148 Keysight InfiniiVision 2000 X-Series Oscilloscopes User's Guide
11 Trigger Mode/Coupling
To select the Auto or Normal trigger mode
When the oscilloscope is running, the trigger mode tells the oscilloscope what to
do when triggers are not occurring.
In the Auto trigger mode (the default setting), if the specified trigger conditions are
not found, triggers are forced and acquisitions are made so that signal activity is
displayed on the oscilloscope.
In the Normal trigger mode, triggers and acquisitions only occur when the
specified trigger conditions are found.
To select the trigger mode:
1 Press the [Mode/Coupling] key.
2 In the Trigger Mode and Coupling Menu, press the Mode softkey; then select
either Auto or Normal.
See the following “When to Use Auto Trigger Mode" on page 149 and “When
to Use Normal Trigger Mode" on page 149 descriptions.
You can also configure the [Quick Action] key to toggle between the Auto and
Normal trigger modes. See “Configuring the [Quick Action] Key" on page 262.
Triggering and the
Pre- and
Post-Trigger
Buffers
After the oscilloscope starts running (after pressing [Run] or [Single] or changing
the trigger condition), the oscilloscope first fills the pre-trigger buffer. Then, after
the pre-trigger buffer is filled, the oscilloscope starts searching for a trigger, and
sampled data continues to flow data through the pre-trigger buffer in a first-in
first-out (FIFO) manner.
When a trigger is found, the pre-trigger buffer contains the events that occurred
just before the trigger. Then, the oscilloscope fills the post-trigger buffer and
displays the acquisition memory. If the acquisition was initiated by [Run/Stop], the
process repeats. If the acquisition was initiated by pressing [Single], the acquisition
stops (and you can Pan and Zoom the waveform).
In either Auto or Normal trigger mode, a trigger may be missed if the event occurs
while the pre-trigger buffer is being filled. This may be more likely, for example,
when the horizontal scale knob is set to a slow time/div setting, such as
500 ms/div.
Trigger Indicator The trigger indicator at the top right of the display shows whether triggers are
occurring.
In the Auto trigger mode, the trigger indicator can show:
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