Schematic diagrams have the advantage that they provide a visual representation of the circuit. However, for complex designs it can be tedious to edit and maintain a large set of schematics. Maintaining and editing a set of HDL files is much easier, though one can `get lost' somewhat if there are many levels of hierarchy. Some HDL tools provide helpful visual representations for HDL designs.
It is sometimes helpful to use a mix of schematic and VHDL source files in a design project. We will do so here, and use a schematic diagram to express top-level relationships, so the schematic will essentially be a block diagram. Specifically, we design a 4-bit adder using VHDL to describe the 1-bit full adder, and we use a schematic to show the interconnections between full adder modules and the external world.
ANU Engineering - ENGN3213