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Timing Calculations

The Timing Calculator is used to measure timing between any two packets.

  • Go to Report > Timing Calculations in the Menu Bar

OR

  • Click att_4_for_337087195.png in the toolbar to display the Timing Calculator screen:

att_5_for_337087195.jpeg
Timing Calculations Report

  1. In the From beginning field, enter the first packet number or Markers.

  2. In the To beginning of field, enter the last packet number or Markers.

  3. In the Total Time field, select nanoseconds, microseconds, milliseconds, or seconds.

  4. Click the Show Formulas button to display the Formulas window (see image below).

  5. If you want to include only acknowledged packets, select Acknowledged. This excludes non-acknowledged data transfers from the calculations, leaving only the effective data transfer that the higher layers will see. (No re-tries, etc.)

    att_6_for_337087195.jpeg
    Formulas Window

  6. Click Calculate in the left side to display the Bus Utilization, Time Usage, and Bandwidth. Bus Utilization is:

    • Global USB 3.2

    • Global 3.2 A Host RX

    • Global 3.2 A Host TX

    • Global USB 2.0

    • High Speed

    • Full Speed

    • Low Speed

    • Transactions (High Speed with Idle)

    • Transactions (Classic Speed with Idle)

    • Transactions (High Speed without Idle)

    • Transactions (Classic Speed without Idle)
      Total Time is in the Total Time field.

      timecalc.png
      Timing Calculator Report

  7. Click Calculate (see red arrow in the figure above) in the right side to display:

    • Address

    • Endpoint

    • Direction

    • No Idle Time Usage

    • No Idle Bandwidth

    • With Idle Time Usage

    • With Idle Bandwidth

    • Data only Time Usage

    • Data only Bandwidth

You can also click the Acknowledged checkbox.

NOTE: The larger the range, the more accurate bandwidth and other calculations will be. You should choose a range that includes at least a few USB frames or Microframes so that the measurements give realistic values.

USB4

For USB4, there are two calculation methods:

  • Bus Utilization (the left side of the window) includes all HS packets except Idle symbols, and calculations are performed on a per-lane and per-port basis.

  • Device Utilization (the right side of the window) includes only TLPs, and calculations are performed on a per-HopID basis.

The following formulas are used:

  • Time Usage: Total duration of all packets, divided by time.

  • Bandwidth: Total size of all packets, divided by time.

  • Payload-Only Time Usage: Total duration of all payloads, divided by time.

  • Payload-Only Bandwidth: Total size of all payloads, divided by time.