Technical Knowledge

EtherCAT bus servo communication protocol
Release Date : 2020-07-09 18:25:32


PMM series integrated servo motor is an EtherCAT bus servo control motor. What is the EtherCAT bus servo protocol?
 
Since its introduction in 2003, the EtherCAT protocol with "dynamic processing" and data transmission speeds of up to 100 Mbit/s has been widely used in automation and process control applications.
 
The core functions of EtherCAT include distributed clocks, flexible topology, network-wide diagnostics, and "instant" telegram processing.
 
The maximum data capacity of one frame of EtherCAT is up to 1470 bytes. Data can be modified or added during message transmission without stacking, buffering or disassembling/combining
Each node directly uses hardware to perform calculations, without the need for software participation, which greatly reduces the message delay. The communication delay of a servo axis is only 1us
 
Synchronous clock
1. Each EtherCAT slave has a clock mechanism inside the slave controller ESC, called slave clock
2. Each EtherCAT master station also has a clock mechanism inside, called the master station clock
3. The EtherCAT bus network regards the first slave station clock as the reference clock, and uses the reference clock as the system clock of the entire system. All clocks including the master station clock are synchronized to the reference clock.
4. In the EtherCAT bus network, the distributed clock can make all EtherCAT bus devices use the same system time through the synchronization signal (SYNC signal), thereby controlling the synchronous execution of the tasks of each device;
5. The SYNC signal transmission cycle is the synchronization cycle
 
In 2018, Beckhoff (the developer of EtherCAT) brought significant performance improvements to EtherCAT in the form of EtherCAT G and EtherCAT G10-the new version of the EtherCAT protocol runs at 1 Gbit/s and 10 Gbit/s respectively .
 
The development of EtherCAT G and G10 has not changed the EtherCAT protocol or EtherCAT main software, and the new EtherCAT G and G10 also comply with the IEEE 802.3 Ethernet standard.
 
It is expected that the standard EtherCAT will still be the preferred solution for most bus servo applications, while EtherCAT G and G10 will provide the best performance for applications that require large amounts of data (for example, applications with a large number of motion axes or data-intensive equipment). Such as vision systems and IoT devices. The increased bandwidth provided by the new version will also benefit these applications. For example, for the branch model, the network may include machine vision systems running through EtherCAT G or G10, and slave devices running through standard 100 Mbit/s EtherCAT. This topology provides the bandwidth required to process visual data and the fast communication time required to process and execute commands generated by the visual data.
 
The combination of EtherCAT bus technology and integrated servo motor driver technology not only improves the communication efficiency, but also increases the control effect of the servo motor.

 
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