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Register Settings for ADV7401

Question asked by rperry on Feb 20, 2012
Latest reply on Feb 22, 2012 by DerekBurke

I would like some help regarding the correct register settings for the ADV7401 in standard definintion mode.

Table 126 of rev B users guide (page 303) list the following register settings for the ADV7401 encoding a CVBS input.

Documented     Register     Register

  register            Address     Value                              Notes

    yes                    0x00          0x0e               CVBS Ain10

    yes                    0x17          0x41               Select SH1

    yes                    0x1d          0x47               Enable 28.63636MHz crystal

    yes                    0x3a          0x17               Set latch clock and power down ADC1,ADC2 and ADC3

    yes                    0x3b          0x80               Enable External Bias

    no                      0x3d          0xa2               MWE Enable Manual Window, color kill threshold to 2

    no                      0x3e          0x6a               BLM optimization

    no                      0x3f           0xa0               BGB optimization

    yes                    0x86          0x0b               Enable STDI Line Count Mode

    yes                    0xf3           0x01               Enable Anti Alias Filter on ADC0

    yes                    0xf9           0x03               Set max v lock range

    hidden               0x0e          0x80               ADI recommended sequence

    hidden               0x52          0x46               ADI recommended sequence

    hidden               0x54          0x00               ADI recommended sequence

    hidden               0x7F          0xFF               ADI recommended sequence

    hidden               0x81          0x30               ADI recommended sequence

    hidden               0x90          0xC9               ADI recommended sequence

    hidden               0x91          0x40               ADI recommended sequence

    hidden               0x92          0x3C               ADI recommended sequence

    hidden               0x93          0xCA               ADI recommended sequence

    hidden               0x94          0xD5               ADI recommended sequence

    hidden                0xB1          0xFF               ADI recommended sequence

    hidden               0xB6          0x08               ADI recommended sequence

    hidden               0xC0          0x9A               ADI recommended sequence

    hidden               0xCF          0x50               ADI recommended sequence

    hidden                0xD0          0x4E               ADI recommended sequence

    hidden                0xD1          0xB9              ADI recommended sequence

    hidden                0xD6          0xDD             ADI recommended sequence

    hidden                0xD7          0xE2              ADI recommended sequence

    hidden                0xE5          0x51               ADI recommended sequence

    hidden                0x0E          0x00               ADI recommended sequence


     My register settings are identical to the above with the following exections:

    yes                    0x13          0x04               External TTL clock

    yes                    0x1d          0x07               Enable 27.00000MHz crystal (default)


     The problem I'm having is that after deploying about 70+ products in the field at 3 ADV7401s per product, we are getting comments back from our

      customers that the video recording is somewhat degraded eg. colors are changing and poor recording at low light.

     I've been able to reproduce the colors changing condition in the lab and then was able to solve it by changing the crystal frequency to 28.636360MHz.

     So my question is simply this - is the above settings optimized for a ADV7401 running with the default 27.000000MHz crystal versus the 28.636360MHz

     crystal. Since a majority of the register settings above are not documented  in the users guide, I can't determine which registers would be sensitive

     to the absolute crystal frequency. The clock source to all 3 ADV7401s is from the same clock oscillator but buffered independantly. Changing

     the crystal frequency would be a very diffcult option since our products are geared to the military and all our qual testing (both emi and radiated) is

     completed. Any feedback will be appreciated.