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[ADV7181D] Auto Gain Control (AGC).

Question asked by Tamu on Jul 25, 2015
Latest reply on Aug 18, 2015 by XavE

Hello,

 

I have some questions about AGC(Auto Gain Control) of ADV7181D.

 

We use AGC function with AGC_TAR_MAN = 0 (AGC_TAR is not used) and AGC_FREEZE AGC = 0(AGC is not frozen).
The input is Component YPbPr with an embedded synchronization pulse with CP core.

When the power is turned on and the video signal inputs to ADV7181D, sometimes CP_AGC_GAIN[9:0] is all high (1111111111), sometimes CP_AGC_GAIN[9:0] is all low (0000000000).
The input component YPbPr is the same in both cases. (It's not changed.)
The registers setting is the same in both cases, too.
I don't know why the CP_AGC_GAIN changes like this.

 

Question 1:
Does the AGC function always work after reset and register setting?
Or does the AGC function work during only a specific section (only after power-up, etc)?

 

Question 2:
Does the "CP_AGC_GAIN[9:0] = all low (0000000000)" mean that AGC does not work?

 

Question 3:
What conditions cause "CP_AGC_GAIN[9:0] = all low (0000000000)"?
May it be depends on the input wave form?

 

The input component YPbPr is connected to ADV7181D board with FFC (flexible flat cable).
So the input can't be changed.
I don't know why the CP_AGC_GAIN changes like above.
What do you think?

 

Thank you!
Best regards.

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