www.advantech.com/products Online Download Motion Control Overview EtherCAT EtherCAT (Ethernet Control Automation Technology) is a high-performance, Ethernet-based fieldbus industrial network system. The protocol is standardized in IEC 61158 and applies to automation applications that need faster and more efficient communications. Short data update times with precise synchronization make EtherCAT suitable for real-time requirements in automation technology. Functional Principle In EtherCAT network, the Master sends Ethernet frames through all of the slave nodes. The Standard Ethernet packet or frame is no longer received, interpreted, and copied as process data at every node. Instead, slave devices read the data addressed to them and input data are also inserted in the same time while the telegram passes through the device, processing data "on the fly". Typically the entire network can be addressed with just one frame. Protocol Data exchanges are cyclically updated between EtherCAT Masters and Slaves. Data in EtherCAT frames is transported directly within the IEEE 802.3 Ethernet frame using Ethertype 0x88a4 and are processed by the EtherCAT Slave Controller on the fly. Each EtherCAT datagram is a command that consists of a header, data and a working counter. The datagram header indicates what type of access the master device would like to execute: Read, write, read-write Access to a specified slave device through direct addressing Access to multiple slave devices through logical addressing Logical addressing is used for the cyclical exchange of process data. The header and data are used to specify the operation that the slave must perform, and the working counter is updated by the slave to let the master to know that a slave has processed the command. Every EtherCAT datagram ends with a 16 Bit Working Counter (WKC). The Working Counter counts the number of devices that were successfully addressed by this EtherCAT datagram. EtherCAT datagrams are processed before receiving the complete frame. In the case that the data is invalid, the frame check sum (FCS) is not valid and the slave will not set data for the local application. Topology EtherCAT supports a variety of network topologies, including line, tree, ring and star. The line and tree topologies are more conducive to fieldbus applications because they require fewer connections and utilize a much simpler and more flexible cabling schema that switches and hubs are not necessary for lines or trees topology. Inexpensive industrial Ethernet cable can be used between two nodes up to 100m apart in 100BASE-TX mode. EtherCAT makes a pure bus or line topology with hundreds of nodes possible without the limitations. Up to 65,535 devices can be connected to EtherCAT, so network expansion is almost unlimited. EtherCAT supports individual nodes to be connected/disconnected during operation. If one of the slaves in the network is removed, the rest of the network can continue to operate normally. EtherCAT also enables other communication features such as cable redundancy or master redundancy with Hot Standby. Synchronization Distributed Clocks (DC) mechanism provides highly precise time synchronization between slaves in an EtherCAT network, which is equivalent to the IEEE 1588 Precision Time Protocol standard. By using distributed clocks, EtherCAT is able to synchronize the time in all local bus devices within a very narrow tolerance range. All EtherCAT slaves are provided with an internal clock which named as System Time (tLocal Time ). One EtherCAT Slave, is used as a Reference Clock and distributes its Clock cyclically. Possible misalignment between the reference clock and the clocks of the other slaves are caused when a slave is switched on, the internal free-running register that holds the current time is reset to zero. Unfortunately, this action doesn't happen at the same time, and this result in an initial offset (toffset) among clocks has to be compensated. Typically, masters send a broadcast to all other slaves in the system. Having received the message, slaves will latch the value of their internal clock. There are two latch values, one is receiving and the other is returning back. Thus, the master can read all latched values and calculate the delay for each slave (tPropagation Delay). Delays will be stored into offset register. In the following, the master will send a message periodically to all other slaves in EtherCAT network to make the first slave the reference clock and forcing all other slaves to set their internal clock by the calculated offset. Because synchronization between slaves in DC mode is done by internal clocks in hardware, EtherCAT guarantee the time jitter is less than 1us. Diagnosis with Exact Localization EtherCAT is an ultra-fast I/O system. To reach the best high-speed communication, high communication accuracy is demanded. EtherCAT comprises a wide range of system-inherent diagnostic features which help detect and locate system errors precisely. Every EtherCAT datagram ends with a 16 Bit Working Counter (WKC) to count the number of devices that were successfully addressed by this EtherCAT datagram. The Master can check the data exchange situation by WKC in the same cycle and the error frame can be detected by analyzing the nodes’ error counters. The slave application will be executed only as the frame is received correctly. The automatic evaluation of the associated error counters enables precise localization of critical network sections. Bit errors during transmission are detected reliably by the analysis of the CRC (Cyclic Redundancy Check ) check sum. CRC is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data. In addition to the error detection and localization protocol, transmission physics and topology of the EtherCAT system allow an individual quality monitoring of every single transmission path. AMONet AMONet makes machine building with motion control easier. The savings made on wiring and programming effort, as well as the compatibility with a wide range of popular motors have already led to many requests for AMONet products. Structure AMONet products are also categorized as Master cards or Slave modules. While the Master card is kept in the host PC, the slave modules can be distributed so that they are next to motor drivers on the factory floor. Communication The communication speed between the AMONet RS-485 slave modules can be up to 20 Mbps. This makes it possible to scan 2048 I/O points within 1.04 ms (or 1024 I/O points in 0.56 ms). Furthermore, an AMONet RS-485 master will update the I/O status automatically, and map data into local memory. Software running on the host PC can then read the status by simply reading the onboard memory, so no polling of slave modules is necessary. Flexibility Each port of a master card can control up to 2048 I/O connections or 256 motion axes, so future extensions are easily implemented. The distance between a master card and its slave modules can be up to 100 meters, and this distance is covered with a cost-effective Cat 5 network cable. In addition to saving wiring costs, debugging and maintenance are also simplified. Compatibility Another advantage of AMONet RS-485 is its compatibility with motor drivers from different vendors. Advantech provides specially designed wiring boards for popular motion drivers from vendors such as Panasonic, Mitsubishi, Yaskawa and Delta . This makes configuration easier, as pin-to-pin cables can be used. You can also connect to a manual pulse generator directly to adjust and calibrate the system without having to write programs first. Motion control and I/O functions with AMONet RS-485 use the same library. This unique feature saves time, as programmers do not need to study both a motion library and an I/O library. Power & Energy Automation 8 5 4 4 10 Panel PCs 9 iDoor Technology Modules 8 Industrial monitors 7 Industrial IoT Gateways 6 Control Cabinet PCs High-Performance Control Panels Industrial Operator Panels 3 2 IntelligentMotionControl andMachineVision 1 WebAccess+ Solution 11 Control IPCs 12 Remote DA&C Systems 13 Wireless IoT Sensing Devices 14 15 RS-485 I/O Modules 16 Thin-Client Terminals Industrial Ethernet Solutions 17 IP Gateway and Serial Device Servers iNetworking 18 19 Ethernet I/O Modules Chapter 2 Table of Contents Table of Contents