Teledyne LeCroy QPHY-USB - Manual (Page 29)

QPHY-USB Software Option
QPHY-USB Operator’s Manual Rev F
29
HOST HIGH-SPEED CHIRP TIMING
A High-Speed USB port must also be compatible with Full-Speed operation (12 Mb/s). High-Speed operation is
detected using the K and J chirp sequences. Full-Speed operation uses a higher impedance load. When a HS
capable host asserts a reset, an HS capable device must respond with the Chirp K to signal HS support. The Host
then responds with a Chirp J/K sequence to also signal HS support. This test measures the timing and voltages of
the HS handshake. The SQ Device section of the Test Fixture is used for chirp timing measurements.
Host High-Speed Chirp Timing
1. Select Host in the Mode control and HS Chirp Timing in the Test control of the USB Test Wizard.
2. Follow the instructions in the wizard menu to setup the test and acquire the chirp timing waveforms. Two
waveforms are acquired as follows:
CHIRP K DURATION
P1 MEASUREMENT
Figure 27. Chirp Response Time