Count Squares with 500Hz

Question

Hi!
I've generated with the ExpressVI "Simulate Signal" a Square with the maximum frequency of 500Hz (it varies). Now I want to count the falling flanks.
I tried this with the "Trigger Counter.vi"-Example which I slightly changed for my purposes. (see attached file) But it seems as if the Counter is not fast enough for my Signal (- it counts too slow).
Does anybody have an idea how I can solve the problem and count the correct value of squares?
Shorty to my system: I tried it with a 2GHz Sempron with LabView8 
                                      and with a 1,3GHz Centrino with LabView7.1
Thank you in advance
  Hendrik

Answer 1

If you have a simulated square wave waveform, you can count falling edges by simple emulating what a counter does, essentially for each poind threshold it.  If it is above some threshold it is a high value, and if it is below th it is low, use a shift register to compare sequential hi/low booleans.  Check for a high to low transition (if n-1 is high and n is low there is a falling edge) use another shift reg to count these events.  Do this for every point in the waveform.  If you have simulated a noisy signal, you can get more advanced usint techniques such as a schmitt trigger (hysterisis).
Paul
Paul Falkenstein
Coleman Technologies Inc.
CLA, CPI, AIA-Vision
Labview 4.0- 2013, RT, Vision, FPGA