ADLINK Technology NuDAQ PCI-9812/10 User Manual

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ADLINK Technology NuDAQ PCI-9812/10 User Manual Manual pdf 37 page image

Operation Theorem • 295.3.3 Trigger ModesSoftware-Trigger AcquisitionThis trigger mode does not need any external trigger source. Thetrigger event occurs when you call _9812_AD_DMA_Start( )function to start the operation.Post-Trigger AcquisitionUse post-trigger acquisition in applications when you want to collectdata after a specified trigger event. The trigger can either be anexternal analog trigger or digital trigger.DMA start External trigger Event DMA StopPre-Trigger AcquisitionUse pre-trigger acquisition in applications where you want to collectdata before a specified trigger event. The trigger can either be anexternal analog trigger or digital trigger.The data acquisition starts when DMA operation starts. Theoperation stops when the external trigger event occurs. If theexternal trigger occurs before the specified count of data (specifiedby _9812_AD_DMA_Start( ) function, refer to section 6.2.3) is read,the number of retrieved data will be fewer than the specified count.However if the external trigger occurs after the specified count ofdata is read, the program only samples the specified count of data.DMA start External trigger EventAcquire N A/D dataafter trigger eventTimeAcquisition StartAcquire A/D databefore trigger event TimeAcquisition Stop