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// ==================================================================
// >>>>>>>>>>>>>>>>>>>>>>> COPYRIGHT NOTICE <<<<<<<<<<<<<<<<<<<<<<<<<
// ------------------------------------------------------------------
// Copyright (c) 2006-2011 by Lattice Semiconductor Corporation
// ALL RIGHTS RESERVED
// ------------------------------------------------------------------
//
// IMPORTANT: THIS FILE IS AUTO-GENERATED BY THE LATTICEMICO SYSTEM.
//
// Permission:
//
// Lattice Semiconductor grants permission to use this code
// pursuant to the terms of the Lattice Semiconductor Corporation
// Open Source License Agreement.
//
// Disclaimer:
//
// Lattice Semiconductor provides no warranty regarding the use or
// functionality of this code. It is the user's responsibility to
// verify the user's design for consistency and functionality through
// the use of formal verification methods.
//
// --------------------------------------------------------------------
//
// Lattice Semiconductor Corporation
// 5555 NE Moore Court
// Hillsboro, OR 97214
// U.S.A
//
// TEL: 1-800-Lattice (USA and Canada)
// 503-286-8001 (other locations)
//
// web: http://www.latticesemi.com/
// email: techsupport@latticesemi.com
//
// --------------------------------------------------------------------
// FILE DETAILS
// Project : LatticeMico32
// File : lm32_adder.v
// Title : Integer adder / subtractor with comparison flag generation
// Dependencies : lm32_include.v
// Version : 6.1.17
// : Initial Release
// Version : 7.0SP2, 3.0
// : No Change
// Version : 3.1
// : No Change
// =============================================================================
`include "lm32_include.v"
/////////////////////////////////////////////////////
// Module interface
/////////////////////////////////////////////////////
module lm32_adder (
// ----- Inputs -------
adder_op_x,
adder_op_x_n,
operand_0_x,
operand_1_x,
// ----- Outputs -------
adder_result_x,
adder_carry_n_x,
adder_overflow_x
);
/////////////////////////////////////////////////////
// Inputs
/////////////////////////////////////////////////////
input adder_op_x; // Operating to perform, 0 for addition, 1 for subtraction
input adder_op_x_n; // Inverted version of adder_op_x
input [`LM32_WORD_RNG] operand_0_x; // Operand to add, or subtract from
input [`LM32_WORD_RNG] operand_1_x; // Opearnd to add, or subtract by
/////////////////////////////////////////////////////
// Outputs
/////////////////////////////////////////////////////
output [`LM32_WORD_RNG] adder_result_x; // Result of addition or subtraction
wire [`LM32_WORD_RNG] adder_result_x;
output adder_carry_n_x; // Inverted carry
wire adder_carry_n_x;
output adder_overflow_x; // Indicates if overflow occured, only valid for subtractions
reg adder_overflow_x;
/////////////////////////////////////////////////////
// Internal nets and registers
/////////////////////////////////////////////////////
wire a_sign; // Sign (i.e. positive or negative) of operand 0
wire b_sign; // Sign of operand 1
wire result_sign; // Sign of result
/////////////////////////////////////////////////////
// Instantiations
/////////////////////////////////////////////////////
lm32_addsub addsub (
// ----- Inputs -----
.DataA (operand_0_x),
.DataB (operand_1_x),
.Cin (adder_op_x),
.Add_Sub (adder_op_x_n),
// ----- Ouputs -----
.Result (adder_result_x),
.Cout (adder_carry_n_x)
);
/////////////////////////////////////////////////////
// Combinational Logic
/////////////////////////////////////////////////////
// Extract signs of operands and result
assign a_sign = operand_0_x[`LM32_WORD_WIDTH-1];
assign b_sign = operand_1_x[`LM32_WORD_WIDTH-1];
assign result_sign = adder_result_x[`LM32_WORD_WIDTH-1];
// Determine whether an overflow occured when performing a subtraction
always @(*)
begin
// +ve - -ve = -ve -> overflow
// -ve - +ve = +ve -> overflow
if ( (!a_sign & b_sign & result_sign)
|| (a_sign & !b_sign & !result_sign)
)
adder_overflow_x = `TRUE;
else
adder_overflow_x = `FALSE;
end
endmodule
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