Subversion Repositories xilinx_virtex_fp_library

`timescale 1ns / 1ps

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// Company: 

// Engineer: 

// 

// Create Date:    00:32:10 11/19/2013 

// Design Name: 

// Module Name:    ClosePath 

// Project Name: 

// Target Devices: 

// Tool versions: 

// Description: A ± B when |Ea-Eb| < 2

//

// Dependencies: 

//

// Revision: 

// Revision 0.01 - File Created

// Additional Comments: 

//

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module ClosePath        #(      parameter size_in_mantissa                      = 24, //1.M

                                                        parameter size_out_mantissa             = 24,

                                                        parameter size_exponent                         = 8,

                                                        parameter pipeline                                      = 0,

                                                        parameter pipeline_pos                          = 0,     // 8 bits

                                                        parameter size_counter                          = 5,    //log2(size_in_mantissa) + 1 = 5)

                                                        parameter double_size_in_mantissa   = size_in_mantissa + size_in_mantissa)

                                                (       input [size_in_mantissa - 1     : 0] m_a_number,

                                                        input [size_in_mantissa - 1 : 0] m_b_number,

                                                        input [size_exponent     : 0] exp_inter,

                                                        input exp_difference,

                                                        output[size_out_mantissa-1:0] resulted_m_o,

                                                        output[size_exponent - 1 : 0] resulted_e_o,

                                                        output ovf);

        wire [size_counter - 1 : 0] lzs;

        wire [size_exponent- 1 : 0] unadjusted_exponent;

        wire [1 : 0] adjust_exponent;

        wire [2 : 0] dummy_bits;

        wire init_shft_bit, shft_bit;

        wire [size_in_mantissa-1: 0] shifted_m_b;

        wire [size_in_mantissa+1: 0] adder_mantissa;

        wire [size_in_mantissa  : 0] unnormalized_mantissa;

        wire [size_in_mantissa  : 0] rounded_mantissa;

        wire [size_in_mantissa-1: 0] r_mantissa;

        assign {shifted_m_b, init_shft_bit} = (exp_difference)? {1'b0, m_b_number[size_in_mantissa-1:0]} : {m_b_number, 1'b0};

        //compute unnormalized_mantissa

        assign adder_mantissa = {1'b0, m_a_number} - {1'b0, shifted_m_b};

        assign {unnormalized_mantissa, shft_bit} =

                                                                (adder_mantissa[size_in_mantissa + 1])? ({~adder_mantissa[size_in_mantissa : 0], ~init_shft_bit}) :

                                                                                                                                                ({adder_mantissa[size_in_mantissa       : 0], init_shft_bit});

        //compute leading_zeros over unnormalized mantissa

        leading_zeros #(        .SIZE_INT(size_in_mantissa + 1), .SIZE_COUNTER(size_counter), .PIPELINE(pipeline))

                leading_zeros_instance (.a(unnormalized_mantissa[size_in_mantissa : 0]),

                                                                                .ovf(unnormalized_mantissa[size_in_mantissa]),

                                                                                .lz(lzs));

        //compute shifting over unnormalized_mantissa

        shifter #(      .INPUT_SIZE(size_in_mantissa + 2),

                                        .SHIFT_SIZE(size_counter),

                                        .OUTPUT_SIZE(size_in_mantissa + 3),

                                        .DIRECTION(1'b1), //0=right, 1=left

                                        .PIPELINE(pipeline),

                                        .POSITION(pipeline_pos))

                shifter_instance(       .a({unnormalized_mantissa, shft_bit}),//mantissa

                                                                .arith(adder_mantissa[size_in_mantissa + 1]),//logical shift

                                                                .shft(lzs),

                                                                .shifted_a({r_mantissa, dummy_bits}));

        assign rounded_mantissa = (adder_mantissa[size_in_mantissa + 1])? {1'b0, r_mantissa} + 1'b1 : {1'b0, r_mantissa};

        assign resulted_m_o = (rounded_mantissa[size_in_mantissa])? rounded_mantissa[size_in_mantissa : 1] :

                                                                                                                                rounded_mantissa[size_in_mantissa-1:0];

        assign adjust_exponent = rounded_mantissa[size_in_mantissa]? 2'd2 : 2'd1;

        assign ovf = adder_mantissa[size_in_mantissa+1];

        assign unadjusted_exponent = exp_inter - lzs;

        assign resulted_e_o =  unadjusted_exponent + adjust_exponent;

endmodule