AK8851 Datasheet, PDF (26/80 Pages) Asahi Kasei Microsystems – NTSC/PAL/SECAM Digital Video Decoder

ASAHI KASEI
[AK8851]
16. Auto Color Control ( ACC )
This function adjusts the input signal’s Color Burst level to its appropriate level (NTSC:286 [mV]/ PAL:300 [mV]).
The ACC control value can be frozen by register settings. The input color signal level is detected from the Color Burst
signal. ACC characteristics are set by [ACC1: ACC0]-bit of [AGC and ACC Control Register](R/W)[Sub Address 0x06].
Bit allocation of [AGC and ACC Control Register] is shown below.
Sub Address 0x06
bit 7
bit 6
ACCFRZ
ACC1
0
0
bit 5
ACC0
0
bit 4
bit 3
AGCFRZ
AGCC1
Default Value
0
0
bit 2
AGCC0
0
Default Value : 0x00
bit 1
bit 0
AGCT1
AGCT0
0
0
[ACC1:ACC0]-bit:
This selects enabling/disabling ACC function and its time constant.
[ACC1:ACC0]-bit
ACC Time Constant
[00]
Disable
[01]
Fast
[10]
Middle
[11]
Slow
Note
The ACC and Color Saturation functions operate independently (when the ACC is enabled, Color Saturation adjustment is
done on the properly adjusted signal by the ACC).
*[ ACCFRZ]-bit:
This is a control bit to freeze the ACC control value.
[ACCFRZ]-bit
ACC Status
0
ACC function is working
1
ACC control Value is frozen
Note
17.Color Killer
The Chroma signal quality is evaluated from the input signal’s Color Burst level.
The incoming signal quality’s threshold level is setusing the [Color Killer Control Register].
When the input chroma signal level is lower than the preset level, the input chroma signal is treated as insufficient and it
is processed as a Black and White signal.
When the Color Burst signal level is lower than the Standard signal levels (NTSC:286 [mV] / PAL:300 [mV]), the Color
Killer function is activated.
In this case, Cb/Cr data from the AK8851 is fixed at 0x80 in 601 levels.
Note)
When the Color Killer function is activated, all input signals fed to the YC separation module are processed as Y signal in
the same way as in the Black and White mode which is set by [B/W]-bit of [Input Video Standard Register].
Bit allocation of [Color Killer Control Register](R/W)[Sub Address 0x0D] is shown below.
Sub Address 0x0D
bit 7
bit 6
COLKILL
Reserved
0
0
bit 5
CKSCM1
0
bit 4
bit 3
CKSCM0
CKLVL3
Default Value
0
1
bit 2
CKLVL2
0
Default Value : 0x08
bit 1
bit 0
CKLVL1
CKLVL0
0
0
*[COLKILL]-bit:
This selects to enable or disable the Color Killer function.
COLKILL-bit
Color Killer
0
Enable
1
Disable
Note
*[CKLVL3:CKLVL0]-bit:
This sets the level to activate the Color Killer function.
MS0244-E-03
26
Confidential
2005 / 07