(ADV7611)Why ADV7611 output SCLK befor HDMI input?

Hi !

Various register settings are made after the ADV7611 power is turned on, regardless of the TMDS input.

At that time, “TRI_AUDIO, IO, Address 0x15 [4]”: 1 → 0 was also set, and 9.8437MHz SCLK was output even HDMI is not input.

This frequency is considered to be determined by the ADV7611 device, but as the description can not be found on the specifications including "UG-180.pdf".

Q1)
Why ADV7611 output this frequency?

Q2)

Is the frequency always constant at 9.8437 MHz?

Best regards

Kawa

Parents Reply
  • 0
    •  Analog Employees 
    •  Super User 
    on Jun 18, 2019 2:05 PM in reply to donadona999s

    Hi

    I do not know where the 9MHz clock rate originates from, my guess would be the audio PLL is free running and maxing out.  I'd have to research this some to figure out the exact root cause

    As part of your initialization you can tri-state the audio pins until HDMI is connected and see stable audio from the source.

    TRI_AUDIO 0x15[4] = 1

Children