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/* =============================================================== (C) 2006 Robert Finch All rights reserved. rob@birdcomputer.ca cntpop.v - count number of one bits in a byte - simple fast approach - lookup table This source code is free for use and modification for non-commercial or evaluation purposes, provided this copyright statement and disclaimer remains present in the file. If the code is modified, please state the origin and note that the code has been modified. NO WARRANTY. THIS Work, IS PROVIDEDED "AS IS" WITH NO WARRANTIES OF ANY KIND, WHETHER EXPRESS OR IMPLIED. The user must assume the entire risk of using the Work. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY INCIDENTAL, CONSEQUENTIAL, OR PUNITIVE DAMAGES WHATSOEVER RELATING TO THE USE OF THIS WORK, OR YOUR RELATIONSHIP WITH THE AUTHOR. IN ADDITION, IN NO EVENT DOES THE AUTHOR AUTHORIZE YOU TO USE THE WORK IN APPLICATIONS OR SYSTEMS WHERE THE WORK'S FAILURE TO PERFORM CAN REASONABLY BE EXPECTED TO RESULT IN A SIGNIFICANT PHYSICAL INJURY, OR IN LOSS OF LIFE. ANY SUCH USE BY YOU IS ENTIRELY AT YOUR OWN RISK, AND YOU AGREE TO HOLD THE AUTHOR AND CONTRIBUTORS HARMLESS FROM ANY CLAIMS OR LOSSES RELATING TO SUCH UNAUTHORIZED USE. Ref: Webpack 8.1i Spartan3-4 xc3s1000-4ft256 11 LUTs / 6 slices / 12.2 ns =============================================================== */ module cntpop8( input [7:0] i, output reg [3:0] o ); always @(i) case (i) 8'b00000000: o = 0; 8'b00000001: o = 1; 8'b00000010: o = 1; 8'b00000011: o = 2; 8'b00000100: o = 1; 8'b00000101: o = 2; 8'b00000110: o = 2; 8'b00000111: o = 3; 8'b00001000: o = 1; 8'b00001001: o = 2; 8'b00001010: o = 2; 8'b00001011: o = 3; 8'b00001100: o = 2; 8'b00001101: o = 3; 8'b00001110: o = 3; 8'b00001111: o = 4; 8'b00010000: o = 1; 8'b00010001: o = 2; 8'b00010010: o = 2; 8'b00010011: o = 3; 8'b00010100: o = 2; 8'b00010101: o = 3; 8'b00010110: o = 3; 8'b00010111: o = 4; 8'b00011000: o = 2; 8'b00011001: o = 3; 8'b00011010: o = 3; 8'b00011011: o = 4; 8'b00011100: o = 3; 8'b00011101: o = 4; 8'b00011110: o = 4; 8'b00011111: o = 5; 8'b00100000: o = 1; 8'b00100001: o = 2; 8'b00100010: o = 2; 8'b00100011: o = 3; 8'b00100100: o = 2; 8'b00100101: o = 3; 8'b00100110: o = 3; 8'b00100111: o = 4; 8'b00101000: o = 2; 8'b00101001: o = 3; 8'b00101010: o = 3; 8'b00101011: o = 4; 8'b00101100: o = 3; 8'b00101101: o = 4; 8'b00101110: o = 4; 8'b00101111: o = 5; 8'b00110000: o = 2; 8'b00110001: o = 3; 8'b00110010: o = 3; 8'b00110011: o = 4; 8'b00110100: o = 3; 8'b00110101: o = 4; 8'b00110110: o = 4; 8'b00110111: o = 5; 8'b00111000: o = 3; 8'b00111001: o = 4; 8'b00111010: o = 4; 8'b00111011: o = 5; 8'b00111100: o = 4; 8'b00111101: o = 5; 8'b00111110: o = 5; 8'b00111111: o = 6; // 44 - 1 8'b01000000: o = 1; 8'b01000001: o = 2; 8'b01000010: o = 2; 8'b01000011: o = 3; 8'b01000100: o = 2; 8'b01000101: o = 3; 8'b01000110: o = 3; 8'b01000111: o = 4; 8'b01001000: o = 2; 8'b01001001: o = 3; 8'b01001010: o = 3; 8'b01001011: o = 4; 8'b01001100: o = 3; 8'b01001101: o = 4; 8'b01001110: o = 4; 8'b01001111: o = 5; 8'b01010000: o = 2; 8'b01010001: o = 3; 8'b01010010: o = 3; 8'b01010011: o = 4; 8'b01010100: o = 3; 8'b01010101: o = 4; 8'b01010110: o = 4; 8'b01010111: o = 5; 8'b01011000: o = 3; 8'b01011001: o = 4; 8'b01011010: o = 4; 8'b01011011: o = 5; 8'b01011100: o = 4; 8'b01011101: o = 5; 8'b01011110: o = 5; 8'b01011111: o = 6; 8'b01100000: o = 2; 8'b01100001: o = 3; 8'b01100010: o = 3; 8'b01100011: o = 4; 8'b01100100: o = 3; 8'b01100101: o = 4; 8'b01100110: o = 4; 8'b01100111: o = 5; 8'b01101000: o = 3; 8'b01101001: o = 4; 8'b01101010: o = 4; 8'b01101011: o = 5; 8'b01101100: o = 4; 8'b01101101: o = 5; 8'b01101110: o = 5; 8'b01101111: o = 