Description

EtherCAT is a real-time Ethernet protocol which uses standard Ethernet frames. An EtherCAT network in general consists of one EtherCAT master and one or more EtherCAT slaves. The master sends Ethernet frames to the network. The slaves extract and/or insert data "on the fly".

Configuration

The stack offers a mailbox interface for configuration and can be configured by packets or by database (config.nxd). An EtherCAT master in general reads out vendor ID, product code and revision number of a slave. These three parameters have to be provided to the stack (among others). An EtherCAT Slave Information (ESI) file has to be provided. The ESI file describes the device. In general a complex EtherCAT slave has a slave information interface (SII) and an object dictionary (OD). For access to the OD CAN application protocol over EtherCAT (CoE) is used. The SII and the OD can be created and initialized during configuration process when using so called "application controlled" startup.

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Cyclic Data Exchange

EtherCAT uses the concept of a cyclic process data image. Each master or slave of an EtherCAT network has an image of input and output data. This image is updated using cyclic Ethernet frames. An application can get access to the cyclic process data using DPM or using direct function calls.

Acyclic Data Exchange

For acyclic data exchange between an EtherCAT slave and an EtherCAT master the EtherCAT mailbox is used. An application can register eg. for read and/or write indications to CoE objects. This means that if an EtherCAT master reads or writes objects in the CoE object dictionary an application can react on that master access. The layout of the process data image can be described by CoE objects. An application also can register for read and/or write indications to the SII.

EtherCAT State Machine

The Hilscher EtherCAT slave stack provides mechanisms for user applications to get informed about state changes of the EtherCAT State Machine (ESM). Furthermore an application can control state changes of the ESM if necessary (eg. to proceed to a certain state only if synchronization is established). If no interaction from user application is necessary the stack handles the ESM on its own.

Important Specifications

For an EtherCAT slave at least the following specifications of EtherCAT Technology Group (ETG) apply:

ETG.1000
ETG.1020
ETG.1300
ETG.2000
ETG.7000