How can I write handshaked Data to an external device using LAB-PC+?

[kaktus]

Hi experts

I want to write data into an external DAC via the LAB -PC+ Card. The problem is that I must generate with this external DAC a sine or cosine wave. I have to update the internal DAC data registers every constant time steps. From my point of view I can use the internal timer(8253) to generate a clk signal for the handshaking and for the necessary data clk of the DAC. With this clock (maybe rising edge) I want to update the date at the DAQ Port.

Now the questions:

What mode should I set of the card (mode 1 or mode 2)?
which signal should I connect to the output of the 8253 (ACK,REQ.STB,.......)?
How fast can I set the clock frequency?
Has anybody other solutions?


thanks a lot

kaktus

PS.: the usage of the internal DAC is not possible for me..

[Geneva L.]

If you just want to output one pulse, you can use mode 1, and if you want to generate a continuous pulse train, you can use mode 2. Using two counters, you can generate a finite pulse train. There are examples to do so that come with the NI-DAQ driver software. For instance, with LabWindows/CVI, you can use the 8253generateSquareWave example located in the samples >> daq >> ctr directory. LabVIEW has the examples in the Examples >> daq >> counter >> 8253 directory.

The output from the card will be the OUT pin of whatever counter (B0, B1, or B2) you are using. If you use counter B0, the maximum internal timebase is 2 MHz, and you can divide it down by any integer between 2 and 65,535. Or you can input a signal to counters B1 and B2 using the CLK pins.

You can
find this information in the Lab-PC+ User Manual, from the http://www.ni.com/manuals page or searching the Technical Resources as the http://www.ni.com/support page.

Regards,

Geneva L.
Applications Engineer
National Instruments
http://www.ni.com/ask