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How to deal with the DE/VSYNC/HSYNC pin of DM8168 when using VIN0 in 16bit-Embedded mode?

Haoran Li1
Expert 1850 points
Other Parts Discussed in Thread: TVP7002

Hi,

    I am now using EVM8168 for developing.  In order to capture 1080p60 BT.1120 video stream, I managed to use the VIN0 Port as a 16bit-Embedded Sync Mode.  It seems that VIN0[15:0] and VIN0_ACLK are all what I should concerned about, when interacing such a 16-bit-Embedded Sync Mode.

    However, by referencing schematics of xIO Daughter Card of EVM8168, I noticed that VIN0_DE, VIN0_VSYNC and VIN0_HSYNC are also connected to dedicated pin of TVP7002 (TVP7002_FID, VSYNC, HYNC, respectively).

    Since I DO NOT want to evaluate or support for discrete sync video input mode (eg. BT.601), these three pins (DE, VSYNC, HSYNC) are useless, aren't they?  Shall I assigned them to DGND, or leave them alone, floating, with No Connection?


    I don't know much about the hardware interfacing.  Could you please help me?

Naroah

Feb/26/2014

  • 0
    TI__Genius 13460 points

    It is OK to left it open/

  • 0 in reply to Eason Wang
    Expert 1850 points

    Hi Eason,

         Thank you for your support!

    Naroah

    Feb/26/2014

  • 0 in reply to Haoran Li1
    TI__Mastermind 43875 points

    Sort of.

    It is not advisable to leave any inputs floating/unconnected unless they have internal pull up/downs enabled.

    You should really configure the internal pull up/down of all unused pins. It does not matter which polarity you set though.

    Alternatively you can leave the pin disconnected and configure it as an output.

    Bottom line is that ALL pins (not just the VIn) should either be configured as outputs (with nothing connected), have an internal pull up/down enabled, have an external pull up/down or be driven actively.

    Floating inputs are never good.

    From a functional perspective these pins are not needed hence do not need to be driven by the TVP7002.

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Expert 1850 points

    Hi Steve,

        Thank you for your suggestion.  It's really reasonable to configure the unused pin with an internal/external pull up/down for cutting down noise and avoiding interference.  I think I should do these:

        1. Set unused pins (VIN0A_DE, HSYNC, VSYNC) as "output pin" by configuring dedicated registers, respectively.

        2. Assign these pins with an internal pull up/down by configure registers, similarly.  Assigning these pins with external pull up/down resistors is an alternative choice.

        Am I right?

    Naroah

    Feb/27/2014

  • 0 in reply to Haoran Li1
    TI__Mastermind 43875 points

    It is actually more of a power issue than noise. Floating inputs can cause the input circuits to consume more power then when driven correctly due to partially biased transistors. In any circuit you should never have any floating inputs.

    Either #1 or #2 is fine, but if you assign the pins as outputs then make sure that you don't have anything external driving the pins too.

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Expert 1850 points

    Hi Steve,

         Thank you for your tips!  You really help me a lot!

    Naroah

    Feb/28/2014