module binary_adder_2bit
(
input [1:0] a_i,
input [1:0] b_i,
input cin_i,
output [1:0] s_o,
output cout_o
);

wire cout_fa1;

full_adder_hier FA1 
(
.a_i    (a_i[0]),
.b_i    (b_i[0]),
.cin_i  (cin_i),
.s_o    (s_o[0]),
.cout_o (cout_fa)
);

full_adder_hier FA2 
(
.a_i    (a_i[1]),
.b_i    (b_i[1]),
.cin_i  (cout_fa),
.s_o    (s_o[1]),
.cout_o (cout_o)
);

endmodule