Exams/m2014 q4j

Problem Statement

Implement the following circuit:

("FA" is a full adder)

module top_module (
    input [3:0] x,
    input [3:0] y, 
    output [4:0] sum);
	
    reg [2:0] cout;
    reg cin;
    
    FA U1(
        .x(x[0]),
        .y(y[0]),
        .sum(sum[0]),
        .cout(cout[0])
    );
    
    FA U2(
        .x(x[1]),
        .y(y[1]),
        .cin(cout[0]),
        .sum(sum[1]),
        .cout(cout[1])
    );
    
    FA U3(
        .x(x[2]),
        .y(y[2]),
        .cin(cout[1]),
        .sum(sum[2]),
        .cout(cout[2])
    );
    
    FA U4(
        .x(x[3]),
        .y(y[3]),
        .cin(cout[2]),
        .sum(sum[3]),
        .cout(sum[4])
    );
    
    
endmodule

module FA (
	input x,y,cin,
    output sum,cout
);
    assign {cout,sum} = x + y + cin;
    
endmodule