1000BASE-T/100BASE-TX/10BASE-T Physical Layer Compliance Tests Manual
Intel Confidential
37
100BASE-TX Waveform Overshoot
4. Select the horizontal cursors. Move one cursor to +V
OUT
and the other cursor to the maximum
overshoot voltage.
Note:
Overshoot is defined as the difference in voltage between the average peak voltage measured in
and the peak of the
first
ripple.
If there is no overshoot visible in step 4, then overshoot settling time is not applicable. The tester
should record “not applicable” for overshoot settling time, and testing for
is completed (make sure to check for both positive and negative waveform
overshoot). An example of a 100BASE-TX waveform without overshoot is shown in
.
However, if overshoot is present, the test should proceed to the next step (step 5).
Table 9-2. Setting for Negative Waveform Overshoot
Scope Parameter
Setting
Horizontal Scale
~25 ns/division
Vertical Range
-1125 mV to +75 mV (1200 mV over the full vertical scale)
Trigger Type
Negative pulse width triggering:
116 ns lower bound, 128 ns upper bound
Trigger Level
-500 mV
Record Length
Large enough to enable viewing of one complete MLT-3 (3-level)
waveform by scrolling horizontally
Display Type
Average
Pulse Width Triggering
Triggering information is provided to give a good starting point for measurement. The
following guidelines will help the tester achieve the most stable display.
1. Set the trigger level to approximately 500 mV.
2. Select pulse width triggering.
3. Set the upper bound parameter to approximately 200 ns and the lower bound
parameter to approximately 116 ns.
4. Set the trigger mode to normal.
5. Increase the lower bound parameter gradually until the triggering is lost.
6. Decrease the lower bound parameter slowly in 5 ns increments until triggering
resumes.
7. Decrease the upper bound parameter until it is 5 ns to 15 ns above the lower trigger
bound parameter.