I am developing a test where I want to use a PXIe-6556 to generate a continuous 100MHz clock on one signal in an 8bit bus. Once the clock is up and running I then need to use an Agilent N3280 PMU to make a DC measurement on another pin on my Device Under Test (DUT). I am using LabView 2012 on a Win 7 system. The PXIe-6556 card is a 200MHz 64Mb version. I am relatively new to LabView and in particular programming the PXIe-6556, having been working at for about 9 months. After some suggestions from colleagues I decided to try using a software script to generate the continous clock. I couldn't attach the VI so I've taken a screenshot of the block diagram and added it here - The script to generate the continuous clock is very short - script dcoinToggle repeat until scriptTrigger0 generate myWfm end repeat end script After the PMU measurement is made I send a software trigger to a previously configured trigger (Trigger0) to stop the script. While this seems to work the clock is not running at a 50% duty cycle like I expected. In fact the duty cycle constantly changes. Here's what the screenshot of the clock signal looks like. In this picture I'm only running at 2MHz just to prove out the concept. You can see that the pulse width is 500ns (or 2MHz), but the duty cycle is not 50%. Just curious if anybody has any ideas why I'm not getting a 50% duty cycle clock? Have I missed something in the setup of the PXIe-6556? Is the concept just wrong? After some more research I'm going to investigate using the NIHSDIO Configure Generation Repeat VI to try to generate the continuous clock. I would use the Abort VI after the DC measurement (not currently added) is made to stop the clock. Here's the block diagram for this VI - I have not tried this yet as I don't get tester time until later this week. Any comments on this method? Any obvious flaws that I have missed? I have the same questions - Have I implemented the concept properly? Is one method better than the other? Thanks in advance for any help.

LabVIEW

PXIe-6556 Continuous Generation with PMU measurement

I forgot to mention, this is the Dynamic Generation with Repeat Mode Example.vi in the example finder. I just manipulated it to work with your specifications.

Brad S. | National Instruments | CLA

Message 11 of 11

(712 Views)

LabVIEW

PXIe-6556 Continuous Generation with PMU measurement

Re: PXIe-6556 Continuous Generation with PMU measurement