ADLINK PXI-2022 - Manual (Page 46)

38 Function Block and Operation Theory
The trigger event occurs after the specified amount of data has
been acquired. However, if the trigger event occurs before the
specified amount of data has been acquired, the acquisition
engine will ignore the trigger signal until the specified amount of
data has been acquired. Refer to Figure 4-12 for an example.
Figure 4-12: Pre-trigger Mode Operation
4.6.3 Middle-trigger Acquisition
Use middle-trigger acquisition when you want to collect data
before and after the trigger event. The amount of stored data
before and after trigger event can be set individually (M and N
samples), as illustrated in Figure 4-13.
Figure 4-13: Middle-trigger Mode Operation
Please note that trigger event can only accepted when the speci-
fied amount of data has been acquired (M samples). If the sam-
pled data is not enough, the trigger event will be ignored.
Time
Operation start
Acquisition start
Trigger
Data
Trigger Event Occurs
Acquisition stop
Begin to transfer data to system
N samples
X samples have been acquired
before trigger occurs, where
X<N
Trigger signals that occur before
the specified amount of data has
been acquired will be ignored.
Time
Operation start
Acquisition start
Trigger
Data
Acquisition stop
Begin to transfer data to system
N samples M samples
Trigger event occurs