6; 8'b01110000: o = 3; 8'b01110001: o = 4; 8'b01110010: o = 4; 8'b01110011: o = 5; 8'b01110100: o = 4; 8'b01110101: o = 5; 8'b01110110: o = 5; 8'b01110111: o = 6; 8'b01111000: o = 4; 8'b01111001: o = 5; 8'b01111010: o = 5; 8'b01111011: o = 6; 8'b01111100: o = 5; 8'b01111101: o = 6; 8'b01111110: o = 6; 8'b01111111: o = 7; // - 2 8'b10000000: o = 1; 8'b10000001: o = 2; 8'b10000010: o = 2; 8'b10000011: o = 3; 8'b10000100: o = 2; 8'b10000101: o = 3; 8'b10000110: o = 3; 8'b10000111: o = 4; 8'b10001000: o = 2; 8'b10001001: o = 3; 8'b10001010: o = 3; 8'b10001011: o = 4; 8'b10001100: o = 3; 8'b10001101: o = 4; 8'b10001110: o = 4; 8'b10001111: o = 5; 8'b10010000: o = 2; 8'b10010001: o = 3; 8'b10010010: o = 3; 8'b10010011: o = 4; 8'b10010100: o = 3; 8'b10010101: o = 4; 8'b10010110: o = 4; 8'b10010111: o = 5; 8'b10011000: o = 3; 8'b10011001: o = 4; 8'b10011010: o = 4; 8'b10011011: o = 5; 8'b10011100: o = 4; 8'b10011101: o = 5; 8'b10011110: o = 5; 8'b10011111: o = 6; 8'b10100000: o = 2; 8'b10100001: o = 3; 8'b10100010: o = 3; 8'b10100011: o = 4; 8'b10100100: o = 3; 8'b10100101: o = 4; 8'b10100110: o = 4; 8'b10100111: o = 5; 8'b10101000: o = 3; 8'b10101001: o = 4; 8'b10101010: o = 4; 8'b10101011: o = 5; 8'b10101100: o = 4; 8'b10101101: o = 5; 8'b10101110: o = 5; 8'b10101111: o = 6; 8'b10110000: o = 3; 8'b10110001: o = 4; 8'b10110010: o = 4; 8'b10110011: o = 5; 8'b10110100: o = 4; 8'b10110101: o = 5; 8'b10110110: o = 5; 8'b10110111: o = 6; 8'b10111000: o = 4; 8'b10111001: o = 5; 8'b10111010: o = 5; 8'b10111011: o = 6; 8'b10111100: o = 5; 8'b10111101: o = 6; 8'b10111110: o = 6; 8'b10111111: o = 7; // 44 - 3 8'b11000000: o = 2; 8'b11000001: o = 3; 8'b11000010: o = 3; 8'b11000011: o = 4; 8'b11000100: o = 3; 8'b11000101: o = 4; 8'b11000110: o = 4; 8'b11000111: o = 5; 8'b11001000: o = 3; 8'b11001001: o = 4; 8'b11001010: o = 4; 8'b11001011: o = 5; 8'b11001100: o = 4; 8'b11001101: o = 5; 8'b11001110: o = 5; 8'b11001111: o = 6; 8'b11010000: o = 3; 8'b11010001: o = 4; 8'b11010010: o = 4; 8'b11010011: o = 5; 8'b11010100: o = 4; 8'b11010101: o = 5; 8'b11010110: o = 5; 8'b11010111: o = 6; 8'b11011000: o = 4; 8'b11011001: o = 5; 8'b11011010: o = 5; 8'b11011011: o = 6; 8'b11011100: o = 5; 8'b11011101: o = 6; 8'b11011110: o = 6; 8'b11011111: o = 7; 8'b11100000: o = 3; 8'b11100001: o = 4; 8'b11100010: o = 4; 8'b11100011: o = 5; 8'b11100100: o = 4; 8'b11100101: o = 5; 8'b11100110: o = 5; 8'b11100111: o = 6; 8'b11101000: o = 4; 8'b11101001: o = 5; 8'b11101010: o = 5; 8'b11101011: o = 6; 8'b11101100: o = 5; 8'b11101101: o = 6; 8'b11101110: o = 6; 8'b11101111: o = 7; 8'b11110000: o = 4; 8'b11110001: o = 5; 8'b11110010: o = 5; 8'b11110011: o = 6; 8'b11110100: o = 5; 8'b11110101: o = 6; 8'b11110110: o = 6; 8'b11110111: o = 7; 8'b11111000: o = 5; 8'b11111001: o = 6; 8'b11111010: o = 6; 8'b11111011: o = 7; 8'b11111100: o = 6; 8'b11111101: o = 7; 8'b11111110: o = 7; 8'b11111111: o = 8; endcase endmodule module cntpop16( input [15:0] i, output [4:0] o ); wire [3:0] cnt1, cnt2; cntpop8 u1 (i[ 7:0],cnt1); cntpop8 u2 (i[15:8],cnt2); assign o = cnt1 + cnt2; endmodule // 76 slices / 147 LUTs / 19 ns module cntpop32( input [31:0] i, output [5:0] o ); wire [3:0] cnt1, cnt2, cnt3, cnt4; // cntpop8 results in faster result than cntpop16 cntpop8 u1 (i[ 7: 0],cnt1); cntpop8 u2 (i[15: 8],cnt2); cntpop8 u3 (i[23:16],cnt3); cntpop8 u4 (i[31:24],cnt4); assign o = cnt1+cnt2+cnt3+cnt4; endmodule // 156 slices / 300 LUTs / 22.2 ns module cntpop64( input [63:0] i, output [6:0] o ); wire [4:0] cnt1, cnt2, cnt3, cnt4; cntpop16 u1 (i[15: 0],cnt1); cntpop16 u2 (i[31:16],cnt2); cntpop16 u3 (i[47:32],cnt3); cntpop16 u4 (i[63:48],cnt4); assign o = cnt1+cnt2+cnt3+cnt4; endmodule
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