21
Counter Name
Length
Valid value
Description
Scan Intrv
24-bit
1 - 16777215
Scan Interval Counter
This counter is a TIMEBASE divider to the
achieve equivalent sampling rate of digitizer.
The equation is:
Sampling rate = TIMEBASE / Scan Intrv The
value of TIMEBASE depends on the card
type. Take the PCI/PXI-69846 (40 MS/s)
as an example, Scan Intrv = 1 results in 40
MS/s and Scan Intrv = 2 results in 20 MS/s,
and so on.
Data Cnt
29-bit 1 - 536870911
Data Counter
You can specify the amount of data to
be acquired. The digitizer equips 512MB
memory to store acquired data.
trig Delay Ticks
32-bit
1 - 536870911
Delay Trigger Counter
The delay trigger counter is used to indicate
the time between a trigger event and the
start of an acquisition. The unit of a delay
count is the period of the TIMEBASE. For
PCI/PXI-69816, the unit is 100ns and for
PCI/PXI-69846 the unit is 25ns. Refer to
section 3.5.4 for more detail.
Re Trg Cnt
24-bit
1 - 16777215
Re-Trigger Counter
The digitizer can enable re-trigger to accept
multiple triggers. Refer to section 3.5.5 for
more detail.
Table 3-1: Basic Counters
Refer to Figure 3-4 and use post trigger mode as an example. When a trigger is accepted by
digitizer, the acquisition engine of the digitizer will begin to acquire data that coming from
ADC and store these sampled data to onboard memory. The sampled data is generated
continuously at the rising edge of timebase according to the scan interval counter setting.
While sampled data reaches customer specified number, in this example is 256, the
acquisition ends. Once the acquisition ends, acquisition engine begins to send request to
system and transfer data from onboard memory back to system by DMA.
