Av Mute; Tx Squelch Feature; Table 82 : Tx Squelch Configuration Options - Analog Devices ADV7850 Hardware Manual

Function
HDMI_MODE
0 <<
1

13.4 AV MUTE

The AV mute status is sent to the downstream sink through the general control packet. One purpose of the AV mute is to alert the sink of
a change in the TMDS clock so the sink can mute audio and video while the TMDS clock it receives is unstable. Setting AV mute also
pauses HDCP encryption, so the HDCP link between the HDMI Tx and the sink is maintained while the TMDS clock is not stable. Note
that AV mute is not sufficient as a means to hide protected content because the content is still sent even when AV mute is enabled.
To use AV mute:
• Enable the GCP by setting gcp_pkt_en to 1
• To set AV mute, clear
• To clear AV mute, clear
Note that setting both set_avmute
set_avmute, Addr B8 (Main), Address 0x4B[6]
This control is used to set the set AV mute signal.
Function
set_avmute
0 
1
clear_avmute, Addr B8 (Main), Address 0x4B[7]
This control is used to set the clear AV mute signal.
Function
clear_avmute
0 
1

13.5 TX SQUELCH FEATURE

The ADV7850 provides a squelch feature to mute the video clock when there is no input connected to the HDMI Input. This feature
ensures that no spurious clocks signals are output to the backend device when a cable is disconnected or an input source switches off.
The feature can mute the video based on TMDS detection in the HDMI Receiver and/or on the incoming HSync signal to the HDMI
Receiver. This feature should be disabled for Analog input modes. The following table highlights the available options.
HSync Activity TMDS Clock Detect
Detect
0 0
1 0
0 1
1 1
Rev. A May 2012
Description
DVI
HDMI
clear_avmute and set set_avmute
set_avmute and set clear_avmute
and clear_avmute is not a valid configuration.
Description
Clear the set AV mute signal
Set the set AV mute signal
Description
Clear the clear AV mute signal
Set clear AV mute signal

Table 82 : TX Squelch Configuration Options

Functionality
Use TMDS Clock detect to power down HDMI Tx clock and data lines
Use HSync Activity Detect and TMDS Clock detect to power down HDMI Tx clock and
data lines
Disable the feature ( Recommend setting for analog input modes)
Reserved – Not Used
351
ADV7850