DP83TC812R-Q1: PING fail with recommended pull up resistance

Frank QIN

Expert 7450 points

Part Number: DP83TC812R-Q1
Other Parts Discussed in Thread: AM62A7

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

4 months ago

0 Avtar Dhaliwal 4 months ago

TI__Expert 4720 points

Hello Frank,

Can you please check master / slave status for the PHY when pulling high with either 2.49k or 500 ohms I believe the issue may be caused because the voltage on LED_0 is causing the Mode to switch.

Are the PHY's linked up the whole time? As in does link drop?

1. As long as voltage read at pin is stable and at correct level there is no risk from my understanding.

3. Can you elaborate on this point? Is PHY unrecognizable by driver when not connected to another unit?

Regards,
Avtar

0 ?? ? 4 months ago in reply to Avtar Dhaliwal

Prodigy 30 points

thank your support

3.the issue is solved

We adjusted the wake sequence. Before the modification, the wake sequence was later when the MAC was powered on. As a result, when the MAC went to find the PHY after reset, the wake of the IC was not raised and the IC was in hibernation state. After we power on wake a little earlier, the mac can perform local wake normally, find the phy address, and perform remote ping

DP83TC812S-Q1: MDIO communication failed - Interface forum - Interface - TI E2E support forums

0 Avtar Dhaliwal 4 months ago in reply to ?? ?

TI__Expert 4720 points

Hi,

Im glad the issue is resolved, please let me know if there are any other issues.

Regards,
Avtar

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DP83TC812R-Q1: PING fail with recommended pull up resistance