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) | (cin&a);
    // 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 w1,w2,w3,w4,w5,w6,w7;
     full_adder_1bit fa1 (.a(a[0]), .b(b[0]), .cin(cin), .sum (w1), .cout(w5));
     full_adder_1bit fa2 (.a(a[1]), .b(b[1]), .cin(w5), .sum (w2), .cout(w6));
     full_adder_1bit fa3 (.a(a[2]), .b(b[2]), .cin(w6), .sum (w3), .cout(w7));
     full_adder_1bit fa4 (.a(a[3]), .b(b[3]), .cin(w7), .sum (w4), .cout(cout));
     assign sum = {w4,w3,w2,w1};

    // TODO: Declare internal ripple carries

    // TODO: instantiate 4 full adders and chain carries


    // TODO: drive cout


endmodule