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Operating Principle:

There are several Ethernet solutions available today for providing real-time functionality. For example, some systems disable the CSMA/CD access procedure at a higher protocol layer and replace it with time-slicing or polling mechanisms. Others use dedicated switches to distribute Ethernet packets with precise timing control. Although these approaches enable faster and more accurate packet delivery to connected nodes, they often suffer from low bandwidth utilization, especially for typical automation devices where even small data transfers require an entire Ethernet frame. Additionally, the time needed to redirect data to output or drive controllers, as well as read input data, depends heavily on the execution method. In modular I/O systems, a sub-bus like the Beckhoff K-bus is often used to speed up communication, but such synchronization does not eliminate delays in bus transmission.

By adopting EtherCAT technology, Beckhoff overcomes these limitations of traditional Ethernet solutions. Instead of receiving and decoding Ethernet frames at each node, EtherCAT allows each device—whether it's a terminal or a slave—to directly read the relevant data from the frame as it passes through. Input data can also be inserted into the frame during its traversal. Once the frame has passed (with only minimal delay), the slave processes the command. This process is implemented in hardware within the EtherCAT Slave Controller, making it independent of the real-time operating system or software stack performance. The last EtherCAT slave in the segment returns the fully processed message, which is then sent back as a response to the master station.

From an Ethernet perspective, an EtherCAT bus segment functions as a large Ethernet device capable of receiving and sending frames. However, instead of a single Ethernet controller with a microprocessor, the "device" consists of multiple EtherCAT slaves. Like any other Ethernet network, EtherCAT doesn't require a switch to establish communication, resulting in a purely EtherCAT-based system.

Terminals Implement Ethernet:

Every device in the system uses the full Ethernet protocol, including each I/O terminal, without requiring a separate sub-bus. The coupler simply converts the transmission medium from twisted pair (100BaseTX) to E-Bus to meet the requirements of the electronic terminal block. The E-Bus signal type (LVDS) in the terminal block is not proprietary and can support up to 10 Gigabit Ethernet. At the end of the terminal strip, the physical characteristics are converted back to the 100BaseTX standard.

A standard Ethernet MAC or a cost-effective network card (NIC) is sufficient for use in the controller. Data is transferred using DMA (Direct Memory Access) to the PC, ensuring that network activity does not impact CPU performance. The same principle applies to the Beckhoff multiport card, which integrates up to four Ethernet channels into a single PCI slot.

Free choice of topology | Maximum flexibility in cabling: Whether you use a switch, a bus topology, or a tree topology, you can choose any combination. Automatic address assignment eliminates the need to manually set IP addresses.

Distributed Clock:

Precise synchronization is crucial in applications where multiple actions must occur simultaneously, such as when several servo axes perform coordinated tasks. Accurate calibration of the distributed clock offers the most efficient solution for synchronization. Unlike full synchronization, which can be affected by communication errors, the step-by-step calibration approach in EtherCAT allows for some tolerance in delay. Since EtherCAT operates entirely on hardware, the "master clock" can accurately determine compensation for each "slave clock," and vice versa. This enables a very precise clock base with less than 1 microsecond of jitter across the network.

High-performance distributed clocks are not only used for synchronization but also provide accurate local time information during data acquisition. Thanks to new extended data types, measured values can be assigned highly precise timestamps.

Hot Connection:

Many applications require changes to the I/O configuration while the system is running. For example, a processing center with dynamic features, a tool system with sensors, an intelligent transmission device, a flexible workpiece actuator, or a printing machine that can individually turn off printing units. EtherCAT supports this with its "hot connection" feature, allowing parts of the network to be dynamically reconfigured without interrupting operations.

High Availability:

Cable redundancy is optional and helps increase system availability, allowing devices to be replaced without shutting down the network. EtherCAT also supports redundant master stations with hot standby. Because the EtherCAT Slave Controller automatically returns the frame upon detecting an interruption, a single device failure won’t cause the entire network to go down. For example, cable protection can be configured as a short bar to prevent wire breakage.

Safety:

Security functions are typically implemented separately from automation networks, either through hardware or dedicated secure bus systems. With TwinSAFE (Beckhoff’s security technology), it’s now possible to use the EtherCAT safety protocol for both safety-related communication and regular control communication on the same network. This protocol operates at the application layer and doesn’t interfere with lower layers. Certified according to IEC61508, it can achieve SIL3 and even SIL4 with additional measures. The protocol supports variable data lengths, making it suitable for both secure I/O data and drive technology. Secure data can be routed without the need for a dedicated router or gateway.

Diagnosis:

Network diagnostic capabilities are essential for improving availability and reducing debugging time. Quick and accurate error detection is key to eliminating issues efficiently. During testing, the actual configuration of I/O terminals is verified against the specified setup, and the topology matches the configuration. Built-in topology identification allows I/O confirmation at system startup or via auto-topology configuration.

Bit errors during data transmission can be detected using a valid 32-bit CRC. In addition to identifying and locating faults, the physical layer and topology are transported through the EtherCAT system protocol, enabling high-quality monitoring of each individual transmission segment. By analyzing error counters automatically, critical network segments can be pinpointed. It can detect and locate sources of changing errors such as electromagnetic interference, faulty connectors, or damaged cables, even if they haven’t significantly impacted the network’s self-healing capabilities.

Openness:

EtherCAT is fully compatible with Ethernet and features a unique openness design. The protocol can coexist with other Ethernet protocols that offer various services, all on the same physical medium with minimal impact on overall performance. Standard Ethernet devices can connect to an EtherCAT system via switch terminals without affecting cycle time. Devices with traditional fieldbus interfaces can be integrated through the EtherCAT fieldbus master terminal. The UDP protocol variant allows for integration into any slot interface. EtherCAT is a completely open protocol and has been recognized as a formal IEC specification (IEC/PAS62407).

EtherCAT Technology Organization:

The EtherCAT Technology Group (ETG) is an association of automation users and vendors aimed at supporting the development of EtherCAT technology. It represents a wide range of industries and applications, ensuring that EtherCAT functions and interfaces are optimally utilized across different use cases. The organization ensures that EtherCAT can be easily and cost-effectively integrated into a variety of automation devices and that interoperability is maintained. The ETG is a member of the official IEC partner organization for fieldbus standardization and is open to all companies seeking to participate.