ADLINK cPCI-9116 - Manual (Page 50)

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• Operation Theory
Acquisition_in_progress
Scan_start
AD_conversion
Scan_in_progress
(SSH_OUT)(pin47)
(M_counter = M = 3, DIV_counter=4, SC_counter=0)
Aquired data
Acquired & stored data
(M scans)
Operation start
ExtTrg(pin46)
Figure 10: Pre-trigger (trigger occurs after M scans)
Note: If an external trigger event occurs when a scan is in progress, the data
acquisition won’t stop until this scan completes, and the stored M scans
of data include 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 DIV_counter), no matter when the
trigger signal occurs, as illustrated in Fig 11, where M_counter = M =3,
DIV_counter = 4, SC_counter = 0.
Acquisition_in_progress
Scan_start
AD_conversion
Scan_in_progress
(SSH_OUT)(pin47)
(M_counter = M = 3, DIV_counter =4, SC_counter=0)
Aquired data
Acquired & stored data
(M scans)
Operation start
ExtTrg(pin46)
Data acquisition
won’t stop until a
scan completes
Trigger occurs
Figure 11: Pre-trigger (trigger with scan is in progress)