[full_subtractor] 1. Structural Modeling

Schematic

 

Code:

`timescale 1ns / 1ps
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// Company: 
// Engineer: 
// 
// Create Date: 2024/03/10 22:49:18
// Design Name: 
// Module Name: full_subtractor_1
// Project Name: 
// Target Devices: 
// Tool Versions: 
// Description: 
// Full Subtractor in Structural Modeling
// Dependencies: 
// 
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
// 
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module half_subtractor_1(x, y, b, d);
input   x,  y   ;
output  b,  d   ;
// half subtractor body
// instantiate primitive gates
    xor (d, x, y)   ;
    and (b, ~x, y)  ;
endmodule

module full_subtractor_1 (x, y, b_in, b_out, d);
input   x, y, b_in  ;
output  b_out, d    ;
wire    b1, b2, d1  ;
// full subtractor body
// instantiate the half subtractor
    half_subtractor_1 hs_1 (x, y, b1, d1);
    half_subtractor_1 hs_2 (d1, b_in, b2, d);
    or (b_out, b1, b2);
endmodule