ADLINK Technology PXIe-9834, User Manual, Page: 49 / 65

Operations 37
PXIe-9834
3.6 Acquisition Timing Control
The PXIe-9834 commences acquisition upon receipt of a trigger
event originating with software command, external digital trigger,
analog trigger, PXI_STAR, PXI Trigger Bus, or PXIe_DSTARB.
Trigger mode allows collection of data when the trigger event
occurs, depending trigger mode type. timebase provides an
essential timing clock for ADC operation. To achieve different
acquisition timing, more configurations may be required.
Using Post-Trigger mode as an example, as shown in the follow-
ing figure, when a trigger is accepted by the digitizer, the acquisi-
tion engine commences acquisition of data from ADC and stores
the sampled data to onboard memory. When onboard memory is
not empty, data will be transferred to system memory automati-
cally via the DMA (Direct Memory Access) engine. The sampled
data is generated continuously at the rising edge of timebase
according to the scan interval counter (ScanIntrv) setting. When
sampled data reaches a specified value (DataCnt), acquisition is
complete.
Figure 3-13: Varying Sampling Rates via Scan Interval Counter
Timebase
DATA
sampled
D1
Acquisition
In Progress
Trigger
Acquisition starts right after this clock edge
D1
ScanIntrv = 1
D2 D3 D4 D5 D6 D7 D8 D9 D10
D2
D1
ScanIntrv = 2
ScanIntrv = 3
D4
D6 D5 D3
D2 D3 D5