L64704 LSI Logic Corporation, L64704 Datasheet - Page 161

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

Figure 7.16
122-bit Burst
Example
7.3.2
Features
7.3.1.3 Error Handling and Correction
A bit error occurs when a transmitted zero is received as a one or vice
versa. A byte error occurs when one or more bits in the byte have errors.
For example, a byte with only one bit error is counted as one byte error,
and a byte with m bit errors (all bits are inverted) is also counted as one
byte error. As long as a code word has no more than T =
errors, the RS Decoder corrects all errors. When a code word has more
than T =
excessive errors and asserts the ERROROUT signal to notify the user.
Assume that the byte size is 8, the redundant check parameter is 32, and
a 122-bit burst error is input to the RS decoder. The RS decoder can cor-
rect up to T = 16 byte errors. A 122-bit burst can be divided into 17 bytes
as shown in
Because the redundancy is 32, the decoder corrects up to 16 byte errors.
Because the 122-bit burst corrupts 17 consecutive bytes, the maximum
guaranteed correctable burst length in this example is 121 bits.
The Reed-Solomon Decoder features:
Reed-Solomon Decoder
62.5 Mbits/s throughput
Flag for corrected errors
Complies with CCITT recommended CCIR723 standard for digital TV
transmission
DVB compliant
Decoder channel output counts for uncorrected data and error vector
data
ERROROUT signal flags uncorrectable errors
(204, 188) Reed-Solomon Code Format
e e e e e e e e e
R
Figure
2
1 Byte
byte errors, the RS decoder detects the presence of
7.16, where each e represents a one bit error.
17 Bytes
122 Bits
. . . . . .
e e e e e e e e
R
2
byte
7-17