![Agilent Technologies E5382A Скачать руководство пользователя страница 58](http://html.mh-extra.com/html/agilent-technologies/e5382a/e5382a_user-manual_2868081058.webp)
58
Operating the Probe
Grabber Clip and Right-angle Ground Lead
Eye opening
The eye opening at the logic analyzer is the truest measure of an analyzer's ability
to accurately capture data. Seeing the eye opening at the logic analyzer is
possible with Eye Scan. Eye opening helps you know how much margin the logic
analyzer has, where to sample and at what threshold. Any probe response that
exhibits overshoot and ringing, probe non-flatness, noise and other issues all
deteriorate the eye opening seen by the logic analyzer. The following eye
diagrams were measured using Eye Scan probed mid-bus on a 50
Ω
transmission
line load terminated at the receiver. The data patterns were generated using a
2
23
−
1 pseudo random bit sequence (PRBS). These measurements show the
remaining eye opening at the logic analyzer while using the grabber clip and right-
angle ground lead configuration.
Eye opening measurement schematic
The logic analyzer Eye Scan measurement uses the same circuitry as the
synchronous state mode analysis. Therefore, the eye openings measured are
exact representations of what the logic analyzer sees and operates on in state
mode. The following measurements demonstrate how the eye opening starts to
collapse as the clock rate is increased. The severe overshoot and ringing observed
with this configuration on the preceding step-response graphs deteriorates the
eye opening for faster rise times. At 500 ps rise times the eye opening shows
excessive ring-back and collapsing of the eye. Therefore, it is recommended that
this configuration not be used for rise times faster than 1ns or clock rates in
excess of 600 Mb/s. The analyzer may still function at faster speeds, but will not
meet state speed and setup/hold specifications.
NOTE
It is critical to maintain good probing techniques on the clock signal. If the clock
being probed has
<
1 ns rise times, use an alternative configuration for probing.
E5382A
Probe
Z0=50
Ω
Rterm
Driver
Receiver
Rsource
PRBS
output
50
Ω
Z0=50
Ω
50
Ω
Logic
Analyzer
w/ EyeScan
Содержание E5382A
Страница 4: ...4 Contents ...
Страница 5: ...1 General Information ...
Страница 13: ...2 Operating the Probe ...
Страница 64: ...64 Operating the Probe Combining grounds ...