Programming instructions

Chapter 21 671X Devices
DAQ Hardware Overview Guide 21-2 www.ni.com
671 X Waveform Generation Using Onboard Memory
All 671X devices 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
(
WFM_Group_Control) 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.