Teledyne LeCroy QPHY-USB - Manual (Page 28)

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QPHY-USB Operator’s Manual Rev F
HIGH-SPEED PACKET PARAMETERS
Packet parameters represent timing measurements of the communications between host, hub, and device. USB
2.0 transmits data in bi-directional packets. The timing of these packets is critical for proper communication. The
sync field at the start of the packet, the width of the EOP (end of packet), and the inter-packet timing is measured
in this test.
Select Host, Hub, or Device in the Mode control and HS Packet Param in the Test control of the USB Test
Wizard.
Follow the instructions in the USB Test Wizard menu to setup the test and acquire the waveform. The captured
trace should look like the following image. The waveform in the center of the upper display contains three packets.
The test measures the sync field and EOP width of the center packet, and two time intervals between the three
packets.
Figure 26. Host High-Speed packet parameters trace
Note: The image shown is for a Host test, but the waveform also looks similar for Hub and Device tests.