• State Resolved
  • Locked Locked
  • Replies 12 replies
  • Answers 1 answer
  • Subscribers 35 subscribers
  • Views 996 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMDS171: How can you enable Pre-emphasis through Eye scan GUI?

user4779049
Expert 2345 points
Part Number: TMDS171
Other Parts Discussed in Thread: TMDS181, TMDS181RGZEVM

Hi Team,

Please advise me resolving a problem I encountered.

I tried to enable Pre-emphasis through Eye Scan tool GUI but could not do it.
When I set Pre-emphasis (either 2dB or 5 dB) mode and applied Write All,
The indicator got back to no-Pre-emphasis.

I also tried it through register menu (Address 0x0c bit 1:0 are set to 11b) but
register value got back to 00b. I confirmed that I2C_EN pin was set to High on the EVM.

I also set the re-timer mode in all case from 250Mbps to 6Gbps.

The termination mode behaves as Pre-emphasis mode too.

Please let me know how to configure the device in Pre-emphasis mode through the GUI.

Mita

  • 0
    TI__Guru**** 177396 points
    Mita

    You need to have a valid input before you can change the termination and pre-emphasis level.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Guru 19785 points

    Hi David-san,

    I couldn't change the emphasis setting with the valid HDMI input signal applied.

    However, after I connected with the sink HDMI monitor, I was able to change the setting.

    What is the trigger for TMDS171 to be able to change the emphasis setting ?

    Is there any way to know from the register value if you could change the emphasis setting or not ?

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Guru**** 177396 points
    Kawai-san

    You need to have the sink connected before changing the pre-emphasis setting. I was not able to find anything in the TMDS171 register that can trigger the emphasis setting without the sink connected.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Guru 19785 points
    Hi David-san,

    Does TMDS171 disable the outputs when there is no sink device connection ?

    I also have another question on this topic.
    TMDS171 requires valid input signal from source AND sink must be connected to change (control) the emphasis function.
    I believe that device register programming would only run just once after system power up.
    However, in this case, customer would need to detect both source and sink connection, then access to the registers again to change emphasis.
    Is this normal for general HDMI repeater/retimer devices ?

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Guru**** 177396 points
    Kawai-san

    If no sink device connected, then I assume the HPD_SNK is low. When HPD_SNK is low, the output is in a high-z state.

    For the pre-emphasis level. you are able to write to the register and change the pre-emphasis level. It is only when reading back, it will be read back as 0 if input is not connected. If input is connected, then you will able to read back the written value.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Guru 19785 points
    Hi David-san,

    Thanks for the information.
    I was able to confirm that the PreEmphasis level will change to the written setting (value) when valid input "AND" SINK device is connected.

    It seems the device also requires the SINK device connection for PreEmphasis and termination settings to be applied.

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Guru**** 177396 points
    Kawai-san

    There could a difference in the hardware design. On the EVM I am testing, write and read can be performed as long as the source is connected. Sink device does not need to be connected.

    But even without source or the sink connected, you can do the write. Only when you need to read back, source has to be connected.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Guru 19785 points

    Hi David-san,

    Thanks for your continuous support!!

    Could you please allow us to know the hardware difference what the criteria is so that we could understand why our EVM requires to connect the SINK device to read the settings correctly ?

    By the way, would there be a difference when you have I2C_EN PIN to High or Low ?

    I tested with the two EVMs and showed the same behavior.
    - TMDS171 (Board Rev : DP159/TMDS181_RGZ_EVM_REVB)
    - TMDS181 (Board Rev : TMDS181RGZEVM INT018 REV A)

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    Guru 19785 points
    > By the way, would there be a difference when you have I2C_EN PIN to High or Low ?

    Also in PIN mode, I could only read the Pre-Emphasis setting when Source AND Sink device are connected.

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Guru**** 177396 points
    Kawai-san

    When I2C_EN is low, you can read the I2c registers, but you can't write to the registers. I2C registers can only be controlled when I2C_EN is high.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Guru 19785 points
    Hi David-san,

    I am not sure why we cannot read the correct setting without the SINK device.
    We see different behavior from your EVM, however, I am closing this issue.

    Thanks for your support!!

    Best Regards,
    Kawai