CLC031VEC datasheet(13/31 Pages) NSC

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Device Operation (Continued)

Ancilliary Data Functions

The CLC031 can recover Ancilliary Data from the serial

data stream. This ancilliary data and related control charac-

ters are defined in the relevant SMPTE standards and may

reside in the horizontal and vertical blanking intervals. The

data can consist of different types of message packets in-

cluding audio data. The serial ancilliary data space must be

formatted according to SMPTE 291M. The CLC031 sup-

ports ancilliary data in the chrominance channel (C’r/

C’b) only for high-definition operation. Ancilliary data for

standard definition follows the requirements of SMPTE

125M.

The Ancilliary Data FIFO is sized to handle a maximum

length ANC data Type 1 or Type 2 packet without the ANC

Flag, 259 words. Defined in SMPTE 291M, the packet con-

sists of the Ancilliary Data Flag, a 3-word Data ID and Data

Count, 255 8- or 10-bit User Data Words and a Checksum.

The design of the CLC031 Ancilliary Data FIFO also allows

storage of up to 8 shorter length messages with total length

not exceeding 259 words including all ID information. Ancil-

liary Data is copied from the data stream into the Ancilliary

Data FIFO. The parallel ancilliary data will still be present in

the parallel chroma output DV[9:0]. Ancilliary flag informa-

tion is not extracted into the FIFO.

Copying of ANC data from the video data into the FIFO is

controlled by the ANC Mask and ANC ID bits in the control

registers. A system of flags, ANC FIFO Empty, ANC FIFO

90% Full, ANC FIFO Full and ANC FIFO Overrun are used

to monitor FIFO status. The details and functions of these

and other control words are explained later in this datasheet.

20020109

FIGURE 2. Control Data Read Timing (2 read and 1 write cycle shown)

20020110

FIGURE 3. Control Data Write Timing

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