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TFP401PZPEVM: TFP401 outputs unexpected pulse under Blanking Period

Kazuhiro Mochizuki
Prodigy 10 points

Part Number: TFP401PZPEVM
Other Parts Discussed in Thread: TFP401

Dear Sirs,

In my project, the following issue is found:

 "TFP401 outputs unexpected pulses under Blanking Period."

 

unexpected_pulses.pdf 

 

Condition:

My project: Video data converter between DVI to 3G-SDI

(1) Video data root: PC >HMDI >HDMI-DVI cable >DVI-D input of Converter >TFP401 >FPGA

(2) EDID 1.3 (256byte) in the converter

(3) PC Video output: 1920x1080, 60Hz, RGB

please, show me the causes of issue by your knowledge and experience.

 

  • 0
    TI__Guru**** 190381 points

    Hi,

    Three TMDS channels are used to receive RGB pixel data during active display time, DE = high. The same three channels also receive control signals, HSYNC, VSYNC, and user-defined control signals CTL[3:1]. These control signals are received during inactive display or blanking-time. Blanking-time is when DE = low.

    Can you include the DE for your measurement and what is the frequency between each pulse?

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 10 points

    Hi, David

    Thank you very much for your support.

    For DE`s behavior, please, refer to the attached sheet of my measurement.

    It seems like HSYNC period and other signals' period on DE.

    Thanks

    unexpected_pulses_Freq.pdf

    Kazuhiro

  • 0 in reply to Kazuhiro Mochizuki
    TI__Guru**** 190381 points

    Kazuhiro-san

    On the source itself, does it have the audio disabled and only the video being sent to TFP401?

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 10 points

    David

    Thank you for your quick reply.

    I don't have the information of audio enable /disable setting sent from PC to TFP401.

    But, I have other information as follows:

    (1) TFP401's HSYNC output is stop when PC is changed to another PC having DVI-D interface.

    (2) Video-data converter does not support audio.

    Thanks,

    Kazuhiro

  • 0 in reply to Kazuhiro Mochizuki
    TI__Guru**** 190381 points

    Kazuhiro-san

    Can you please share your schematic for review?

    (1) TFP401's HSYNC output is stop when PC is changed to another PC having DVI-D interface.

    Are you able to see the video output? This look to be a different issue from outputs unexpected pulses under Blanking Period.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 10 points

    Hi, David

     I apologize for the late response. I have been studying of finding a solution in this week.

    At last, I found out that unexpected pulses had vanished with revised EDID in the converter.

    Revised point of EDID is: 

    PC accessible EDID block area is limited to 128 bytes.

    This means that PC can use information from Base Block of EDID, and Extended Block of EDID is ignored.

    According to my idea, the extended block has audio function descriptor and PC send audio data during blanking period, so, PC must be sending audio data to the converter by getting information in the extension block of EDID.

    By disabling extend block of EDID, unexpected pulses disappear from planking period. (see attached wave forms.)

     I resolved this issue by updating present EDID in the converter.

    Thank you very much for your help and advice.DE_waveform_revised_EDID.pdf