L64704 LSI Logic Corporation, L64704 Datasheet - Page 158

• Manufacturer Part Number: L64704
• Description: Satellite Decoder Technical Manual 5/97
• Manufacturer: LSI Logic Corporation

7.3
Reed-Solomon
Decoder
7.3.1
Terms and
Concepts
7-14
The Reed Solomon Decoder is a Forward Error Correction unit that looks
at the check bytes that are appended to the data stream and either cor-
rects any errors that it finds in the data stream or asserts the
ERROROUT pin when it cannot correct the data.
Error Correction Code (ECC) devices have a specific lexicon associated
with their ability to correct transmission messages. This section defines
the terms used for variables in the Reed-Solomon Core. The terms are
used throughout this document.
R
d
K
m
N
T
The FEC Decoder Pipeline
Check Bytes
The encoder generates and appends check bytes to the
incoming message according to the Reed-Solomon error
correction encoding. The decoder uses check bytes to
locate and correct errors caused by transmission. The
system designer specifies the size of the check byte field
within the limitations.
Detection power
Detection power specifies the maximum number of
detectable errors. Detection power has a minimum value
of:
Message Length
The message is comprised of multiple bytes. The size of
the message varies, depending on the code word length
and the check bytes used, where K = N – R.
Symbol Size
A data transfer is comprised of multiple symbols and the
symbol size, m, is eight bits.
Codeword Length
This variable is the sum of the number of message bytes
and the number of check bytes (K + R). The value of N
is 204.
Number of Error Corrections
This variable is the maximum number of error corrections
performed by the decoder. The value of T is 8.
R
--- -
2
and a maximum value of R.