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csantifort |
//////////////////////////////////////////////////////////////////
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// //
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// Barrel Shifter for Amber 25 Core //
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// //
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// This file is part of the Amber project //
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// http://www.opencores.org/project,amber //
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// //
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// Description //
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// Provides 32-bit shifts LSL, LSR, ASR and ROR //
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// //
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// Author(s): //
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// - Conor Santifort, csantifort.amber@gmail.com //
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// //
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//////////////////////////////////////////////////////////////////
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// //
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// Copyright (C) 2011 Authors and OPENCORES.ORG //
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// //
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// This source file may be used and distributed without //
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// restriction provided that this copyright statement is not //
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// removed from the file and that any derivative work contains //
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// the original copyright notice and the associated disclaimer. //
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// //
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// This source file is free software; you can redistribute it //
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// and/or modify it under the terms of the GNU Lesser General //
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// Public License as published by the Free Software Foundation; //
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// either version 2.1 of the License, or (at your option) any //
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// later version. //
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// //
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// This source is distributed in the hope that it will be //
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// useful, but WITHOUT ANY WARRANTY; without even the implied //
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// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR //
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// PURPOSE. See the GNU Lesser General Public License for more //
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// details. //
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// //
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// You should have received a copy of the GNU Lesser General //
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// Public License along with this source; if not, download it //
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// from http://www.opencores.org/lgpl.shtml //
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// //
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//////////////////////////////////////////////////////////////////
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module a25_barrel_shift (
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input i_clk,
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input [31:0] i_in,
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input i_carry_in,
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input [7:0] i_shift_amount, // uses 8 LSBs of Rs, or a 5 bit immediate constant
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input i_shift_imm_zero, // high when immediate shift value of zero selected
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input [1:0] i_function,
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output [31:0] o_out,
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csantifort |
output o_carry_out,
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output o_stall
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);
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wire [31:0] quick_out;
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wire quick_carry_out;
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wire [31:0] full_out;
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wire full_carry_out;
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reg [31:0] full_out_r = 'd0;
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reg full_carry_out_r = 'd0;
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reg use_quick_r = 1'd1;
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csantifort |
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assign o_stall = (|i_shift_amount[7:2]) & use_quick_r;
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assign o_out = use_quick_r ? quick_out : full_out_r;
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assign o_carry_out = use_quick_r ? quick_carry_out : full_carry_out_r;
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csantifort |
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// Capture the result from the full barrel shifter in case the
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// quick shifter gives the wrong value
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always @(posedge i_clk)
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begin
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full_out_r <= full_out;
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full_carry_out_r <= full_carry_out;
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use_quick_r <= !o_stall;
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end
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csantifort |
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// Full barrel shifter
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a25_shifter #(
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.FULL_BARREL (1)
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)
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u_a25_shifter_full (
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.i_in ( i_in ),
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.i_carry_in ( i_carry_in ),
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.i_shift_amount ( i_shift_amount ),
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.i_shift_imm_zero ( i_shift_imm_zero ),
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.i_function ( i_function ),
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.o_out ( full_out ),
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.o_carry_out ( full_carry_out )
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);
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csantifort |
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// Quick barrel shifter
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a25_shifter #(
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.FULL_BARREL ( 0 )
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)
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u_a25_shifter_quick (
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.i_in ( i_in ),
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.i_carry_in ( i_carry_in ),
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.i_shift_amount ( i_shift_amount ),
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.i_shift_imm_zero ( i_shift_imm_zero ),
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.i_function ( i_function ),
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.o_out ( quick_out ),
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.o_carry_out ( quick_carry_out )
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);
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endmodule
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