ADLINK USB-2405 - Manual (Page 46)

36 Operation
Post-Trigger Acquisition Mode (no retrigger)
Post-trigger acquisition is indicated in applications where data
is to be collected after a trigger event, as shown.
Figure 3-9: Post Trigger without Retrigger
Pre-trigger Acquisition (no retrigger)
Collects data before the trigger event, with acquisition starting
once specified function calls are executed to begin the pre-trig-
ger 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 trig-
ger event by a specified amount, as shown. Note that N must
be equal to or less than 8k samples for all analog input chan-
nels.
Figure 3-10: Pre-trigger Mode Operation (valid trigger only)
Time
ƔOperation
start
Trigger
N samples Data
ƔTrigger Event Occurs
ƔAcquisition start
ƔAcquisition stop
ƔBegin to transfer data to system
Time
ƔOperation start
ƔAcquisition start
Trigger
Data
ƔTrigger Event Occurs
ƔAcquisition stop
ƔBegin to transfer data to
system
N samples
This data is
discarded.
Only acquired N
samples will be
transferred back to
system.