ADLINK PXI-2022 - Manual (Page 45)

Function Block and Operation Theory 37
4.6 Trigger Modes
There are four trigger modes working with trigger sources to initi-
ate different data acquisition timing when a trigger event occurs.
They are described in this section.
4.6.1 Post-trigger Acquisition
Use post-trigger acquisition when you want to collect data after the
trigger event, as illustrated in Figure 4-10.
Figure 4-10: Post-trigger Acquisition
4.6.2 Pre-trigger Acquisition
Use pre-trigger acquisition to collect data before the trigger event.
The acquisition starts once specified function calls are executed to
begin the pre-trigger operation, and it stops when the trigger event
occurs. If the trigger event occurs after the specified amount of
data has been acquired, the system only stores the data before
the trigger event with specified amount, as illustrated in Figure 4-
11.
Figure 4-11: Pre-trigger Mode Operation
Time
Operation
start
Trigger
N samples Data
Trigger Event Occurs
Acquisition start
Acquisition stop
Begin to transfer data to system
Time
Operation start
Acquisition start
Trigger
Data
Trigger Event Occurs
Acquisition stop
Begin to transfer data to
system
N samples
These data will be
discarded.
Only acquired N
samples will be
transfer back to
system.