Tektronix 222 Operator's Manual page 89

Making Measurements-222 DSO Operators
8. When the single sequence has been triggered and completed,
another acquisition is started when the
button is pressed again
to rearm the trigger circuit.
NOTE
Changing a control that affects the acquisition
(VOLTSIDIV, SECIDIV, etc.) also reinitializes the
SSEQ, and a new acquisition is done.
In ROLL mode, SSEQ Trigger Mode is very useful for capturing an
event that occurs either randomly or infrequently. If the event is also
very narrow, use the ENV acquisition mode as well. ENV acquisition
mode samples the signal at the maximum sampling rate and displays
the peaks found. Initialize the SSEQ and let the oscilloscope watch
for the event. Data will be continually acquired up to the trigger point.
When the trigger event happens, the remaining data needed to fill the
rest of the display is acquired. At that point the acquisition is halted
and the waveform (with triggering event captured) remains displayed
until reinitialized.