Create a structural HDL description of the 4-bit adder/subtractor circuit in Figure 4.54(b). Be sure to first create a behavioral HDL description of each component used in your structural HDL design. Figure 4.54 Two's complement adder/subtractor using a mux, (b) alternative circuit for Busing XOR gates.

0 1 N-bit 2x1 B A Adder cin s B N-bit -sub b7 b6 adder's B inputs (b) sub