Support Question of the Week: Using a Protocol Analyzer, How Does the Data Center Software Capture USB Trace Files and Display the Data?

I have a question about results I see when I capture USB trace files. Using a BeagleTM USB Protocol Analyzer , I was browsing two separate USB trace files with the DataTM Center Software. On one window, the trace appeared to show some data that didn’t make sense for a short sequence in the packet view. Also, it did not agree with the block view. When I looked at the sequence numbers, some of the packets were out of order. For example, the earlier packets were inserted in a later sequence. Then, after scrolling the window up and down, those packets vanished. Can you explain why I saw that? By the way - the block view was always correct.

Thanks for your question! When you use the Class View or the Transaction View in the Data Center software, the records may not be displayed in the correct time-order. This is due to how the data is grouped for higher level parsing. You can see the records in time-order by switching to Packet View, which disables the higher level parsing. Please note - only the captures that are run in the sequential mode can be viewed in the packet view.

To select a Capture View, use the Capture View Menu in the Transaction Window Controls section of the application.

    1. Select Analyzer and then select Capture Sections.
    2. Under the USB tab, select Sequential as the Capture Mode.
      Step 1 for selling the desired capture mode in the Data Center Software. Figure 1: Step 1 - Select the Capture Setting in the Data Center Software


  1. At Protocol Lens, from the second drop menu (that shows icons) select Packet Level as the classification view. The selection will be displayed under Command Line.
Step 2 for selecting the desired capture mode in the Data Center Software. Figure 2: Step 2 - Select Packet Level

For additional information, please refer to section 6.7 of the Data Center Software User Manual. Following is a summary of that information:

  • Packet View – Protocol-level decoding is performed, and records are in time-order. Collapsed groups, such as SOFs and IN-NAKs are broken up as necessary to ensure the records are in timestamp order. Only captures that are run in Sequential Mode can be viewed in Packet View.
  • Transaction View – Protocol-level decoding is performed. Records may not be in time-order. Collapsed groups are not broken up for time-order preservation. As there is no time-order restriction, captures generally appear more compact in the Transaction View than in the Packet View.
  • Class View – Class-level parsing is performed. Records may not be in time-order. Captures generally appear high-level and more compact in this view.

For more information, please refer to the following documents:

For more information, please refer to the following documents:

We hope this answers your question. If you have other questions about our software, host adapters, protocol analyzers or other Total Phase products, feel free to email us at or submit a request for technical support.

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