Synchronizing two usb 6289 using a counter

[Rsilva]

Hi folks!

I'm trying to sync 2 USB-6289 M Series boards using a counter.

I searched the forum and have already seen the tutorials :

"M Series Synchronization with LabVIEW and NI-DAQmx - Developer Zone - National Instruments"

"Synchronizing USB Data Acquisition - From One Device to Multiple Systems - Developer Zone - National Instruments"

"Timing and Synchronization Features of NI-DAQmx - Developer Zone - National Instruments" .

However I still have some doubts (hence the post ) regarding the following points:

- if i want to use the counter as trigger for both boards do I have to export it to an PFI line and connect to the other board?

- do I do the same with clock signal (export it to the other board using an PFI line) or using the same frequency for both the counters is enough? Or both? 

- do I use the same value for the frequency in the counter and both clocks?

Hope someone can help me out.

If possible, point to some examples or posting would be great.

Thanks in advance for the help!

Cheers! 

[Kevin_Price]

You will need to connect wires between the boards to make sure that the same trigger and clock signals are used by both.  Depending on where those signals come from, you may or may not need to explicitly export them to PFI lines.  For example, if you are generating a pulse or pulse train, the signal will be available at the counter's output terminal pin without any need to explicitly export it.

It is not enough to have each one generate its own internal clock even if you specify the same freq.  The on-board oscillators have tolerances and the resulting frequencies will not be exactly the same.  They're spec'ed to be accurate to 50 parts per million.

I'm not sure exactly what you mean by the question, "do I use the same value for the frequency in the counter and both clocks?".  Very likely the answer you need is yes, but it's important to realize that it's the wiring connection which causes actual real-life sync whereas using the same freq value in the software configs is more of a convenience and good practice. 

-Kevin