100Base-TX Test Procedure for the 82544 Chip
1000BASE-T/100BASE-TX/10BASE-T Physical Layer Compliance Tests Manual
142
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5. Set both the Trigger Position and the Horizontal Position to appear on the display.
6. Gradually increase the lower trigger limit, until all triggering is lost,
7. Then slowly decrease the lower trigger limit by (about 5 nsec), until triggering resumes.
8. Decrease the upper trigger limit until it is ~5 nsec to 12 nsec above lower trigger limit.
9. Following the above method should ensure a good trigger with minimal added jitter.
10. Use the horizontal offset to position the waveform, as shown in
.
11. Change the Oscilloscope’s signal acquisition mode to “Single Sequence” and/or “One-Shot”
acquisition mode. (Do NOT use averaging. Do NOT use sampling mode.)
12. Push the trigger button; then scroll all the way to the left edge and all the way to the right edge
of the captured pulse. Note the MLT-3 mid-level shoulders (are they at least 20 nseconds
wide?). Keep doing manual triggers, until a pulse is acquired that has mid-level “shoulders” on
both sides; with each shoulder being at least 20 nseconds wide (see
, and
13. Scroll horizontally through the waveform, until the left shoulder is occupying the width of the
oscilloscope display. Select the horizontal cursors. Move one cursor to the top side of the mid-
level shoulder. Move the other cursor to the bottom side of the mid-level shoulder. Record the
values of both cursors. [See
and
Figure I-5. Lower-left MLT-3 mid-level, lower cursor
