Introduction
1000BASE-T/100BASE-TX/10BASE-T Physical Layer Compliance Tests Manual
2
Intel Confidential
1.2.2
Triggering
Determining the appropriate trigger point can mean the difference between passing and failing the
physical layer conformance tests. Triggering guidelines are provided throughout this document and
provide a good starting point for measurement. Fine tuning adjustments may be necessary in order
to achieve the best display.
1.2.2.1
Signal with an Ambiguous Trigger Level
An ambiguous trigger level (either width or height) can prevent a stable display.
1. Try to reduce the delta between the minimum and maximum pulse widths as much as possible.
2. Determine where the trigger level falls on the waveform.
If the line passes through more than one point on the rising edge of the waveform, raise or
lower the trigger until a point is found that is unambiguous as illustrated in
.
Figure 1-1. Ambiguous Trigger Level
1.2.2.2
Signal Does Not Appear
If the signal does not appear or appears only for an instant, the trigger level may be too high.
Reducing the trigger level should cause the signal to appear (or re-appear).
1.2.3
Displaying Waveforms
When observing waveforms on the scope display, it is important to understand the purpose of the
measurement being performed. If the purpose is simply to see a complete waveform, then the
horizontal and vertical scales only need to be small enough to fit the waveform on the screen and
the display does not need to be set to average or infinite persistence. However, if the purpose is to
obtain the most accurate measurements, more care is needed. The recommended scope settings
listed throughout the procedures should allow the desired waveform to be displayed on the screen.
For the best resolution, zoom in as much as possible on the waveform as observed in the following
three screen shots.
Trigger Level
3 possible
points for one
trigger level
Choosing this
trigger point will
provide a
cleaner display.
