Operating Basics
TDS5000B Series Quick Start User Manual
39
Triggers
This section contains concepts and procedures for using the trigger system. Detailed information is available in
the online help.
Triggering Concepts
Trigger Event
The trigger event establishes the time-zero point in the waveform record. All waveform record data are located
in time with respect to that point. The instrument continuously acquires and retains enough sample points to fill
the pretrigger portion of the waveform record (that part of the waveform that is displayed before, or to the left
of, the triggering event on screen). When a trigger event occurs, the instrument starts acquiring samples to
build the posttrigger portion of the waveform record (displayed after, or to the right of, the trigger event). Once
a trigger is recognized, the instrument will not accept another trigger until the acquisition is complete and the
holdoff time has expired.
Trigger Types
Edge triggers are the simplest a nd most commonly used trigger type, used with both analog and digital signals.
An edge trigger event occurs when the trigger source passes through a specified voltage level in the specified
direction (rising or falling signal voltage).
Pulse triggers are special-purpose triggers that are primarily used with digital signals. The following types of
pulse triggers are available: Glitch, Runt, Window, Width, Transition, and Timeout. Pulse triggers are available
on the main trigger only.
Logic triggers are special-purpose triggers that are primarily used with digital logic signals. Two of the types,
Pattern and State, trigger the instrument based on the Boolean operator you select for the trigger sources. A
third type, Set up and Hold, triggers when Data on one trigger source changes state within the setup and hold
times that you s pecify relative to a Clock on another t rigger source. Logic triggers are available on the main
trigger only.
Communication triggers (available only with Option SM) are used on communication signals. Mask testing
automatically uses Communication triggers.
Video triggers are used to trigger t he instrum ent on specified f ields or lines of a video signal. You can use one
of several preset video signal formats or set a custom format.
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