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DP83867IR: How to work LED pins of the DP83867IRPAP?

Manwoo Kim
Intellectual 565 points
Part Number: DP83867IR

Hi,

I have some questions about operating of LED pins.

1. LED_2 pin has function of strap configuration.

 1) PAP type doesn't have this function?

 2) Is this pin's strap configuration for clock skew setting only?

2. For example, our circuit is implemented as mode 3.

 1) Firstly, this pin set the clock skew, and then is this pin work as output driver?

 2) What's the output level? Is output level I/O level? Isn't this level related to strap configuration?

Thanks,

Manwoo Kim

  • 0
    TI__Genius 9920 points

    Hi Manwoo,

    In our datasheet we specify: LED_2: By default, this pin indicates receive or transmit activity. Additional functionality is configurable via LEDCR1[11:8] register bits. NOTE: This pin is a Strap Configuration pin for RGZ devices only

    (3) RGMII TX and RX DLL Skew straps are only available on RGZ devices


    Hope that helps clarify your confusion with certain straps for specific packages. For either package you are able to configure these skews through register writes, however.

    Thanks,

    Cecilia

  • 0 in reply to Cecilia Reyes
    Intellectual 565 points

    Hi Cecilia.

    Thanks for your kind answer.

    How about my 2nd question? (if I use PGZ device)

    I want to know initial operation and output mode operation exactly.

    Thanks,

    Manwoo Kim

  • 0 in reply to Manwoo Kim
    TI__Genius 9920 points

    Hi Manwoo,

    Sure but I am confused about your question, do you mean RGZ device as in the 48 pin? LED pin works as a pin but also a strap for certain settings on the PHY. Depending on the strap resistors you use, will determine the threshold voltage at the output of the pin. 

    Thanks,

    Cecilia

  • 0 in reply to Cecilia Reyes
    Intellectual 565 points

    Hi, Cecilia.

    Thanks for your answer.

    Sorry, there was typo. I want to say "RGZ", because RGZ type only has strap configuration as you mentioned.

    Anyway, When this pin works as output driver, it's level will determined by resistor, right?

    In datasheet(8.5.3), It works as Mode 2, output level of LED_2 pin is 1.8*(2.49/12.49)=0.36V, right?

    Actually, I wonder below case.

    Our circuit use PAP type(LED_2 pin can't be set by HW setting), but there are strap configuration resistors like upper example.(In datasheet 8.5.3)

    How about this case? What's the output voltage level of LED_2 pin, when this pin works as output driver.

    We checked this pin, this pin level is 1.8V. Is it correct? (It means that case doesn't care about resistor divider)

    Please give me a answer!

    Thanks,

    Manwoo Kim

  • 0 in reply to Manwoo Kim
    TI__Genius 9920 points

    Hi Manwoo are you using resistors on LED2 even for the PAP package and you are seeing 1.8V at the output? 

    We have a precision labs video on how the bootstraps work and how to calculate the voltage:

    https://training.ti.com/ti-precision-labs-ethernet-bootstraps

    https://training.ti.com/sites/default/files/docs/ti_precision_labs_-_ethernet_bootstraps.pdf

    Thanks,

    Cecilia

  • 0 in reply to Cecilia Reyes
    Intellectual 565 points

    Hi, Cecilia.

    Thanks for your answer.

    I understand how to work before booting and after booting.

    But, I don't understand clearly about output level, when this pin works as output pin.

    This pin is driven at 1.8V level, but outside of this chip level is not 1.8V.

    What's the level of this pin? It can be calculated by superposition easily?

    Thanks,

    Manwoo Kim

  • 0 in reply to Manwoo Kim
    TI__Genius 9920 points

    Hi Manwoo,

    Can you please provide what your schematic looks like on LED_2, what components you have on the pin, and what voltage you are measuring and where? 

    I'd like to understand and see where you are seeing the 1.8V

    Thanks,

    Cecilia