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12 bit Digital Control of frequency synthesizer

I'm trying to control the frequency synthesizer using 12bit TTL control.
The question is;
How to make the "For Loop" with pre-determined time duration? The whole loop (from 0 to 4095) should be performed during 1.8ms. Is there any way to set the loop time?
Usually, one port has 8 bit, so it is easy to sweep from 0 to 255. In my case, i use 12bit, which needs one port and additional four lines at the other port. Is there any idea how to sweep from 0 to 4095 using 12 bits?
I hope to get an idea from this forum..

Message Edited by yjkim_nsi on 12-01-2005 06:36 PM

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Hi yjkim_nsi-
What type of hardware are you using?  I don't know of a method to precisely time a FOR loop, but if your card features hardware-timed digital I/O then that will be the best method to update values rapidly and with hardware-timed precision.  Based on the type of hardware you're using I can offer more suggestions.
Tom W
National Instruments
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Thanks a lot..

I'm using DAQPad-6507.  What i want to do is to sweep the frequency synthesizer controlled by 12bits TTL signals with  the sweep time of 1.5ms, i.e. from 000000000000 to 111111111111 in binary.


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Hi yjkim_nsi-
The fastest operation you will be able to perform will be to write digital values to both ports within a FOR loop.  Your device works with the Traditional (Legacy) NI-DAQ driver, and it is highly unlikely that you will be able to execute 4096 instructions in only 1.5ms.  This would require an update rate of more than 2MHz, and the DAQpad-6507 is only capable of 60S/s per the user manual.
You really need a board that features hardware-timed operation such as the NI 6534 or an M Series card.
Hopefully this helps-
Tom W
National Instruments
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