Tektronix TDSUSB2, Руководство пользователя

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Operating Basics
Hubs and Hosts for Downstream Signal Quality Check
Ports of a Hub for Droop Test
Devices for Inrush Current
Signal Quality Check
The application performs Signal Quality tests that include the following tests:
Table 6. Signal Quality checks
Area Option Description
Signal Quality Check Eye Diagram Checks whether the USB signal is aligned with its corresponding
eye diagram
Signal Quality Check Signal Rate Measures the inverse of the average bit-time that gives the
transmission rate of the USB signal
Signal Quality Check Paired JK Jitter Measures the jitter time for paired (JK next to KJ) differential
data transition
Signal Quality Check Paired KJ Jitter Measures the jitter time for paired (KJ next to JK) differential
data transition
Signal Quality Check Consecutive Jitter Measures the jitter at every consecutive data bit calculated
using the signal rate
Signal Quality Check EOP Width Measures the width of the end-of-packet of a USB signal
Signal Quality Check Cross-Over voltage Measures the voltage at which the D+ voltage crosses the D–
voltage
Signal Quality Check Rise Time Measures the elapsed time from when a rising edge crosses the
low reference voltage level and then the high reference voltage
level
Signal Quality Check Fall Time Measures the elapsed time from when a falling edge crosses the
high reference voltage level and then the low reference voltage
level
Signal Quality Check Monotonic Property (For High Speed only) Measures the Monotonic Signal if the data [i] < data [i-1] where
data[l] is the record point in the acquired waveform. This is in the
case of consistently increasing (rising Slope) only. If the data [i]
> data [i-1] in case of consistently decreasing) falling Slope) and
never increasing in value where i ranges from 0 to n, the signal I
is said to be monotonic
Note: The USB2.0 specifications recommend that you should test the signal
quality for upstream and downstream traffic. In upstream testing, the application
captures the signals transmitted from the device to the host. In downstream
testing, the application captures the signals transmitted from the host to the
device.
Downstream testing is performed on ports of a hub. When testing a hub, you need
to connect the USB2.0 unit to Tier 6 to ensure the worst case. Each hub level is
referred to as a Tier. The hub under test is connected to the Tier 5, so that you
can test the hub on the Tier 6.
TDSUSB2 Universal Serial Bus Measurement Package 29