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 p,q,r;

    // TODO: instantiate 4 full adders and chain carries
    full_adder_1bit F1 (.a(a[0]), .b(b[0]), .cin(cin), .sum(sum[0]), .cout(p));
    full_adder_1bit F2 (.a(a[1]), .b(b[1]), .cin(p), .sum(sum[1]), .cout(q));
    full_adder_1bit F3 (.a(a[2]), .b(b[2]), .cin(q), .sum(sum[2]), .cout(r));
    full_adder_1bit F4 (.a(a[3]), .b(b[3]), .cin(r), .sum(sum[3]), .cout(cout));

    // TODO: drive cout


endmodule