Agilent Technologies 54621A Programmer's Manual page 3

Capture
Once you initialize the oscilloscope, you can begin capturing data for
analysis. Remember that while the oscilloscope is responding to
commands from the controller, it is not performing acquisitions. Also,
when you change the oscilloscope configuration, any data already
captured will most likely be rendered.
To collect data, you use the :DIGitize command. This command clears
the waveform buffers and starts the acquisition process. Acquisition
continues until acquisition memory is full, then stops. The acquired data
is displayed by the oscilloscope, and the captured data can be measured,
stored in trace memory in the oscilloscope, or transferred to the
controller for further analysis. Any additional commands sent while
:DIGitize is working are buffered until :DIGitize is complete.
You could also put the oscilloscope into run mode, then use a wait loop
in your program to ensure that the oscilloscope has completed at least
one acquisition before you make a measurement. Agilent does not
recommend this because the needed length of the wait loop may vary,
causing your program to fail. :DIGitize, on the other hand, ensures that
data capture is complete. Also, :DIGitize, when complete, stops the
acquisition process so that all measurements are on displayed data, not
on a constantly changing data set.
Analyze
After the oscilloscope has completed an acquisition, you can find out
more about the data, either by using the oscilloscope measurements or
by transferring the data to the controller for manipulation by your
program. Built-in measurements include frequency, duty cycle, period,
and positive and negative pulse width.
Using the :WAVeform commands, you can transfer the data to your
controller. You may want to display the data, compare it to a known good
measurement, or simply check logic patterns at various time intervals in
the acquisition.
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