Great discrepancies of frequencies of the arbitrary waveform using niFGEN 5401

Hi all!
I'm using niFGEN PCI 5401 to generate an arbitrary waveform defined previously in the Soft Front Panel.
The reference guide says, that I can produce a frequency up to 1 MHz. Does this value refer to the whole waveform or to each sample of the 16384 samples? And how can you explain, that at last the arbitrary waveform takes about 600 ms for one cycle even though the frequency was set to 1 MHz?!
Thanks in advance
Steffi

Hi Jerry!
I generally understood how DDS works, but I'm bemused why the output frequencies do not correspond to the input frequencies?
1.) Yesterday I made a test with the GIVEN Soft Front Panel and even this does not work as it should: If I want a standard square function of 1 MHz, I get a square function of 2,5 Hz! (The same with 100 kHz = 0,25 Hz and 10 kHz = 0,025 Hz.) Where does this factor come from?
2.) This factor also corresponds more or less to the generated arbitrary function in my program: with 1 MHz I get 1,6 Hz, with 100 kHz = 0,16 Hz ...
3.) I thought changing the ratio between pulse length and length of the whole signal period (it's first a square and then a long time zero) I could generate a short pulse anyway accepting the mentioned f
requency discrepancies. E.g.: One period takes 600 ms (although my input frequency is 1 MHz). If I have a ration of 1 (square) to 100 (whole signal) I should get at least a pulse of 6 ms. But the shortest pulse I ever got was about 20 ms.
The IMPORTANT QUESTION: is there a physical limit for generating pulses (e.g. due to the inertia of the DDS method)?
I hope I could explain my problem more precisely. Thank you anyway!
Steffi

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Sincerely,
Marni
PS- Please only post question once.
Attachments:
pulsecount.vi ‏22 KB

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Chris:
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Error -200290 occurred at an unidentified location
Possible reason(s):
The generation has stopped to prevent the regeneration of old samples. Your application was unable to write samples to the background buffer fast enough to prevent old samples from being regenerated.
To avoid this error, you can do any of the following:
1. Increase the size of the background buffer by configuring the buffer.
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http://zone.ni.com/devzone/devzoneweb.nsf/opendoc?openagent&2E07CE2019CCB1D3862568650057930A&cat=99368070225FE073862567E6006C8DD7
You're entering a (slightly) complicated but (very) interesting world. Good job!
Roberto
Proud to use LW/CVI from 3.1 on.
My contributions to the Developer Zone Community
If I have helped you, why not giving me a kudos?

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Great discrepancies of frequencies of the arbitrary waveform using niFGEN 5401

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