| // 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 A, | 
 |     output wire Y | 
 | ); | 
 |  | 
 |     parameter [0:0] INV_A = 1'b0; | 
 |  | 
 | endmodule | 
 |  | 
 | (* keep_hierarchy *) | 
 | module child ( | 
 |     input  wire       I, | 
 |     output wire [1:0] O | 
 | ); | 
 |  | 
 |     wire d; | 
 |  | 
 |     \$_NOT_ n (.A(I), .Y(d)); | 
 |  | 
 |     box b0 (.A(I), .Y(O[0])); | 
 |     box b1 (.A(d), .Y(O[1])); | 
 |  | 
 | endmodule | 
 |  | 
 |  | 
 | module top( | 
 |     input  wire       di, | 
 |     output wire [4:0] do | 
 | ); | 
 |  | 
 |     wire [1:0] d; | 
 |  | 
 |     \$_NOT_ n0 (.A(di), .Y(d[0])); | 
 |     \$_NOT_ n1 (.A(di), .Y(d[1])); | 
 |  | 
 |     box   b0 (.A(d[0]), .Y(do[0])); | 
 |     box   b1 (.A(d[1]), .Y(do[1])); | 
 |     child c  (.I(d[1]), .O({do[3], do[2]})); | 
 |  | 
 | endmodule |