance demand of automation often requires solutions more robust than those available using basic IT technology.

Profinet addresses these concerns by providing various levels of redundancy, with the specific aim of providing uninterrupted communications.

Using a ring network configuration, Media Redundancy Protocol (MRP) provides communications recovery within a few milliseconds of networking loss due to a cable, device or switch failure.

These networks can be designed with external switches to form a ring. Designs can be simplified for industrial controller and I/O systems by incorporating on-board embedded multi-port switches within controllers and I/O devices, enabling a ring network to be created without the need for external switches.

Controller redundancy is often needed in the most critical applications, which requires PLCs, PACs, or industrial edge controllers that can be installed in pairs on an MRP ring. One controller is the primary and the second is the hot back-up, configured to take over seamlessly if the primary fails.


Should there be a problem with an industrial automation I/O system, operators and maintenance personnel need to know about it as soon as possible. This still applies to systems that have been configured with MRP and redundant controllers, because even though operation will continue unabated after a single failure, the system may then be just one additional failure away from an outage.

Profinet provides diagnostics to help users debug industrial I/O systems. Controllers can be configured to recognize I/O failures, notify users, and even initiate an orderly shutdown. Users can also access diagnostic tools to monitor I/O network performance and system health, providing them with an early indication of any impending issues.

Industrial I/O roadmap

In addition to providing I/O interoperability, redundant architectures and helpful diagnostics, Profinet has further features that make it an ideal solution for PLCs, PACs and industrial edge controllers. A specified profile enables data to be easily shared between Profinet and OPC UA networks.

Another standard profile makes it possible to connect IO-Link sensors and devices to Profinet. Time-sensitive networking (TSN) represents a set of networking standards for improving performance by minimizing latency to provide high availability data transmission over deterministic Ethernet networks.

In conclusion, Profinet enables users to create the highest performance I/O networks that can support the most demanding applications such as motion control, while further improving their overall network capabilities, robustness and security.

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