AK8851 Datasheet, PDF (25/80 Pages) Asahi Kasei Microsystems – NTSC/PAL/SECAM Digital Video Decoder

ASAHI KASEI
[AK8851]
14. Digital Pedestal Clamp
The input signal’s digitally-converted Pedestal position is clamped in the digital signal-processing block. It handles 2
types of input signals (286 mV-type SYNC signal and 300 mV-type SYNC signal) and it outputs the pedestal position as
code 16 (8-bit Rec.601 level) for both input cases.
The digital pedestal clamp function sets the time constant ( including ON/OFF ) and it also sets the coring level.
Digital Pedestal Clamp characteristics are set by [DPCT1:DPCT0]-bit and [DPCC1:DPCC0]-bit of [Pedestal Level Control
Register](R/W)[Sub Address 0x0C].
Bit allocation of [Pedestal Level Control Register] is as follows.
Sub Address 0x0C
bit 7
bit 6
DPCC1
DPCC0
0
0
bit 5
DPCT1
0
bit 4
bit 3
DCPT0
BKLVL3
Default Value
0
0
Bit 2
BKLVL2
0
Default Value : 0x00
bit 1
bit 0
BKLVL1
BKLVL0
0
0
*[DPCT1:DPCT0]-bit:
This sets the time constant of the digital pedestal clamp.
[DPCT1:DPCT0]-bit
Time constant of Digital Pedestal Clamp
[00]
Fast
[01]
Middle
[10]
Slow
[11]
Disable
*[DPCC1:DPCC0]-bit:
This sets the non-sensing bandwidth (coring level) of the digital pedestal clamp.
[DPCC1:DPCC0]-bit
Non-sensing bandwidth of digital
pedestal clamp
[00]
1-bit
[01]
2-bit
[10]
3-bit
[11]
No non-sensing range
Note
Note
15.YC Separation
The AK8851 employs adaptive, two-dimensional Y/C separation.
In the adaptive YC separation function, a correlator detector selects a best-correlated direction among vertical, horizontal
and diagonal samples and an optimized YC separation method is selected.
For NTSC-4.43,PAL 60 and SECAM signal input, a primary dimensional Y/C separation mode is selected, regardless of
the bit setting.
YC separation control register is set by [Control 1 Register](R/W)[Sub Address 0x08].
Bit allocation of [Control 1 Register] is as follows.
Sub Address 0x08
bit 7
bit 6
CLKMODE1 CLKMODE0
bit 5
INTPOL1
0
0
0
bit 4
bit 3
INTPOL0 16BITOUT
Default Value
0
0
bit 2
UVFILSEL
0
Default Value : 0x00
bit 1
bit 0
YCSEP1
YCSEP0
0
0
*[YCSEP1:YCSEP0]-bit:
this selects YC separation method.
[YCSEP1:YCSEP0]-bit
[00]
[01]
[10]
[11]
YC Separation mode
Adaptive YC Separation mode
1-Dim YC Separation mode
2-Dim YC Separation mode
Reserved
Note
1-D YC separation mode is selected when
SECAM signal is input
1-D YC separation mode is selected when
SECAM signal is input
MS0244-E-03
25
Confidential
2005 / 07