National Instruments Data Acquisition Device NI USB-621x User Manual page 10

Contents
Other Counter Features.................................................................................................. 8-32
Sample Clock .................................................................................................. 8-32
Cascading Counters......................................................................................... 8-33
Counter Filters................................................................................................. 8-33
Prescaling ........................................................................................................ 8-34
Duplicate Count Prevention ............................................................................ 8-35
Chapter 9
Isolation and Digital Isolators on USB-6215/6216/6218 Devices
Digital Isolation ............................................................................................................. 9-2
Benefits of an Isolated DAQ Device ............................................................................. 9-2
Reducing Common-Mode Noise................................................................................... 9-3
Creating an AC Return Path............................................................................ 9-3
Chapter 10
Digital Routing and Clock Generation
80 MHz Timebase ......................................................................................................... 10-1
20 MHz Timebase ......................................................................................................... 10-1
100 kHz Timebase......................................................................................................... 10-1
Chapter 11
Bus Interface
USB Signal Stream........................................................................................................ 11-1
Data Transfer Methods .................................................................................................. 11-1
Changing Data Transfer Methods ................................................................... 11-2
Chapter 12
Triggering
Triggering with a Digital Source................................................................................... 12-1
NI USB-621x User Manual
Example Application That Works Correctly
(No Duplicate Counting) ............................................................... 8-35
Example Application That Works Incorrectly
(Duplicate Counting) ..................................................................... 8-36
Example Application That Prevents Duplicate Count...................... 8-36
Enabling Duplicate Count Prevention in NI-DAQmx...................... 8-37
Isolated Systems ............................................................................... 9-4
Non-Isolated Systems ....................................................................... 9-4
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