AK8850 Datasheet, PDF (49/99 Pages) Asahi Kasei Microsystems – NTSC Digital Video Decoder

ASAHI KASEI
[AK8850]
7-4-8 BLACK & WHITE MODE
Black & White mode outputs all input signals as luminance (Y) only. In this mode, the C-signal output becomes 0 level
(output code 0x80) and Y/C Separation function is turned off ( Black & White mode ).
If Y/C and Component signals are input, the Chroma signal to be output is fixed to 0x80. The Black & White mode is user
programmable and it is turned on and off by the [ INPUT VIDEO STANDARD REGISTER ].
Black & White Mode Control Register Description:
Black & White mode is controlled by the [ INPUT VIDEO STANDARD REGISTER ]
* [ INPUT VIDEO STANDARD REGISTER ]
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
Reserved
NENT
B/W
SETUP
VS3
VS2
VS1
VS0
Default Value
0
0
0
0
0
0
0
0
* ON / OFF of Black & White mode function is controlled by B/W-bit
B/W-bit (bit-5)
B/W mode set
0
OFF (Color Video signal : default)
1
ON (B/W video signal
( bit-5 )
* Output Status in Black & White mode ( at B/W-bit = 1 ).
Output data
Y Singal out
Level converted value to Rec.601 level.
Cb/Cr Signal out Fixed value at 0x80
Above output status is applicable for NTSC ( Composite Y/C ) and 525 & 625 Component signals.
7-4-9 PICTURE ADJUSTING FUNCTION
The AK8850 has Picture Quality Adjusting functions which include Contrast, Brightness, Color Saturation and HUE
adjustments.
( 1 ) CONTRAST
The Contrast adjustment is made by multiplying the Luminance signal ( Y ) by the gain factor which is set by the
[ CONTRAST CONTROL REGISTER ].
The Contrast adjustment is made within the range of 0 ~ 2 ( 1/ 255 step ).
These arithmetic operations areperformed on 10-bit data. When the result exceeds the specified range,it is clipped to 1023
( upper limit ) or to 0 ( lower limit ).
Contrast
Contrast Control Register :
* [ CONTRAST CONTROL REGISTER ]
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
CONT7
CONT6
CONT5
CONT4
CONT3
CONT2
CONT1
CONT0
Default Value
1
0
0
0
0
0
0
0
Sets a multiplying factor over the Luminance signal. Adjustable range is from 0 ~ 2 in 0.008 fraction per step. Default value
is 0x80.
Rev.0
49
2003/01