ADLINK PXI-2208 - Manual (Page 56)

44 Operation Theory
Note that if a trigger event occurs when a scan is in progress, the
data acquisition won't stop until the scan completes, and the
stored M scans of data includes the last scan. Therefore, the first
stored data will always be the first channel entry of a scan (that is,
the first channel entry in the Channel Gain Queue if the number of
entries in the Channel Gain Queue is equivalent to the value of
NumChan_counter), no matter when a trigger signal occurs, as
illustrated in Figure 16, where M_counter = M =3,
NumChan_counter = 4, PSC_counter = 0.
Figure 4-5: Pre-trigger (Trigger with scan in progress)
Acquisition_in_progress
Scan_start
AD_conversion
Scan_in_progress
(SSHOUT)(pin8 on CN2)
(M_counter = M = 3, NumChan_counter =4, PSC_counter=0)
Aquired data
Acquired & stored data
(M scans)
Operation start
Trigger
Data acquisition
won’t stop until a
scan completes
Trigger occurs