[etherlab-users] [PATNI] Regarding DC Synchronisation

[Dhake, Yogesh]

Hi,
EtherCAT master performs DC synchronization as below:
1)       Initially EtherCAT master calculates Propagation delay time between slaves.
2)       Time Delay calculated (actual frame send from Master state machine - application start time) and deducted from System Time read from slave. New Offset time (new offset = old offset from slave + time difference between Master Application Start Time and Slave System Time) is send to slaves.
3)       After this, Master sends synchronization datagram (with command FRMW-First READ MULTIPLE WRITE) to reference clock slave as well as to other EtherCAT slaves on network.
4)       FRMW command reads reference clock slave system time (lower 32 bit) (0x0910 to 0x0927) and writes to lower 32 bit of other EtherCAT slave system time register (0x0910 to 0x0927).
5)       Activity number 2 to 4 happens at every 10ms in user application.
6)       Our observation is difference between master time and slave system time is around 16-20 seconds after step 2.
7)       Slave System Time is not accessible to us for checking whether Slave System Time synchronized with Master Application Time.


Our query is:
1.       How can we reduce difference between Master Application Time and Slave System Time in step 2?
2.       How to check System Time register of BECKHOFF slave after step 4?

Please let us know your valuable inputs regarding synchronization of Distributed clocks of EtherCAT slaves.

Please find attached DC synchronization process. Rename file to .png type.

Regards,
Yogesh

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