General purpose counter stops or inverts its output

[Jason S.]

I am trying to use GPCTR0 on a PCI-6024E. I have an encoder hooked up, with the Z index triggering the count, and the A channel as the source. I wish to count 10 pulses on the A channel and then output a pulse on GPCTROUT (I'm essentially re-locating the index for some other hardware). It seems to work fine most of the time, but sometimes the counter output inverts or just stops (stays high, sometimes stays low). It then re-triggers on the next Z pulse (re-triggerable single pulse generation).

For now, I am turning the encoder by hand to test my other hardware, so it is difficult to figure out when/why this happens. It is clear on the scope and when I restart my app, it works fine for a while, so it's not noise or
bad connections.

What can cause the counter to stop working or invert it's output? I'm looking for possibilities like: "getting a second gate pulse while it's already counting", or something similar that is to blame. Knowing this would really help me debug the problem.

[Jason S.]

Sorry, I accidentally posted this here instead of the Multifunction I/O group... please ignore the newbie mistake.

JS

[Filipe A.]

Hello;

That is strange. It can be noise that is falling withing the TTL levels and is making the counter to count extra pulses, it can be something wrong in the Software itself, and it can be a problem on the counter.

Give that a try on counter 1 and see if the same behavior shows. If it doesn't, counter 0 of your DAQ device is bad.

Hope this helps.
Filipe A.
Applications Engineer
National Instruments