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DP83848I: Value for "SPEED STATUS" bit of PHYSTS register when unplug Ethernet cable

Hisao Uchikoshi
Genius 14880 points
Part Number: DP83848I

Hi Experts,

SPEED STATUS bit of PHYSTS is defined as below.

At Auto-negotiation mode, this bit is updated when plugging Ethernet cable and Link is established. When unplugging Ethernet cable, is this bit cleared?

Regards,

Uchikoshi

  • 0
    TI__Mastermind 18425 points
    Hi Uchikoshi-san,

    The Speed Status bit is valid only when there is a valid link. So when the cable is removed, that bit should not be used. In order to detect link down, use bit 0.

    -Regards
    Aniruddha
  • 0 in reply to Aniruddha Khadye
    TI__Genius 14880 points
    Hi Aniruddha,
    This post is related to below post.

    e2e.ti.com/.../795796

    Before adding a wait loop for "AUTO-NEG COMPLETE" flag to be set, a software read "SPEED STATUS" bit just after "LINK STATUS" bit becomes to 1. On Auto-negotiation mode, when connecting to a pear device whose PHY speed is fixed to 10Mbps, a "SPEED STATUS" bit was indicating to "0"(100 mbps). This is what the datasheet is explaining. We have to wait "AUTO-NEG COMPLETE" flag is set to 1. After that, "SPEED STATUS" bit becomes to "1"(10mbps). Then, disconnect the cable and re-connect a cable again then read "SPEED STATUS" bit just after "LINK STATUS" bit is set, "SPEED STATUS" bit is 0. It looks like "SPEED STATUS" bit is cleared to 0 when disconnecting a cable. So I want to know if this behavior is expected.

    Regards,
    Uchikoshi
  • 0 in reply to Hisao Uchikoshi
    TI__Mastermind 18425 points
    Hello Uchikoshi-san,

    The default value of Speed Status bit is 0 so it is expected that the bit will go back to its default value when the link is dropped.

    -Regards
    Aniruddha