Subversion Repositories mips789

//This file is based on YACC ->alu.v 
 
 
 
/////////////////////////////////////////////////////////////////////
////  Author: Liwei                                              ////
////                                                             ////
////                                                             ////
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////  Email: mcupro@yahoo.com.hk or mcupro@opencores.org         ////
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////  Downloaded from:                                           ////
////     http://www.opencores.org/pdownloads.cgi/list/mips789    ////
/////////////////////////////////////////////////////////////////////
////                                                             ////
//// Copyright (C) 2006-2007 Liwei                               ////
////                         mcupro@yahoo.com.hk                 ////
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////                                                             ////
//// This source file may be used and distributed freely without ////
//// restriction provided that this copyright statement is not   ////
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////     THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY     ////
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/////////////////////////////////////////////////////////////////////
////                                                             ////
////                                                             ////
//// Date of Creation: 2007.8.1                                  ////
////                                                             ////
//// Version: 0.0.1                                              ////
////                                                             ////
//// Description:                                                ////
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////                                                             ////
/////////////////////////////////////////////////////////////////////
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//// Change log:                                                 ////
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/////////////////////////////////////////////////////////////////////
 
`define                ALU_ADD      12                
`define                ALU_ADDU     13
`define                ALU_SUB      14
`define                ALU_SUBU     15
`define                ALU_SLTU     16
`define                ALU_SLT      17
`define                ALU_OR       18
`define                ALU_AND      19
`define                ALU_XOR      20
`define                ALU_NOR      21
`define                ALU_PA       22
`define                ALU_PB       23
 
module alu (a,b,alu_out,alu_func);
 
    input [31:0] a,b;
    output reg [31:0] alu_out;
    input [4:0]	alu_func;
 
    wire [31:0] c;
 
    reg [32:0] sum;
 
    always @(*)
    begin
        case (alu_func)
            `ALU_PA     : alu_out=a;
            `ALU_PB     : alu_out=b;
            `ALU_ADD    : alu_out=a+b;
            `ALU_SUB  ,
            `ALU_SUBU      : alu_out=a + (~b)+1;
            `ALU_OR     : alu_out=a | b;
            `ALU_AND     : alu_out=a & b;
            `ALU_XOR       : alu_out=a ^ b;
            `ALU_NOR        : alu_out=~(a | b);
            `ALU_SLTU : alu_out=(a < b)?1:0;
            `ALU_SLT :
            begin
                sum={a[31],a}+~{b[31],b}+33'h0_0000_0001;
                alu_out={31'h0000_0000,sum[32]};
            end
            default : alu_out=32'h0;
        endcase
    end
endmodule
 
/*
this file is based on YACC's alu.v
*/