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heshamelma |
//////////////////////////////////////////////////////////////////
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// //
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// ALU decoder for Edge core //
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// //
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// This file is part of the Edge project //
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// http://www.opencores.org/project,edge //
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// //
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// Description //
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// ALU decoder decodes functions encoded in MIPS instruction //
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// and sends out the appropriate command to ALU unit. //
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// //
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// Author(s): //
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// - Hesham AL-Matary, heshamelmatary@gmail.com //
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// //
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//////////////////////////////////////////////////////////////////
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// //
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// Copyright (C) 2014 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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`define ADD_ALUOP 4'b0000
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`define SUB_ALUOP 4'b0001
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`define LOOK_FUNCT 4'b0010
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`define INVAL 4'b0011
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`define SLTI_ALUOP 4'b0100
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`define ANDI_ALUOP 4'b0101
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`define ORI_ALUOP 4'b0110
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`define XORI_ALUOP 4'b0111
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`define MUL_ALUOP 4'b1000
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/* ALUControl output defines */
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`define ADD_ALUCTRL 4'b0010
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`define SUB_ALUCTRL 4'b0110
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`define AND_ALUCTRL 4'b0000
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`define OR_ALUCTRL 4'b0001
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`define SLT_ALUCTRL 4'b0111
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`define XOR_ALUCTRL 4'b0011
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`define NOR_ALUCTRL 4'b0100
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`define MUL_ALUCTRL 4'b1000
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/* FUNCT defines INST[5:0] */
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`define SLL_FUNCT 6'b000000 // 0
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`define SRL_FUNCT 6'b000010 // 2
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`define SRA_FUNCT 6'b000011 // 3
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`define SLLV_FUNCT 6'b000100 // 4
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`define SRLV_FUNCT 6'b000110 // 6
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`define SRAV_FUNCT 6'b000111 // 7
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`define ADD_FUNCT 6'b100000 // 32
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`define ADDU_FUNCT 6'b100001 // 33
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`define SUB_FUNCT 6'b100010 // 34
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`define SUBU_FUNCT 6'b100011 // 35
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`define AND_FUNCT 6'b100100 // 36
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`define OR_FUNCT 6'b100101 // 37
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`define XOR_FUNCT 6'b100110 // 38
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`define NOR_FUNCT 6'b100111 // 39
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`define SLT_FUNCT 6'b101010 // 42
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`define SLTU_FUNCT 6'b101011 // 43
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module alu_decoder
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(
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input[3:0] ALUop,
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input[5:0] Funct,
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output reg[3:0] ALUControl
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);
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always @*
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begin
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case(ALUop)
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`ADD_ALUOP : ALUControl <= `ADD_ALUCTRL;
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`SUB_ALUOP : ALUControl <= `SUB_ALUCTRL;
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`SLTI_ALUOP: ALUControl <= `SLT_ALUCTRL;
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`ANDI_ALUOP: ALUControl <= `AND_ALUCTRL;
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`ORI_ALUOP : ALUControl <= `OR_ALUCTRL;
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`XORI_ALUOP: ALUControl <= `XOR_ALUCTRL;
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`MUL_ALUOP : ALUControl <= `MUL_ALUCTRL;
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`LOOK_FUNCT: ALUControl <= funct_decode(Funct);
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`INVAL : ALUControl <= 3'b000; /* (nop) Mapped to be add operation */
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default : ALUControl <= `ADD_ALUCTRL;
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endcase
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end
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function[3:0] funct_decode (input[5:0] funct);
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case (funct)
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`ADD_FUNCT,
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`ADDU_FUNCT:
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funct_decode = `ADD_ALUCTRL;
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`SUB_FUNCT,
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`SUBU_FUNCT:
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funct_decode = `SUB_ALUCTRL;
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`NOR_FUNCT,
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`OR_FUNCT:
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funct_decode = `OR_ALUCTRL;
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`XOR_FUNCT:
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funct_decode = `XOR_ALUCTRL;
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`SLT_FUNCT, `SLTU_FUNCT:
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funct_decode = `SLT_ALUCTRL;
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default:
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funct_decode = 5'b00000;
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endcase
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endfunction
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endmodule
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