Port Selection; Fast Switching And Background Port Selection - Analog Devices ADV7850 Hardware Manual

Note: The Transition Minimized Differential Signaling (TMDS) equalization frequency of the active HDMI port can be read back in the
tmdsfreq[8:0] and tmdsfreq_frac[6:0] registers.

7.14 PORT SELECTION

hdmi_port_select allows the selection of the active HDMI port.
hdmi_port_select[2:0], Addr 68 (HDMI), Address 0x00[2:0]
This control is used to select the HDMI primary port.
Function
hdmi_port_select[2:0]
000 
001
010
011

7.15 FAST SWITCHING AND BACKGROUND PORT SELECTION

The ADV7850 incorporates a fast switching feature. This feature allows the user of a system containing the ADV7850 to switch seamlessly
between HDCP encrypted sources. There is no delay in achieving video output previously caused by HDCP authentication. The time
required to switch between HDMI sources with HDCP encryption is reduced to a fraction of a second.
If an HDMI port is not selected by hdmi_port_select, this port is disabled by default. Asserting en_bg_port_x allows this unselected port
to be enabled in background mode (where x is a, b, c or d). Once a port is in background mode, the ADV7850 establishes an HDCP link
with its source even though it is not selected by hdmi_port_select. This background authentication allows for fast switching of the HDMI
ports.
Note: en_bg_port_x has no effect if the port is selected by hdmi_port_select.
en_bg_port_a, Addr 68 (HDMI), Address 0x02[0]
This control is used to set Port A in background mode to establish a HDCP link with its source even if the port is not selected by
hdmi_port_select. This control has no effect if the port is selected by hdmi_port_select.
Function
en_bg_port_a
0 
1
en_bg_port_b, Addr 68 (HDMI), Address 0x02[1]
This control is used to set Port B in background mode to establish a HDCP link with its source even if the port is not selected by
hdmi_port_select. This control has no effect if the port is selected by hdmi_port_select.
Function
en_bg_port_b
0 
1
Rev. A May 2012
Description
Port A
Port B
Port C
Port D
Description
Disable port unless selected with hdmi_port_select
Enable port in background mode
Description
Disable port unless selected with hdmi_port_select
Enable port in background mode
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ADV7850