Beckhoff EL6692, Документация

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Product overview
EL6692 19 Version: 3.2
• However, an external reference slave such as EL6688 (IEEE1588 PTP) takes a few seconds before it
can supply a reference time that is synchronized with the higher-level clock.
• As soon as the external reference time is available, the offset to the local time is calculated and
corrected by ±½ cycle time to ensure that both tasks run in phase, and the EtherCAT master Info Data
are made available to the user for reconciliation with the local time values.
• From this time the offset is kept constant, depending on the selected control direction.
TwinCAT system behavior
External reference clock outage
If the external reference clock signal fails, both timebases will naturally drift apart again. Once the signal is
available again, the system will once again be controlled based on the previous offset values.
TwinCAT can start without external clock signal. In this case the offset is calculated and maintained as
described above, as soon as a stable external reference clock signal is received.
Settings in TwinCAT 2.11
External synchronization via EtherCAT is supported from TwinCAT 2.11. The synchronization direction can
be set in the associated dialog.
Distributed clock timing settings
Fig. 14: TwinCAT 2.11 distributed clock settings - Sample for EL6688 in PTP slave mode as time reference
for the local EtherCAT system
• Independent DC Time: one of the EL terminals (generally the first terminal supporting DC) is the
reference clock to which all other DC terminals are adjusted. Selection of the reference clock in the
dialog above.
• DC Time controlled by TwinCAT: the DC reference clock is adjusted to the local TwinCAT time.
• DC Time controlled by External Sync Device : if the EtherCAT system is to be adjusted to a higher-
level clock, the external sync device can be selected here.
Process data settings
TwinCAT 2.11 can display the current offsets in [ns] in the EtherCAT master info data.
• These offsets are calculated once after EtherCAT has started.
• The synchronization control keeps these offsets constant.
• If local DC time values in the synchronized EtherCAT system are to be related to the absolute
reference from the higher-level EtherCAT system (e.g. from EL1252 timestamp terminals), the user
must adjust this offset with each local timestamp.