16 bit RIPPLE CARRY ADDER

module rip(s,cout,a,b,cin);

//main module of 16 bit Ripple carry adder

input [15:0]a;

input [15:0]b;

input cin;

output cout;

output [15:0]s;

wire c4,c8,c12,cout;

rip2 m1(s[3:0],c4,a[3:0],b[3:0],cin);

rip2 m2(s[7:4],c8,a[7:4],b[7:4],c4);

rip2 m3(s[11:8],c12,a[11:8],b[11:8],c8);

rip2 m4(s[15:12],cout,a[15:12],b[15:12],c12);

endmodule

module rip2(s,cout,a,b,cin);

 //sub module for 4 bit Ripple carry adder

  input [3:0]a;

  input [3:0]b;

  input cin;

  output cout;

  output [3:0]s;

  wire c2,c3,c4,cout;

  fa m1(s[0],c2,a[0],b[0],cin);

  fa m2(s[1],c3,a[1],b[1],c2);

  fa m3(s[2],c4,a[2],b[2],c3);

  fa m4(s[3],cout,a[3],b[3],c4);

endmodule

module fa(s,cout,a,b,cin);

//sub module for Full adder

input a,b,cin;

output s,cout;

wire w1,w2,w3;

ha m1(w1,w2,a,b);

ha m2(s,w3,w1,cin);

or m3(cout,w2,w3);

endmodule

module ha(s,cout,a,b);

 //sub module for Half adder

  input a,b;

  output s,cout;

  xor m1(s,a,b);

  and m2(cout,a,b);

endmodule