Trigger
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Note:
9.3
Trigger Mode
The oscilloscope’s trigger mode includes Auto, Normal, and Single. Trigger mode affects the way in which the oscilloscope
searches for the trigger.
After the oscilloscope starts running, the oscilloscope operates by first filling the pre-trigger buffer. It starts searching
for a trigger after the pre-trigger buffer is filled and continues to flow data through this buffer while it searches for the
trigger. While searching for the trigger, the oscilloscope overflows the pre-trigger buffer and the first data put into the
buffer is first pushed out (First Input First Out, FIFO).
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.
To select the trigger mode, press the key corresponding to the desired mode.
Auto
If the specified trigger conditions are not found, the triggers are forced and acquisitions are made so that signal activity
is displayed on the oscilloscope.
Auto
trigger mode is appropriate when:
•
Checking DC signals or signals with unknown levels or activity.
•
When trigger conditions occur often enough that forced triggers are unnecessary.
Normal
Triggers and acquisitions only occur when the specified trigger conditions are found. Otherwise, the oscilloscope holds
the original waveform and waits for the next trigger.
Normal
trigger mode is appropriate when:
•
Only specific events specified by the trigger settings are to be acquired.
•
Triggering on an infrequent signal from a serial bus such as I2C, SPI, CAN, LIN, etc. or another signal that arrives
in bursts.
Normal trigger mode stabilizes the display by preventing the oscilloscope from auto-triggering.
Single
The oscilloscope waits for a trigger and displays the waveform when the trigger condition is met, the acquisition is stopped
when the trigger conditions are met.
Single
trigger mode is appropriate when:
•
Capturing a single event or a periodic signal.
•
Capturing a burst or other unusual signals.
