Advanced search and marking capabilities complement the Pinpoint trigger system

Advanced Search and Mark is a powerful tool for designers facing signal integrity and timing challenges, which complements and enhances the Pinpoint® trigger system in the Tektronix DPO7000 and MSO/DPO/DSA70000 oscilloscope series. When used in conjunction with Advanced Search and Mark, the Pinpoint trigger system provides unprecedented flexibility, improves the accuracy of locating points of interest in the signal, and thus improves debug efficiency and allows more information to be obtained in waveform analysis.

 

Advanced Search and Mark (ASM) uses most of the same trigger types as the Pinpoint trigger system to analyze acquired waveforms and identify events of interest. While hardware triggering monitors one event type at a time, ASM scans multiple event types simultaneously. For example, it can scan for setup or hold time violations on multiple channels, or it can scan for burst starts and ends simultaneously, such as reads or writes on DDR memory data waveforms. Coupled with high sampling rates, ASM scanning provides finer resolution than hardware-based triggering methods when dealing with high signaling speeds. In addition, it can apply triggered searches on math waveforms that have already applied functions (such as filtering or spectrum analysis) to the acquired waveform.

 

Figure 1. FastAcq review function showing potential problems (gray).

Figure 1 illustrates the ASM feature and its benefits in a typical debug scenario. The screen shot shows a waveform visualized using FastAcq, revealing potential problems in the signal. The gray trace shows infrequent events, with misplaced edges occasionally visible in the waveform.

 

Figure 2. Glitch event detected using the Pinpoint trigger type.

When a glitch or corrupted signal transition is suspected, the Pinpoint trigger system can be used to isolate the pulse that is narrower than the expected width in the system. In this way, we detect a glitch event, as shown in Figure 2.

 

Figure 3. Pinpoint trigger type search method.

Figure 4. Select and copy the Glitch Search method into Advanced Search and Marking.

ASM can then be used to gain further insight into what is happening, providing clues to the root cause. As shown in Figure 3, the acquired waveform can be scanned using the search method corresponding to each Pinpoint trigger type. The search method palette is suitable for isolating a variety of signal integrity defects and problems, including setup and hold violations. In Figure 4, Glitch is selected from the Search menu and the user can continue to configure parameters for this search.

 

The Pinpoint trigger system integrates with ASM so that trigger settings in one system can be quickly applied to another. In this example, we use the Settings Copy feature to copy settings directly from the Pinpoint Glitch Trigger to the ASM Glitch Search with the push of a button, saving time and reducing errors when moving between the real-time trigger system and the post-processing search function.

 

Figure 5. Search results for a 5M sample waveform.

After defining a Search using the Glitch trigger, the display updates to show the location of the match in the waveform. Figure 5 shows the results for a 5 Msample waveform. We searched for positive pulses with a width less than 4 ns.

[page]

The light green symbol box at the top of the display above the waveform (Figure 5) is actually a collection of individual markers placed by ASM to indicate events that meet the search criteria. Although the waveform appears uniform, ASM finds many events that meet the Glitch criteria, starting at the center of the screen because that is the trigger position on the display and the first point where the Pinpoint trigger detected the first glitch using the same criteria.

 

Figure 6. Display scaling.

In Figure 6, we use the display zoom to examine one of the markers in more detail. The Previous and Next navigation controls on the right side of the screen are used to select the marker to view. The top of the display shows the entire acquisition record of 5 Msamples, covering a time period of 100 s in this example.

 

The lower view of the oscilloscope display (Figure 6) shows the waveform at Mark 2, centered in the Zoom display area. It spans only 1 s and shows the area around Mark 2 in more detail. The zoom factor can be increased to get more detailed information or decreased to include more overview information. In this example, Markers 1 to 4 can be roughly compared. Note that there is a clear periodicity in these events, which provides potential clues to their cause.

 

Traditional hardware trigger systems focus on one set of signal characteristics at a time, excluding other conditions, so isolating a wide range of problems often requires sequencing through different trigger types. Tektronix Search and Mark complements the Pinpoint trigger system with the ability to perform multiple searches simultaneously, so you can efficiently detect multiple conditions on multiple signals.

 

Figure 7. Advanced search and multiple search methods of Cunji.

Figure 7 illustrates how multiple searches within ASM can be applied to a signal to search for problems simultaneously. ASM allows up to eight searches to be applied simultaneously, so a large number of events can be detected on one or more waveforms. FastAcq reveals signal problems including misplaced edges and occasional transitions that stay between thresholds too long or never complete.

 

Figure 8. Glitch and window search selected.

 

In Figure 8, we have selected Glitch Search and Window Search from the Search palette, which appear in the table on the right. Up to six additional searches can be defined and applied to Channel 1 or other channels. The user can scan multiple channels for multiple problem conditions without having to reconfigure. Each search has unique settings, such as defining additional glitches for Ch1.

Search, but use different threshold or width values.

 

Figure 9. Window search.

The controls used to define a window search are similar to glitch search. In Figure 9, the window trigger is configured to capture signals that enter the region specified by the upper and lower thresholds and remain in that region for more than 5 ns. Other forms of window search can detect signals that pass outside of the specified region, such as excessive overshoot above or below the normal range of the signal.

[page]

Figure 10. Glitch search and window search results.

 

Figure 11. Results table.

Figure 10 shows the results of applying these two searches. Note the green markers at the top of the screen indicating that any of the search criteria have been met. In this example, the user has navigated to the last marker, viewed in the zoomed view. Figure 11 is a table of the results of these two searches. Note the combination of window and glitch events found, along with the time location and description information.

 

In addition to being able to exchange devices with the Pinpoint trigger system, which increases productivity by finding repetitive, complex events in long record acquisitions, Advanced Search and Mark provides much more functionality to deliver useful results to the user.

 

Figure 12. Results table.

As shown in Figure 12, the ASM results table provides an efficient tool for summarizing trigger events, navigating each event in a long record, and calculating precise timing measurements over large intervals.

 

ASM has the ability to stop waveform acquisition when an event is found, which can work as a pseudo-trigger mode, where waveforms are acquired and scanned using one or more search methods. If at least one match is found, acquisition stops and a marker is placed to indicate each match. If no match is found, another record is acquired (assuming Run Continuous acquisition mode), and the process repeats.

 

Therefore, you can use ASM to search for real-time or math waveforms as pseudo triggers. This mode of operation is not as vigilant as a hardware trigger because it takes longer to perform software-based post-processing to find the event than a hardware-based trigger acquisition, but the ASM search method provides additional flexibility and accuracy when events occur frequently.