You are given a module

`add16`

that performs a 16-bit addition. Instantiate two of them to create a 32-bit adder. One add16 module computes the lower 16 bits of the addition result, while the second add16 module computes the upper 16 bits of the result, after receiving the carry-out from the first adder. Your 32-bit adder does not need to handle carry-in (assume 0) or carry-out (ignored), but the internal modules need to in order to function correctly. (In other words, the`add16`

module performs 16-bit a + b + cin, while your module performs 32-bit a + b).https://hdlbits.01xz.net/wiki/Module_add

Note: See the HDLBits site for a diagram.

The key to this exercise is just implementing the circuit exactly as it’s depicted on the HDLBits website.

```
module top_module (
input logic [31:0] a, b,
output logic [31:0] sum );
// Define internal logic
logic cout_low;
logic [15:0] sum_high, sum_low;
// Module instantiations
add16 add16_low_i (
.a (a[15:0]),
.b (b[15:0]),
.cin ('0),
.sum (sum_low),
.cout (cout_low) );
add16 add16_high_i (
.a (a[31:16]),
.b (b[31:16]),
.cin (cout_low),
.sum (sum_high),
.cout () );
// Assign output logic
assign sum = {sum_high, sum_low};
endmodule : top_module
```

The unused *cout* output for the *add16_high_i* adder instantiation can either be left unconnected, as it is above, or removed entirely from the port list.