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) | (a & cin);

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 cout01, cout02, cout03, cout04;

    // TODO: instantiate 4 full adders and chain carries
    full_adder_1bit fa01(
        .a(a[0]),
        .b(b[0]),
        .cin(cin),
        .sum(sum[0]),
        .cout(cout01)
    );

    full_adder_1bit fa02(
        .a(a[1]),
        .b(b[1]),
        .cin(cout01),
        .sum(sum[1]),
        .cout(cout02)
    );

    full_adder_1bit fa03(
        .a(a[2]),
        .b(b[2]),
        .cin(cout02),
        .sum(sum[2]),
        .cout(cout03)
    );

    full_adder_1bit fa04(
        .a(a[3]),
        .b(b[3]),
        .cin(cout03),
        .sum(sum[3]),
        .cout(cout04)
    );


    // TODO: drive cout
    assign cout = cout04;

endmodule