AK8859VN Datasheet, PDF (38/72 Pages) Asahi Kasei Microsystems – NTSC/PAL/SECAM Digital Video Decoder

[AK8859VN]
[7.31.] VBI information decoding
The AK8859VN 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 AK8859VN reads each
data bit in Request VBI Information Register (Sub Address: 0x13 [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 (Sub Address: 0x16
[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
Closed Caption
Closed Caption Extended Data
VBID
WSS
Superimposed line
Line21
Line284
Line20 / 283
Line20 / 333
Line23
Notes
525-Line
525-Line
525-Line
625-Line
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 (Sub Address: 0x19 ~ 0x20).
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
[Request VBI Information Register]
xxRQ-bit = 1
(Decode request)
[Status 2 Register] Read
(Check Decode Detection)
No
Request-bit = 1 ?
YES
Read each storage register
END
MS1179-E-00
AKM Confidential
- 38 -
2010/04