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AHA4012B-006 Datasheet(PDF) 6 Page - List of Unclassifed Manufacturers

Part No. AHA4012B-006
Description  1.5 MBytes/sec Reed-Solomon Error Correction Device
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AHA4012B-006 Datasheet(HTML) 6 Page - List of Unclassifed Manufacturers

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PS4012B-0100
Advanced Hardware Architectures, Inc.
1.2.1
DEFINITION OF CORRECTION TERMS
*
For every 2 check bytes, the AHA4012B can correct either 2 erasures or 1 error.
**
An erasure is detected by a parity detector or a signal dropout detector. The presence of an erasure is
indicated by asserting the ERASE signal when the erased byte is clocked into the AHA4012B.
2.0
FUNCTIONAL DESCRIPTION
This section describes an architectural
overview of the chip and its many functions,
features and operating modes. The block diagram
for the chip shows the Reed-Solomon ECC module,
the Input and Output Buffers and their associated
control. All input and output data are clocked on the
rising edge of CLK.
2.1
FUNCTIONAL OVERVIEW
The AHA4012B Reed-Solomon codec (coder/
decoder) is the lowest cost member of the AHA
PerFEC
TM family of forward error correction (FEC)
devices. This single chip, three-layer metal, CMOS
device can operate in encode, decode or pass-
through modes.
The ECC core implements a full error
correcting Reed-Solomon decoder. This code is
capable of correcting up to 10 (t
= 10) byte-errors or
20 (t
= 10) erasures in a block.
TERM
NAME
(other references)
DEFINITION
RANGE
(number of bytes)
K
Message Length
(user data or message
bytes)
Number of user data symbols in one message block.
Size of a symbol in AHA4012B is 8-bits. Message
length is K
= N − R. The first message byte is
referred to as X
K
−1; the last message byte is X0.
1 through 253
(1, 2, 3, 4 . . . 253)
R
Check symbols
(parity or redundancy)
Symbols appended to the user data to detect and
correct errors. The number of check symbols
required in a system is R
≤ E + 2e.* The first check
symbol is referred to as Y
R
−1; the last check symbol
is Y
0.
2 through 20 in
increments of 1
(2, 3, 4 . . . 20)
N
Codeword Length
(block length)
Sum of message and check symbols. N
= K + R. 3 through 255
(3, 4, 5, 6 . . . 255)
t
Error Corrections
Maximum number of error corrections performed
by the device. The value is t
= Integer
.
1 through 10
(1, 2, 3 . . . 10)
P
Error Threshold
The threshold limit to determine uncorrectability
of a Codeword and the number of check bytes
allocated for correction-only purposes (not for
detection).
2 through 20
(2, 3, 4 . . . 20)
e
Number of Errors
An error is defined as an erroneous byte whose
correct value and position within the message
block are both unknown.
0 through N
E
Number of Erasures
An erasure is defined as an error whose position is
known within the message block.**
0 through N
G
Burden of Correction
A measure of the burden of correction being placed
on the capabilities of the device for that message
block. The value G
= 2e + E.
0 through R
NK
2
--------------


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