Name: National Instruments USB-621 Series
Brand: National Instruments
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Chapter 11 Bus Interface

NI USB-621x User Manual 11-2 ni.com

Changing Data Transfer Methods

USB-621x devices have four dedicated USB Signal Stream channels. To

change your data transfer mechanism between USB Signal Streams and

programmed I/O, use the Data Transfer Mechanism property node

function in NI-DAQmx.

Table of Contents5
About this Manual13
Conventions13
Related Documentation14
Getting Started19
Installing NI-Daqmx19
Installing Other Software19
Installing the Hardware19
Device Pinouts20
Device Self-Calibration20
Device Specifications20
Applying Signal Labels to the USB-621X21
USB Cable Strain Relief22
Desktop Use24
DIN Rail Mounting24
Mounting the USB-621X24
Panel Mounting25
USB Device Security Cable Slot26
DAQ Hardware27
DAQ System Overview27
Calibration Circuitry28
Daq-Stc228
Sensors and Transducers29
Signal Conditioning29
Cables and Accessories30
USB-621X Mass Termination Custom Cabling30
Programming Devices in Software31
Connector and LED Information32
I/O Connector Signal Descriptions32
+5 V Power34
+5 V Power as an Input34
+5 V Power as an Output34
USB Chassis Ground35
USB Device Fuse Replacement35
PWR/ACT LED Indicator37
Analog Input38
Analog Input Range39
Analog Input Ground-Reference Settings40
Configuring AI Ground-Reference Settings in Software42
Multichannel Scanning Considerations42
Analog Input Data Acquisition Methods45
Analog Input Digital Triggering47
Field Wiring Considerations47
Analog Input Timing Signals48
AI Sample Clock Signal51
Other Timing Requirements51
Routing AI Sample Clock to an Output Terminal51
Using an External Source51
Using an Internal Source51
AI Sample Clock Timebase Signal52
AI Convert Clock Signal53
Routing AI Convert Clock to an Output Terminal53
Using an External Source53
Using an Internal Source53
Other Timing Requirements54
Using a Delay from Sample Clock to Convert Clock54
AI Convert Clock Timebase Signal56
AI Hold Complete Event Signal56
AI Start Trigger Signal57
Routing AI Start Trigger to an Output Terminal57
Using a Digital Source57
AI Reference Trigger Signal58
AI Pause Trigger Signal59
Getting Started with AI Applications in Software59
Routing AI Reference Trigger to an Output Terminal59
Using a Digital Source59
Connecting Analog Input Signals on USB-6210/6211/6212 Devices60
Connecting Floating Signal Sources62
What Are Floating Signal Sources62
When to Use Differential Connections with Floating Signal Sources62
When to Use Referenced Single-Ended Connections with Floating Signal Sources62
When to Use Non-Referenced Single-Ended Connections with Floating Signal Sources63
Using Differential Connections for Floating Signal Sources64
Using Non-Referenced Single-Ended Connections for Floating Signal Sources67
Connecting Ground-Referenced Signal Sources68
Using Referenced Single-Ended Connections for Floating Signal Sources68
What Are Ground-Referenced Signal Sources68
When to Use Differential Connections with Ground-Referenced Signal Sources69
When to Use Non-Referenced Single-Ended Connections with Ground-Referenced Signal Sources69
When to Use Referenced Single-Ended Connections with Ground-Referenced Signal Sources70
Using Differential Connections for Ground-Referenced Signal Sources71
Using Non-Referenced Single-Ended Connections for Ground-Referenced Signal Sources72
Connecting Analog Input Signals on USB-6215/6216/6218 Devices73
Taking Differential Measurements73
Taking Referenced Single-Ended Measurements74
Taking Non-Referenced Single-Ended Measurements75
Analog Output76
Analog Output Data Generation Methods77
AO Range77
Minimizing Glitches on the Output Signal77
Analog Output Digital Triggering79
Connecting Analog Output Signals79
Analog Output Timing Signals80
AO Start Trigger Signal80
Using a Digital Source80
AO Pause Trigger Signal81
Routing AO Start Trigger to an Output Terminal81
Using a Digital Source82
AO Sample Clock Signal83
Other Timing Requirements83
Routing AO Sample Clock to an Output Terminal83
Using an External Source83
Using an Internal Source83
AO Sample Clock Timebase Signal84
Getting Started with AO Applications in Software85
