Is USB-6221 suitable for 1 MHz digital waveform?

[bts3063]

I am currently evaluating the use of NI USB-6221 for a specific project. For this project, I need to create a digital waveform (8 bits) of duration 200 us with a 1 us hardware-timed update. In reading the USB-6221 documentation, the following points are unclear to me:

- There is a "global spec" of 250 ks/sec. Is this only for analog input, or does this apply to digital I/O as well?
- Am I restricted to using an external source for my 1 MHz clock, or is there a way for me to generate the 1 MHz clock internally?

Your help is greatly appreciated.

[stilly32]

Hi,

Check out the specifications on page 6. For the "DI or DO Sample Clock Frequency" you'll see 0 to 1 Mhz - so this is not limited by the AI sample rate. You'll also see a spec for "DO or DI Sample Clock Source" - basically for 1 Mhz you'll want to use one of the internal counters to generate a 1 Mhz pulse train and use that as the clock for your digital ouput.

If you have further questions, I would contact NI from www.ni.com/contact and talk to a sales representative - they are great at making sure that you have taken every consideration into account and have the correct HW for the application. From your details, it sounds like the USB-6221 should be fine, though if you think there may be a possibility of needing to go faster on the DO, I would consider the USB 6251 (0-10MHz on DO).

Hope this helps,

Andrew S

National Instruments