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106 lines
3.7 KiB
C++
106 lines
3.7 KiB
C++
// Copyright 2007 Altera Corporation. All rights reserved.
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// Altera products are protected under numerous U.S. and foreign patents,
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// maskwork rights, copyrights and other intellectual property laws.
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//
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// This reference design file, and your use thereof, is subject to and governed
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// by the terms and conditions of the applicable Altera Reference Design
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// License Agreement (either as signed by you or found at www.altera.com). By
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// using this reference design file, you indicate your acceptance of such terms
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// and conditions between you and Altera Corporation. In the event that you do
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// not agree with such terms and conditions, you may not use the reference
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// design file and please promptly destroy any copies you have made.
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//
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// This reference design file is being provided on an "as-is" basis and as an
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// accommodation and therefore all warranties, representations or guarantees of
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// any kind (whether express, implied or statutory) including, without
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// limitation, warranties of merchantability, non-infringement, or fitness for
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// a particular purpose, are specifically disclaimed. By making this reference
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// design file available, Altera expressly does not recommend, suggest or
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// require that this reference design file be used in combination with any
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// other product not provided by Altera.
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/////////////////////////////////////////////////////////////////////////////
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// baeckler - 7-21-2006
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#include <stdio.h>
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int bit_count (int c)
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{
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int cnt = 0;
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int n = 0;
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for (n=0;n<6; n++)
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{
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if ((c & 1) != 0) cnt++;
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c >>= 1;
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}
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return (cnt);
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}
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int main (void)
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{
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int code = 0;
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int diff[4];
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int best_diff = 0;
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fprintf (stdout,"//////////////////////////////////////////////\n");
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fprintf (stdout,"// 2 to 6 bit ECC encoder\n");
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fprintf (stdout,"//////////////////////////////////////////////\n");
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fprintf (stdout,"module ecc_encode_2bit (d,c);\n");
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fprintf (stdout,"input [1:0] d;\n");
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fprintf (stdout,"output [5:0] c;\n");
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fprintf (stdout,"wire [5:0] c;\n\n");
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fprintf (stdout," assign c = {d[1],d[1],d[0],d[0],^d,^d};\n");
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fprintf (stdout,"endmodule\n\n");
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fprintf (stdout,"//////////////////////////////////////////////\n");
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fprintf (stdout,"// the error flag indicates\n");
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fprintf (stdout,"// [2] 2 or more bit error\n");
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fprintf (stdout,"// [1] 1 bit error (corrected)\n");
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fprintf (stdout,"// [0] no error\n");
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fprintf (stdout,"//////////////////////////////////////////////\n");
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fprintf (stdout,"module ecc_decode_2bit (c,d,err_flag);\n");
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fprintf (stdout,"input [5:0] c;\n");
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fprintf (stdout,"output [1:0] d;\n");
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fprintf (stdout,"output [2:0] err_flag;\n");
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fprintf (stdout,"reg [1:0] d;\n");
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fprintf (stdout,"reg [2:0] err_flag;\n");
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fprintf (stdout," always @(c) begin\n");
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fprintf (stdout," case (c)\n");
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fprintf (stdout," // bit distance to codes 0 .. 3\n");
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for (code = 0; code<64; code++)
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{
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fprintf (stdout," 6'h%02x : ",code);
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// look at the bit distance from input to the codes
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diff[0] = bit_count(code ^ 0x00);
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diff[1] = bit_count(code ^ 0x0f);
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diff[2] = bit_count(code ^ 0x33);
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diff[3] = bit_count(code ^ 0x3c);
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best_diff = 0;
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if (diff[1] < diff[best_diff]) best_diff = 1;
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if (diff[2] < diff[best_diff]) best_diff = 2;
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if (diff[3] < diff[best_diff]) best_diff = 3;
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// select data
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fprintf (stdout, "{d,err_flag} = {2'b%d%d, 3'b%d%d%d};",
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(best_diff>>1) & 1, best_diff & 1,
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diff[best_diff] >= 2 ? 1 : 0,
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diff[best_diff] == 1 ? 1 : 0,
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diff[best_diff] == 0 ? 1 : 0);
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fprintf (stdout," // %d %d %d %d\n",diff[0],diff[1],diff[2],diff[3]);
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}
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fprintf (stdout," endcase\n");
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fprintf (stdout," end\n");
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fprintf (stdout,"endmodule\n");
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return (0);
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} |