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AM3357: Common clock source for EtherCAT

Daisuke Maeda
Guru 20345 points

Part Number: AM3357
Other Parts Discussed in Thread: TMDSICE3359, AM3359, TMDXICE110, AMIC110, TMDSCNCD28388D, TMS320F28388D,

Beckhoff's documentation describes that all PHYs connected to one ESC and the ESC itself must share the same clock source.

https://download.beckhoff.com/download/document/io/ethercat-development-products/an_phy_selection_guidev2.7.pdf
"All PHYs connected to one ESC and the ESC itself must share the same clock source, so a TX FIFO can be omitted."
"The clock source of Ethernet PHYs and ESC has to be the same quartz or quartz oscillator."
"Shared 25 MHzclock source between ESC and PHY"

Should the reference clock inputs of two PHY and the XTALIN of AM335x share the same 25 MHz clock source?

Best regards,

Daisuke

  • 0
    Guru 20345 points

    Hi,

    I checked the evaluation boards that support EtherCAT.

     - TMDSICE3359

       The reference clock inputs of two PHYs share the same 25MHz clock source, but the XTALIN of AM3359 does not.

     - TMDXICE110

       Each of the reference clock inputs of two PHYs and the XTALIN of AMIC110 has a different 25MHz clock source.

     - TMDSCNCD28388D

       The reference clock inputs of two PHYs share the same 25MHz clock source, but the X1 of TMS320F28388D does not.

    Should the reference clock inputs of two PHYs and the XTALIN of AM3357 share the same 25 MHz clock source?

    Best regards,

    Daisuke

  • 0 in reply to Daisuke Maeda
    TI__Mastermind 43296 points

    Daisuke,

    With the same reference clock for PHYs and the XTALIN, it helps reduce the jitter of sync signal. When the different 25 MHz clock domain presents, the jitter is mainly reduced by the software/firmware based drift compensation algorithm in EtherCAT.

    Regards,

    Garrett

  • 0 in reply to Garrett Ding
    Guru 20345 points

    Hi, Garrett-san,

    Thank you for your reply.

    Best regards,

    Daisuke