65. Ripple Carry Adder

How do you plan to solve it?

// 1-bit Full Adder (to be used by the 4-bit RCA)
module full_adder_1bit (
    input  a, b, cin,
    output sum, cout
);
    // TODO: implement 1-bit full adder (structural or dataflow)
    assign sum=a^b^cin;
    assign cout=(a&b)|(b&cin)|(cin&a);

endmodule

// 4-bit Ripple Carry Adder – chain 4 full adders
module rca4_chain (
    input  [3:0] a,
    input  [3:0] b,
    input        cin,
    output [3:0] sum,
    output       cout
);
    // TODO: Declare internal ripple carries
    wire w1,w2,w3;

    // TODO: instantiate 4 full adders and chain carries


    // TODO: drive cout
    full_adder_1bit f1(.a(a[0]), .b(b[0]), .cin(cin), .sum(sum[0]), .cout(w1));
    full_adder_1bit f2(.a(a[1]), .b(b[1]), .cin(w1), .sum(sum[1]), .cout(w2));
    full_adder_1bit f3(.a(a[2]), .b(b[2]), .cin(w2), .sum(sum[2]), .cout(w3));
    full_adder_1bit f4(.a(a[3]), .b(b[3]), .cin(w3), .sum(sum[3]), .cout(cout));


endmodule