L64767 LSI Logic Corporation, L64767 Datasheet - Page 8

• Manufacturer Part Number: L64767
• Description: Smatv Qam Encoder
• Manufacturer: LSI Logic Corporation

Bytes to m-tuple Converter
Differential Encoder and QAM Mapper
Nyquist Filter
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The interleaver is a (B, N) periodic interleaver with the following
characteristics:
The bytes to m-tuples converter organizes bytes into symbols (tuples) of
m = 1, 2, 3, 4, 5, 6, 7, and 8 bits. To process the data stream, the L64767
feeds the converter packets of eight bytes together with a valid signal
from the general control unit. The order of the conversion process starts
with the MSB of the oldest byte first (see the document
DTVB1190/DTVC37, Revision 3 for details).
This block performs differential encoding and mapping for 16 to 256 QAM,
as specified in the document DTVB1190/DTVC37, Revision 3 .
The Nyquist filter shapes signals for DVB compliance. This filter
implements the square root raised cosine filtering function with roll off
factor of 15%, as specified in DTVB1190/DTVC37, Revision 3 . You can
use other non-DVB filtering functions by downloading the appropriate
filter coefficients.
The precision of the internal computations and the width of the output
data bus are suitable up to 256 QAM. The filter interpolates the input
data by a factor of two or four so that the filter output data rate is two or
four times the filter input data rate. You specify the interpolation factor
(oversampling) using a configuration register.
L64767 SMATV QAM Encoder
The minimum separation at the interleaver output is B symbols for
any two symbols that are separated by less than N symbols at the
interleaver input.
Any burst of b < B errors inserted by the channel results in single
errors at the deinterleaver output.