Tektronix TDSUSB2, Manual

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Operating Basics
Monotonic Property
While performing a USB2.0 High Speed compliance test, you need to verify that
the signal to be tested is monotonic.
The following graph shows the monotonic behavior of a USB2.0 high-speed
signal with a rise time of 500 ps.
To verify the monotonic behavior of a signal, the oscilloscope must have a
sample rate high enough to capture as many sample points as possible on a rising
or falling edge. In addition, the oscilloscope should have enough bandwidth to
ensure that the high frequency non-monotonic transition is not attenuated.
The application coupled with a high performance Tektronix oscilloscope
automates the process and ensures repeatability of test results.
Configuring a Measurement
To access the Configure: Measurement, go to Measurements> Configure. The
application also provides a Configure option with each measurement area to
allow you to configure the selected measurements.
Note: If you select the Run button before configuring a measurement, the
application displays the message ‘The selected measurements have not been
configured. Do you want to continue? In this case, the application runs with the
default settings. If you select the Run button before configuring the measurement
and have enabled the File> Preferences> General option, the application
displays the warning message ‘Warn if configuration was not changed since last
run, when the run button is pressed.
34 TDSUSB2 Universal Serial Bus Measurement Package