cx25840 Conexant Systems, Inc., cx25840 Datasheet - Page 70

• Manufacturer Part Number: cx25840
• Description: Video Decoder And Broadcast Audio
• Manufacturer: Conexant Systems, Inc.

Detailed Functional Description
3.6.4
3-44
VBI Data Output
Low bit-rate VBI standards can be read back from the memory-mapped registers that
are accessible by either the two-wire serial communication or VIP host port. The VBI
data registers, which contain data for both even and odd fields, are updated every
frame during the vertical blanking interval after capturing and decoding the data. The
data standards available through the memory-mapped registers are the following:
There are four payload data FIFOs for Closed Caption, Gemstar 1x, Gemstar 2x, and
WSS standards. The CC and Gemstar 1x FIFOs are 10 bytes deep, the Gemstar 2x are
20 bytes deep, and the WSS FIFO are 6 bytes deep. By reading the Closed Caption
Data (0x445), Gemstar 1x Data (0x447), Gemstar 2x Data (0x449) and WSS Data
(0x44B) registers, the user can access the FIFOs for each of these standards.
After the data is read, the data FIFO pointer is automatically incremented to the next
byte of information. With each data byte loaded to a register for reading, a status byte
is updated accordingly. The status byte indicates whether a parity error has occurred
for CC, Gemstar 1x, Gemstar 2x. It also indicates if the byte was captured from the
odd or even field (CC or XDS), and the byte number. Two bits indicating FIFO
overflow or empty are also included in the status byte.
Both high bit-rate and low bit-rate sliced data can be inserted in the video output
stream during horizontal blanking intervals (areas labeled A in
ancillary data. The VBI slicer uses a FIFO and related control signals to pass the data
to the video output formatter for insertion. Ancillary data insertion is enabled by
setting high the ANC_DATA_EN bit in the Video Out Control 1 (0x404) register.
Closed Caption/Extended Data Services (EIA-608)
Wide Screen Signaling (625 line: ITU-R BT.1119, 525 line: EIAJ CPR-1204)
including the Copy Generation Management System (CGMS)
Gemstar1x
Gemstar2x
Conexant
Figure
CX25840/1/2/3 Data Sheet
3-15) as
102284B
8/3/05