In this transformation, data, bandwidth, and networks have grown exponentially, driving machine-to-machine communication, creating so-called smart factories, and enabling more responsive automation at all levels.
When people think of automation, they are more likely to think of large systems such as robots and coordinated production lines. However, the automation we know as it would be impossible without various sensors and actuators constantly communicating with the programmable logic controllers (PLCs) running the production line. The number of sensors and actuators operating locally and remotely often far exceeds the number of complex systems they support. To meet the diverse requirements of systems of all sizes, it is necessary to optimize communication throughout the factory.
In practical applications, the common solution for factory floor fieldbuses is to adapt Ethernet to industrial uses through specialized communication protocols. These industrial Ethernet protocols (such as EtherCAT® and Profinet) possess various characteristics required for automated manufacturing, including high bandwidth, long physical connections, low latency, and deterministic data transmission. Field networks built on these standards can easily connect to larger factory data networks and the Internet. However, for sensors and actuators, using such robust industrial Ethernet is overkill, as these devices typically require point-to-point communication rather than fieldbus, and their bandwidth requirements are often not high. IO-Link is an innovative solution for this need. It is a bidirectional communication protocol based on standard cabling and physical interconnects that not only effectively brings data from the factory floor to the PLC but also improves installation, diagnostics, and maintenance, complementing existing fieldbus cabling.
IO-Link and Industrial Ethernet complement each other. Designers of networked factory systems can benefit from understanding how these two standards work together. This white paper explains the differences between these technologies and discusses a range of solutions from Texas Instruments (TI) that aid in industrial communication design. These products and solutions meet communication needs in both general and general industrial applications, many specifically designed for communication in industrial automation, and are backed by the expertise TI has gained through long-term collaborations with its customers. Leveraging its strengths in manufacturing technologies and in-depth design support, TI helps industrial system developers meet the needs of today's smart factories.
Low-bandwidth IO-Link
Sensors and actuators are the cornerstones of automation units, providing information to networked systems and taking actions based on their instructions. In traditional designs, they connect to control units via various interfaces, which lack any intelligent functionality and rarely exchange configuration and diagnostic information. Consequently, manual configuration is required at the point of use whenever new equipment is installed, and the lack of diagnostic capabilities hinders timely preventative maintenance.
IO-Link (International Electrotechnical Commission [IEC] 61131-9) is an open standard protocol that meets the needs of intelligent control of small devices such as sensors and actuators. This standard enables low-speed point-to-point serial communication between devices and a master controller, which typically acts as a gateway to the fieldbus and PLC. The intelligent link established by IO-Link allows for easy exchange of data, configuration, and diagnostic information.
IO-Link connections are established via an unshielded three-core cable no longer than 20 meters, typically using an M12 connector. The maximum data transfer rate is 230 kbps, with a minimum asynchronous cycle time of 400 µs (+10%). Four operating modes are supported: bidirectional input/output (I/O), digital input, digital output, and disabled. No security mechanisms or deterministic data transfer are specified. The protocol uses a configuration file called an "IO Device Description" (IODD), which contains communication attributes, device parameters, identification, process and diagnostic data, and specific information about the device and manufacturer.
IO-Link systems offer numerous advantages, including standardized cabling, improved data availability, remote monitoring and configuration, simplified equipment replacement, and advanced diagnostics. Factory managers can receive continuously updated sensor data through IO-Link, providing crucial information for future maintenance and replacement planning. With IO-Link master control, sensors or actuators can be replaced and new equipment configured directly from the PLC without manual setup, reducing downtime. Furthermore, IO-Link allows for remote switching of production configurations, eliminating the need for on-site personnel and simplifying the production of customized products. Factories can easily upgrade their production lines to IO-Link because it is backward compatible with existing standard I/O devices and cabling. In summary, IO-Link's various functions can reduce overall costs, improve production process efficiency, and increase machine utilization.
Industrial Ethernet: The backbone of smart factories
In recent years, Industrial Ethernet has demonstrated its value in highly automated factories, becoming the preferred external network interconnection standard for large field networks (including complex systems), PLCs, and gateways. Ethernet's advantages include high transmission speeds, universal interfaces, and long connection distances, making it ubiquitous in data networks. Furthermore, Industrial Ethernet uses a modified Media Access Control (MAC) layer, enabling deterministic data transmission with low latency and supporting time-triggered events. Industrial Ethernet supports ring and star topologies as well as traditional linear connections, ensuring safety and reliability even in the event of cable breaks.
Industrial Ethernet is not a single specification, but rather a series of protocol implementations for field-level applications driven by multiple industrial equipment manufacturers. Common protocols include EtherCAT, Profinet, Ethernet/IP, Sercos III, and CC-Link IE Field. The white paper "An inside look at industrial Ethernet communication protocols" compares these protocols and also discusses earlier non-Ethernet serial fieldbus protocols such as Controller Area Network (CAN), Modbus, and Profibus.
