Omron 3G3MX2 Series, Connection Manual

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2. Terms and Definition
2
2. Terms and Definition
Terms 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 EtherCAT port built into the NJ-series CPU Unit uses process data
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.
Variables are used to access from the NJ-series CPU Unit 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 EtherCAT port built into the NJ-series CPU Unit uses SDO
communications for commands to read and write data, such as for
parameter transfers, at specified times.
You can read/write the following specified slave data with the
EC_CoESDORead (Read CoE SDO) instruction or the
EC_CoESDOWrite (Write CoE SDO) instruction.
•SDO data in slave units (parameters, error information, etc.)
Slave Unit There are various types of slaves such as Servo Drives that handle
position data and I/O terminals that control the bit signals.
The slave receives output data sent from the master, and transmits input
data to the master.
Node address An address to identify the unit connected to the EtherCAT network.
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 easily allocate slave process
data and make other settings.