Analog Devices ADSP-BF506F Hardware Reference Manual page 961

When the
SKIP_EN
either the odd or the even elements in an input datastream. This is useful,
for instance, when reading in a color video signal in YCbCr format (Cb,
Y, Cr, Y, Cb, Y, Cr, Y...). Skipping every other element allows the PPI to
only read in the luma (Y) or chroma (Cr or Cb) values. This could also be
useful when synchronizing two processors to the same incoming video
stream. One processor could handle luma processing and the other (whose
bit is set differently from the first processor's) could handle
SKIP_EO
chroma processing. This skipping feature is valid in ITU-R 656 modes
and RX modes with external frame syncs.
The bit only has meaning when the PPI port width (selected by
PACK_EN
) is eight bits. Every
DLEN[2:0]
(that is, an input or output operation) handles 16-bit entities. In other
words, an input port width of ten bits still results in a 16-bit input word
for every
PPI_CLK
bits also results in a 16-bit input word, with the upper eight bits all 0s. In
the case of 8-bit data, it is usually more efficient to pack this information
so that there are two bytes of data for every 16-bit word. This is the func-
tion of the
PACK_EN
Consider this data transported into the PPI via DMA:
0xCE, 0xFA, 0xFE, 0xCA....
• With
PACK_EN
This is read into the PPI, configured for an 8-bit port width:
0xCE, 0xFA, 0xFE, 0xCA...
• This is transferred onto the DMA bus:
0xFACE, 0xCAFE,...
• With
PACK_EN
This is read into the PPI:
0xCE, 0xFA, 0xFE, 0xCA,...
ADSP-BF50x Blackfin Processor Hardware Reference
bit is set, the
SKIP_EO
PPI_CLK
; the upper 6 bits are 0s. Likewise, a port width of eight
bit. When set, it enables packing for all RX modes.
set:
cleared:
Parallel Peripheral Interface
bit allows the PPI to ignore
-initiated event on the DMA bus
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