AK8857VQ Datasheet, PDF (67/105 Pages) Asahi Kasei Microsystems – Dual Channel Digital Video Decoder

[AK8857VQ]
VBI information decoding
The AK8857 decodes closed-caption, closed-caption-extended, VBID(CGMS), and WSS signals on
the vertical blanking signal, and writes the decoded data into a storage register. The AK8857 reads
each data bit in Request VBI Information Register(R/W)-[3:0] as a decoding request and thereupon
enters a data wait state. Data detection and decoding to the storage register are then performed
which indicates the presence or absence of data at STATUS 2 Register-[3:0] for host. The host can
therefore determine the stored values by reading the respective storage registers. The value in each
storage register is retained until a new value is written in by data renewal. For VBID data (CGMS-A),
the CRCC code is decoded and only the arithmetic result is stored in the register.
Signal type
Superimposed line
Notes
Closed Caption
Line21
525-Line
Closed Caption Extended Data
Line284
525-Line
VBID
Line20 / 283
Line20 / 333
525-Line
625-Line
WSS
Line23
625-Line
The storage registers for each of the signal types are as follows. For storage bit allocations, please
refer to the respective register setting descriptions.
Closed Caption 1 Register, Closed Caption 2 Register
WSS 1 Register, WSS 2 Register
Extended Data 1 Register, Extended Data 2 Register
VBID 1 Register, VBID 2 Register
Start
ʲRequest VBI Info Registerʳ
xxRQ-bit = 1
(decode requestʣ
If Closed Caption : CCRQ-bit
If Closed Caption Extended : EXTRQ-bit
If VBID/WSS : VBWSRQ-bit
ʲStatus RegisterʳRead
ʢσίʔυऴྃ֬ೝʣ
RequestʹରԠ͠
ͨϏοτ= 1
Yes
No
Closed Caption ͳΒ͹ CCDET-bit
Closed Caption Extended ͳΒ͹ EXTDET-bit
VBID/WSS ͳΒ͹ VBWSDET-bit
ϦΫΤετʹରԠͨ͠σʔλ
ϨδελͷϦʔυ
Closed Caption ͳΒ͹ʲClosed Caption 1ɾ2 Registerʳ
Closed Caption Extended ͳΒ͹ ʲExtended Data 1ɾ2 Registerʳ
VBID/WSS ͳΒ͹ʲVBID/WSS 1ɾ2 Registerʳ
Internal status indicators
○NOSIG-bit: Indicates presence or absence of signal
NOSIG –bit
Status of signal input
[0]
Signal detected
[1]
No signal detected
Notes
MS1189-E-01
-67-
2010/12