Implementation Of Industrial Ethernet Protocol Master Based On EtherCAT

With the continuous advancement of industrial automation, traditionalindustrial bus is unable to meet the industrial demand, because it is slow, and hasa small amount of data. At the same time, with the development of computernetwork, Ethernet technology used in industrial control fieldbus has become animportant development direction. EtherCAT proposed by BECKHOFF ofGermany in2003, it is high-speed, high data efficiency and supports a variety ofphysical topology. What’s more, the system is composed simply, for example,masters use common ARM development board and slaves use dedicate controlchips. In order to overcome the uncertainty of MAC layer in traditi onal Ethernet,EtherCAT modifies the traditional Ethernet protocol. Ethernet data frame type isthe specific0x88A4.In the EtherCAT protocol, time-critical data sends using periodic processdata manner, and the non-time critical data using aperiodic manner. Aperiodicdata communicates in two ways, namely, communication primitives and mailboxcommunication. The communication primitives are mainly used for theinitialization and configuration of masters and slaves, such as basic registerinitialization, mailbox configuration and so on. The mailbox communication is inapplication layer, realizing COE protocol for the operation of service data andPDO. Periodic process data uses the method of logical addressing, and it canmulticast. One packet can operate multiple slaves, each slave removing theincoming data, and at the same time inserting its data to the packet. Because ofthe real-time, periodic process data communication method is mainly used foractual control. In testing section slave state machine is the main clue. The systemconfigures the slaves’ relevant parameters in turn until slaves reaching theOperational status, and makes the functional tests for two main methods ofcommunication. Finally, make the performance testing, including system delay.In this article, the master system ECOU realizes the EtherCAT protocolusing the embedded operating system of UC/OS II, and has a good real-time.