ADV7181 CP 8bit mode

We use the ADV7181-D connected to freescale IMX-6 (using a Vairiscite SOM-SOLO module).

When in SD (CVBS) mode this works fine. output of the ADV7181 is 8Bits BT565 mode.

We also want to use the CP (VGA) mode but this gives some problems.

Can the ADV7181 in CP mode output data in 8 BITS (SDR) ?

if yes,  Can it enable the BT565 mode ?

If not, is there an alternative chip (eg ADV7842) which can output 8 bit (SDR) in VGA mode ?

Regards,

Rini

  • 0
    •  Analog Employees 
    on Nov 10, 2015 7:22 PM

    You can't output RGB in 8-bit mode.  The only option is RGB in DDR mode.  Check Table 10 for available Pixel Output Formats

    The best you can do is use a part like the ADV7842 and convert RGB to YCbCr 422 and then output BT.656.  Any higher resolution then VGA will not work due to clock limitations.

  • Hi  Guenter,

    Thanks for your reply!

    Table 10 refers to the input formats isn't it ?

    We would like to intput a VGA /XGA signal (RGB) and output it on a 8 bits bus as YCbCr 422.

    Are you saying this is impossible with the ADV7181 and only possible for VGA resolution with the ADV7842 ?

    Any other device you know which can handle XGA RGB to YCbCr 422 conversion ?

    Regards,

    Rini

  • 0
    •  Analog Employees 
    on Nov 10, 2015 8:54 PM

    Table 10 in the ADV7181C data sheet shows the output pixel format.

    The real problem is you want BT.656 output on an 8-bit bus.  BT.656 calls for YCbCr with AV code insertion and the ADV7842 AV code insertion is limited to a max clock rate of 54MHz.  So it could convert VGA (640x480) with 24MHz clock to YCbCr 422 at 48 MHz and output it over an 8-bit bus inserting AV codes.  XGA (800x600) would have a clock that is too fast for the AV code insertion.

    VGA is confusing, it defines a 640x800@60Hz format and sometimes it is used to describe any PC output.  XGA is 800x600@60Hz

  • Hi.

    When not using BT.656 output, the 7842 can output XGA to 8 bits with external sync signals?

    Regards,

    Rini

  • 0
    •  Analog Employees 
    on Nov 12, 2015 7:02 PM

    BTB.656 implies you are embedding AV codes in the stream.  You don't have to embed the AV codes, you can use separate sync signals.