DP83822I: Set the output signal drive individually for TX side and RX side

Part Number: DP83822I

Hi team,

I received a question about the DP83822I from my customer. Could you please help with the questions below from the customer?

Is it possible to set the output signal drive individually for TX (transmitting side) and RX (receiving side) in Ethernet communication?

To be more specific
I think there are TD terminals (TD_P, TD_M) and RD terminals (RD_P, RD_M) respectively. Is it possible to change the signal amplitude, for example, by register setting between the TD terminal and RD terminal?

I think that if bit[15] of PHYCR in the register settings is set to 1, MDI/MDIX is automatically switched, so no matter whether a signal is received from the TD or RD pin, the pin that did not receive the signal automatically becomes the transmitter and responds without any problem.

However, if different drive settings can be made for the TD and RD terminals as described in the question, even if AUTO-MDI/X is used, I think that the response waveform may differ depending on which terminal the signal is received from.

Regards,

Yamaguchi

  • Hi Yamaguchi-san,

    Let me consult with my team and get back to you tomorrow on whether this is possible.

    Regards,

    Adrian Kam

  • Hi Yamaguchi-san,

    I apologize as it seems to be taking longer than expected to get this information. I can get the information and answer your question by Friday at the latest.

    Regards,

    Adrian Kam

  • Hi Yamaguchi-san,

    It is possible to set the output signal drive for the TX pins in register 0x0403. If you have MDI-X configured, then the RX pins will have the same output signal drive configuration as the TX pins when the pairs are swapped. If you want different output signal drive configurations depending on whether the pairs are swapped or not, then that is not possible. 

    Regards,

    Adrian Kam

  • Hi Adrian-san,

    Thank you so much for the answer. I understood, but could you allow me to ask one more question?

    Even when AUTO-MDI/X is off (default is fixed MDI, TX transmits and RX receives), if I input a signal to the TX pin, will I get some kind of response from the RX pin?

    Background;

    On the board currently in use, AUTO-MDI / X of the PHY is turned off by the register setting. 
    In addition, when I input a signal to TX/RX (either one of them) from a simple signal generation board, instead of a PC or a hub with AUTO-MDI/X function, I can observe the response waveform from RX/TX respectively. -->If I force the signal into the transmitter, will it still respond? (I thought that if AUTO-MDI/X was off, it would not respond unless I entered the correct one.)

    Although I was able to observe the waveform, the response waveform (amplitude, etc.) differed depending on the input terminal (TX or RX), which is why I asked the previous question.

    Regards,

    Yamaguchi

  • Hi Yamaguchi-san,

    I have a few questions:

    1. What is the issue that the customer is seeing? What are they trying to fix with this information?
    2. Can you provide a block diagram and description of the customer's application?
    3. What application does the customer have that requires this information?
    4. In your previous reply, what kind of response are you referring to or expecting? Can you provide more details on that?

    Regards,

    Adrian Kam