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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