User Manual

Appendix - "Bus analysis" mode
147
12.17.3. Measurements (USB)
Diagnosis
Use this table to troubleshoot problems on a measurement :
Measurement
Description
Diagnosis
VHIGH
Measurement of the high level

Termination problem

Junction connection (oxidation, bad contact,
etc.)

Cable length not compliant with standard

Significant noise (check the cable route, ground
braid not connected, faulty chassis-ground, etc.)
 …
VLOW
Measurement of the low level
Time Rise
Rise time between 10% and 90% of
the signal amplitude

Unsuitable or damaged cable

Termination impedance incorrectly positioned

Significant noise (check the cable route, ground
braid not connected, faulty chassis-ground, etc.)
 …
Time Fall
Fall time between 90% and 10% of
the signal amplitude
TRise-TFall
Difference between the rise time at
10% 90% and the fall time at 90%
10%

Unsuitable or damaged cable (the rise and fall
times increase with the cable impedance)

Significant noise (check the cable route, ground
braid not connected, faulty chassis-ground, etc.)
 …
Time Data
Measurement made using the bit time
total

Unsuitable or damaged cable

Termination impedance incorrectly positioned

Significant noise (check the cable route, ground
braid not connected, faulty chassis-ground, etc.)
 …
Jitter
Measurement made using the bit time
total

Significant noise (check the cable route, ground
braid not connected, faulty chassis-ground, etc.)

…