EtherCAT G – ultimate I/O performance for high-performance machines

The EtherCAT G technology extension can superimpose itself on Gigabit Ethernet for data-intensive applications. It is compatible with EtherCAT, which uses 100 Mbit/s. In addition, the operation of parallel network segments is possible with the branch concept introduced for EtherCAT G.

EtherCAT G uses the 1 Gbit/s data transmission rate of standard Ethernet; while the EtherCAT G10 variant, achieves data rates of up to 10 Gbit/s. The increase in data rates compared with the standard 100 Mbit/s EtherCAT increases the possible data throughput. In conjunction with the new branch concept, EtherCAT G (1 Gbit/s) enables a two- to seven-fold increase in performance in relation to communication times and up to 10 times the bandwidth, depending on the application. A hundred times the bandwidth is even possible with EtherCAT G10.

A fully compatible technology extension
With EtherCAT G, the success principle of EtherCAT can be used to leverage the high Ethernet data transmission rates that are technologically available today – without any changes to the EtherCAT protocol itself. The telegram sent by the EtherCAT master continues to pass through all network devices. Every EtherCAT slave reads the output data addressed to it on the fly and places its input data in the forwarded frame, but now with data rates of 1 to 10 Gbit/s. As before, the last device in a segment (or branch) will detect an unused port and send the telegram back to the master. The full-duplex property of the Ethernet physics is utilised for this capability.

All other EtherCAT properties are also retained. Devices with three or four ports (junctions) make flexible topologies possible that can be individually adapted to the respective machine architecture. Optional machine modules can be plugged in or out by Hot Connect as required. An internal network diagnostic function helps to minimise machine or plant downtimes and therefore increase availability with familiar efficiency. The integrated distributed clocks concept also remains available and enables synchronisation accuracies of better than 100 ns between devices. Conformity with the Ethernet standard IEEE 802.3 is also guaranteed.

Rollout of EtherCAT G made easy
Performance is key to EtherCAT G. Not only the protocol, but also the fundamental mechanisms and the configuration options remain the same. Only the function blocks necessary for physical access to the communication cables have been replaced by corresponding Gbit/s variants. The master therefore requires no new software, just one Gbit/s port. The existing cable types can also continue to be used: Cat.5e cables for EtherCAT G or Cat.6 cables for EtherCAT G10.

Consequently, EtherCAT G slaves can be operated on an existing EtherCAT master, provided it has the aforementioned Gbit/s port. Several special protocol extensions for EtherCAT G are currently being prepared that will allow for even higher-performance use. However, the extensions required for this on the master side will not be mandatory for the network to be operational.

Branch concept for mixed operation with maximum efficiency
EtherCAT and EtherCAT G can be operated within the same network, i.e. EtherCAT G slaves will work in a 100 Mbit/s EtherCAT network and vice versa. However, all EtherCAT G devices will switch back to the 100 Mbit/s mode in such a mixed network. In order to prevent this, the new branch concept makes EtherCAT branches possible, which enable the parallel operation of 100 Mbit/s segments in a 1 or 10 Gbit/s network through appropriate speed implementations. In this way, a branch of an EtherCAT G segment can be implemented on a 100 Mbit/s network, for example, using the new EK1400 EtherCAT G Coupler, therefore allowing the wide range of standard EtherCAT terminals to be used within the EtherCAT G network environment. The 1 Gbit/s speed of EtherCAT G communication segment is retained.

The EtherCAT G branch concept offers efficiency benefits that minimise propagation times. The CU14xx multi-port branch controllers are designed for this purpose and enable the interconnection of several EtherCAT and EtherCAT G segments. The individual branches are addressed with a single telegram from the master, which will then be processed simultaneously. This makes much shorter signal propagation times possible and therefore shorter communication and cycle times, because the telegram of a segment travels directly from the branch controller back to the master and not through all other connected segments as well. In most applications, the parallel operation of network segments results in an improved performance increase compared to a slight increase in the transmission bandwidth would render possible.

Application and performance examples
For most present-day applications the high performance of standard EtherCAT is fully adequate. Accordingly, EtherCAT G communication was developed with large-scale applications and many devices in mind, as well as the increasing use of particularly data-intensive devices such as vision cameras, complex motion systems or measurement applications with high sampling rates. Machine vision, condition monitoring or the innovative transport systems XTS and XPlanar require transmission of several hundred bytes of process data per cycle for each device. In conjunction with short cycle times of less than a millisecond, the high transmission bandwidths provided by EtherCAT G are called for in this context.

The first practical EtherCAT G application is the XPlanar transport system, which was shown for the first time at the SPS IPC Drives 2018. This planar motor system enables motion control and highly precise positioning of passive free-floating movers with six degrees of freedom. Due to the continuous position feedback required for the unique new system, extremely large data quantities are produced that have to be transmitted within a few microseconds. This would hardly be possible without the high performance of EtherCAT G.