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DP83822I: How to use LED_0

Shinichi Inoue
Guru 21721 points
Part Number: DP83822I

Dear Specialists,

My customer is considering DP83822.

He'd like to confirm how to use LED_0.

I would be grateful if you could advise.

---

Could you please confirm my understanding.

(1)LED_0 has an internal pull-down resistor only, there is not pull-down resistor.

(2)LED_0 can connect to logic device like FPGA.

In this case, I think it doesn't require pull-up or pull-down resistor.

Because LED_0 isn't for LED lighting. 

Is this correct?

(3)LED SPEED of Table 13. is LED_1 control of 0101(100Base) or 0110(10Base) of LEDCFG(bit 11:8)

(4)If LED_0 is ON , logic H is output.

Also polarity can be changed by LED_0 Polarity.

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I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Mastermind 19780 points
    Hi Shinichi,

    (1)LED_0 has an internal pull-down resistor only, there is not pull-down resistor.
    The LED_0 pin should have an external pull-down at all times.

    (2)LED_0 can connect to logic device like FPGA.
    yes, it can.

    (3)LED SPEED of Table 13. is LED_1 control of 0101(100Base) or 0110(10Base) of LEDCFG(bit 11:8)
    I am not sure what your question is. If CRS pin is strapped to mode 2 or 3, then LED_1 will indicate speed of linke, either ON for 100M, or OFF for 10M speed.

    (4)If LED_0 is ON , logic H is output.
    If LED_0 is pulled low during power up, LED_0 = H when LED is on.
    If LED_0 is pulled high during power up, LED_0 = L when LED is on.

    Best Regards,
  • 0 in reply to Rob Rodrigues
    Guru 21721 points

    Hi Rob,

    Thank for your reply.

    I'd like to organize your comments.

    I would be grateful if you could advise. 

    ---

    question (1) and (2)

    When the customer use Mode1 and connect to FPGA I/O, the connection is listed below.

    Is it correct?

    Previous mail I wrote LED_0 is pull-down, but pull-up is correct.

    (3) I understand if CRS pin is set to mode2 or 3, LED_1 indicates speed of link.

    In this case, Which address does LED_SPEED correspond to?

    (4) I understand.

    Also polarity is able to change  by LED_0 Polartity of LEDCR bit7(TAble 38.)

    Is it correct?

    I appreiciate your great help and cooperation.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    Guru 21721 points
    Dear all,

    This is just a reminder I'm looking forward to waiting the advise from you.

    Best regards,
    Shinichi
  • 0 in reply to Shinichi Inoue
    TI__Mastermind 18425 points
    Hi Shinichi,

    For mode 1 on LED_0, the strap that you have shown is correct. I would also recommend to check if FPGA has internal pull resistors and what is the behavior of that IO pin during power up.

    CRS pin will control the functionality of of LED_1. This is reflected in register 0x460 bit [11:8].

    Yes, LED_0 polarity can be changed from register 0x18 bit 7.

    -Regards,
    Aniruddha
  • 0 in reply to Aniruddha Khadye
    Guru 21721 points
    Hi Aniruddha,

    Thank you for your reply.

    I'll share your information with the customer.

    I appreciate your great help and cooperation.

    Best regards,
    Shinichi