bt829bkrf ETC-unknow, bt829bkrf Datasheet - Page 52

• Manufacturer Part Number: bt829bkrf
• Description: Video Streamii Decoders
• Manufacturer: ETC-unknow

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1.0 Functional Description
1.10 Closed Captioning and Extended Data Services Decoding
The Bt829B provides a 16 x 10 location FIFO for storing CC/EDS data. Once the
video decoder detects the start signal in the CC/EDS signal, it captures the low
byte of CC/EDS data first and checks to see if the FIFO is full. If the FIFO is not
full, then the data is stored in the FIFO, and is available to the user through the
CC_DATA register (0x1D). The high byte of CC/EDS data is captured next and
placed in the FIFO. Upon being placed in the 10-bit FIFO, two additional bits are
attached to the CC/EDS data byte by Bt829B’s CC/EDS decoder. These two bits
indicate whether the given byte stored in the FIFO corresponds to CC or EDS
data and whether it is the high or low byte of CC/EDS. These two bits are avail-
able to the user through the CC_STATUS register bits CC_EDS and LO_HI,
respectively.
Bt829B stores the results of the parity check in the PARITY_ERR bit in the
CC_STATUS register.
Figure 1-25. Closed Captioning/Extended Data Services FIFO
per line. Initially when the FIFO is empty, the DA bit in the CC_STATUS register
(0x1C) is set low and indicates that no data is available in the FIFO. Subse-
quently, when data has been stored in the FIFO, the DA bit is set to logical high.
Once the FIFO is half full, the CC_VALID interrupts pin signals to the system
that the FIFO contents should be read in the near future. The CC_VALID pin is
enabled via a bit in the CC_STATUS register (0x1C). The system controller can
then poll the CC_VALID bit in the STATUS register (0x00) to ensure that it was
the Bt829B that initiated the CC_VALID interrupt. This bit can also be used in
applications where the CC_VALID pin is disabled by the user.
The parity bit is stored in the FIFO as shown in Figure 1-25. Additionally, the
The 16-location FIFO can hold eight lines worth of CC/EDS data, at two bytes
9 8 7 6
MSB
D829BDSA
...
LSB
7-bit ASCII code available through CC_DATA Register
Parity Bit Available Through CC_DATA Register
LO_HI Available Through CC_STATUS Register
CC_EDS Available Through CC_STATUS Register
0
Location 0
Location 1
Location 15
VideoStream II Decoders
Bt829B/827B