How to call DMA function to work with PCI-6602 counter in Labview

[wtaurus]

How can i use the DMA (direct memory access) in the labview? The hardware is PCI-6602 counter/timer board. What's the highest time resolution i can get from DMA? Right now i can run the counter down to 1 micronsecond for a measurement period of 1 second. Is it possible to push further down to 50 ns time resolution?

[DavidMN]

Hi wtaurus,

The PCI-6602 has 3 designated DMA channels.  As long as you access those channels within the task in LabVIEW, you will enable DMA transfer.  Along those lines, DMA is a transfer protocol, and thus does not affect resolution.  The PCI 6602 has an 80 MHz timebase, and as such the maximum resolution you can achieve is 12.5 ns [1/(80*10^6)].  This information can be found in the specifications for the device found here.

David

Applications Engineer

National Instruments

[ds10]

Hi I'm trying to run a similar system. I can get down to 500 ns for a finite collection of points. Are there any examples out there that allow one to get down to 12.5 ns

[DavidMN]

Hi ds10,

Would you please elaborate on your application?  What do you mean you can get down to 500 ns? What type of counter task are you performing? 

Thanks!

[ds10]

Hi David,

I have a 6602 PCI counter/timer and I want to count how many TTL signals i recieve from a photodiode detector within a specified amount of time (bin time). So far I have set up my system as follows: I use an external clock and set it to a rate (1/rate=bin time) and then run a finite collection of edge counts. So far the lowest  bin time I can get before the computer gives me an error is 500 ns. Is it possible to get a lower bin time of 12.5 ns? 50 ns would be really great too! Thanks!

Cheers,

David

[DavidMN]

Hi David,

To achieve the max resolution, the counter source signal (ext clock) will need to be 80 MHz.  What error is the computer throwing?  Thanks!