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SN65DSI86: question about SN65DSI86ZQER

Jimmy Huang
Genius 3515 points
Part Number: SN65DSI86

Tool/software:

Hello：

1. When designing with SN65DSI86ZQER, AUXP and AUXN are reversed. Can I switch between AUXP and AUXN internally in the TI chip?

2. What are the impacts of reversing? Does it affect the normal display of the screen? The current EDP eye diagram test is passed.

3. There are 100K up and down buttons on AUX P/N, and if PN is reversed, the up and down buttons will also be reversed; Does it affect the normal operation of the chip?

4. The up and down buttons of this aux are used not only for communication, but also to inform the screen that the source side is ready; Does this reversal have an impact on the mechanism?

Thanks！！！

  • 0
    TI__Mastermind 22830 points

    Hi Jimmy,

    There is no register to invert the polarity of the AUX lanes of the DP output. The DP main link data lanes (MLxP/N) can be inverted, but not the aux lanes. So please route the AUX P/N accordingly and follow the schematic recommendation.

    I can see that H8/H9 are mislabeled in the schematic snippet you shared. Is there an issue with routing? Or is the issue that the schematic label was incorrect? Please correct the labels and the AUX external components/schematic for the next build.

    Best regards,
    Ikram

  • 0 in reply to Ikram Haque
    Genius 3515 points

    Hi Ikram：

    Thank you for your feedback. 

    The customer is currently not using the AUX signal, will there be any impact if AUX is reversed?
    In addition, during the customer's morning startup process, the AUX signal on the TI chip (disconnected from the series capacitor with the external device) was only at a high level and there was no signal, indicating that AUX was not used. Can this be understood?
    The screen display is normal

  • 0 in reply to Jimmy Huang
    TI__Mastermind 22830 points

    Hi Jimmy,

    In the customer's system, will the DP AUX lines be used for any link training, re-initializing link training (if needed), DPCD reads, etc? What is the AUX channel requirement from the display/sink side?

    - Ikram

  • 0 in reply to Ikram Haque
    Genius 3515 points

    Hi Ikram：

    The resolution of the screen is set by the TI chip, and there is no need for training during startup and sleep wake-up. The screen's EDID is determined through software.

    Please help confirm the four questions above, thank you!!!

    Also, Please help confirm, if the AUX signal is not used, what are the effects of reversing it? Is there any risk involved?

  • 0 in reply to Jimmy Huang
    TI__Mastermind 22830 points

    Hi Jimmy, 

    If AUX channel is not used, then I'm assuming fast link training is used.

    To answer your initial questions:

    1. No, the AUX polarity cannot be reversed by register writes

    2. The AUX channel is used for link training and maintenance transactions between source and sink. The video itself is transmitted over the eDP main link lanes. 


    3. If the AUX channel are unused (as you described), then you can leave them floating or disconnected, and NC the AUX line pullup and pull down resistors.

    4. What are the up and down buttons you are referring to here?

    I am not sure of the exact effects of this, but the recommendation would be to correct the schematic, and if AUX is not used, it can be left floating.

    Can the HPD be used to inform that sink is present?

    Best regards,
    Ikram