ADLINK USB-2405 - Manual (Page 47)

Operation 37
USB-2405
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 ignores the trigger signal until the specified amount of
data has been acquired, as shown.
Figure 3-11: Pre-trigger Mode Operation (w/ invalid trigger)
Delay-Trigger Acquisition (no retrigger)
Delays data collection after the trigger event, as shown. The delay
count is specified by a 32-bit counter value, such that the maxi-
mum delay count is (2
32
-1) when the minimum delay count is 1.
Figure 3-12: Delay-Trigger Mode Operation
Middle-Trigger Acquisition
Middle-trigger acquisition is indicated when data is to be collected
before and after the trigger event. The amount of stored data
Time
ƔOperation start
ƔAcquisition start
Trigger
Data
ƔTrigger Event Occurs
ƔAcquisition stop
ƔBegin to transfer data to system
N samples
X samples have been acquired
before trigger occurs, where
X<N
ƔTrigger signals that occur before
the specified amount of data has
been acquired are ignored
Time
ƔOperation
start
Trigger
Data
ƔTrigger Event
Occurs
ƔAcquisition stop
ƔBegin to transfer data
to system
N samples
ƔAcquisition start
Delay Time