Subversion Repositories mips789

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////  Author: Liwei                                              ////

////                                                             ////

////                                                             ////

////  If you encountered any problem, please contact :           ////

////  Email: mcupro@yahoo.com.hk or mcupro@opencores.org         ////

////                                                             ////

////  Downloaded from:                                           ////

////     http://www.opencores.org/pdownloads.cgi/list/mips789    ////

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////                                                             ////

//// Copyright (C) 2006-2007 Liwei                               ////

////                         mcupro@yahoo.com.hk                 ////

////                                                             ////

////                                                             ////

//// This source file may be used and distributed freely without ////

//// restriction provided that this copyright statement is not   ////

//// removed from the file and any derivative work contains the  ////

//// original copyright notice and the associated disclaimer.    ////

////                                                             ////

//// Please let the author know if it is used                    ////

//// for commercial purpose.                                     ////

////                                                             ////

////     THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY     ////

//// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED   ////

//// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS   ////

//// FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR      ////

//// OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,         ////

//// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES    ////

//// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE   ////

//// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR        ////

//// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF  ////

//// LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT  ////

//// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT  ////

//// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE         ////

//// POSSIBILITY OF SUCH DAMAGE.                                 ////

////                                                             ////

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//// Date of Creation: 2007.8.1                                  ////

////                                                             ////

//// Version: 0.0.1                                              ////

////                                                             ////

//// Description:                                                ////

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//// Change log:                                                 ////

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`define EXT_SIGN              1

`define EXT_UNSIGN            2

`define EXT_J                 3

`define EXT_B                 4

`define EXT_SA                5

`define EXT_S2H               6

`define EXT_NOP               0

module ext(

    input [31:0] ins_i ,

    output reg [31:0] res ,

    input [2:0]ctl);

    wire [25:0] instr25_0;

    assign instr25_0 = ins_i[25:0] ;

    wire[15:0] sign = {instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15],instr25_0[15]}   ;

    always @ (*)

    case (ctl)

        `EXT_SIGN    :res ={sign,instr25_0[15:0]};//sign

        `EXT_UNSIGN  :res ={16'b0,instr25_0[15:0]};//zeroext

        `EXT_J       :res ={4'b0,instr25_0[25:0],2'b0};//jmp

        `EXT_B       :res ={sign[13:0],instr25_0[15:0],2'B0};//brach

        `EXT_SA      :res ={27'b0,instr25_0[10:6]} ;//sll,srl

        `EXT_S2H     :res ={instr25_0[15:0],16'B0};//shift to high

        default: res=0;

    endcase

endmodule