Why does FPGA LED stop working?

[dj143]

I use the FPGA LED to indicate that the main FPGA VI is running.  Attached is the scrren shot of how the FPGA LED is driven.  I'm not sure when, but some time later (i.e. a day later) the flashing stops.  The FPGA VI continues to run OK, it's just that the LED stops flashing.  Why is this?

[reddog]

The iteration terminal is an I32 value.  Once the loop executes 2^31 times or more, the value of the iteration terminal will remain stuck at the maximum value of the data type (2,147,483,647) rather than wrapping around to zero (or the maximum negative value).  I suspect this is what's causing your problem.  The easiest way to deal with this is probably to create a U32 or U64 value outside of the loop, wire it to a shift register, and increment the value by one each iteration of the loop yourself.

[dj143]

Hi Reddog,

Sorry for the delayed reply.  I'm surprised that the iteration counter stops and holds at 2"31 counts.  This must be only for FPGA because I haven’t had this problem with other projects such as real time and the usual VI"s that runs in Windows.  If this is true, then the iteration output cannot be used for FPGA projects, which difficult to comprehend.  Please confirm this is true or that I understand this correctly.

Thanks,

Dave

[Donovan_B]

The iteration terminal behaves this way on all platforms.  For more information see the LabVIEW Help.  You most likely don't see this on other platforms because the loops typically are not running nearly as fast as they are on the FPGA.