Failure Mode Wizard

The Failure Mode Wizard is a tool that enables you to define failure modes associated with fault locations. A design location may be subject to a failure mode which must be reflected in the tests and diagnostics in order to achieve accurate diagnostics. For example a single design location may be susceptible to fail in several modes: voltage, gain and frequency. In this case, in order for the test to be comprehensive, the location must be tested for voltage, gain and frequency. Here, three different tests may be implemented to evaluate the design location for three different attributes, or failure modes. You can only model these tests accurately if you can identify the different failure modes as distinct ways in which the circuit can fail. If you don't, then in run-time, a test passing at that location would indicate that the part is fully functional, when it actually may not be. The Diagnostic Profiler treats design locations as potential fault locations. The Failure Mode Wizard lets you define failure modes for specific fault locations.

To access the Failure Mode Wizard, you must access the Specify Tests tool under the Specify Tests and Repairs tab. At the lower left corner of the Specify Tests screen is a button labeled Failure Mode Wizard. Press that button to access the Failure Mode Wizard.

At the left of the Failure Mode Wizard screen is a list of common failure modes. You can add your own failure mode names by pressing Add Mode. A text entry box will appear, allowing you to add your own failure mode names.

At the right is a list of all fault locations in the model. In using the Failure Mode Wizard, you attribute failure modes to fault locations. To attribute failure modes to fault locations:

1. Highlight the failure mode(s) you wish to attribute to fault location(s). To highlight multiple failure modes, press the Ctrl key while clicking each item.

2. Highlight the fault location(s) you wish to attribute the selected failure mode(s) to. To select multiple fault locations, press the Ctrl key while clicking each item.

3. Press the Arrow box between the two boxes to attribute the selected falure mode(s) to the selected fault location(s). The list box will now be updated to reflect that the selected faults have the failure modes that you had selected.

Note: You can define failure modes for any number of fault locations from this screen. However, it is recommended that you go on to the next screen to define/refine the test coverage for the newly added failure modes.

Note: Since the reason for defining a failure mode is to provide a higher level of distinguishment than the single fault location, you shoud define more than one failure mode for a fault location. Defining only one failure mode for a fault location does not provide any additional distinguishment.

To use the Failure Mode Wizard to step through existing tests to define coverage of failure modes

The next step in the process is to verify the test coverage for each effected test. (see graphic)

1. Press the Next pushbutton after defining the failure modes.

2. You can set the Wizard to step you through all tests' measurements, just those tests' measurements where the fault is reachable by the measurement or just those tests' measurements where the original fault location is currently set to covered. These options are set through the toggle buttons at the upper left portion of the screen. The option most often useful is stepping through the tests' measurements where the original fault location is currently set to covered, the middle option.

3. Press the Next Measurement and Previous Measurement pushbuttons to traverse through the effected tests and measurements. For each measurement, set the failure mode coverage as appropriate.

4. Press Back to return to previous screen to define another failure mode, or press Done to return to the Specify Tests tool.