DAQ
PCI-4451/4452 User Manual
Dynamic Signal Acquisition Device for PCI
April 1998 Edition
Part Number 321891A-01
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© Copyright 1998 National Instruments Corporation. All rights reserved.
Important Information
Warranty
The PCI-4451/4452 is warranted against defe cts in mate ria l s and workmanship for a period of one year from the date of
shipment, as evidenced by receipts or other documentation. National Instruments will, at its option, repair or replace
equipment that proves to be defective during the warranty period. This warranty includes parts and labor.
The media on which you receive National Instruments software are warranted not to fail to execute programming
instructions, due to defects in materials and workmanship, for a period of 90 days from date of shipment, as evidenced
by receipts or other documentation. National Instruments will, at its option, repair or replace software media that do not
execute programming instructions if National Instruments receives notice of such defects during the warranty period.
National Instruments does not warrant that the operation of the software shall be uninterrupted or error free.
A Return Material Authorization (RMA) number must be obtained from the factory and clearly marked on the outside
of the package before any equipment will be accepted for warranty wo rk. National Instru ments will pay the shippi ng costs
of returning to the owner part s which are c overed by warranty.
National Instruments believes that the informatio n in this manual is accurate. The document ha s been careful ly reviewed
for technical accurac y. In the even t that te chn ical or t ypograp hic al errors ex ist, Nation al Inst rumen ts res erves the righ t to
make changes to subsequent editions of this document without prior notice to holders of this edition. The reader should
consult National Instruments if errors are suspected. In no event shall National Instruments be liable for any damages
arising out of or related to this document or the information contained in it.
XCEPT AS SPECIFIED HEREIN
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provided herein does not cover damages, defects, malfunctions, or service failures caused by owner’s failure to follow
the National Instruments installation, operation, or maintenance instructions; owner’s modification of the product;
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ATIONAL INSTRUMENTS WILL NOT BE LIABLE FOR DAMAGES RESULTING FROM LOSS OF DATA, PROFITS, USE OF PRODUCTS
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ATIONAL INSTRUMENTS MAKES NO WARRANTIES, EXPRESS OR IMPLIED, AND SPECIFICALLY DISCLAIMS
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Trademarks
ComponentWorks™, CVI™, LabVIEW™, Measure™, NI-DAQ™, and VirtualBench™ are trademarks of Nationa l
Instruments Corporation.
Product and company names listed are trademarks or trade names of their respective companies.
WARNING REGARDING MEDICAL AND CLINICAL USE OF NATIONAL INSTRUMENTS PRODUCTS
National Instruments products are not designed with components and testing intended to ensure a level of reliability
suitable for use in treatment and diagnosis of humans. Applications of National Instruments products involving medical
or clinical treatment can create a potential for accidental injury caused by product failure, or by errors on the part of the
user or application des igner. An y use or ap plica tion of Na tiona l Instrume nts p roducts for or inv olvi ng medic al or c linica l
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and safety in medical or clinical treatment.
Contents
About This Manual
Organization of This Manual.........................................................................................ix
Conventions Used in This Manual.................................................................................x
National Instruments Documentation............. ...... ..... ........................................ ............xi
Related Documentation..................................................................................................xi
Customer Communication.............................................................................................xi
Chapter 1
Introduction
What You Need to Get Started......................................................................................1-2
Unpacking......................................................................................................................1-2
Software Programming Choices....................................................................................1-3
National Instruments Application Software....................................................1 -3
Optional Equipment.......................................................................................................1-4
Custom Cabling .............................................................................................................1-4
Chapter 2
Installation and Configuration
Software Installation......................................................................................................2-1
Hardware Installation.....................................................................................................2-1
Device Configuration................................................................................... ..................2-2
Chapter 3
Hardware Overview
Analog Input..................................................................................................................3-3
Input Mode ............................................................................... .......................3-3
Input Coupling......................................................... ..... ...................................3-3
Input Polarity and Input Range........................................................................3-3
Considerations for Selecting Input Ranges.....................................................3-4
Analog Output................................................................................................................3-5
Output Mode....................................................................................................3-5
Output Polarity and Output Range..................................................................3-5
Trigger ...........................................................................................................................3-6
RTSI Triggers ..................................................................................................3-9
Digital I/O......................................................................................................................3-10
Timing Signal Routing...................................................................................................3-11
Programmable Function Inputs....................................................................... 3 -11
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National Instruments Corporation v PCI-4451/4452 User Manual
Contents
Device and RTSI Clocks.................................................................................3-11
Selecting Sample/Update Clock Frequency..................................................................3-12
Device Configuration Issues......................... ...... ...... ....................................... ..............3-13
Chapter 4
Signal Connections
I/O Connectors...............................................................................................................4-1
Analog I/O Connector Signal Descriptions ....................................................4-2
Digital I/O Connector Signal Descriptions.....................................................4-5
Analog Input Signal Connections..................................................................................4-9
Types of Signal Sources................................................................................................4-10
Floating Signal Sources ..................................................................................4-10
Ground-Referenced Signal Sources................................................................4-10
Analog Output Signal Connections...............................................................................4-11
Analog Power Connections........................................................................................... 4-12
