Duplicate output function names (on the same object) are interpreted within eXpress analyses as an indication that the same function is visible at multiple locations.Following are two examples demonstrating this capability:
Simple Bidirectional Part
In this example, both ports have been named "R"
In this example, both ports have been assigned the same abbreviation ('R'). Using duplicate port names results in the same name being assigned to each automatic output function since, by default, automatic output function names are derived from abbreviations of the objects and ports for which they are defined. As a consequence of the two output functions having the same name (regardless of whether the port names match), eXpress analyses will treat this object as having only a single function. For example, if a test were to prove that the resistor works properly when a signals flows through it in one direction, the eXpress diagnostics would also consider the function on the other side of the resistor to be working properly as well (or, more properly, the diagnostics would recognize that both outputs constitute the same function, so the resistor needs only be tested in a single direction).On the other hand, if each port (and therefore the output function) were to be named differently, each side would have to be tested explicitly.
Although our example shows a resistor, the same logic holds true for any component (including many passive components) where the a single function acts in both directions. The following table lists some additional examples of simple bidirectional parts, indicating whether the output functions would typically be assigned the same name or a different name on both ports:
Typical Single Port Name Utilized
TypicalMultiple Port Names Utilized
Capacitor
Diode
Inductor
Battery
Wires, Traces, Cables, Pipes, etc.
Ball Valve
Built-In Test Coverage on a Component
Another common situation encountered is that of internal BIT coverage. Components that contain built-in testing often expose functionality through the BIT testing ports. Consider the case of a part with boundary scan capability. The normal functionality of the part can be modeled as usual (with whatever names are desirable). When modeling the BIT, typically a single port is used for the BIT port. On that port, automatic functionality should be overridden, the Analyst creating a set of output functions that duplicate the function on every other port of the object. In this way, all functions can be detected and proven through the BIT port, without having to write tests through the other functional areas of the component.
