|  | // 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 |