National Instruments USB-621 Series User Manual page 10

Contents
Counter n Gate Signal ..................................................................................... 8-29
Counter n Aux Signal...................................................................................... 8-29
Counter n A, Counter n B, and Counter n Z Signals ...................................... 8-30
Counter n Up_Down Signal............................................................................ 8-30
Counter n HW Arm Signal.............................................................................. 8-30
Counter n Internal Output and Counter n TC Signals..................................... 8-31
Frequency Output Signal ................................................................................ 8-31
Default Counter/Timer Pinouts ..................................................................................... 8-32
Counter Triggering ........................................................................................................ 8-33
Other Counter Features.................................................................................................. 8-34
Sample Clock .................................................................................................. 8-34
Cascading Counters......................................................................................... 8-35
Counter Filters................................................................................................. 8-35
Prescaling ........................................................................................................ 8-36
Duplicate Count Prevention ............................................................................ 8-37
Chapter 9
Isolation and Digital Isolators on USB-6215/6216/6218 Devices
Digital Isolation ............................................................................................................. 9-2
Benefits of an Isolated DAQ Device ............................................................................. 9-3
Reducing Common-Mode Noise................................................................................... 9-3
Creating an AC Return Path............................................................................ 9-4
NI USB-621x User Manual
Routing a Signal to Counter n Gate.................................................. 8-29
Routing Counter n Gate to an Output Terminal ............................... 8-29
Routing a Signal to Counter n Aux .................................................. 8-29
Routing Signals to A, B, and Z Counter Inputs................................ 8-30
Routing Signals to Counter n HW Arm Input .................................. 8-31
Routing Counter n Internal Output to an Output Terminal .............. 8-31
Routing Frequency Output to a Terminal......................................... 8-31
Example Application That Works Correctly
(No Duplicate Counting) ............................................................... 8-37
Example Application That Works Incorrectly
(Duplicate Counting) ..................................................................... 8-38
Example Application That Prevents Duplicate Count...................... 8-38
Enabling Duplicate Count Prevention in NI-DAQmx...................... 8-39
Isolated Systems ............................................................................... 9-4
Non-Isolated Systems ....................................................................... 9-4
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