HP 54645A User's And Service Manual page 30

Front-Panel Overview
Important Oscilloscope Considerations
Delayed Sweep
Delayed sweep on the HP 54645A/D is a simultaneous display of the
waveform at two different sweep speeds. Because of the deep memory in the
MegaZoom technology, it is possible to capture the main display at 1 ms/div,
and redisplay the same trigger in the delayed display at any desired faster
time base.
There is no limit imposed on the zoom ratio between the main and delayed
displays. There is, however, a useful limit—when the samples are spaced so
far apart that they are of little value. See the chapter "MegaZoom Concepts
and Oscilloscope Operation" for more information about delayed sweep and
time reference.
Post Acquisition Processing
In addition to changing display parameters after the acquisition, you can do
all of the measurements and math functions after the acquisition.
Measurements and math functions will be recalculated as you pan and zoom
and turn on and off channels. As you zoom in and out on a signal, you affect
the resolution of the display. Because measurements and math functions are
performed on displayed data, you affect the resolution of functions and
measurements.
The two scope channels are always acquired, so you can turn them on and
look at them even if they were off during the acquisition. See "To turn digital
channels off (HP 54645D)" later in this chapter for more information about
the combination of events and displayed channels.
The XY horizontal display mode changes the oscilloscope display to
volts-versus-volts. The Roll horizontal display mode causes the waveform to
move across the screen from right to left.
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