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DP83867IR: Speed selection by ANEG_SEL

K.Hamamoto
Guru 12155 points
Part Number: DP83867IR

Hi

Regarding speed selection, I referred the following post. I understood the reason for separating to two mode.(to reduce the mode and pins and strap)

https://e2e.ti.com/support/interface/ethernet/f/903/p/565272/2124699?tisearch=e2e-sitesearch&keymatch=ANEG_SEL#2124699

However is there any other merit or demerit ? For example, at the mode of "100/1000 only" is the startup is faster than another mode. Or something.

Regards,

Koji Hamamoto

  • 0
    TI__Mastermind 23675 points
    Hi Hoji,

    Auto-Negotitation will still take the same amount of time.
    It just prevents the PHY from ever being able to establish a 10Mbps link when only 100/1000 is advertised.
    No merit or demerit. It is an application decision for more flexibility in the control at power-up.
  • 0 in reply to Ross Pimentel
    Guru 12155 points

    Hi Ross,

    Thank you for your support.

    I understood.

    I have one more question. On the datasheet, it is mentioned as below.

    Is it possible to be disable auto-negotiation by changing BMCR bit12 even if Auto-negotiation is enable at strap option?

    Regards,

    Koji Hamamoto

  • 0 in reply to K.Hamamoto
    TI__Mastermind 23675 points
    Hi Koji,

    Yes, you can disable Auto-Negotiation using BMCR and then re-enable it later.
  • 0 in reply to Ross Pimentel
    Guru 12155 points

    Hi Ross,

    Thank you.

    I would like to confirm again about Auto-negotiation and strap option.

     

    #1:

    At the above my question, it is possible to re-enable it later by BMCR bit[12] even if the auto-negotiation is enable  by strap option.

    However at the datasheet , it is mentioned it is not possible to re-enable by register if the auto-negotiation is disabled by strap option.

    Is that about "Autoneg Disable"  at the below register?

    #2

     Regarding the strap option "ANEG_SEL", it is selected "10/100/1000 mode" and "100/1000 mode".

    If "ANEG_SEL " is 1, which register will be set?  (If the strap of ANEG_SEL is set to "1", the BMCR[12] will be set "1" as well?) 

    Also at some register (ANAR), the default of ANAR [8:5] is set by strap option.

    Which strap option can be set this register?

    I have got confused about the strap option.

    Regards,

    Koji Hamamoto

  • 0 in reply to K.Hamamoto
    TI__Mastermind 23675 points
    Hi Koji-san,

    You can re-enable auto-negotiation after turning it off in register map.
    If you disable auto-negotiation in hardware (bootstrap) then you will not be able to re-enable it.

    If ANEG_SEL is set, BMCR, ANAR, and CFG1 will indicate it.