2. Terms and Definitions 2 2. Terms and Definitions Term Explanation and Definition PDO communications (Communications using Process Data Objects) This method is used for cyclic data exchange between the master unit and the slave units. PDO data (i.e., I/O data that is mapped to PDOs) that is allocated in advance is refreshed periodically each EtherCAT process data communications cycle (i.e., the period of primary periodic task). The NJ-series Machine Automation Controller uses the PDO communications for commands to refresh I/O data in a fixed control period, including I/O data for EtherCAT Slave Units, and the position control data for the Servomotors.
It is accessed from the NJ-series Machine Automation Controller in the following ways. •With device variables for EtherCAT slave I/O •With Axis Variables for Servo Drive and encoder input slaves to which assigned as an axis SDO Communications (Communications using Service Data Objects) This method is used to read and write the specified slave unit data from the master unit when required. The NJ-series Machine Automation Controller uses SDO communications for commands to read and write data, such as for parameter transfers, at specified times.
The NJ-series Machine Automation Controller can read/write the specified slave data (parameters and error information, etc.) with the EC CoESDORead (Read CoE SDO) instruction or the _ EC CoESDOWrite (Write CoE SDO) instruction. _ Slave Unit There are various types of slaves such as Servo Drives that handle position data and I/O terminals that handle the bit signals. The slave unit receives output data sent from the master, and transmits input data to the master. Node address An address to identify the unit connected to EtherCAT. ESI file (EtherCAT Slave Information file) The ESI files contain information unique to the EtherCAT slaves in XML format.
Install an ESI file into the Sysmac Studio, to allocate slave process data and make other settings.