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 sum1, cout1, cout2;
    // first half
    xor summ1 (sum1, a, b);
    and and1 (cout1, a, b);

    // second half
    xor summ2 (sum, sum1, cin);
    and and2 (cout2, sum1, cin);

    // or
    or (cout, cout1, cout2);

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 cout0, cout1, cout2, cout3;
    // TODO: instantiate 4 full adders and chain carries
    full_adder_1bit one (a[0], b[0], cin, sum[0], cout0);
    full_adder_1bit two (a[1], b[1], cout0, sum[1], cout1);
    full_adder_1bit three (a[2], b[2], cout1, sum[2], cout2);
    full_adder_1bit four (a[3], b[3], cout2, sum[3], cout3);

    // TODO: drive cout
    assign cout = cout3;

endmodule