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TVP5151 Sync Issue

William Wyatt-Millington
Prodigy 70 points
Other Parts Discussed in Thread: TVP5151

This is probably the wrong forum for TVP5151 but I do not seem to be able to get to an appropriate forum. I have designed the TVP5151 into a new product using the device to generate the sync signals (I am not uisng the embedded sync capability). When the PAL input video signal is removed the VSYNC and HSYNC signals are still being generated. Is there a way of preventing this as I do need to be able to detect the loss of sync from the video source?

I am assuming that there is a register setting which has been set incorrectly.

  • 0
    Prodigy 70 points

    I have approached a UK based FAE to see if I can get an answer that way.

  • 0
    TI__Mastermind 43875 points

    William,

    Sorry for the delay in responding.

    There are registers that will report the current horizontal, vertical and color lock status. You should poll these registers to determine the current lock status. All three bits should be locked for correct and full signal lock.

    There are also 'lost lock' status registers which will indicate a historical rather than instant lock status. This lost lock bit is cleared by reading the status register.

    Even when lock is lost the TVP will generate free running syncs.

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Prodigy 70 points

    Hi Steve

    That is the wrong answer for the system design that I am involved in... Right I think I understand: the only way to detect loss of sync with this device is by interrogating the status register, but as I need to detect loss of sync instantaneously then this is the wrong device for me (it was inherited from an earlier design).

    Does TI have a PAL decoder which would enable me to detect loss of sync instantanteously? This is required as our customer has a requirement to detect loss of sync and in that case output a grey scale image on the full image if vertical sync is lost and on the line if horizontal sync is lost.

  • 0 in reply to William Wyatt-Millington
    TI__Mastermind 43875 points

    You can use the interrupt output to quickly flag H, V or C lock status changes.

    See section 3.21.26 in the datasheet.

    This indicates a change in status so you then need to read the status registers to see what actually changed.

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Prodigy 70 points

    I have implemented a hardware solution to my problem by the use of external sync separator device.