ADLINK PCI-9810 - Manual (Page 46)

34 Operation Theory
Trigger Modes
X Software-trigger acquisition
This trigger mode does not require any external trigger source.
The trigger event occurs when the _9812_AD_DMA_Start( )
function is called to start the operation.
X Post-trigger acquisition
Use post-trigger for applications where data needs to be
collected after a specified trigger event. The trigger can either
be an external analog trigger or digital trigger.
Figure 5-1: Post-trigger Acquisition
X Pre-trigger acquisition
Use pre-trigger to collect data before a specified trigger event.
The trigger can either be an external analog trigger or digital
trigger. Data acquisition starts when DMA operation starts. The
operation stops when the external trigger event occurs. If the
external trigger occurs before the specified count of data is
read (Specified by the _9812_AD_DMA_Start( ) function.
Refer to section 6.2), the amount of retrieved data would be
less than the specified count. However, if the external trigger
occurs after the specified count of data is read, the application
only samples the specified count of data.
Figure 5-2: Pre-trigger Acquisition