MC-ACT-RSENC
April 24, 2003
Reed-Solomon Encoder
Datasheet v1.1
MemecCore
Product Line
3721 Valley Centre Drive
San Diego, CA 92130 USA
Americas:
+1 800-752-3040
Europe:
+41 (0) 32 374 32 00
Asia:
+(852) 2410 2720
E-mail: actel.info@memecdesign.com
URL: www.memecdesign.com/actel
TM
Product Summary
Intended Use
•
•
•
•
Data communication channels
DTV/HDTV broadcast
Data storage systems
Satellite communications
Key Features
•
Core design is customized using the following specs
o
o
o
o
o
o
•
•
•
•
•
Primitive polynomial
Generator polynomial
Number of parity symbols
Symbol size
Symbol clock rate
System clock rates
Message Block length configured by end user
Continuous or burst mode operation
Supports high speed applications (>900Mbps)
Simple core interface for ease of integration
Encoder available with or without Variable Parity Check Bytes
Targeted Devices
•
•
Axcelerator Family
ProASIC
PLUS
Family
General Description
Reed-Solomon coding is a method of forward error correction in the form of block coding. Block coding consists of
calculating a number of parity symbols over a number of message symbols. The parity symbols are appended to
the end of the message symbols forming a codeword. Reed-Solomon coding is described in the form RS(n,k),
where k is the number of message symbols in each block and n is the total number of symbols in the codeword.
The value t defines the number of symbols that can be corrected by the Reed-Solomon code, where t=(n-k)/2 and
the number of parity symbols is equal to 2t.
April 24, 2003
1
Optimized for
Reed-Solomon Encoder
m
Memec Design
Reed-Solomon codes are calculated in a finite field of elements, or Galois fields GF(2 ). The Galois field is defined
by a primitive polynomial P(x). The degree of the primitive polynomial m defines the number of bits per data symbol
m
(m = bits per symbol) and the maximum length of the Codeword (2 -1=maximum Codeword length n). The
generator polynomial G(x) further defines the field of Codewords that the parity symbols are derived from.
MC-ACT-RSENC is a "core" logic module specifically designed for Actel FPGAs. The logic symbol of this core is
shown in Figure 1.
Core Deliverables
•
Netlist Version
o
o
•
o
o
•
All
o
o
User Guide
Test Bench
Compiled RTL simulation model, compliant with the Actel Libero environment
Netlist compatible with the Actel Designer place and route tool
Verilog Source Code
VHDL Source Code
RTL Version
Synthesis and Simulation Support
•
•
•
•
•
Synthesis: Synplicity
Simulation: ModelSim
Other tools supported upon request
Verification
Test Bench
Test Vectors
IN_RS
RS_CALC
CLKEN
RST
CLK
OUT_RS
MDS1028
Figure 1: Logic Symbol
April 24, 2003
Optimized for
2
Reed-Solomon Encoder
Memec Design
IN_RS
REG
FF
ADD
FF
MULT
FF
MULT
FF
MULT
FF
MULT
FF
MULT
RS_CALC
REG
REG
FF
ADD
REG
FF
ADD
REG
FF
ADD
FF
ADD
REG
MDS1029
0
REG
OUT_RS
1
Figure 2: Block Diagram
Functional Description
The Reed-Solomon encoder core is partitioned into modules as shown in Figure 2, and described below.
All registers are driven by common clock (CLK), clock enable (CLKEN), and asynchronous reset (RST) signals. This
provides ultimate flexibility in integration of the core into larger systems. The registers are clocked on the rising
edge of CLK, enabled by a high on CLKEN, and asynchronously reset by a high on RST.
The RS_CALC signal controls whether the core is calculating the parity (high) or shifting out the calculated parity
(low). Logic external to the core is required to generate this control signal. This allows the user to vary the message
block length as desired for shortened codes. The RS_CALC pin must be held at a low for 2t enabled clock cycles to
ensure all parity register values are shifted out and the registers are cleared.
FFADD Blocks perform modulo 2 addition of the input symbols.
FFMULT Blocks perform a finite field multiplication, over the Galois field, of a constant and the input symbol.
Timing
Figure 3 shows a simple timing diagram of the RSENC interfaces for a Reed-Solomon block code of RS(204,188).
CLKEN
CLK
RS_CALC
IN_RS[7:0]
OUT_RS[7:0]
M186 M187
M0
M0
M1
M2
M3
M184 M185 M186 M187
P0
P1
P14
P15
M0
M1
MDS1030
Figure 3: RSENC Timing
April 24, 2003
Optimized for
3
Reed-Solomon Encoder
Reed-Solomon Encoder Variations
Memec Design
Various forms of the core have been developed. One supports high data rates where area is a secondary concern.
Another supports low data rates where a high-speed system clock is available and area is a primary concern. The
cores work for any valid codeword length and can be customized to support either fixed or variable values of parity
symbols. The core has been developed in two different approaches. One approach is optimized for encoders with a
single value of t. The other approach is optimized for encoders with selectable values of t.
