Speed of Digital I/O not specified in Manual?

[dhruvish]

I knwo that the Min and Max sampling is 1 and 5 MS/s. But, is it also true for Digital I/O. If not what are the rates and If I use all Diff. Inputs and Digital I/O, what rates can be sustained? Is there any problem with the allocated buffer on the RAM?
Please answer ASAP

[Doug_Norman]

You will get better help if you provide more details. Are the min and max sampling rates you refer to for analog input? What board do you have? For many boards the digital lines are software timed, so your PC speed is a factor.

Regards,
Doug Norman

[dhruvish]

I should have given details. I am talking about NI PCI 6110 board. The max the board can run is 20MHz. There are Digital and Analog I/Os. Can I run one pin on X rate and the other on Y rare? I want to run Analog and Digital I/O with different speeds. I think I can achieve it by using PFI pins, but I am not sure. Could those be used as timing signals for Digital I/O?

And again, what is maximum Digital I/O speed that can be achieved on the board, which simultaneously samples analog inputs too. Any buffer problem (On-Board) or RAM problem?

Attempt to solve any of these Questions are appreciated.

[Ames]

dhruvish,

The maximum sampling rate (analog input) is 5MS/s for the PCI-6110. The maximum update rate (analog output) is 4MS/s. The digital I/O port is not hardware timed for the PCI-6110, so there is no speed associated with it. The rate of your digital output will be completely software timed.

You can definitely run your analog and digital operations at different speeds.

I am not sure I understand your statement about PFI pins. From what you have explained thus far there is no need to use any of the PFI pins. The PFI pins are in general used to access external signals or export internal signals.

Ames
Applications Engineering
National Instruments

[dhruvish]

From your comments, can't I use hardware clock for driving my Digital I/O. Here is the scenario of my application.

I use 20 MHz on-board generated clock form pin GPCTR_OUT1. I use that to supply clocks to other boards. I divide the 20 MHz clock externally and generate 5 MHz and 1.25 MHz. I want to drive my 6110 board Analog I/O @ 5 MHz and Digital I/O @ 1.25 MHz. So, the only way I can think this can be achieved is by feeding externally generated 5 MHz and 1.25 MHz to two PFI pins and use those as clocks to Analog and Digital I/O respectively.

Let me know if that's going to work. I dont want software clock for Digital I/O.

Thanks a lot for your help.

[Ames]

dhruvish,

Unfortunately the PCI-6110 only has software timed digital I/O. Only the PCI-6115 and PCI-6120 (as well as our 653x boards) have hardware timed digital I/O. You can try using the timed loop (new to LabVIEW 7.1 & NI-DAQmx) and use the sample clock from another task or the output of a counter as the timing. This isn't a hardware timed solution, but it will tie your software timed digital I/O to a hardware signal. The digital output rate will still be tied to how fast the timed loop is able to iterate on your specific computer.

Ames
Applications Engineering
National Instruments