ADLINK USB-1210 - Manual (Page 39)

Operation & Calibration 29
USB-1210
Figure 3-10: Middle Trigger
Pre-Trigger Mode
Pre-trigger acquisition is indicated when data is to be collected
before the trigger event. Acquisition commences once specified
function calls are executed to begin the pre-trigger operation, and
stops 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 shown.
Figure 3-11: Pre-Trigger
Post-Trigger or Delayed-Trigger Acquisition Mode with
Retriggering
Post-trigger or Delayed-Trigger acquisition with re-trigger function
is indicated when data is to be collected after several trigger
events. An example is shown, in which N samples of data are
Time
ƔOperation initiates
ƔAcquisition initiates
Trigger
Data
ƔAcquisition stops
ƔData transfer to system begins
N samples M samples
ƔTrigger event occurs
Time
ƔOperation initiates
ƔAcquisition initiates
Trigger
Data
ƔTrigger Event Occurs
ƔAcquisition stops
ƔData transfer to system begins
N samples
This data is
discarded
Only the N acquired
samples are
returned to system