Hi,
Using the 80 MHz timebase, you can get generate frequencies f_x = 80 MHz / i, i =4, 5,.....The closest you can get this devided timebase is 432.29 Hz I believe. The timebase stability is 50 ppm which means that the accuracy in this case would be +/- 0.02 Hz.
Hope it helps.
Pelle S
Account Manager
National Instruments Sweden