AK8850 Datasheet, PDF (46/99 Pages) Asahi Kasei Microsystems – NTSC Digital Video Decoder

ASAHI KASEI
[AK8850]
It is also possible to program the non-sensing bandwidth of the AGC by [ AGCC1 : AGCC0 ]-bit of the [ CONTROL 1
REGISTER ].
[AGCC1:AGCC0](bit-3:bit-2)
286mV Sync
300mV Sync
Non-Sensing
Bandwidth
[0,0]
Sync level is not 224, AGC Sync level is not 236, AGC
function works.
function works.
No Non-Sensing
Bandwidth
[0,1]
Sync level is not in the range of Sync level is not in the range of
222 - 225, AGC function works. 234 - 237, AGC function works.
1-bit Non-Sensing
Bandwidth
[1,0]
Sync level is not in the range of Sync level is not in the range of
220 - 227, AGC function works. 232 - 239, AGC function works.
2-bit Non-Sensing
Bandwidth
[1,1]
Sync level is not in the range of Sync level is not in the range of
218 - 229, AGC function works. 230 - 241, AGC function works.
3-bit Non-Sensing
Bandwidth
Same gain as for the Y signal input case is multiplied to the C-signal in Y / C input and the Pb / Pr signals in Component
signal input.
The gain constant value set for the AGC does not affect to any of the [ PGA1 / PGA2 / PGA3 GAIN CONTROL
REGISTER ], regardless of input sources.
7-4-5 Y / C SEPARATION
The Y / C Separation function separates the Composite Video input signal into Luminance ( Y ) and Chroma signals ( C ).
Three register-selectable Y / C Separation methods are available: Primary Y/C Separation ( Band Pass Filter ), Two
Dimensional Y/C Separation ( 3-Line Comb Filter ) and an Adaptive Y/C Separation Filter.
For Y/C Separation, the input data is converted CCIR601 compatible formats and it is output as a Y signal when the
Black & White mode is selected, during the VBI interval set by [ VBIL4 : VBIL0 ]-bit of the [ VERTICAL BLANKING
LENGTH REGISTER ]. The output Cb/Cr signal is at 0x80, or Black level.The resulting output on the AK8850 is selected
by VBIDEC-bit of the [ VERTICAL BLANKING LENGTH REGISTER ]. Black level output ( Y= 0x16,Cb/Cr=0x80) at
VBIDEC-bit = 0 and Black & White output at VBIDEC-bit=1.
The Y/ C Separation function is enabled only when a Composite signal is input.
Y/C Separation Control Register Description :
The Y/C Separation is controlled by the [ Y/C SEPARATION CONTROL REGISTER ].
* [ Y/C SEPARATION CONTROL REGISTER ]
bit 7
bit 6
bit 5
bit 4
bit 3
Reserved Reserved Reserved Reserved CBPFS1
Default
0
0
0
0
0
bit 2
CBPFS0
1
bit 1
YCSEP1
1
The Y/C Separation mode is set as follows.
[YCSEP1:YCSEP0] (bit-1:bit-0)
YC-Separation mode
00
3-Line 2-D YC-Separation
01
1-Line BPF YC-Separation
10
Adaptive 3-Line 2-D YC-Separation (Default)
11
Reserved
bit 0
YCSEP0
0
3 types of the Color Band–Limiting Filters are selectable which are used for Y/C Separation. Use the[ Y/C SEPARATION
CONTROL1 REGISTER ] to select.
The Band Limiting Filters are applicable for all Y/C Separation modes ( in Black & White mode, filter selection becomes
invalid since the Y/C Separation function is disabled ).
[CBPFS1:CBPFS0] (bit-3:bit-2)
Chroma Bandwidth
Filter characteristic -3dB
00
OFF
OFF
01
Wide (Default)
+/- 1MHz
10
Middle
+/- 750kHz
11
Narrow
+/- 500kHz
Rev.0
46
2003/01