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DP83822I: DP83822: Clarification on autonegotiation and register bit behavior

Pascal REGACHE
Prodigy 240 points
Part Number: DP83822I

Hello,

An auto negotiation can be restarted writing bit 9 of BMCR. According to the datasheet, the bit is iself clearing when the auto negotiation has started.

At the same time bit 4 of PHYSTS and bit 5 of BMSR are cleared while the autonegotiation process is in progress.

Are the PHYSTS.4 / BMSR.5 bits cleared when BMCR.9 is written to 1, or are they cleared when the auto negotiation procecess has started, that is BMCR.9 cleared ?

Also what are the conditions for an autonegotiation not ending (PHYSTS.4 statys low) besides no party connected ?

Or is this status bit guaranteed to return high after some timeout and it is up to the management software to make sense of the situation (link status for instance) ? Or shall have my own timer for the non completion of an auto negotiation restart ?

Thanks

Best regards

Pascal 

  • 0
    TI__Mastermind 19780 points
    Hi Pascal,

    PHYSTS.4/BMSR.5 is cleared when BMCR.9 is cleared and the new auto-negotiation process has started.

    Auto-negotiation may complete without a link present. PHYSTS.4 would stay low only when no link partner is connected. The PHY will continue to send auto-negotiation link pulses until a link partner is detected.

    If you are restarting auto-negotiation in a situation where you KNOW a link partner is connected and you want a timeout timer, you would have to implement one yourself. Auto-negotiation does not have a completion time requirement, and as such, auto-negotiation will continue to send link pulses until a partner is detected.

    Best Regards,