DAQ VXI-SC-1102 Manual de Instruções descarregar pdf (Página 25)

Chapter 1 MIO and AI Devices

DAQ Hardware Overview Guide 1-8 www.ni.com

output channels depend on the value of the numbers in the buffer, the level

of the reference voltage, and the polarity setting.

Note (E Series devices on VXI, ISA, PCI, PXI and 1394 buses only) NI-DAQ can use

either DMA or interrupt service routines to generate waveforms on the analog output

channels. By default, NI-DAQ uses DMA because DMA is simply more efficient. If you

prefer to reserve the DMA channels for the Data Acquisition functions or for other devices

in the system, call

Set_DAQ_Device_Info, described in the NI-DAQ Function Reference

Online Help, or the

Set_DAQ_Device_Info.vi in the LabVIEW DAQ Online Reference

to force NI-DAQ not to use DMA for waveform generation.

E Series Waveform Generation Using Onboard

Memory

All E Series devices with analog output FIFOs support FIFO mode

waveform generation. In this mode, waveform data is transferred to the

onboard DAC FIFO memory only once. These values are then cycled

through to generate the waveform continuously or for a finite number of

iterations. No interrupt service or DMA operation is required to transfer

more data to the device during waveform generation.

The following conditions must be satisfied to use FIFO mode waveform

generation:

• One cycle worth of waveform data can be held entirely on the device

DAC FIFO memory.

• Double-buffered waveform generation mode is disabled.

• The number of cycles to generate can be infinite, denoted by the

value 0, or between 1 and 16,777,216 inclusive.

There are two variations possible in FIFO mode waveform generation:

• Continuous cyclic waveform generation—An onboard counter or an

external signal provides the update pulses. Once started, the waveform

generation continues until you call the clear function to stop the

waveform.

• Programmed cyclic waveform generation—An onboard counter or an

external signal provides the update pulses. A separate onboard counter

terminates the waveform after a finite number of cycles has been

generated.

Refer to your DAQ device manual to determine the size of the analog output

FIFO and for more information on waveform generation.

1 2 ... 20 21 22 23 24 25 26 27 28 29 30 ... 150 151

Sem comentários

DAQ VXI-SC-1102 Manual de Instruções Página 25