|  | // Copyright (C) 2020-2021  The SymbiFlow Authors. | 
|  | // | 
|  | // Use of this source code is governed by a ISC-style | 
|  | // license that can be found in the LICENSE file or at | 
|  | // https://opensource.org/licenses/ISC | 
|  | // | 
|  | // SPDX-License-Identifier:ISC | 
|  |  | 
|  | (* blackbox *) | 
|  | module box( | 
|  | (* invertible_pin="INV_A" *) | 
|  | input  wire [1:0] A, | 
|  | input  wire [1:0] B, | 
|  |  | 
|  | output wire Y | 
|  | ); | 
|  |  | 
|  | parameter [1:0] INV_A = 2'b00; | 
|  |  | 
|  | endmodule | 
|  |  | 
|  |  | 
|  | module top( | 
|  | input  wire [3:0] di, | 
|  | output wire       do | 
|  | ); | 
|  |  | 
|  | wire [3:0] d; | 
|  |  | 
|  | \$_NOT_ n0 (.A(di[0]), .Y(d[0])); | 
|  | \$_NOT_ n1 (.A(di[1]), .Y(d[1])); | 
|  | \$_NOT_ n2 (.A(di[2]), .Y(d[2])); | 
|  | \$_NOT_ n3 (.A(di[3]), .Y(d[3])); | 
|  |  | 
|  | box #(.INV_A(2'b01)) the_box ( | 
|  | .A ({d[1], d[0]}), | 
|  | .B ({d[3], d[2]}), | 
|  |  | 
|  | .Y (do) | 
|  | ); | 
|  |  | 
|  | endmodule |