Teledyne LeCroy QPHY-USB User Manual
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QPHY-USB Operator’s Manual Rev F
Figure 24. Host High-Speed Downstream Signal Quality Analysis
Device and Hub Upstream High-Speed Signal Quality
Select the appropriate mode (device or hub) and test (HS Upstream Signal Quality) in the USB test wizard. The
device or hub upstream port is connected to the host computer through the SQ Device section of the Test Fixture.
Note: Select Device HS Upstream NE Signal Quality for a device without a captive cable. Select Device HS Upstream FE Signal Quality
for a device with a captive cable.
The captured waveform should appear as follows (shown for the device test). Cursors (dashed vertical lines in the
image) must appear on either side of the packet, as shown. Use the Cursors knobs on the oscilloscope’s front
panel to adjust the position of the cursors (if necessary). The waveform between the cursors is processed by the
USB-IF signal quality test script to obtain an eye pattern and jitter measurements.
Note: After the device or hub upstream signal quality test is completed, the power to the device or hub must be cycled in order to stop the
transmission of the test packets. The device or hub does not respond to further test commands until the power is cycled. Cycle the power by
unplugging and re-plugging the USB connector and the power cord for a self-powered device or hub.