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DP83867IR: Strap Configuration for Autoneg Disable = Mode 3

Noriyuki Takahashi
Genius 10980 points
Part Number: DP83867IR

Hi team

Customer would like to make RX_DV/RX_CTRL Mode3 for Gigabit ethernet.  In current their design, Pull-up resistor = 5.6kOhm, Pull-down resistor = 2.4kOhm.

And they observed that the link is established when the partner(FPGA) is powered-on, while the link is not established when the partner(FPGA) is not powered-on.

Is this correct behavior?

I think their resistors value can violate +/- 1% tolerance of the recommended resistors, Pull-up resistor = 5.76kOhm, Pull-down resistor = 2.49kOhm.

So if the voltage of RX_DV/RX_CTRL-pin is out of target voltage, what kinds of things may happen?

Regards,

Noriyuki Takahashi

  • 0
    TI__Genius 11900 points

    Hello Noriyuki-san,

    In table "Table 4. 4-Level Strap Resistor Ratios" voltage ranges are also provided, do the resistors used by customer violate the voltage range? Even after considering the tolerance on their resistors?

    Please check this first. Modes 1 and 2 can put the device in an unknown state while mode 4 can disable auto-negotiation.

    Thanks,

    Vibhu