DP83TC812R-Q1: PING fail with recommended pull up resistance

Tool/software:

Hi Team,

We are developing a new CMS platform with DP83TC812SRHARQ1 based on AM62A7.

1. When we are using ECU(master) to PING DP83TC812R EVM(slave), the ping would fail.

• LED_0 is pulled high with 2.49k, divided with internal 9k resistance, the IO port voltage is 2.5V. Which is higher than datasheet request, but cannot PING successfully.
• After LED_0 pull ups adjust to 500 Ohm, the IO voltage is 3.1V, it can PING successfully.

Please advise the reason of this, can we adjust the pull ups to 500 Ohm? Would it be any risk?

2. When we apply ECU PHY as slave mode, all the PING can be success.

3. With AN62A7 Linux, PHY need connect with the other unit with PMA, then the MDIO on our board can recognize the PHY on ECU. If there is no paired unit connected, the PHY cannot be recognized on local ECU.

 Schematic:

Looking forward your insights.

Thanks

Best,

Frank