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'Distributed Clock' Editor (EtherCAT Slave Device)

This topic contains the following sections:

The following information refers to a specific, typical device type. Your screen may differ.

This help topic describes the 'Distributed Clock' editor of an EtherCAT slave device in the PLANT. EtherCAT slave devices are child elements of the 'EtherCAT' node (which represents the EtherCAT Master).

General information on Distributed Clock synchronization

Distributed Clocks (DC) enable EtherCAT network-spanning, exact time synchronization when generating output signals and reading inputs. Timestamps for events are also synchronized in this way. Such a precise time synchronization is especially necessary in motion applications where several axes are moved in a precisely (time) coordinated manner.

To support DC, a slave must implement a synchronizable clock. After PowerOn, the slave first uses its own, internally generated local time. As soon as one slave device is specified to deliver the reference system time, all accordingly configured slaves synchronize their local clocks with the system time. This is always the first slave station connected to the Master which supports the DC functionality.

The synchronization of the distributed clock system (and thus in each slave) takes place at the transition from Pre-Op to Op state, i.e. at the start-up of the EtherCAT system. Consequently, after changing DC-related parameters, an EtherCAT restart must be performed for the changes to take effect.

Currently, PLCnext Engineer does not support any user-defined DC-related settings.

Further Info
For details please refer to the documentation of the EtherCAT Technology Group.

Activating DC for a slave

To use DC for a slave, proceed as follows:

  1. Double-click the slave node in the PLANT and open the 'Distributed clock' editor.
  2. In the drop-down list, specify whether the slave clock should be synchronized.
    The possible settings are described in the section "Possible settings" above.

Note
Using the EtherCAT Online Functions you can get DC-related diagnostic information on each slave.