ADLINK PXIe-9848 - Manual (Page 33)

Operations 23
PXIe-9848
3.4.1 Post Trigger Mode
Post-trigger acquisition is applicable when data is to be collected
after the trigger event, as shown. When the operation starts,
PXIe-9848 waits for a trigger event. Once the trigger signal is
received, acquisition begins. Data is generated from ADC and
transferred to system memory continuously. The acquisition stops
once the total data amount reaches a predefined value.
Figure 3-7: Post-Trigger Acquisition
3.4.2 Pre-trigger Mode
Collects data before the trigger event, starting once specified func-
tion calls are executed to begin the pre-trigger operation, and
stopping when the trigger event occurs.If the trigger event occurs
after the specified amount of data has been acquired, the system
stores only data preceding the trigger event by a specified
amount, as follows.
Figure 3-8: Pre-trigger Acquisition
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
Data transfer to system begins
X samples
X samples acquired
Despite acquired samples not reaching
N, acquisition stop and X samples in
memory are returned to system.
Specified amount of data,
(N samples)