AK8850 Datasheet, PDF (61/99 Pages) Asahi Kasei Microsystems – NTSC Digital Video Decoder

ASAHI KASEI
[AK8850]
7-4-15 NON-SIGNAL INPUT DETECTION
The AK8850 detects non-signal input conditions and, when detected, outputs a Black level signal ( Y=0x10,Cb/Cr=0x80 ).
The non-signal input condition is detected by checking for the existence of the VSYNC signal. In order to have higher
margin against non-Standard signal inputs, the non-signal detection is made only when the VSYNC is not detected two or
more consecutive times. The result is output via the NSIG output pin.
Output State:
NSIG=1 ( non-signal input )
NSIG=0 ( valid input signal )
7-4-16 STANDARD SIGNAL DETECTION
The AK8850 has a Standard Signal Detection function. When a non-Standard input signal is detected, the NSTD output
pin changes to “ high ”. The NSTD output becomes “ low ” (Standard signal input ) when either ( a ) or ( b ) conditions
below are met.
( a ) with Component input ( 525 / 625 ), the Frame configuration during the past 2 Frames is made with ODD / EVEN or
EVEN / ODD sequence.
( b ) with Composite input ( including Y/C input ), the SCH phase is within +/- 67.5 degrees and the Frame configuration is
made with ODD / EVEN or EVEN / ODD sequence.
7-4-17 OUTPUT FORMAT ( 601 FORMATTER )
The AK8850 outputs the decoded data in ITU-R BT.601 compatible format ( Y/Cb/Cr 4:2:2 ). The min. and max. values of
the output code are selectable by 601LIMIT-bit of the [ OUTPUT FORMAT REGISTER ].
At 601LIMIT-bit = 0 Y : 1 ~ 254
Cb/Cr : 1 ~ 254
At 601LIMIT-bit = 1 Y : 16 ~ 235
Cb / Cr : 16~ 240
Output Format Related Register :
bit 7
bit 6
bit 5
ACTSTA[2] ACTSTA[1] ACTSTA[0]
0
0
0
bit 4
bit 3
YCDELAY[2] YCDELAY[1]
Default Value
0
0
bit 2
YCDELAY[0]
0
bit 1
601LIMIT
0
bit 0
ERRHND
0
Rev.0
61
2003/01