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=(cin&(a^b))|(a&b);
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 intcarry[2:0];
    // TODO: instantiate 4 full adders and chain carries
    full_adder_1bit fa1(a[0],b[0],cin,sum[0],intcarry[0]);
    full_adder_1bit fa2(a[1],b[1],intcarry[0],sum[1],intcarry[1]);
    full_adder_1bit fa3(a[2],b[2],intcarry[1],sum[2],intcarry[2]);
    full_adder_1bit fa4(a[3],b[3],intcarry[2],sum[3],cout);  
    // TODO: drive cout


endmodule