Each of the ports is specified by clicking on New , typing the name of the port in the Name field, selecting the Direction of the port, and choosing the bus width of the port with the arrow buttons in the Bus section. Click Next to enter the Design Wizard Attributes window, where comments can be added to the module. Click Next again and subsequently Finish to leave the Design Wizard. Now that we have the nutshell for the new module, we can create the schematic for its internals. Select the Hierarchy Push option in the Hierarchy pull-down menu of the Schematic Editor.
Buses are the analogous abstraction for interconnections that modules are for the logic.
Logic is grouped into modules to hide the details of the implementation of a module. Wires are grouped into buses to hide the details of interconnections between modules. Next, we connect the bus terminals with the corresponding half-adder ports. First, we extend the buses to run close by the half-adder ports. Click on the Draw buses button in the vertical tool bar, just beneath the Draw wires button.