Digital I/O Signal Connections ..................................................................................... 4-12
Digital Power Connections............................................................................................ 4-14
Timing Connections...................................................................................................... 4-14
Programmable Function Input Connections ...................................................4-14
Acquisition Timing Connections.......................... ...... ..... ...............................4-15
Waveform Generation Timing Connections...................................................4-18
General-Purpose Timing Signal Connections.................................................4-19
Field Wiring Considerations..........................................................................................4-24
PFI0/TRIG1 (EXT_TRIG) Signal....................................................4-16
PFI1/TRIG2 (PRETRIG) Signal ...................................................... 4-17
CONVERT* Signal..........................................................................4-17
EXTSTROBE* Signal......................................................................4-18
WFTRIG Signal................................................................................4-18
UPDATE* Signal .............................................................................4-18
GPCTR0_SOURCE Signal ..............................................................4-19
GPCTR0_GATE Signal ........................................................... ...... ..4-20
GPCTR0_OUT Signal......................................................................4-20
GPCTR0_UP_DOWN Signal...........................................................4-20
GPCTR1_SOURCE Signal ..............................................................4-21
GPCTR1_GATE Signal ........................................................... ...... ..4-21
GPCTR1_OUT Signal......................................................................4-22
GPCTR1_UP_DOWN Signal...........................................................4-22
FREQ_OUT Signal....................................... ..... ...... .........................4-24
PCI-4451/4452 User Manual vi
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National Instruments Corporation
Chapter 5
Calibration
Loading Calibration Constants......................................................................................5-1
Self-Calibration..............................................................................................................5-2
External Calibration.......................................................................................................5-2
Traceable Recalibration.................................................................................................5-3
Chapter 6
Theory of Analog Operation
Functional Overview......................................................................................................6-1
Analog Input Circuitry................................................................................................... 6 -1
Input Coupling......................................................... ..... ...................................6-2
Calibration............ ...... ....................................... ..............................................6-2
Antialias Filtering........................................ ...... ...... ....................................... .6-3
The ADC .........................................................................................................6-8
Noise................................................................................................................6-9
Analog Output Circuitry................................................................................................6-10
Anti-Image Filtering........................................................................................6-10
The DAC .........................................................................................................6-12
Calibration.......................................................................................................6-12
Mute Feature........................................... ..... ...... ........................................ ......6-13
Contents
Appendix A
Specifications
Appendix B
Pin Connections
Appendix C
Customer Communication
Glossary
Index
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National Instruments Corporation vii PCI-4451/4452 User Manual
Contents
Figures
Figure 3-1. Digital Function Block Diagram...........................................................3-1
Figure 3-2. Analog Function Block Diagram..........................................................3-2
Figure 3-3. Below-Low-Level Triggering Mode.....................................................3-7
Figure 3-4. Above-High-Level Triggering Mode.................................................. ..3-8
Figure 3-5. Inside-Region Triggering Mode ...........................................................3-8
Figure 3-6. High-Hysteresis Triggering Mode........................................................ 3-8
Figure 3-7. Low-Hysteresis Triggering Mode.........................................................3-9
Figure 3-8. RTSI Bus Signal Connection................................................................3-10
Figure 4-1. Analog Pin Connections .......................................................................4-2
Figure 4-2. Digital Pin Connections........................................................................4-5
Figure 4-3. Analog Input Stage ...............................................................................4-9
Figure 4-4. Analog Output Channel Block Diagram............................................... 4-11
Figure 4-5. Digital I/O Connections........................................................................4-13
Figure 4-6. Typical Posttriggered Acquisition ........................................................4-15
Figure 4-7. Typical Pretriggered AcquisitionPFI1.................................................. 4-16
Figure 4-8. EXTSTROBE* Signal Timing .............................................................4-18
Figure 4-9. GPCTR0_SOURCE Signal Timing......................................................4-19
Figure 4-10. GPCTR0_OUT Signal Timing .............................................................4-20
Figure 4-11. GPCTR1_SOURCE Signal Timing......................................................4-21
Figure 4-12. GPCTR1_OUT Signal Timing .............................................................4-22
Figure 4-13. GPCTR Timing Summary ....................................................................4-23
Figure 6-1. Input Frequency Response....................................................................6-5
Figure 6-2. Input Frequency Response Near the Cutoff..........................................6-6
Figure 6-3. Alias Rejection at the Oversample Rate...............................................6-7
Figure 6-4. Comparison of a Clipped Signal to a Proper Signal .............................6-8
Figure 6-5. Signal Spectra in the DAC....................................................................6-11
Figure A-1. Idle Channel Noise (Typical)................................................................A-4
Figure B-1. 68-Pin Digital Connector for any Digital Accessory............................B-2
Tables
Table 3-1. Actual Range and Measurement Precision...........................................3-4
Table 3-2. Actual Range and Measurement Precision...........................................3-6
Table 4-1. Analog I/O Connector Pin Assignment................................................4-3
Table 4-2. Analog I/O Signal Summary.................................................................4-4
Table 4-3. Digital I/O Connector Pin Assignment................................................. 4-6
Table 4-4. Digital I/O Signal Summary .................................................................4-8
PCI-4451/4452 User Manual viii
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National Instruments Corporation
About This Manual
This manual describes the electrical and mechanical aspects of the
PCI-4451 and PCI-4452 devices and cont ains information co ncerning their
operation. Unless otherwise noted, the text applies to both devices.
