AK8851 Datasheet, PDF (36/80 Pages) Asahi Kasei Microsystems – NTSC/PAL/SECAM Digital Video Decoder

ASAHI KASEI
[AK8851]
22. Closed Caption/Closed Caption Extended Data/ VBID ( CGMS )/WSS
The AK8851 decodes Closed Caption, Closed Caption extended, , VBID (CGMS) and WSS signals that are
super-imposed on the Vertical Blanking signal. Decoded data is written into a register.
When the request bit [bit3:bit0] of [Request VBI INFO Register](R/W)[Sub Address 0x15] is set, the AK8851 is put into a
data wait state as each data decode request is made.
After data detect and decoding, [bit3:bit0] of [Status 2 Register](R)[Sub Address0x17] tells a host that decoding is complete.
Decoded results are written into [Closed Caption 1/2 Register],[Extended Data 1/2 Register],[WSS 1/2 Register] and [VBID
1/2 Register] respectively.
Each data is super-imposed on the lines listed below. As for the VBID data (CGMS-A), CRCC code is decoded and its
result only is stored in register.
Signal
Closed Caption
Closed Caption Extended
VBID
WSS
NTSC:
NTSC:
NTSC:
PAL:
PAL:
Decoded Line
Line-21
Line-284
Line-20/283
Line-20/333
Line-23
525-Line System
525-Line System
525-Line System
625-Line System
625-Line System
Note
Bit allocation of [Request VBI INFO Register] is shown below.
Sub Address 0x15
bit 7
bit 6
bit 5
bit 4
bit 3
Reserved
Reserved
Reserved
Reserved
WSSRQ
Default Value
0
0
0
0
0
bit 2
VBIDRQ
0
bit 1
EXTRQ
0
bit 0
CCRQ
0
Bit allocation of [Status 2 Register] is shown below.
Sub Address 0x17
bit 7
bit 6
bit 5
bit 4
Reserved
Reserved
Reserved
REALFLD
bit 3
WSSDET
bit 2
VBIDDET
bit 1
EXTDET
bit 0
CCDET
VBI interval Read operation of is shown in the following flow chart.
Start
[Request VBI Info Register]
xxRQ-bit = 1
(Decode Request )
[Request VBI Info Register] Read
(Confirm the decoding done)
Closed Caption: CCRQ-bit
VBID: VBIDRQ-bit
WSS: WSSRQ-bit
Correspondat bit
for Request is 1?
Yes
Read the correspondant data
register
No
Closed Caption: CCDET-bit
VBID: VBIDDET-bit
WSS: WSSDET-bit
Closed Caption: [Closed Caption 1/2 Register]
VBID: [VBID 1/2 Register]
WSS: [WSS 1/2 Register]
MS0244-E-03
36
Confidential
2005 / 07