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
);
assign sum = a^b^cin;
assign cout = a&b | b&cin  | a&cin; 
    // TODO: implement 1-bit full adder (structural or dataflow)

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
);
wire [2:0]c;

    full_adder_1bit u1(.a(a[0]),.b(b[0]),.cin(cin),.sum(sum[0]),.cout(c[0]));
    full_adder_1bit u2(.a(a[1]),.b(b[1]),.cin(c[0]),.sum(sum[1]),.cout(c[1]));
    full_adder_1bit u3(.a(a[2]),.b(b[2]),.cin(c[1]),.sum(sum[2]),.cout(c[2]));
    full_adder_1bit u4(.a(a[3]),.b(b[3]),.cin(c[2]),.sum(sum[3]),.cout(cout));
    // TODO: Declare internal ripple carries

    // TODO: instantiate 4 full adders and chain carries


    // TODO: drive cout


endmodule