HP 54645A User's And Service Manual page 73

Triggering HP 54645A/D Oscilloscopes
Trigger types
Specifying a Logic Threshold
You can specify a threshold for the logic channels. See "To change the logic
threshold for input signals" in chapter 4 for information about setting a
threshold on the HP 54645D.
Advanced Pattern Trigger
In advanced pattern trigger, you define a maximum of two pattern and
edge sources that are combined with a variety of operators to form the
complete trigger specification.
Advanced pattern trigger is best when the events you want to capture are
defined by a series of waveform events in the system, and neither pattern
mode nor edge mode are capable of clearly resolving the necessary sequence.
For example, suppose the events you want to capture are defined by a
pattern with a certain minimum duration, or by a pattern followed by another
pattern. Advanced pattern trigger gives you this and more.
Figure 3-4
HP 54645D Advanced Pattern Triggering Overview Menu
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