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Operating Principle:

There are several Ethernet solutions available today that provide real-time functionality. For instance, some systems disable the CSMA/CD access procedure by using a higher-level protocol layer and replace it with time-slicing or polling mechanisms. Others use dedicated switches to distribute Ethernet packets in precise time-controlled ways. 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 amounts require sending an entire Ethernet frame. Additionally, the time needed to redirect to output or drive controllers, as well as read input data, depends largely on how the system is executed. In modular I/O systems, a sub-bus like the Beckhoff K-bus is often used to speed up communication via a synchronous bus system, but such synchronization cannot eliminate delays in the main communication bus.

By adopting EtherCAT technology, Beckhoff overcomes these limitations of traditional Ethernet solutions. Instead of receiving, decoding, and copying Ethernet packets at each connection point, EtherCAT allows each device (including terminal devices) to read only the data relevant to itself as the frame passes through. Similarly, input data can be inserted into the message while it travels. When the frame is passed (with only minimal delay), the slave recognizes and processes the relevant command. This process is implemented in hardware within the EtherCAT Slave Controller, making it independent of the real-time operating system or processor performance of the protocol stack software. The last EtherCAT slave in the segment returns the fully processed message, which then serves as a response from the first slave back to the master station.

From an Ethernet perspective, an EtherCAT bus segment functions like a large Ethernet device capable of receiving and sending Ethernet frames. However, this "device" does not consist of a single Ethernet controller with a downstream microprocessor; instead, it comprises numerous EtherCAT slaves. Like any other Ethernet network, EtherCAT does not require a switch to establish communication, enabling a pure EtherCAT system.

Terminals Implement Ethernet:

Every device in the system uses the full Ethernet protocol, including each I/O terminal, without the need for a 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 exclusive and can support 10 Gigabit Ethernet. At the end of the terminal strip, the physical bus characteristics are converted back to the 100baseTX standard.

A standard Ethernet MAC or a low-cost network card (NIC) is sufficient for use as hardware in the controller. Direct Memory Access (DMA) is used to transfer data to a PC, ensuring that network access has no impact on CPU performance. The same principle applies to the Beckhoff multiport card, which bundles 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 set an IP address.

Distributed Clock: Precise synchronization is crucial in distributed processes requiring simultaneous actions, such as when multiple servo axes perform tasks simultaneously. Accurate calibration of the distributed clock offers the most efficient synchronization solution. If full synchronization is used, communication errors can significantly affect the quality of synchronized data. In EtherCAT, data exchange is based entirely on hardware. Since the communication utilizes a logical ring structure and a full-duplex Fast Ethernet with an actual ring structure, the "master clock" can accurately determine the operational compensation for each "slave clock" and vice versa. This enables a very accurate clock base with signal jitter less than 1 microsecond across the network.

Hot Connection: Many applications require changes to the I/O configuration during operation, such as in a processing center with dynamic characteristics, a tool system equipped with sensors, or a flexible workpiece actuator. EtherCAT supports hot connection, allowing parts of the network to be connected, disconnected, or dynamically reconfigured to respond to changing configurations flexibly.

High Availability: Optional cable redundancy meets the growing demand for increased 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 encountering an interrupt, a device failure does not cause the entire network to shut down. For example, cable protection can be configured in the form of a short bar to prevent wire breakage.

Safety: Security functions are typically implemented separately from an automation network, either through hardware or using a dedicated secure bus system. Thanks to TwinSAFE (Beckhoff's security technology), it is now possible to use the EtherCAT security protocol for both safety-related communication and control communication on the same network. This protocol operates at the application layer of EtherCAT and does not affect the lower layers. It has been certified according to IEC61508 to achieve SIL3, and can even reach SIL4 after implementing additional measures. The protocol supports variable data lengths, making it applicable to both secure I/O data and secure drive technology. Secure data can be routed without the need for a secure router or gateway, just like other EtherCAT data.

Diagnosis: Network diagnostic capabilities are essential for enhancing network availability and reducing debugging time (thereby lowering overall costs). Errors must be detected quickly and accurately, with clear indication of their location. During the development of EtherCAT, special attention was given to typical diagnostic features. During the test run, the specified configuration is used to verify the continuity of the actual I/O terminal configuration. The topology also matches the configuration. Due to built-in topology identification, I/O can be confirmed at system startup or through auto-topology configuration. Bit errors during data transmission can be detected using a valid 32-bit CRC. In addition to breakpoint detection and location, the physical layer and topology are transported through the EtherCAT system protocol, enabling high-quality monitoring of each individual transmission segment. By automatically analyzing error counters, critical network segments can be identified. The system can detect and locate sources of changing errors such as EMC interference, faulty connectors, or damaged cables, even if they have not severely impacted the network’s self-healing capabilities.

Openness: EtherCAT technology is not only fully compatible with Ethernet but also designed with openness in mind. The protocol can coexist with other Ethernet protocols that provide various services, all sharing the same physical medium—usually with minimal impact on overall network performance. Standard Ethernet devices can be connected to an EtherCAT system via switch terminals without affecting cycle time. Devices with traditional fieldbus interfaces can be integrated via the connection of an EtherCAT fieldbus master terminal. The UDP protocol variant allows devices to be integrated 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. The group represents a wide range of industries and applications, ensuring that EtherCAT technology is optimally utilized in various scenarios. The organization ensures that EtherCAT is easily and cost-effectively integrated into a wide range of automation devices, promoting interoperability among devices. The ETG is a member of the official IEC partner organization for fieldbus standardization. Membership is open to all companies.