ADLINK Technology DAQ/PXI-20 Series, User Manual

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34 Operation Theory
post scan count is 0 because there is no sampling after the trig-
ger event in pre-trigger acquisition. The total stored amount of
data = Number of enabled channels * M_counter.
Figure 4-4: Pre-trigger (trigger occurs after at least M scans acquired)
Note that If the trigger event occurs when a conversion is in
progress, the data acquisition won’t stop until this conversion is
completed, and the stored M scans of data include the last scan,
as illustrated in Figure 4-5, where M_counter = M =3,
PSC_counter = 0.
Figure 4-5: Pre-trigger scan acquisition (trigger occurs when a conversion
is in progress)
When the trigger signal occurs before the first M scans of data are
con-verted, the amount of stored data could be fewer than the
originally speci-fied amount M_counter, as illustrated in Figure 4-6.