DFTVisualizer Highlights and Tips
New Task Manager provides quick access to useful windows based on task to be performed
How do you know which window in DFTVisualizer is the best to use to perform a particular task? The Task Manager provides a list of common tasks and automatically opens the most useful windows to match the task you're performing. The Task Manager comes up at start-up but you can open it again later by using the “Windows” menu option.
One of the features of the Browser window is the display of fault and DRC violations in both textual and graphical views. This is very helpful when looking at a large amount of data where the absolute number of faults or DRCs may not be as meaningful. By knowing that a large percentage of faults or DRCs is attributed to a particular instance, problem areas can be quickly identified. When debugging, it sometimes helps to see the data from an instance in multiple windows. Objects can be selected and added to other windows by using the “Add” option in the right mouse button drop down menu. Another option is to hold down the “Ctrl” key while selecting one or more objects and dragging and dropping them into another window.
Additionally, the Browser window will clearly mark no-faulted instances so that it is easy to distinguish blocks that have 0.00% coverage or 0 DS faults with other blocks that were no-faulted by the user (issuing the ‘add nofault’ command). This feature eliminates the extra time needed to confirm that a particular block with coverage issues has been no-faulted at command line.
One of the features of DFTVisualizer is to display gates that are impacted by DRC violations and show the relevant simulation data on their pins. For example, a T3 trace violation results in this view where we see the scan cell which is blocked.
One of the features of DFTVisualizer is to provide statistics on test coverage, faults, and DRCs for each instance in the design. When looking at faults such as AUs, it sometimes helps to breakdown the faults even further so see why some faults are classified as AU. Traditionally, this was done at command line by issuing the command “report testability data –class AU” but in DFTVisualizer you can quickly access this data by clicking on the “expand” button in the header of any of the fault classes.
The AU faults are quickly listed in more detail and broken down to faults that may be connected to untestable RAMs or tied to unknown (X) values. You can hover the mouse pointer over any of the sub-headers in order to get a full description of the testability data classification. Similar to the “expand” button, you can return to the single AU fault category by clicking the “collapse” button in the header.
In addition to what DFTVisualizer does for analyzing DRC violations, you can also use the new trace to value functionality on any pin in the design. For example, you may like to know where the unknown value (X) on the input of this flip-flop comes from.
Instead of tracing back one gate at a time or even using the “Trace Backward Endpoint” option, you can trace back to a specific data value, in this case X. Use the right mouse button menu to select the X to trace to. Note that when there are multiple data values shown on a pin, this feature allows you to select the specific value of interest.
As you can see, DFTVisualizer traces the X value through synthesized gating logic and automatically selects the correct path to trace through. |
