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Original question:

DP83822I: Oscillator : Pull-down Resistor for XI

DP83822I: Signal/Energy Loss in FLD

Shunsuke Nagata
Genius 13070 points
Part Number: DP83822I

Hi,

Could you please check the Fast Link Down criteria. One of the criteria shows Signal / Energy loss in datasheet. I guess it is for drop power or line of link partner, and it should be normal matter. Please let me know if there is special feature for FLD.

Will the link be keep when bit 0 of 0x000b is disabled even if the line is drop?
Will the link be drop after 10us when the line drop when bit 0 of 0x000b is enabled? (Datasheet doesn't show the 10us window in Signal/Energy loss sentence.)

Regards,
Nagata.

  • 0
    TI__Genius 16030 points

    Hello Nagata,

    I am looking into it and will get back to you.

    --

    Regards,

    Vikram

  • 0 in reply to Vikram Sharma
    TI__Genius 13070 points

    Vikram -san,

    Could you please let me know the status of my question?

    Regards,
    Nagata.

  • 0 in reply to Shunsuke Nagata
    TI__Genius 16030 points

    Hello Nagata-san,

    Sorry for the delay. I am following up for the answers from the team. I should be able to get back to you in a day.

    --

    Regards,

    Vikram

  • 0 in reply to Vikram Sharma
    TI__Genius 16030 points

    Hello Nagata-san,

    When Fast-link-drop is enabled, PHY can be selected to look for loss of energy (energy below a threshold) in 4us window and it drops the link if energy is lower than threshold in this window. For normal case, PHY will look for energy lower than threshold in 32us and drop the link if energy is low in that window.

    As mentioned in the data-sheet, other than usual criteria of low energy PHY can be programmed to drop link for criteria of Rx errors, MLT3 errors etc.

    --

    Regards,

    Vikram

  • 0 in reply to Vikram Sharma
    TI__Genius 13070 points

    Vikram -san,

    I would like to follow up about your comment :

    > For normal case, PHY will look for energy lower than threshold in 32us and drop the link if energy is low in that window.

    Does it work in the case which FLD is disabled? I believe this is normal that link would loss when link partner is disappeared. 

    Could you please let me know the each case when link partner drop.
    Case 1: Enabling FLD :  FLD feature check the line voltage threshold in 32us.
    Case 2: Disabling FLD : ?? Will PHY keep the link even if link partner is disappeared?

    Regards,
    Nagata.

  • 0 in reply to Shunsuke Nagata
    TI__Genius 16030 points

    Hello Nagata-san,

    If link-partner will disappear, link will also disappear. By default fast link down is disabled.

    Case 1 : Enabling FLD :  FLD feature check the line voltage threshold in 4us.

    Case 2 : Disabling FLD(default) :  Instead of 4us, it looks at 32us window for the energy from link-partner.

    --

    Regards,

    Vikram

  • 0 in reply to Vikram Sharma
    TI__Genius 13070 points

    Hi, Vikram,

    Thank you very much for your supports.

    Could you please let me know detail about Case 2?
    The datasheet shows Link loss detection take about 250us in Disabling FLD as below.

    ----------------------------------------------------------

    Link Loss Recovery:

    1 = Enable Link Loss Recovery mechanism

    0 = Normal Link Loss operation

    This mode allows recovery from short interference and continue to

    hold the link up for a few additional mSec until the short interference is

    gone and the signal is OK. Under Normal Link Loss operation, Link

    status will go down approximately 250μs from signal loss.

    ----------------------------------------------------------

    Will device check several times with 32us window to detect link loss? (e.g. 8 times x 32us ≒ 250us)

    Regards,
    Nagata.