JYTEK NuDAQ PCI-69222, Руководство пользователя

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40 Operation Theory
PCI-69223 operates in waveform generation mode, the
waveform patterns are stored in FIFO with 512 samples.
Waveform patterns larger than 512 samples are also supported
using bus-mastering DMA transfer via the PCI controller. Data
format in FIFO is shown in Figure 4-9.
Figure 4-9: FIFO Data In/Out Structure
DMA transfers data according to channel order. Figure 4-10 shows
DA channel 0 to channel 3 data, while channel 2 is disabled.
Figure 4-10: Waveform Generation for Three Channels Update
With hardware-based waveform generation, D/A conversions
are updated automatically by the FPGA rather than by the
application software. Compare with the conventional software-
based waveform generation, the precise hardware timing
control guarantees non-distorted waveform generation even
when the host CPU is under heavy loading.
NOTE When using waveform generation mode, both DACs
must be configured in a single mode. However, any indi -
vidual DAC can be disabled.
Waveform Generation Clock Source
When the onboard DAC receives a conversion clock signal, it
will trigger a D/A update. The update clock of PCI-69222/PCI-
69223 may come from three different clock sources: internal
hardware timer, general purpose input channel (GPI 0 ~ GPI
7), or SSI (system synchronization interface).