HP 54645A User's And Service Manual page 82

Example Suppose you have a pulse train where one of the pulses is of constant
duration (4 s) and all other signals of interest are repeated with that pulse
train, as shown in the following figure.
Figure 3-5
Pulse Train with Constant Duration Pulse
To trigger the oscilloscope on that pulse, you can use one of the trigger setup
in the following table:
Source
Pattern 1
Glitch on channel 1
Example
Suppose you have a state machine whose three outputs, Q0 through Q2,
output the decimal sequence 0-1-6-0-6-1. Q2 is the most significant bit, as
shown in the following figure.
Figure 3-6
Sequential Output from State Machine
If you try to trigger on any of the single output patterns 0, 1, or 6, the display
will not be stable. However, you can use the "Then" operator to trigger on the
sequence of pattern "0" followed by pattern "1." If Q2, Q1, and Q0 are
connected to channels D2, D1, and D0 respectively, you can use the setup in
the following table to trigger the oscilloscope.
Triggering HP 54645A/D Oscilloscopes
To define an advanced pattern trigger
Operator and Pattern/Edge
Parameters
Duration > 3.9 s H on channel 0, others don't care
Duration > 3.9 s,
< 4.1 s
3-23