Give digital code to pci 6251

[Tesi89]

I want to test dac's performance in NI 6251 (PCI bus) .How  can I give the digital code to dac input?

PS I have used DaQmx software but I can programme only voltage value. I need test the analog output corresponding

to a particular digital code

[jasonv]

You can improve performance by using either unscaled or raw writes.  By changing the polymorphic type of the DAQmx Write VI, you can access these lower-level write functions.