Check the documentation on GETDATA.
data = getdata(obj) extracts the number of samples specified by the
SamplesPerTrigger property for each channel contained by obj. data is an
m-by-n array where m is the number of samples extracted and n is the number
By default, you'll get one trigger's worth of data. You can either call
GETDATA repeatedly, or call getdata(obj,samples) to extracts the number of
samples specified by samples for each channel contained by obj. Note that
GETDATA separates triggers with a NaN.