L64777 LSI Logic Corporation, L64777 Datasheet - Page 34

• Manufacturer Part Number: L64777
• Description: DVB Qam Modulator
• Manufacturer: LSI Logic Corporation

2.7 Reed-Solomon Encoder
2-20
SSTARTIN input signal can preset the phase of the inverted
SYNC_BYTE and the whole scrambler sequence.
The microprocessor can switch off the scrambler module through
Register 3 (see Section 4.1.4, “Register 3,” page 4-5). The selected
microprocessor control applies the sequence of Start, Run, and Disable
modes, depending on the programmed sync block length values in
Register 4 (see page 4-6).
Reed-Solomon (RS) error correction codes are systematic and operate
on bytes rather than single-bit data streams. The codes are expressed
by convention as two numbers, the first indicating the total code word
length (N), and the second indicating the number of message bytes (K).
The difference between these two numbers (N
check bytes.
DVB uses this generator polynomial for RS codes:
where R = 16 (checkbytes), and
polynomial:
A data byte (d
d
The error-correcting power of an RS code is related to the number of
redundant check symbols in its code words. In general, an RS code with
2t check symbols per code word can correct up to “t” byte errors per
code word. Higher redundancy allows more errors to be corrected.
ECC devices have a specific lexicon associated with their ability to
correct transmission messages; the terms used for variables in the
Reed-Solomon Core are as follows:
Modulator Architecture
x
7
8
R 1
i
+
=
7
–
0
x
+ d
4
x
+
6
+
x
6
3
i
+...+ d
+
7
x
, d
2
+
6
1
,...d
1
+ d
1
, d
0
0
in GF (256), the finite field with 256 elements.
) is identified with the element
is a root of the binary primitive
K) is the number of