Hi xshang,
The USB-6501 does not have the capability to generate a hardware timed pulse train. However, a pulse train could be produced with a digital line and some software timing. It would involve toggling a digital line within a loop structure. In this situation, the pulse train would of course be software timed, and at the mercy of the operating system.
As an alternative device, our USB-6210 would be a good recommendation. It is a member of our M Series class of data acquisition cards which can output a hardware timed pulse train via the onboard clock source. For more information on this product, please visit the product page here.
Regards,
Andrew W
National Instruments
