lm32_adder.v

changeset 0
cd0b58aa6f83
child 26
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     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/lm32_adder.v	Sun Apr 04 20:40:03 2010 +0100
     1.3 @@ -0,0 +1,115 @@
     1.4 +// =============================================================================
     1.5 +//                           COPYRIGHT NOTICE
     1.6 +// Copyright 2006 (c) Lattice Semiconductor Corporation
     1.7 +// ALL RIGHTS RESERVED
     1.8 +// This confidential and proprietary software may be used only as authorised by
     1.9 +// a licensing agreement from Lattice Semiconductor Corporation.
    1.10 +// The entire notice above must be reproduced on all authorized copies and
    1.11 +// copies may only be made to the extent permitted by a licensing agreement from
    1.12 +// Lattice Semiconductor Corporation.
    1.13 +//
    1.14 +// Lattice Semiconductor Corporation        TEL : 1-800-Lattice (USA and Canada)
    1.15 +// 5555 NE Moore Court                            408-826-6000 (other locations)
    1.16 +// Hillsboro, OR 97124                     web  : http://www.latticesemi.com/
    1.17 +// U.S.A                                   email: techsupport@latticesemi.com
    1.18 +// ============================================================================/
    1.19 +//                         FILE DETAILS
    1.20 +// Project          : LatticeMico32
    1.21 +// File             : lm32_adder.v
    1.22 +// Title            : Integer adder / subtractor with comparison flag generation 
    1.23 +// Dependencies     : lm32_include.v
    1.24 +// Version          : 6.1.17
    1.25 +//                  : Initial Release
    1.26 +// Version          : 7.0SP2, 3.0
    1.27 +//                  : No Change
    1.28 +// Version          : 3.1
    1.29 +//                  : No Change
    1.30 +// =============================================================================
    1.31 +
    1.32 +`include "lm32_include.v"
    1.33 +
    1.34 +/////////////////////////////////////////////////////
    1.35 +// Module interface
    1.36 +/////////////////////////////////////////////////////
    1.37 +
    1.38 +module lm32_adder (
    1.39 +    // ----- Inputs -------
    1.40 +    adder_op_x,
    1.41 +    adder_op_x_n,
    1.42 +    operand_0_x,
    1.43 +    operand_1_x,
    1.44 +    // ----- Outputs -------
    1.45 +    adder_result_x,
    1.46 +    adder_carry_n_x,
    1.47 +    adder_overflow_x
    1.48 +    );
    1.49 +
    1.50 +/////////////////////////////////////////////////////
    1.51 +// Inputs
    1.52 +/////////////////////////////////////////////////////
    1.53 +
    1.54 +input adder_op_x;                                       // Operating to perform, 0 for addition, 1 for subtraction
    1.55 +input adder_op_x_n;                                     // Inverted version of adder_op_x
    1.56 +input [`LM32_WORD_RNG] operand_0_x;                     // Operand to add, or subtract from
    1.57 +input [`LM32_WORD_RNG] operand_1_x;                     // Opearnd to add, or subtract by
    1.58 +
    1.59 +/////////////////////////////////////////////////////
    1.60 +// Outputs
    1.61 +/////////////////////////////////////////////////////
    1.62 +
    1.63 +output [`LM32_WORD_RNG] adder_result_x;                 // Result of addition or subtraction
    1.64 +wire   [`LM32_WORD_RNG] adder_result_x;
    1.65 +output adder_carry_n_x;                                 // Inverted carry
    1.66 +wire   adder_carry_n_x;
    1.67 +output adder_overflow_x;                                // Indicates if overflow occured, only valid for subtractions
    1.68 +reg    adder_overflow_x;
    1.69 +    
    1.70 +/////////////////////////////////////////////////////
    1.71 +// Internal nets and registers 
    1.72 +/////////////////////////////////////////////////////
    1.73 +
    1.74 +wire a_sign;                                            // Sign (i.e. positive or negative) of operand 0
    1.75 +wire b_sign;                                            // Sign of operand 1
    1.76 +wire result_sign;                                       // Sign of result
    1.77 +
    1.78 +/////////////////////////////////////////////////////
    1.79 +// Instantiations 
    1.80 +/////////////////////////////////////////////////////
    1.81 +
    1.82 +lm32_addsub addsub (
    1.83 +    // ----- Inputs -----
    1.84 +    .DataA          (operand_0_x), 
    1.85 +    .DataB          (operand_1_x), 
    1.86 +    .Cin            (adder_op_x), 
    1.87 +    .Add_Sub        (adder_op_x_n), 
    1.88 +    // ----- Ouputs -----
    1.89 +    .Result         (adder_result_x), 
    1.90 +    .Cout           (adder_carry_n_x)
    1.91 +    );
    1.92 +
    1.93 +/////////////////////////////////////////////////////
    1.94 +// Combinational Logic
    1.95 +/////////////////////////////////////////////////////
    1.96 +
    1.97 +// Extract signs of operands and result
    1.98 +
    1.99 +assign a_sign = operand_0_x[`LM32_WORD_WIDTH-1];
   1.100 +assign b_sign = operand_1_x[`LM32_WORD_WIDTH-1];
   1.101 +assign result_sign = adder_result_x[`LM32_WORD_WIDTH-1];
   1.102 +
   1.103 +// Determine whether an overflow occured when performing a subtraction
   1.104 +
   1.105 +always @(*)
   1.106 +begin    
   1.107 +    //  +ve - -ve = -ve -> overflow
   1.108 +    //  -ve - +ve = +ve -> overflow
   1.109 +    if  (   (!a_sign & b_sign & result_sign)
   1.110 +         || (a_sign & !b_sign & !result_sign)
   1.111 +        )
   1.112 +        adder_overflow_x = `TRUE;
   1.113 +    else
   1.114 +        adder_overflow_x = `FALSE;
   1.115 +end
   1.116 +    
   1.117 +endmodule
   1.118 +