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SDS3000X HD Series Digital Oscilloscope User Manual
76 int.siglent.com
16 Trigger
16.1 Overview
The oscilloscope only acquires waveforms of interest (i.e. the ones that satisfy the trigger condition)
and aligns all trigger events at the trigger position to form a stable waveform display. The trigger is
one of the most important features of an oscilloscope since we can only analyze a signal that we can
trigger reliably and stably.
The trigger position is movable on the display. The following diagram shows the structure of the
acquisition memory. The acquisition memory is divided into pre-trigger and post-trigger buffers and
the boundary between them is the trigger position. Before the trigger event arrives, the oscilloscope
fills the pre-trigger buffer first, and then continuously updates it in FIFO mode until the trigger event
arrives. After the trigger event, the data fills the post-trigger buffer. When the post-trigger buffer is full,
an acquisition is completed.
Below is the definition of the states in the process of filling the acquisition memory:
Arm: The pre-trigger buffer is not full, and the oscilloscope does not respond to any trigger events.
Ready: The pre-trigger buffer is full, and the oscilloscope is waiting for the trigger event.
Trig’d: A trigger event is detected and the oscilloscope starts to fill the post-trigger buffer.
Trigger settings should be based on the features of the input signal. For example, a sine wave with a
repeatable period can be triggered on the rising edge; for capturing hazards in a combinational logic
circuit, the pulse trigger can be set. You need to have some knowledge of the signal-under-test to
quickly capture the desired waveform.
Pre-trigger Buffer
Post-trigger Buffer
Trigger Event
Acquisition Memory
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