Duplicate function names can be used to solve a particular problem in refining diagnostic resolution. In analyses, output functions that appear on the same object and have the same name are considered to be the same ouput function observable at multiple locations. Following are two common examples of when the same name should be assigned to output functions on multiple ports of an object.
A Simple Bidirectional Part
When diagnosing a simple bidirectional part (such as a resistor, a wire, or a pipe), the entire functionality of a part can often be considered to be good if the part is able to work successfully in a single direction. If it works correctly in one direction, it can safely be assumed to be working correctly in the other direction (rather than it having to be separately tested in both directions). This is accomplished by assigning the same name (abbreviation) to the output function at each bidirectional output.
Built-In Test on a Component
Another common situation encountered is that of internal BIT (Built-In Test) 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 is modeled as usual (using names that reflect the functionality of each output). When modeling the BIT, a single port is typically used for the BIT port. In eXpress, the functional portion of the object that can be tested by BIT is assigned a unique name (abbreviation) and that output function is listed on both the BIT port and the regular "functional" outputs of the part (separate output functions are created to represent any functionality not covered by BIT). Thus, if the output functions on the BIT port are proven good, a certain amount of the functionality on the "functional" ports is proven good as well.
In more complex examples, of course, there is often
functionality of a part that cannot be tested by BIT
functionality of a part that is exclusively associated with BIT
(that is, not part of the operational functionality of the part)
separate operational functions at different ports, all of which can be tested by BIT.
Between modeling multiple output functions on a single port and modeling functions observable at multiple output ports, the eXpress model can easily be set up to reflect the correct functional visibility and diagnostic resolution for the target system.
