AK8815 Datasheet, PDF (17/37 Pages) Asahi Kasei Microsystems – NTSC/PAL Digital Video Encoder

ASAHI KASEI
[AK8815/16]
( 11 ) Video Data Interface timing
( 1-1 ) Video interface
The AK8815/16 operates in slave mode which is synchronized with the HSYNC / VSYNC sync signals.
A system operational outline is as follows –
Operation clock of the controller device which feeds data to the video encoder is fed from the video encoder. And
such timing signals as HSYNC and VSYNC of the controller are generated by the same clock timing.
The AK8815/16 synchronizes its operation with the generated HSYNC and VSYNC signals.
C o n tro lle r
C LK
HSYNC
VSYNC
D ata
V id e o E n c o d e r
In normal operation, the AK8815/16 checks HSYNC and VSYNC changes at each CLK edge ( CLK
synchronized ).
A Pixel when HSYNC is identified to get low is recognized to be H0 ( zero ), and the 236^th data ( NTSC ) or the
310^th data ( PAL ) is taken as Cb0 square pixel data.
Video field is recognized by VSYNC relation over HSYNC.
Field recognition is made as follows :
The AK8815/16 distinguishes at every Field if it is Odd Field ( 1^st Field ) or not. Even Field Sync signal is not
usually
input.
1 ) When VSYNC timing pulse signal fed to the AK8815/16 becomes low from high while HSYNC input signal is at
low, this Field is interpreted as Odd Field.
The Horizontal line where Odd Field identification is made, functions as Line 4 in NTSC mode and Line 1 in PAL
mode ( even when both VSYNC and HSYNC are identified to get low simultaneously, it is processed as Odd
Field. But it is recommended to input those signals with more than a few clock margin ).
2 ) The AK8815/16 continues operation in self-running mode , based on the sync signals which are fed just before,
if Horizontal / Vertical Sync signals are not fed every time in such timing and pulse count as expected in the
Video Standard Specifications.
But it is recommended to input those sync signals in the specified timing every time in order to prevent
erroneous operation.
3 ) All other VSYNC than those identified to be Odd Field are processed as Even Field.
But a use of VSYNC pulse other than in ODD Field synchronization is not assumed for normal operation.
MS0331-E-00
17
2004 / 08