/*This is the CSA_unit that has been built using
two 1-bit carry save adder. It's purpose in the
whole adder schematic has been shown in the image.

**Please excuse the 1-bit carry save adder module
uploaded twice. Both of then are identical except
for comments in the second upload.
*/
`timescale 1ns / 1ps
module csa_unit(
    input an,
    input bn,
    input cn,
    input cin,
    input s_n_1,
    output sn,
    output sum_n_1,
    output cout
    );

wire cout1;
csa_1Bit a1(an, bn, cn, sn, cout1);
csa_1Bit a2(cin, cout1, s_n_1, sum_n_1, cout);

endmodule