400Khz square wave

[sadeghi]

I'm using pxi-6221. i see that the pulse frequency generation can only be a 4bit (1-16) division of 10Mhz or 100Khz, which cannot prodoce a 400Khz square waveform. Is there anyway to create the 400Khz square waveform with this card?

[Kevin_Price]

I don't have that specific board, but I don't think the counters are limited to 4-bit divisors of the internal timebases.  I've used much bigger divisors on other M-series boards.  Try one of the shipping examples for counter output -- I expect you'll be able to produce a 400 kHz pulse train just fine.

-Kevin P.

[sadeghi]

Thanks for the reply. Please let me know how you were able to use more than 4 bits for dividing the base frequencies. I've tried generating a pulse train from test panel of measurement & automation as well as the ni shipped example. being limited to 4 bits, the frequency skips between 100kHz and 625kHz. I see the same specification for the more expensive M series card on page 10 of the following:

http://www.ni.com/pdf/manuals/371292e.pdf

Please let me know if there is a way to have this card generate a 400kHz pulse train.

Thanks,
Sam

[Kevin_Price]

Ok, I see now.  I was thinking in terms of the "General-Purpose Counter/Timers" on that same page.  The frequency generator you're talking about does indeed show the limits you described. 

If they aren't already tied up in your app, you can still use one of the counter/timers to generate a 400 kHz TTL square wave.  You should be able to do this in MAX -- when you tried, were you generating with a counter?  Or some other way?

If I get a chance, I'll post a very simple example using Ctr0 to generate at 400 kHz.

-Kevin P.

[sadeghi]

Many thanks for the advice. It seems like the counter line is capable of outputting 400Khz but not the freq. out line. Since I needed the signal on PFI 14, I had to make a small addition to the ni shipped example to route the signal to PFI 14 while generating the desired frequency on one of the counter lines, which would be out of commission for the duration of this pulse train generation.