Fast Blanking Configuration; Figure 14: Adv7850 Fast Blanking Configuration - Analog Devices ADV7850 Hardware Manual

overlay functionality. This is a standard definition mode and is enabled by
In this mode, timing extraction is always performed by the SDP on the CVBS signal. However, a combination of the CVBS and RGB video
inputs can be mixed and output on the pixel port. The video selection is under the control of I
one of the trilevel inputs. (The trilevel input is selected using fb_select[3:0].)
By default, the ADV7850 operates in a dynamic switching mode in which the source selection is under the control of the fast blank signal.
This enables dynamic multiplexing between the CVBS and RGB sources. When the fast blank signal is logic HI, the RGB source is
selected; when the fast blank signal is logic LO, the CVBS source is selected. This is suitable for the overlay of subtitles, teletext, and so on.
Typically, the CVBS source carries the main picture and the RGB source has the overlay data.
The source selection can also be controlled manually via the I
sdp_man_fb_en. In manual mode, either the CVBS content or the RGB content can be output under the control of sdp_man_fb. This
mode allows the selection of a full screen picture from either source. Overlay is not possible in manual mode.
fb_select[3:0], AFE, Address 0x14[3:0]
This control is used to select the trilevel input to use as fast blank.
Function
fb_select[3:0]
0000 
0001
0010
0011
0100
0101
0110
0111
1xxx

Fast Blanking Configuration

5.8.10
A block diagram of the ADV7850 fast blanking configuration is shown in
F A S T B L A N K S I G N A L
C V B S
GREEN
RED
BLUE
The CVBS signal is processed by the SDP and converted to YPbPr. The RGB signals are also processed by the SDP and are converted to
YPbPr. Both sets of YPbPr signals are input to the subpixel blender, which can be configured to operate manually using
control or dynamically using the fast blank input signal.
Rev. A May 2012
Description
TRI1
TRI2
TRI3
TRI4
TRI5/HS_IN2
TRI6/VS_IN2
TRI7/HS_IN1
TRI8/VS_IN1
Reserved
S I G N A L
C O N D I T I O N I N G
A D C 0
C L A M P I N G A N D
D E C I M A T I O N
T I M I N G
E X T R A C T I O N
A D C 1
S I G N A L
C O N D I T I O N I N G
A D C 2
C L A M P I N G A N D
D E C I M A T I O N
A D C 3

Figure 14: ADV7850 Fast Blanking Configuration

prim_mode[3:0]
C registers. Manual source selection mode is enabled using
2
Figure 14.
F A S T B L A N K
P O S I T I O N
R E S O L V E R
V I D E O
P R O C E S S I N G
Y P r P b
S U B P I X E L
B L E N D E R
R G B T O
Y P r P b
C O N V E R S I O N
64
and vid_std[5:0]controls.
C registers or a fast blank signal applied to
2
O U T P U T
F O R M A T T E R
S D P
ADV7850
sdp_man_fb