Counter/Timer
CPU resources not released with 6602
Hello,
I am performing continuous semiperiod measurements using a PXI 6602 timer card, along with other DAQ boards (6259...).
The cards are installed in a PXI rack and driven by a 8196 real-time controller.
Our system also acquires digital & analog inputs, as well as generating the same kind of signals. I discovered that from run to run, CPU usage was growing, and I spent quite a lot of time to point out it was due to these semiperiod (PWM) measurements.
Basically, we configure once our system to create appropriate DAQmx tasks, and we start/stop these tasks when needed. When measuring more than 3 PWM inputs (e.g 4 timers of the same 6602 board), I observe through the Real-time System Manager that the CPU usage is increasing each time I restart the tasks.
In top of that, if I clear the PWM DAQmx task and restart the other ones (AI, DI...) this "ghost" CPU usage is still present ! 
The only way to remove the problem is to reset the 6602 card (note that resetting only this one is sufficient, so the problem is not linked to the other cards).
When running the system quite a long time (and applying several DAQmx start/stop), it can lead to almost 100% CPU usage and plenty of RT cycle lost. Very annoying... 
I created 2 VIs to reproduce the problem. As it is a very limited configuration, it is necessary to stop and resume many times before observing this CPU increase. This is generally coming more quickly when using a Timing Loop using hardware counting (Semiperiod measurement - HW TL.vi) but I also saw it running the second example (Semiperiod measurement - SW TL.vi). Using a combination of DMA/IRQ transfers also shows the issue more easily.
Please also note that this problem occurs even if I do not connect input signal to the 6602 card.
Anyone got a similar problem ?
It really looks like an issue of the DAQmx driver for buffered continuous semiperiod measurements...
Message Edité par Inpriser le 06-13-2006 09:02 AM
