Teledyne LeCroy QPHY-USB - Manual (Page 62)

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QPHY-USB Operator’s Manual Rev F
Device and Hub Full- or Low-Speed Upstream Signal Quality Test
1. Start the USB High-Speed Electrical Test Tool, select Device and then press Test.
2. Press Enumerate Bus and verify that the hub or device under test appears in the Select Device window.
If the hub or device under test fails to enumerate, remove Full-Speed hubs one at a time from the end of
the chain until it does. The number of hubs between the host and the device under test plus one is the tier
at which the enumeration takes place.
3. Select the device or hub under test from the list in the Select Device window of the USB High-Speed
Electrical Test Tool and select LOOP DEVICE DESCRIPTOR in the Device Command control.
4. In the USB Test Wizard, select the appropriate mode (Hub or Device) and the appropriate test (FS or LS
Upstream Signal Quality).
5. Press the Single Trigger front panel button until a complete packet is captured. The waveform consists of
both downstream and upstream data. The upstream portion corresponds to the part of the differential
signal (channels 2 and 3) after the last bit in the trigger channel (channel 1). 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.
Figure 64. Isolation of Upstream Data Packet
6. Press Next in the USB Test Wizard to process the waveform. MATLAB generates an eye pattern
waveform file and an HTML signal quality report. These files are stored in the
D:\Applications\USB2\Results directory.