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TMDS181RGZEVM: EDID emulator connection to EVM

Hirokazu Takahashi
Expert 8420 points
Part Number: TMDS181RGZEVM
Other Parts Discussed in Thread: TMDS181, SN65DP159, TDP158, SN75DP159

Dear Support team,

Currently, an EDID emulator is connected to output HDMI 2.0 (6Gbps) from our board.
However, if an EDID emulator is connected via the TMDS181 evaluation board, 6Gbps output is not possible and the default output rate is set.

Is it necessary to modify the evaluation board when connecting the EDID enumerator via the evaluation board to perform DDC communication?

We could find below discription in the User ’s manual.

P.7
• Pop R16, R17, R24, R25. No pop R123, R124, R125, R126 - TMDS181, DDC on
• No pop R16, R17, R24, R25. Pop R123, R124, R125, R126 - TMDS181, DDC snoop only

P.18
Pop 2K resistors on R45, R46 for TMDS181, DDC on
Pop 47K resistors on R45, R46 for TMDS181, DDC snoop only

Since only DDC snoop is used in the initial state of the evaluation board, if we want to use DDC communication with the EDID emulator, should we modify EVM to DDC on condition?

Best Regards,
Hirokazu Takahashi

  • 0
    TI__Guru**** 177646 points

    Takahashi-san

    Is the EDID emulator able to correctly communicate to the HDMI source for HDMI2.0?

    Is the EVM being configured in pin-strap or I2C mode?

    Please check TX_TERM_CTL and make sure TX_TERM_CTL is set to 75 to 150ohm for HDMI2.0, and TMDS_CLOCK_RATIO_STATUS and make sure it is set to 1 for HDMI2.0.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 30 points

    Dear Mr.David,

    Thnak you for your replay, I'm an engineer supported by Takahashi-san.

    I answer above qustions and have addiotional question.

    As a premise, We want to make it work in pin-strap mode.

    >Is the EDID emulator able to correctly communicate to the HDMI source for HDMI2.0?

    - Yes

    >Is the EVM being configured in pin-strap or I2C mode?

    - pin-strap mode

    >Please check TX_TERM_CTL and make sure TX_TERM_CTL is set to 75 to 150ohm for HDMI2.0, and TMDS_CLOCK_RATIO_STATUS and make sure it is set to 1 for HDMI2.0.

    - I confirmeded TX_TERM_CTL is set to  75 to 150ohm.

      About TMDS_CLOCK_RATIO_STATUS,

      Can I change TMDS_CLOCK_RATIO_STATUS In pin strap mode?

      or is this bit automatically set to 1 in pin-strap mode?

    Best Regards,

    Soichiro Todoroki

  • 0 in reply to Soichiro Todoroki
    TI__Guru**** 177646 points

    Todoroki-san

    The TMDS_CLOCK_RATIO_STATUS bit will be set based on the snooping of the DDC bus between the source and the sink. Would you please measure the output clock frequency? What is the input clock frequency?

    Are you changing from HDMI1.4 to HDMI 2.0? 

    Please make sure the source followed these steps:

    1. Source suspends transmission of TMDS data and clock

    2. Source changes TMDS_CLOCK_RATIO_STATUS bit

    3. Source allows min of 1ms and max of 100ms from the time the TMDS_CLOCK_RATIO_STATUS until the resuming transmission of TMDS data and clock at the updated data rate

    4. Source may read the state of CLOCK_DETECT status bit to verify the sink has correctly detected the TMDS clock.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 30 points

    Dear Mr.David,

    Thnak you for your replay, I confirmed following steps.

    >Please make sure the source followed these steps:

    >1. Source suspends transmission of TMDS data and clock

    >2. Source changes TMDS_CLOCK_RATIO_STATUS bit

    >3. Source allows min of 1ms and max of 100ms from the time the TMDS_CLOCK_RATIO_STATUS until the resuming transmission of TMDS data and clock at the updated data rate

    >4. Source may read the state of CLOCK_DETECT status bit to verify the sink has correctly detected the TMDS clock.

    As a result, Our current system is not satisfied with "3. Source allows min of 1ms and max of 100ms from the time the TMDS_CLOCK_RATIO_STATUS until the resuming transmission of TMDS data and clock at the updated data rate"

    Now we are fixing it, thnak you for your support.

    Best Regards,

    Soichiro Todoroki

  • 0 in reply to Soichiro Todoroki
    Prodigy 30 points

    Dear Mr.David,

    Now, we can make tmds181 work automatically, thanks to your help.

    I have additional question related to HDMI redriver; TDP158, SN65DP159, and SN75DP159.

    Can these Redriver/Retimer IC support 6Gbps HDMI Input signal?

    In the specification, these support "AC coupled tmds input",

    but I can't understand whether it include HDMI input.

    Best Regards,

    Soichiro Todoroki

  • 0 in reply to Soichiro Todoroki
    TI__Guru**** 177646 points

    Todoroki-san

    All of them support 6G HDMI. The difference between them and TMDS181 is that TMDS181 supports DC-coupled HDMI source while DP158/159 support AC-coupled HDMI input or DP++.

    Thanks

    David