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DP83848I: Link loss reaction time for EtherCAT

Kzk
Genius 5785 points
Part Number: DP83848I
Other Parts Discussed in Thread: AM3357, TLK110

Hello,

Previously, I posted a related question to Sitara Forum. Can I have one more question?
https://e2e.ti.com/support/arm/sitara_arm/f/791/t/576456

How much time will be "Link loss reaction time" of DP83848 if I enable "Enhanced Link Detection" with AM3357 and DP83848, that is, when I connect pr3_mii1_rxlink and pr1_mii0_rxlink pin of AM3357 to LED_LINK or LED_SPEED pin of DP83848?

Is it 250 us described in PHY selection guide from BECKHOFF, or is it faster than 15 us required by EtherCAT?

In the case of TLK110 which supports "Fast Link Down mode", this mode can recognize the link down in 10 us and notify the link down to Link LED pin. It's clear that this time is faster than 15 us.

Regards,
Kazu

  • 0
    TI__Mastermind 19780 points
    Hi Kazu,

    The DP83848 link down time is 250us without ELD.

    With ELD, the DP83848 satisfies the 15us requirement by Beckhoff. See section 4.1 of the Beckhoff PHY selection guide. "Some Ethernet PHYs require Enhanced Link Detection to be activated in order to achieve sufficient link loss reaction times." The DP83848 is one of these PHYs.

    I hope this helps.

    Best Regards,
  • 0 in reply to Rob Rodrigues
    Genius 5785 points

    Hi Bob,

    Thank you for your quick reply. Let me check the method for enabling "Enhanced Link Detection".

    - DP83848: Connect PHY LED pin to ESC(AM3357).

    - TLK110: Connect PHY LED pin to ESC(AM3357). In addition, enable Fast Link Down by SWSCR3(bit 3 and 0) control.

    Is it correct?

    Regards,
    Kazu

  • 0 in reply to Kzk
    TI__Mastermind 19780 points
    Hi Kazu,

    ELD works by monitoring receive errors(RX_ER). You will have to check with the Sitara forum to see if the LED connecting is necessary while using ELD.

    If a PHY can detect link down <15us not using ELD, then the LED is connected directly to the ESC.

    - DP83848: Enable ELD on ESC(AM3357).

    - TLK110: Enable ELD on ESC(AM3357). Connect PHY LED pin to ESC(AM3357). In addition, enable Fast Link Down by SWSCR3(bit 3 and 0) control.

    Best Regards,