National Instruments NI USB-621x - Manual (Page 10)

Contents
NI USB-621x User Manual x ni.com
Counter n A, Counter n B, and Counter n Z Signals ...................................... 9-28
Routing Signals to A, B, and Z Counter Inputs................................ 9-28
Counter n Up_Down Signal ............................................................................ 9-28
Counter n HW Arm Signal.............................................................................. 9-28
Routing Signals to Counter n HW Arm Input .................................. 9-28
Counter n Internal Output and Counter n TC Signals..................................... 9-29
Routing Counter n Internal Output to an Output Terminal .............. 9-29
Frequency Output Signal ................................................................................ 9-29
Routing Frequency Output to a Terminal......................................... 9-29
Default Counter/Timer Pinouts ..................................................................................... 9-29
Counter Triggering ........................................................................................................ 9-31
Arm Start Trigger............................................................................................ 9-31
Start Trigger .................................................................................................... 9-31
Pause Trigger .................................................................................................. 9-31
Other Counter Features.................................................................................................. 9-32
Sample Clock .................................................................................................. 9-32
Cascading Counters......................................................................................... 9-33
Counter Filters................................................................................................. 9-33
Prescaling ........................................................................................................ 9-34
Duplicate Count Prevention ............................................................................ 9-35
Example Application That Works Correctly
(No Duplicate Counting) ............................................................... 9-36
Example Application That Works Incorrectly
(Duplicate Counting) ..................................................................... 9-37
Example Application That Prevents Duplicate Count...................... 9-37
Enabling Duplicate Count Prevention in NI-DAQmx...................... 9-38
Chapter 10
PFI
Using PFI Terminals as Timing Input Signals .............................................................. 10-2
Exporting Timing Output Signals Using PFI Terminals ............................................... 10-3
Using PFI Terminals as Static Digital I/Os ................................................................... 10-3
Connecting PFI Input Signals........................................................................................ 10-3
PFI Filters ...................................................................................................................... 10-4
I/O Protection ................................................................................................................ 10-6
Programmable Power-Up States.................................................................................... 10-6