SM-EtherCAT User Guide 55
Issue Number: 2 www.controltechniques.com
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8 Advanced features

8.1 Distributed clocks

SM-EtherCAT supports Distributed clocks. This is the scheme used by EtherCAT to
accurately time synchronize slave devices. Position, speed and current control loops
can all be synchronized.
When the option module is connected to a drive which can take a time synchronization
signal (e.g. a Unidrive SP or Digitax ST), the EtherCAT distributed clocks facility can be
used to provide this signal so the drive speed and current tasks are synchronized to the
network. The position controller, and appropriate motion features will also be
synchronized to the drive speed task.

8.2 SM-EtherCAT protocol support

The following are supported:
• Four Sync Managers. Two are used for the Mailbox Protocol (non-cyclic data)
and two are used for process data (cyclic data)
• Distributed Clocks
• CANopen over EtherCAT (CoE)
• CMP protocol through Modbus RTU (only on the Unidrive SP, Digitax ST,
Mentor MP and Affinity)
In CoE interpolated position mode the position command provided by the master every
interpolation cycle time is used to generate a position command for the drive every
250µs.
NOTE