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DP83867E: 100BASE operation with auto-negotiation enabled

Shota Mago
Expert 8490 points

Part Number: DP83867E

Hi team,

Is there anyway to set 100Mbps with auto-negotiation enabled?

SNLA438 shows below table. There is statement of Auto-negotiation enabled.

While, SPEED SELECTION of address 0000 states "When auto-negotiation is disabled writing this bit allows the port speed to be selected.".

How can we set 100Mbps from startup(no extra writing after power up)?

Best regards,

Shota Mago

  • 0
    TI__Mastermind 25228 points

    Hi Mago-san,

    What speeds are the link partner advertising in auto-negotiation?

    If the link partner only supports 100M in auto-negotiation, then the strap value of ANEG_SEL = 1 (pin 46 mode 3 or 4) is enough to have the device communicate in 100M on startup.

    However, this mode also enables 1000M advertisements. If the link partner supports 1000M speed, then additional register write is required to disable 1000M advertisement and force 100M speed with auto-negotiation. The write for this is 0x9[9:8] = '00'.

    Please let me know if I can clarify further.

    Thank you,

    Evan

  • 0 in reply to Evan Mayhew
    TI__Expert 8490 points

    Hi Evan,

    Thanks for your reply.

    The customer needs to force 100BASE under both 100BASE/1000BASE are available.

    I'll ask the customer to try your suggestion(ANEG_SEL=1 and 0x9[9:8] = '00').

    Is SPEED SELECTION bit effective only for auto-negotiation disabled?

    Best regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Mastermind 25228 points

    Hi Mago-san,

    Sounds good, I will wait for the test result here.

    Shota Mago said:
    Is SPEED SELECTION bit effective only for auto-negotiation disabled?

    Correct, speed selection bits only take effect with auto-negotiation disabled.

    Advertisement registers should be considered for forcing a speed with auto-negotiation enabled.

    Thank you,

    Evan

  • 0 in reply to Evan Mayhew
    TI__Expert 8490 points

    Hi Evan,

    To realize forced 100Mbps link-up immediately after power-up(no link-up of 10/1000Mbps), the customer considers following sequence. 

    1. After reset, keep INT/PWDN Low
    2. Program registers including ANEG_SEL = 1 and 0x9[9:8] = '00' through MDIO
    3. INT/PWDN High

    Is this procedure enough to realize forced 100Mbps link-up after power-up?

    Best regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Mastermind 25228 points

    Hi Mago-san,

    This procedure looks valid. I expect this to work if the opposing device has auto-negotiation enabled with 100M advertisements.

    Thank you,

    Evan