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robfinch |
`timescale 1ns / 1ps
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// ============================================================================
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// __
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// \\__/ o\ (C) 2006-2017 Robert Finch, Waterloo
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// \ __ / All rights reserved.
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// \/_// robfinch<remove>@finitron.ca
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// ||
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//
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// fs2d.v
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// - convert floating point single to double
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//
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//
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// This source file is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published
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// by the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This source file is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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//
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// ============================================================================
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module fs2d(a, o);
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input [31:0] a;
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output [63:0] o;
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reg signo;
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reg [10:0] expo;
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reg [51:0] mano;
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assign o = {signo,expo,mano};
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wire signi;
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wire [7:0] expi;
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wire [22:0] mani;
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wire xinf; // exponent infinite
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wire vz; // value zero
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wire xz; // exponent zero
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fpDecomp #(32) u1 (.i(a), .sgn(signi), .exp(expi), .man(mani), .xinf(xinf), .xz(xz), .vz(vz) );
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wire [4:0] lz;
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cntlz24 u2 ({mani,1'b1}, lz); // '1' bit already unhidden due to denormalized number
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always @(a)
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begin
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// sign out always just = sign in
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signo = signi;
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// special check for zero
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if (vz) begin
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expo <= 0;
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mano <= 0;
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end
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// convert infinity / nan
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// infinity in = infinity out
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else if (xinf) begin
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expo <= 11'h7ff;
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mano <= {mani,29'b0};
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end
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// convert denormal
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// a denormal was really a number with an exponent of -126
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// this value is easily represented in the double format
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// it may be possible to normalize the value if it isn't
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// zero
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else if (xz) begin
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expo <= 11'd897 - lz; // 1023 "zero" -126 - lz
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mano <= {mani << (lz + 1), 29'd0}; // shift one more to hide leading '1'
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end
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// convert typical number
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// adjust exponent, copy mantissa
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else begin
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expo <= expi + 11'd896; // 1023-127
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mano <= {mani,29'd0};
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end
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end
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endmodule
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