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TDP1204: TXPRE Setting for HDMI2.1

Oden Chen
Prodigy 10 points
Part Number: TDP1204

Tool/software:

Dear TI's expert,

When I set the TDP1204 to pin-strap mode, does the TXPRE setting affect the pre-emphasis of the HDMI 2.1 eye diagram test?
I have this question because I don't quite understand Table 8-16—what determines the TXFFE adjustment from 0 to 3?

The picture as below shows the HDMI 2.1 eye diagram test for Lane 0. Regardless of my TXPRE settings, the HDMI 2.1 eye diagram's result didn't change. Even adjusting the EQ settings makes the eye diagram worse.
I would like to confirm whether there is an error in my setting.

Below is my hardware setup:

CFG0 = 0
AC_EN = 0
MODE = 0
LINEAR_EN = 0
CTLEMAP_SEL = 0
EQ0/EQ1 = 00
TXPRE = 1
TXSWG = 0

Thank you for any help you can provide.

  • 0
    TI__Genius 12171 points

    Hi Oden, 

    Oden Chen said:
    When I set the TDP1204 to pin-strap mode, does the TXPRE setting affect the pre-emphasis of the HDMI 2.1 eye diagram test?

    TXPRE setting affects the pre-emphasis. 


    Oden Chen said:
    I have this question because I don't quite understand Table 8-16—what determines the TXFFE adjustment from 0 to 3?

    The de-emphasis setting in Table 8-16 is affected by TXPRE pin setting in table 8-15, but this setting applies for HDMI 2.1.
    Please think of it as below:
    TXFFE0 corresponds to TXPRE pin set to 0.
    TXFFE1 corresponds to TXPRE pin set to R.
    TXFFE2 corresponds to TXPRE pin set to F.
    TXFFE3 corresponds to TXPRE pin set to 1.

    Oden Chen said:
    The picture as below shows the HDMI 2.1 eye diagram test for Lane 0. Regardless of my TXPRE settings, the HDMI 2.1 eye diagram's result didn't change. Even adjusting the EQ settings makes the eye diagram worse.
    I would like to confirm whether there is an error in my setting.


    If adjusting EQ makes the eye diagram worse, this can be due to the source's TXFFE setting. Please disable the HDMI source's TXFFE setting and see increasing the EQ afterwards help the compliance result. This enables TDP1204 to have a full control of the HDMI equalization and TXFFE setting. 
    Please let me know. 

    Best,
    J

  • 0 in reply to J
    Prodigy 10 points

    Hi J,

    Thanks for your detail explanation. I would like to ask you a few more questions:

    1. Does "Disable the HDMI source's TXFFE setting" mean setting TXFFE to 0?

    2. In the picture as below, I set TXFFE to 0 and after adjusting the EQ, the eye diagram seems to improved slightly. However, the jitter doesn't improved. Even though I increased TXSWG, the eye diagram is improved slightly. The result is very margin.
      Do you have any suggestions on which setting I can adjust to improve the eye diagram?



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  • 0 in reply to Oden Chen
    TI__Genius 12171 points

    Hi Oden, 

    Oden Chen said:
    Does "Disable the HDMI source's TXFFE setting" mean setting TXFFE to 0?

    Yes, but not for TDP1204. I am asking to turn the TXFFE setting off for the SOC or FPGA that is generating the HDMI source unless TDP1204 is placed on the sink side. 

    Oden Chen said:
    However, the jitter doesn't improved

    As TDP1204 is a redriver, it will output the random jitter from the input. TDP1204 is only able to filter out ISI jitter. Is it possible for you to measure the jitter at the input of the TDP1204 to see if the signal has a lot of random jitter? Could you also check if the signal is decoupled from the power layer properly as the signal can take the power layer's noise also. 

    It looks like EQ=R1 setting has no mask violation. 

    Oden Chen said:
    Do you have any suggestions on which setting I can adjust to improve the eye diagram?

    Once HDMI source's TXFFE is turned off, adjusting TXFFE setting can also improve the eye diagram. In addition, I noticed that changing TXSWG improved the eye. The combination of three settings (RX EQ, TXFFE, and TXSWG) will help you to pass the compliance test. 

    Best,
    J