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DS90UB983-Q1: HPD handshake process and DP link connection

Comi Li
Expert 7105 points
Part Number: DS90UB983-Q1


Tool/software:

Hi team,

There are two questions that need to be confirmed:

1. If the following connection method is used in DP mode, are there any potential risks? For example, when the DP data line between DS90UB983RTDRQ1 and SOC is relatively short, can only a 0.1uF capacitor be used?

2.The datasheet states that "DS90UB983 does not monitor the common-mode voltage of the eDP AUX terminal from the transmitter side for plug-in detection." In DP mode, the SOC monitors the voltage level of AUX. Is the purpose of monitoring the voltage to configure the drive current and balance level?

In addition, regarding HPD: Is the handshake process as described below?

In DP mode, DS90UB983 uses the LINK result of the DOUT0+/- or DOUT1+/- data line to determine whether there is a DEVICE. When there is a DEVICE, the HPD PIN is set high to notify the SOC that AUX communication can be performed;

In eDP mode, DS90UB983 uses the LINK result of the DOUT0+/- or DOUT1+/- data line to determine whether there is a DEVICE. When there is a DEVICE, if there is no HPD signal, the SOC needs to poll the DP LINK to know that there is a DEVICE and then perform AUX communication.

BR,

Comi

  • 0
    TI__Mastermind 24640 points

    Hi Comi,

    Is there a recommendation/ requirement from the SoC vendor about the DP capacitor?

    Please give me 1-2 days to answer your questions.

    Best regards,
    Ikram

  • 0 in reply to Ikram Haque
    TI__Expert 7105 points

    Hi Ikram,

    Comi Li said:

    2.The datasheet states that "DS90UB983 does not monitor the common-mode voltage of the eDP AUX terminal from the transmitter side for plug-in detection." In DP mode, the SOC monitors the voltage level of AUX. Is the purpose of monitoring the voltage to configure the drive current and balance level?

    In addition, regarding HPD: Is the handshake process as described below?

    In DP mode, DS90UB983 uses the LINK result of the DOUT0+/- or DOUT1+/- data line to determine whether there is a DEVICE. When there is a DEVICE, the HPD PIN is set high to notify the SOC that AUX communication can be performed;

    In eDP mode, DS90UB983 uses the LINK result of the DOUT0+/- or DOUT1+/- data line to determine whether there is a DEVICE. When there is a DEVICE, if there is no HPD signal, the SOC needs to poll the DP LINK to know that there is a DEVICE and then perform AUX communication.

    Could you help about the below question first and give some comments?

    Thanks for your reply.

    BR,

    Comi 

  • 0 in reply to Comi Li
    TI__Mastermind 24640 points

    Hi Comi, I'm checking the 983 datasheet and DP standard. Please give me till tomorrow to get back to you.

    Best regards,
    Ikram

  • 0 in reply to Ikram Haque
    TI__Mastermind 24640 points

    Hi Comi,

    During link training, the AUX channel is used to check whether the sink has recovered the clock. If not, then the sink requests for the source to use new settings for voltage swing and pre-emphasis. This reiterates until the sink does recover the clock or it loops five times. The link training procedure, and related diagrams can be found in the VESA DisplayPort Standard, which your customer might have access to.

    The 983 acts as the DPRX sink device itself. Meaning, it controls HPD to the DPTX that sink is present. After HPD hotplug, the source reads the DPCD capabilities from the sink 983, then link training steps are performed. This happens regardless of whether there is a sink detected on the 984. 


    Best regards,
    Ikram