Teledyne LeCroy QPHY-USB - Manual (Page 55)

QPHY-USB Software Option
QPHY-USB Operator’s Manual Rev F
55
Host Full-Speed Downstream Signal Quality
1. Connect the system as shown in the following figure.
2. Select Host and FS Downstream Signal Quality in the USB Test Wizard on the oscilloscope.
3. Plug a Full-Speed (or High-Speec) device into the last hub and verify enumeration. If the device fails to
enumerate, this could be due to low receiver sensitivity. Remove the last hub in the chain and repeat the
enumeration. The tier control in the USB Test Wizard should be set to 6 when all hubs in the chain are
being used. Decrease this number for each hubs that must be removed to achieve enumeration.
Note: The USB-IF High-Speed Electrical Test Tool is not used for this test and should not be running
4. Follow the steps in the USB Test Wizard on the instrument display to capture the appropriate waveform. It
may be necessary to repeat the acquisition to capture a full screen of data. Use the cursors to select the
downstream portion of the data packet (as the following figure shows). The cursors are set to 1 UI before
the first bit in the sync field on the left and 1 UI after the end of the EOP on the right. The software then
generates an HTML report on the signal quality.
Figure 57. Host Full-Speed Downstream Signal Quality Test Equipment Setup