SPDIF Enable register of ADV7511W.

Hello,

I have questions about "SPDIF Enable" register of ADV7511W.

Question 1:
I had investigated the behavior of "SPDIF Enable" register (0x0B[7]) of ADV7511 by using ADV7612-ADV7511 Eval-Board.
https://ez.analog.com/docs/DOC-1751
EVAL-ADV7612EB1Z_EvalNote_PrA.pdf (There is ADV7511 on this board.)

At result, "SPDIF Enable" register (0x0B[7]) seems to be valid only when MCLK inputs to ADV7511 and "MCLK Enable" register (0x0B[5]) is 1 (MCLK is available).
Is this right behavior?
Is "SPDIF Enable" register (0x0B[7]) invalid when "MCLK Enable" is 0 (MCLK internally generated)?

Question 2:
When MCLK pin is unused, is there any register setting so that SPDIF(audio) is mute except AV mute?
(We want to keep displaying video.)

Thank you.
Best regards.