     1.1 --- a/lm32_adder.v	Sun Mar 06 21:17:31 2011 +0000
     1.2 +++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.3 @@ -1,115 +0,0 @@
     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 -