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DP83849I: Ping command sometimes doesn't work to DP83849

Wayne Wang20
Expert 4390 points
Part Number: DP83849I

Hi team,

My customer uses a laptop to connect to DP83849I and send a 'ping' command to DP83849 to test the communication. We found 2 different situations:

1. Sometimes when we power up the board and then send a 'ping' command, the 'ping' command works well and it is always good when we keep 'ping'.

2. Sometimes when we power up the board and then send a 'ping' command, the 'ping' command doesn't work. You have to re-power up the board then can it work normally.

This issue happens on every board so it is a common issue. 

The DP83849 is configured to RMII interface and auto-negotiation mode. I already checked the schematic and there's nothing wrong. And we also measured the Pin70 and Pin68 and confirmed the 50MHz clk signal is always present. 

We also tried to read out a register dump. When the 'ping' command works, we can read out the right register values. But when the 'ping' command doesn't work, all the register values we read out are 0xFFFF.

At last, the link status LED(Pin19 & Pin43) is always ON and the data acting LED (Pin21 & Pin41) is always blinking no matter if the 'ping' command works or not.

So can you give some advice on this issue? Thanks.

Best regards,

Wayne

，

  • 0
    TI__Genius 11725 points

    Hi Wayne,

    To try and narrow down the issue I have the following questions/suggestions:

    1. Have you tried reading other PHY addresses? Since the problem goes away after a reset the device may be initially strapped to a different PHY address.

    2. What are the strap resistor values being used?

    3. Check that reset is high during normal operation,

    4. check power down pin is high.

    5. Is the clock present before PHY supply ramps up?

    Thank you,

    Nikhil