Hello;
If you input a zero as the iterations parameter, the NI-DAQ driver will probably hang your computer.
The way to keep generating the same waveform on a output channel, is to set up a continuous Analog Output operation, and pass the same array of point (the array that will determine the waveform), and keep running the Analog Output task in a loop.
That will make the same array of point to be generated over and over again, which will accomplish what you need.
Hope this helps.
Filipe A.
Applications Engineer
National Instruments