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// ============================================================================
//        __
//   \\__/ o\    (C) 2013  Robert Finch, Stratford
//    \  __ /    All rights reserved.
//     \/_//     robfinch<remove>@opencores.org
//       ||
//
//
// This source file is free software: you can redistribute it and/or modify 
// it under the terms of the GNU Lesser General Public License as published 
// by the Free Software Foundation, either version 3 of the License, or     
// (at your option) any later version.                                      
//                                                                          
// This source file is distributed in the hope that it will be useful,      
// but WITHOUT ANY WARRANTY; without even the implied warranty of           
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            
// GNU General Public License for more details.                             
//                                                                          
// You should have received a copy of the GNU General Public License        
// along with this program.  If not, see <http://www.gnu.org/licenses/>.    
//                                                                          
// ============================================================================
//
module overflow(op, a, b, s, v);
 
input op;	// 0=add,1=sub
input a;
input b;
input s;	// sum
output v;
 
// Overflow:
// Add: the signs of the inputs are the same, and the sign of the
// sum is different
// Sub: the signs of the inputs are different, and the sign of
// the sum is the same as B
assign v = (op ^ s ^ b) & (~op ^ a ^ b);
 
endmodule