National Instruments USB-621 Series, User Manual

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Contents
NI USB-621x User Manual x ni.com
Co u nter n Gate Signal ..................................................................................... 8-29
Ro u ting a Signal to Co u nter n Gate.................................................. 8-29
Ro u ting Co u nter n Gate to an O u tp u t Terminal ............................... 8-29
Co u nter n A u x Signal...................................................................................... 8-29
Ro u ting a Signal to Co u nter n A u x .................................................. 8-29
Co u nter n A, Co u nter n B, and Co u nter n Z Signals ...................................... 8-30
Ro u ting Signals to A, B, and Z Co u nter Inp u ts................................ 8-30
Co u nter n Up_Down Signal ............................................................................ 8-30
Co u nter n HW Arm Signal.............................................................................. 8-30
Ro u ting Signals to Co u nter n HW Arm Inp u t .................................. 8-31
Co u nter n Internal O u tp u t and Co u nter n TC Signals..................................... 8-31
Ro u ting Co u nter n Internal O u tp u t to an O u tp u t Terminal .............. 8-31
Freq u ency O u tp u t Signal ................................................................................ 8-31
Ro u ting Freq u ency O u tp u t to a Terminal......................................... 8-31
Defa u lt Co u nter/Timer Pino u ts ..................................................................................... 8-32
Co u nter Triggering ........................................................................................................ 8-33
Other Co u nter Feat u res.................................................................................................. 8-34
Sample Clock .................................................................................................. 8-34
Cascading Co
u nters......................................................................................... 8-35
Co u nter Filters................................................................................................. 8-35
Prescaling ........................................................................................................ 8-36
D
u plicate Co u nt Prevention ............................................................................ 8-37
Example Application That Works Correctly
(No D u plicate Co u nting) ............................................................... 8-37
Example Application That Works Incorrectly
(D u plicate Co u nting) ..................................................................... 8-38
Example Application That Prevents D u plicate Co u nt...................... 8-38
Enabling D u plicate Co u nt Prevention in NI-DAQmx...................... 8-39
Chapter 9
Isolation and Digital Isolators on USB-6215/6216/6218 Devices
Digital Isolation ............................................................................................................. 9-2
Benefits of an Isolated DAQ Device ............................................................................. 9-3
Red
u cing Common-Mode Noise ................................................................................... 9-3
Creating an AC Ret u rn Path............................................................................ 9-4
Isolated Systems ............................................................................... 9-4
Non-Isolated Systems ....................................................................... 9-4