PCI 6534 Clock Frequency

[thrillho]

I am using a PCI 6534 card and want to output a clock signal at 345.6 kHz (in addition to several digital waveforms).  My understanding is that the PCI 6534 has an onboard 20 MHz clock, so when I use the DAQmx timing VI "Sample Clock" and set the rate to 345.6 kHz, the actual rate is based off the 20 MHz clock to be 344.828 kHz.

20M / 345.6k (desired rate)= 57.87

20M / 58 = 344.828k (actual sample rate)

I have hardware that I am trying to send the clock to (and data) that needs to be exactly 345.6 kHz.  I have tried using an external clock connected to the PFI6 port and then routing it to either another PFI port or a digital output port, but I get the error message "Export of sample clock is supported by this device only when the Sample Clock Source is OnboardClock". Error Code -200891.

Is there any way I can send the clock and data at exactly 345.6 kHz with the PCI 6534 card?  Is it possible to use an external clock to do this?

Thanks.

[apatil@VTITAN.COM]

Yes, That is possible. Use the Implicit option for the sampling clock VI. give exact frequency rate which you required.

I hope you created the counter output task with frequency.

Good luck...

[thrillho]

The PCI-6534 does not contain a counter, it is strictly a digital I/O card.  If I create a counter task from another card and export the signal to the PCI-6534 digital output port I still am limited by the card's 20 MHz oscillator and the output is 344.828 kHz instead of 345.6 kHz.

[A_Donfigulation_Error_Has]

Hi thrillho,

I looked at the routing map for the PCI 6534, and you should be able to use the PFI6 and PFI2 lines for the Dig0/SampleClock in your code. I know that you are wanting to export the sample clock and this seems to only be possible when you are using internal clocking.

Since you have to bring the PCI 6534 an external clock rate of 345.6KHz, such that the PCI 6534 can generate this clock (with data) back to your DUT, this seems a bit redundant. Could you just tap into the source of your 345.6KHz with your DUT and PFI line such that you can still write out data at the same rate? It doesn't make sense to me why you would need to bring the clock in to export it out, especially when the PCI 6534 only has a 68-pin connnector on the front.

Jason L.

[thrillho]

Jason,

Thanks for your reply, I was able to use the external clock to clock my digital output data without routing it internally.  However, I also have a digital input task that needs to be time correlated to the digital output task.  Without the external clock connected, I can just use the "Start Digital Edge" VI with the same trigger for the input and output task to ensure they start at the same time.  However, with the external clock connected to PFI2, LabVIEW gives me an error when I try to use one of the onboard triggers.  I have tried to use an external trigger, but I also get errors when attempting to trigger both the digital output and digital input tasks off the same source.  Thoughts?

Thanks,

[A_Donfigulation_Error_Has]

Hi Thrillho,

What are the exact error messages that you see in either case? I think this will lead to more clues as to what is going on. If you could provide screenshots of the error message, that would be great.

Jason L.