HP 54645A User's And Service Manual page 81

Triggering HP 54645A/D Oscilloscopes
To define an advanced pattern trigger
Setup rules
Remembering the following rules will make it easier to work with the
advanced triggering capabilities:
Duration operators are valid when only pattern terms are involved.
Duration is not selectable when any edge term is selected as a source.
When you have selected a combination source, like Pattern 1 AND Edge 1,
you cannot directly define the pattern or edge. You must instead select
Pattern 1 as the source, define the pattern, then select Edge 1 as the
source and define the edge. The softkeys change to reflect this.
Understand and relate waveform events to oscilloscope capabilities
The key to setting up a useful waveform display is choosing a known
sequence of waveform events to which you can apply the advanced trigger
capabilities. The HP MegaZoom technology greatly simplifies this task. You
simply press Stop, then pan and zoom through the waveform to find a good
trigger event.
To find these events, you can also ask questions about the waveform, keeping
in mind the capabilities of the oscilloscope.
Does the input data always repeat with respect to a particular waveform's
high or low period of constant duration?
Is there a sequence of waveform events that define the data of interest?
For example, is there a state machine, where the hypothetical sequence
"ac" leads to the events of interest, where "ab" does not?
3-22