Teledyne LeCroy QPHY-USB - Manual (Page 45)

QPHY-USB Software Option
QPHY-USB Operator’s Manual Rev F
45
13. Now further reduce the amplitude of the packet from the data generator in small steps, still maintaining
balance between the outputs until the receiver just ceases to respond with NAK. This is the squelch level
of the receiver.
14. Measure the Zero-to-Positive Peak and Negative Peak of the packet from the data generator, using the
method described in steps 11 and 12. As long as the receiver ceases to NAK the data generator packet
below +/- 100 mV, it is considered to have passed EL_16.
Figure 49. Receiver squelch level – no response to IN tokens
Note: With certain devices, making an accurate zero-to-peak measurement of the IN packet from the data generator may be difficult due to
excessive reflection artifacts. Also, on devices with captive cable, the measured zero-to-peak amplitudes of the IN packet at the test fixture
could be considerably higher than that seen by the device receiver. In these situations, it is advisable to make the measurement near the
device receiver pins on the PCB.