The RSENC-INTELSAT is a precustomized core that calculates a selectable 14, 16, 18, or 20 parity symbols (t = 7,
8, 9, or 10) and is compliant with the IESS-308 Intelsat standard. The primitive polynomial and generator polynomial
8
7
2
120
121
119+2t
implemented is P(x)= x +x +x +x+1 and G(x)= (x-α )(x-α )…(x-α
) over a Galois field of GF(256). A 2
-bit
input control signal selects between four different codeword/message lengths: RS(126,112), RS(194,178),
RS(219,201), and RS(225,205). The RSENC-INTELSAT core is delivered as Verilog RTL source code. Detailed
timing and pin descriptions of the RSENC-INTELSAT can be found in the User’s Guide available from MemecCore.
The RSENC-DVB is a precustomized core that calculates 16 parity symbols and is compliant with the DVB
8
4
3
2
0
standard. The primitive polynomial and generator polynomial implemented is P(x)=x +x +x +x +1 and G(x)=(x-α )(x-
1
15
α
)…(x -α ) over a Galois field of GF(256). The core is adaptable to any message/codeword length RS(n,k) where
n-k=16. Thus, the largest code supported by this core is R(255,239). The DVB standards specify a code of
RS(204,188).
Parameter
Primitive Polynomial
Generator Polynomial
Bits per symbol
Codeword Length
Message Word Length
Parity Symbols (n-k)
Symbol
P(x)
G(x)
m
n
k
2t
8
4
3
0
1
DVB
x +x +x +x + 1
(x-α )(x-α )(x-α )(x-α )…(x-α )
8
204 (Note 1)
188
16
2
3
15
2
Intelsat
x +x +x +1
(x-α
8
126, 194, 219, 225
112, 178, 201, 205 (Note 2)
14, 16, 18, 20
120
8
7
2
)(x-α
121
)…(x-α
119+2t
)
Table 1: Reed-Solomon Encoder Parameters
Notes:
1. Core is adaptable to any RS(n,k) where n-k=16 and largest code being RS(255,239).
2. Selected by 2-bit input control signal for RS(126,112), RS(194,178), RS(219,201), and RS(225,205).
Device Requirements
Family
Axcelerator
PLUS
ProASIC
Device
AX500-3
APA075
COMB
6%
n/a
Utilization
SEQ
10%
n/a
Performance
Total
7%
34%
119 MHz
51 MHz
Table 2: Device Utilization and Performance*
*Note: The data provided is for an encoder with RS(255,225), G(x)=120, P(x)=125, m=8.
Verification and Compliance
Functional and timing simulation has been performed on the RSENC using Verilog Test Benches. Simulation
vectors used for verification are provided with the core. This core has also been used successfully in customer
designs.
April 24, 2003
Optimized for
4
Reed-Solomon Encoder
Signal Descriptions
The following signal descriptions define the IO signals.
Signal
Direction Description
IN_RS[m-1:0]
Input
Message block input.
RS_CALC
Input
Parity Calculate
CLKEN
Input
Clock Enable that enables all registers (active high).
CLK
Input
System Clock that drives all registers.
RST
Input
Asynchronous reset (active high).
OUT_RS[m-1:0]
Output
Coded block output.
Table 3: RSENC I/O Signals
Memec Design
Recommended Design Experience
For the source version, users should be familiar with HDL entry and Actel design flows. Users should be familiar
with Actel Libero v2.2 Integrated Design Environment (IDE) and preferably with Synplify and ModelSim.
Ordering Information
Part Number
MC-A CT-RSENC-NET
MC-ACT-RSENC-VLOG
MC-ACT-RSENC-VHDL
MC-ACT-RSENCU-NET
MC-ACT-RSENCU-VLOG
MC-ACT-RSENCU-VHDL
Description
RS Encoder Netlist
RS Encoder Verilog
RS Encoder VHDL
RS Encoder Netlist with Variable Parity Check Bytes
RS Encoder Verilog with Variable Parity Check Bytes
RS Encoder VHDL with Variable Parity Check Bytes
Table 4: Core Part Numbers
The CORE is provided under license from Memec Design for use in Actel programmable logic devices. Please
contact Memec Design for pricing and more information.
Information furnished by Memec Design is believed to be accurate and reliable. Memec Design reserves the right to
change specifications detailed in this data sheet at any time without notice, in order to improve reliability, function or
design, and assumes no responsibility for any errors within this document. Memec Design does not make any
commitment to update this information.
Memec Design assumes no obligation to correct any errors contained herein or to advise any user of this text of any
correction, if such be made, nor does the Company assume responsibility for the functioning of undescribed
features or parameters. Memec Design will not assume any liability for the accuracy or correctness of any support
or assistance provided to a user.
Memec Design does not represent that products described herein are free from patent infringement or from any
other third-party right. No license is granted by implication or otherwise under any patent or patent rights of Memec
Design.
MemecCore products are not intended for use in life support appliances, devices, or systems. Use of a MemecCore
product in such application without the written consent of the appropriate Memec Design officer is prohibited.
All trademarks, registered trademarks, or service marks are property of their respective owners.
Datasheet Revision History
Version
Datasheet 1.0
Datasheet 1.1
Date
January 10, 2003
April 24, 2003
Description
First Release
Updated corporate address, added CompanionCore logo
April 24, 2003
Optimized for
5
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