6537 Clock Generation

[ricsenior]

Hi all,

We have a NI PCIe-6537 card, which we're using to stream a large but fixed amount of data to another device. The clock must start with and be syncronous with the associated data and immediately stop when the last sample has been output.

In our current implementation, the clock is generated by driving one of the data lines, this limits the maximum clock rate to 25MHz.

My understanding is that rather than using a data line to generate the clock, we can output the 6537 clock via PFI 4, allowing us to generate data at upto 50MHz. Is there a way to control this output clock such that it starts clocking when data is being output and stops when all data has been output?

Thanks

Ric

[Steve_B]

Hi Ric,

You are correct that you are able to export up to a 50MHz clock on PFI 4. The clock will begin when the task is committed and will continue until the device is reset or until you tell the device to route the clock to an empty string. I found this information in the 6536 and 6537 Help Manual under NI 6536/6537 Help>>NI 6536/6537>>Hardware Architecture>>Clocking>>Exporting a Clock. You would have to reset the device or call the Export Signal VI/DAQmxExportSignal function from software.

From the help:
"If you export the Sample clock, while using Pipelined Sample Clock timing, the device begins exporting the free-running Sample clock during a task commit. Like all other events, when the task uncommits, the Sample clock will still continue to be exported. You can stop the clock signal from being exported by calling the Export Signal VI or the DAQmxExportSignal function with the same signal name but with an empty string ("") as the output terminal and commit the task."

NI 6536/6537 Help
http://digital.ni.com/manuals.nsf/websearch/9467F51FD45E36C1862573B000757F1D