Among various industrial Ethernet protocols, Profinet and EtherCAT are the two most widely used, both showcasing the differences between different types of industrial Ethernet and between industrial Ethernet and IO-Link. Both industrial Ethernet protocols specify a transmission speed of 100Mbps and a transmission distance of up to 100 meters. Profinet requires power delivery to be independent of the data cable, while the EtherCAT_P version of EtherCAT transmits both power and data through the same cable. Profinet supports full-duplex communication, capable of sending data packets to every node on the network, and offers three different levels for users to match the performance level required by the network; while EtherCAT sends shared frames in one direction on the network, with all slave devices carrying data within them, thus enabling very fast forwarding.
Both Profinet and EtherCAT have shorter cycle times than IO-Link, but their fault tolerance is much lower. Both are timed based on network synchronization, rather than starting from the beginning of communication like IO-Link. Additionally, there are other protocols for functional safety. Typically, industrial Ethernet protocols offer a variety of services to simplify integration in automation environments.
While most sensors don't utilize the powerful capabilities offered by industrial Ethernet connectivity, vision sensing is a significant exception. Its cameras generate a vast amount of data, which alone justifies its need for a faster data connection than IO-Link. Vision sensing (and sometimes other types of sensing) can provide critical input data for real-time process control, thus requiring the deterministic transmission capabilities of industrial Ethernet.
For example, Time-of-Flight (ToF) applications need to track and predict the three-dimensional motion of objects, with a typical response being a moving robotic arm to intercept the object. IO-Link can provide sufficient transmission rates and resolution for limited presence awareness in these applications, but Industrial Ethernet can also provide enough bandwidth and low enough latency to determine certain features of the object and its surrounding space. Even higher levels of recognition might be possible if camera data were transmitted over Gigabit Ethernet, but the Industrial Ethernet protocol discussed in this paper does not specify such transmission rates.
Figure 3: Specific example: Time of Flight (ToF)
TI Technologies for Smart Factory Communications
Among the various competing industrial Ethernet protocols, there are numerous possibilities for serving cameras, motors, robots, PLCs, and other complex systems; even simple sensors and actuators can operate more efficiently in larger industrial Ethernet environments. The choices for communication between automated devices are plentiful, and industrial system designers need flexible and easy-to-use solutions. TI's industrial communication integration solutions, based on multiple communication standards (including IO-Link and common industrial Ethernet protocols), meet these requirements.
TI's TIOL111x transceiver family provides complete IO-Link functionality, along with electrostatic discharge (ESD) protection, electrical fast transient (EFT) protection, and surge protection for sensors and actuators in automation systems. Evaluation modules (EVMs) allow you to inspect devices in operation, while reference designs help accelerate the development of applications such as transmitters, proximity switches, electromagnetic actuators, and ultrasonic devices.
Application designers requiring higher bandwidth and deterministic timing must determine how many industrial Ethernet protocols they need to support to ensure their systems are compatible with various fieldbus environments. Traditionally, adding protocols requires creating additional interfaces or plugging in replaceable modules to the motherboard. Either approach involves additional hardware design, more materials, and longer testing and certification cycles.
The TI Sitara™ series ARM® processor requires no additional hardware. It provides an integrated programmable real-time unit and industrial communication subsystem (PRU-ICSS) that supports multi-protocol industrial Ethernet.
The PRU can load industrial protocol firmware while the device is running, with selectable protocols including EtherCAT, Profinet, Sercos III, Ethernet/IP, and Ethernet PowerLink. The PRU-ICSS can handle real-time mission-critical tasks that previously had to be built into application-specific integrated circuits (ASICs) or field-programmable gate arrays (FPGAs). If new features or protocols need to be added, the PRU-ICSS provides a software-based, scalable solution. The Sitara processor, based on a scalable ARM core (Cortex®-A8, A9, or A15, depending on the processor), enables single-chip solutions for factory automation using a variety of industrial Ethernet protocols.
TI offers a broad family of interfaces for industrial Ethernet and other standards such as CAN, available as standalone solutions or as technology modules within integrated solutions. Many TI networking products feature reinforced insulation to protect circuitry and personnel, and other devices also offer reinforced insulation for improved design. TI also provides extensive development support, including software, tools, EVMs, and reference designs for a wide range of applications in automated industrial equipment.
Technologies for the Smart Factory of the Future
The development of smart factories relies on multifunctional networks that match the requirements of individual device units with the overall communication needs of the factory. Industrial Ethernet protocols provide high bandwidth and fast, reliable timing for fieldbus connections to PLCs, cameras, robots, and other complex automation systems. IO-Link offers intuitive options for point-to-point connections between fieldbus masters and sensors or actuators, facilitating configuration and maintenance. TI offers a diverse range of solutions and a flexible technology portfolio to help designers leverage these complementary standards as they innovate in the automation landscape of the "Fourth Industrial Revolution."
