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)
    wire xor_ab;
    assign xor_ab = a ^ b;
    assign sum = xor_ab ^ cin;
    assign cout = (a & b) | (cin & xor_ab);
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 c1, c2, c3;
    // TODO: instantiate 4 full adders and chain carries
    full_adder_1bit fa_0(a[0], b[0], cin, sum[0], c1);
    full_adder_1bit fa_1(a[1], b[1], c1, sum[1], c2);
    full_adder_1bit fa_2(a[2], b[2], c2, sum[2], c3);
    full_adder_1bit fa_3(a[3], b[3], c3, sum[3], cout);


    // TODO: drive cout


endmodule