Use the digital scope to view a graph of the expected waveform underneath the actual waveform using the pattern, timing set, and levels, including compare strobe locations, VOH and VOL levels, and expected drive levels. You can use the digital scope to help debug failures to verify that the actual waveform accurately reflects what you expect based on what the pattern and timing define.The Digital Pattern Editor generates digital scope waveforms by repeatedly bursting a pattern while changing levels and the timing of the strobe edge to determine the level of the waveform at each point in time.
The cycles or vectors on which you generate digital scope waveform points must be repeatable for every burst of the pattern. Using opcodes that result in non-deterministic pattern execution, such as using conditional jumps based on the failed or matched state of the pattern, can result in errors and potentially inaccurate results. Remove the pins with such compares from the pin list for the digital scope to avoid such inaccuracies. For example, if you configure the digital scope to start at a cycle, all cycles in the range you specify must always be at the same vectors on every burst. If you configure the digital scope to start at a vector, that vector does not have to always execute on the same cycle, but the number of cycles you specify to plot after the start vector cycle for each burst must correspond to the same vectors on every burst.
Use the following techniques to launch the digital scope:
When you run the Digital Pattern Editor in demo mode and execute a digital scope operation, the generated results reflect the actual pin states from the target pattern and the currently active timing values but do not reflect a realistic execution of patterns. Use the pattern waveform view to see a graph of the pattern without requiring the use of digital pattern instruments.
The digital scope graph can contain the following components:
When you right-click a cell in the pattern document and select Use Digital Scope on Selected Pins and Vectors from the context menu or right-click a cell in the History RAM View and select Use Digital Scope on Selected Pins and Cycles from the context menu, the digital scope preconfigures the Start Vector, Cycle Offset, Number of Cycles, Pins/Pin Groups, and Pattern settings for the digital scope operation based on the vector or cycle you selected.
You can also use the Site drop-down menu on the toolbar to select the site for which you want to display plot results.
While the digital scope is running, the vertical red points mark the point in time for which the levels on each pin are currently being evaluated. Green circles indicate fully evaluated points and always display while executing.
Configuring a small number of steps might result in incomplete waveform information if the signal changes rapidly.
Instrument settings restore to their original values when the digital scope operation completes or when you abort the operation.
Use the two cursors on the digital scope to display the timing and measured voltage values for all pins. You can drag the two cursors independently from each other to compute the time offset difference between the two locations and display the value in the top left corner of the digital scope. The cursors reset to the beginning of the digital scope plot when you restart the digital scope operation.
Use the Toggle Expected Waveforms on Top button to change whether the actual waveform overlays the expected waveform. Use the Always Show Sampled Points button to toggle the display of all points on the plot. The graph always displays the sampled points while executing. Use the Show Levels at Cursor button to toggle the display of the per pin voltage levels at the locations of the cursors.
Use the buttons above the digital scope to control panning and zooming. The pan and zoom locations reset to center when you restart the digital scope operation.
The document stores the specified digital scope settings, but not the graph data itself, in the corresponding .digiprojcache file for the project.
Once the Digital Pattern Editor calculates and applies TDR values, the Digital Scope's timing is now relative to the DUT. The time displayed in the Digital Scope represents the time the DUT drove or received the signal, not the time a digital pattern instrument drove or received the signal. Use the Digital Scope to validate signals driven from the DUT. The Digital Scope displays the expected waveform signals driven the DUT in blue.
Use the Save Plot Data to CSV File button on the toolbar or <Ctrl+S> to save the actual and expected plot data for the active site to a .csv file. Use the Save Screenshot to PNG button on the toolbar to save a screenshot of the state and plot data of the digital scope as an image file. You must expand the settings section to include it in the image.
|Run Digital Scope||F5|
|Control panning||<Ctrl+left-click> and drag|
|Zoom on a region you select||<Shift+left-click> and drag|
|Save actual and expected plot data for the active site to a .csv file||<Ctrl+S>|