AHA4013B View Datasheet(PDF) - Unspecified
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AHA4013B Datasheet PDF : 28 Pages
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Advanced Hardware Architectures, Inc.
Table 4: Continuous Operation for IESS-308 Codes Using 50 MHz Clock and Specified Clocks/Byte,
Forward Output Order
BLOCK
LENGTHS ‘N’
MESSAGE ERROR
LENGTH ‘K’ CAPABILITY ‘t’
MINIMUM
REQUIRED
(clocks/byte)
126
112
7
4
194
178
8
4
208
192
8
4
219
201
9
4
225
205
10
4
MAXIMUM
DATA RATE
(MBytes/sec)
12.5
12.5
12.5
12.5
12.5
MAXIMUM
LATENCY
(# of clocks)
742
1107
1181
1242
1276
MAXIMUM
LATENCY
(µsecs)
14.84
22.14
23.62
24.82
25.52
Appendix B shows a spreadsheet table of block lengths vs. latencies for a 50 MHz clock system.
2.10 REED-SOLOMON (ECC) MODULE AND ERROR RATE PERFORMANCE
The module implements a full error correcting
Reed-Solomon (RS) decoder whose function is to
perform the necessary corrections on the input
blocks. The code used by the decoder is capable of
generating corrections for up to 10 (t = 10) byte-
errors in an RS block over the block length between
R + 1 to 255 bytes. The number of message bytes in
an RS block, K, is equal to the RS block length
minus R (K = N − R). The RS code implemented
uses the primitive polynomial
P(x) = x8 + x7 + x2 + x + 1
to generate GF(256). The generator polynomial for
the code is:
∏ G(x) = 119 + R (x – αi)
i = 120
An RS block consists of message and
redundancy bytes. The number of message bytes in
the block, K, is programmable during initialization.
The number of check bytes is R and can be
programmed during initialization to be 2 through 20
in increments of 1.
The ECC Module may be programmed to
output corrections or corrected data. If
“corrections” is selected, to obtain corrected data,
externally XOR the output correction vector with
the corresponding message or check byte. For
example, if “corrections” is selected for a block of
200 bytes with errors in locations 100, 123, 153, 176
and 199; output block will be 0’s for all locations
except for those positions. The bytes output at these
positions are referred to as correction vectors and
are XOR’d externally with the message bytes to
obtain the correct value. If the output of the
AHA4013B is programmed to output corrected
data, the correction vector is applied internally and
the corrected data is output.
The Symbol Error Rate Performance of the
Reed-Solomon code used is shown in Figure 5.
Figure 5:
Symbol (Byte) Error Rate Performance Curves for Codeword Length = 255 Bytes
10-0
10-2
10-4
10-6
P 10-8
t=1
10-10
10-12
10-14
10-16
10-0
t=8 t=5
t=3
t=10
10-1
10-2
10-3
10-4
10-5
P
10-6
10-7
10-8
PS4013B-0600
Page 11 of 24
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