Texas Instruments TMS320C64x DSP Benutzerhandbuch

3-12

The Y/C capture mode is similar to the BT.656 capture mode but captures 8
or 10-bit 4:2:2 data on separate luma and chroma data streams. One data
stream contains Y samples and the other stream contains multiplexed Cb and
Cr samples co-sited with every other Y sample. The Y samples are written into
a Y FIFO and the chroma samples are demultiplexed and written into separate
Cb and Cr FIFOs for transfer into Y, Cb, and Cr buffers in DSP memory. The
packing and order of the samples is determined by the sample size (8-bit or
10-bit) and the device endian mode.

The Y/C capture mode supports HDTV standards such as SMPTE260,
SMPTE296, and BT.1120 with embedded EAV and SAV codes. It also supports
SDTV YCbCr modes that use separate control signals (sometimes called
CCIR601 mode)

As with the BT.656 capture mode, data bytes where the 8 most-significant bits
are all set to 1 (FF.0h, FF.4h, FF.8h, FF.Ch) or are all cleared to 0 (00.0h, 00.4h,
00.8h, 00.Ch) are reserved for data identification purposes and consequential-
ly only 254 of the possible 256 8-bit words (or 1016 of 1024 10-bit words) may
be used to express signal value.

Because Y/C mode requires the entire VDATA bus, only single channel opera-
tion is supported. If the DCHNL bit in VPCTL is set, then Y/C mode cannot be
selected. Y/C capture takes place on channel A only. Both embedded timing
references and external control inputs are supported.

Many high-resolution Y/C interface standards provide for embedded timing
reference codes. These codes are identical to those used in the BT.656 stan-
dard except that they appear on both the luma (Y) and chroma (CbCr) data
streams in parallel.