Contents
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Using the Watchdog Timer...............................................................................5-14
Getting Started with DO Applications in Software ..........................................5-14
Digital Input/Output Configuration for NI 9401 ......................................................5-14
PFI.....................................................................................................................................5-14
PFI Filters .................................................................................................................5-14
Chapter 6
Counters
Counter Timing Engine ....................................................................................................6-2
Counter Triggering ...........................................................................................................6-3
Counter Input Applications...............................................................................................6-3
Counting Edges.........................................................................................................6-4
Single Point (On-Demand) Edge Counting ......................................................6-4
Buffered (Sample Clock) Edge Counting.........................................................6-5
Controlling the Direction of Counting..............................................................6-5
Pulse-Width Measurement........................................................................................6-6
Single Pulse-Width Measurement ....................................................................6-6
Implicit Buffered Pulse-Width Measurement...................................................6-7
Sample Clocked Buffered Pulse-Width Measurement .....................................6-7
Pulse Measurement ...................................................................................................6-8
Single Pulse Measurement................................................................................6-8
Implicit Buffered Pulse Measurement ..............................................................6-8
Sample Clocked Buffered Pulse Measurement ................................................6-9
Semi-Period Measurement........................................................................................6-10
Single Semi-Period Measurement ....................................................................6-10
Implicit Buffered Semi-Period Measurement...................................................6-10
Pulse versus Semi-Period Measurements .........................................................6-11
Frequency Measurement...........................................................................................6-11
Low Frequency with One Counter....................................................................6-11
High Frequency with Two Counters.................................................................6-12
Large Range of Frequencies with Two Counters .............................................6-13
Sample Clocked Buffered Frequency Measurement ........................................6-14
Choosing a Method for Measuring Frequency .................................................6-15
Which Method Is Best?.....................................................................................6-17
Period Measurement .................................................................................................6-19
Position Measurement...............................................................................................6-19
Measurements Using Quadrature Encoders......................................................6-20
Channel Z Behavior ..................................................................................................6-20
Measurements Using Two Pulse Encoders.......................................................6-21
Buffered (Sample Clock) Position Measurement .............................................6-21
Two-Signal Edge-Separation Measurement .............................................................6-22
Single Two-Signal Edge-Separation Measurement..........................................6-23
Implicit Buffered Two-Signal Edge-Separation Measurement ........................6-23
Sample Clocked Buffered Two-Signal Separation Measurement ....................6-23
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