Digital I/O86
Digital I/O on USB-6210/6211/6215/6218 Devices86
I/O Protection on USB-6210/6211/6215/6218 Devices87
Static DIO on USB-6210/6211/6215/6218 Devices87
Connecting Digital I/O Signals on USB-6210/6211/6215/6218 Devices88
Increasing Current Drive on USB-6210/6211/6215/6218 Devices88
Digital I/O on USB-6212/6216 Devices89
Getting Started with DIO Applications in Software on USB-6210/6211/6215/6218 Devices89
I/O Protection on USB-6212/6216 Devices90
Static DIO on USB-6212/6216 Devices90
Connecting Digital I/O Signals on USB-6212/6216 Devices91
Increasing Current Drive on USB-6212/6216 Devices91
Programmable Power-Up States on USB-6212/6216 Devices91
Getting Started with DIO Applications in Software on USB-6212/6216 Devices92
Pfi93
Using PFI Terminals as Timing Input Signals94
Exporting Timing Output Signals Using PFI Terminals95
Using PFI Terminals as Static Digital I/Os95
Connecting PFI Input Signals96
PFI Filters96
I/O Protection98
Programmable Power-Up States98
Counter Input Applications100
Counters100
Counting Edges100
Single Point (On-Demand) Edge Counting100
Buffered (Sample Clock) Edge Counting101
Controlling the Direction of Counting102
Pulse-Width Measurement102
Single Pulse-Width Measurement102
Buffered Pulse-Width Measurement103
Period Measurement104
Single Period Measurement104
Buffered Period Measurement105
Semi-Period Measurement106
Single Semi-Period Measurement106
Buffered Semi-Period Measurement107
Frequency Measurement108
Choosing a Method for Measuring Frequency112
Position Measurement113
Measurements Using Quadrature Encoders114
Buffered (Sample Clock) Position Measurement116
Measurements Using Two Pulse Encoders116
Two-Signal Edge-Separation Measurement117
Buffered Two-Signal Edge-Separation Measurement118
Single Two-Signal Edge-Separation Measurement118
Counter Output Applications119
Simple Pulse Generation119
Single Pulse Generation119
Retriggerable Single Pulse Generation120
Single Pulse Generation with Start Trigger120
Continuous Pulse Train Generation121
Pulse Train Generation121
Finite Pulse Train Generation122
Frequency Generation123
Using the Frequency Generator123
Frequency Division124
Pulse Generation for ETS124
Counter Timing Signals125
Counter N Source Signal126
Routing a Signal to Counter N Source126
Routing Counter N Source to an Output Terminal126
Counter N aux Signal127
Counter N Gate Signal127
Routing a Signal to Counter N aux127
Routing a Signal to Counter N Gate127
Routing Counter N Gate to an Output Terminal127
Counter N A, Counter N B, and Counter N Z Signals128
Counter N HW Arm Signal128
Counter N Up_Down Signal128
Routing Signals to A, B, and Z Counter Inputs128
Counter N Internal Output and Counter N TC Signals129
Frequency Output Signal129
Routing Counter N Internal Output to an Output Terminal129
Routing Frequency Output to a Terminal129
Routing Signals to Counter N HW Arm Input129
Default Counter/Timer Pinouts130
Counter Triggering131
Other Counter Features132
Sample Clock132
Cascading Counters133
Counter Filters133
Prescaling134
Duplicate Count Prevention135
Example Application that Works Correctly (no Duplicate Counting)135
Example Application that Prevents Duplicate Count136
Example Application that Works Incorrectly (Duplicate Counting)136
Enabling Duplicate Count Prevention in NI-Daqmx137
Isolation and Digital Isolators on USB-6215/6216/6218 Devices138
Benefits of an Isolated DAQ Device139
Digital Isolation139
Creating an AC Return Path140
Reducing Common-Mode Noise140
Isolated Systems141
Non-Isolated Systems141
100 Khz Timebase142
80 Mhz Timebase142
Digital Routing and Clock Generation142
Bus Interface143
Data Transfer Methods143
USB Signal Stream143
Changing Data Transfer Methods144
Triggering145
Triggering with a Digital Source145
Device-Specific Information147
Usb-6210148
Usb-6211/6215150
USB-6212/6216 Screw Terminal152
USB-6212/6216 Mass Termination154
Usb-6212/6216 Bnc159
USB-6218 Screw Terminal165
Usb-6218 Bnc167
Appendix B Troubleshooting173

Brand	National Instruments
Model	USB-621 Series
Category	Measuring Instruments
Language	English

National Instruments USB-621 Series User Manual

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