The PCI-4451 and PCI-4452 are high-performance, high-accuracy analog
input/output (I/O) devices for the PCI bus. These devices also support
digital I/O (DIO) functions, counter/timer functions, and external trigger
functions.
Organization of This Manual
The PCI-4451/4452 User Manual is organized as follows:
• Chapter 1, Introduction, describes the PCI-4451 and PCI-4452
devices, lists what yo u need to get start ed, explains how to u npack your
devices, and describes the optional software and optional equipment.
• Chapter 2, Installation and Configuration, explains how to install and
configure your PCI-4451/4452 device.
• Chapter 3, Hardware Overview, presents an overview of the hardware
functions on your PCI-4451/4452 device.
• Chapter 4, Signal Connections, describes how to make input and
output connections to your PCI-4451/4452 device via the analog I/O
and digital I/O connectors of the device.
• Chapter 5, Calibration, discusses the calibration procedures for your
PCI-4451/4452 device.
• Chapter 6, Theory of Analog Operation, contains a functional
overview and explains the operation of each analog functional unit
making up the PCI-4451/4452.
• Appendix A, Specifications, lists the specifications of the
PCI-4451/4452.
• Appendix B, Pin Connections, describes the pin connections on the
optional 68-pin digital accessories for the PCI-4451/4452 devices.
• Appendix C, Customer Communication, contains forms you can use to
request help from National I nstruments or to comment on our products
and manuals.
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National Instruments Corporation ix PCI-4451/4452 User Manual
About This Manual
•The Glossary contains an alphabetical list and description of terms
used in this manual, including abbreviations, acronyms, metric
prefixes, mnemonics, and symbols.
•The Index contains an alphabetical list of key terms and topics in this
manual, including the page where you can find each one.
Conventions Used in This Manual
The following conventions are used in this manual:
<> Angle brackets enclose the name of a key on the keyboard—for example,
<shift>. Angle brackets containing numbers separated by an ellipsis
represent a range of values associated with a bit or signal name—for
example, DBIO<3..0>.
♦ The ♦ symbol indicates that the text following it applies only to a specific
product, a specific operating system, or a specific software version.
* An asterisk following a signal name denotes an ACTIVE LOW signal.
This icon to the left of bold italicized text denotes a note, which alerts you
to important information.
!
bold italic Bold italic text denotes an activity objective, note, caution, or warning.
DSA DSA refers to dynamic signal acquisition.
italic Italic text denotes v ariables, emphasis, a cross reference, or an introduction
SE SE means referenced single ended (RSE). SE and RSE are equivilant.
PCI-4451/4452 User Manual x
This icon to the left of bold italicized text denotes a caution, which advises
you of precautions to take to avoid injury, data loss, or a system crash.
to a key concept. This font also denotes text from which you supply the
appropriate word or value, as in NI-DAQ 6.x.
©
National Instruments Corporation
National Instruments Documentation
The PCI-4451/4452 User Manual is one piece of the documentation set
for your DAQ system. You could have any of several types of manuals
depending on the hardware and software in your system. Use the manuals
you have as follows:
• Software documentation—You may have both application software
and NI-DAQ software documentation. National Instruments
application software includes ComponentWorks, LabVIEW,
LabWindows/CVI, Measure, and VirtualBench. After you set up your
hardware system, use either your application softw are do cumen t ation
or the NI-DAQ documentation to help you write your application. If
you have a large, complicated system, it is worthwhile to look through
the software documentation before you configure your hardware.
• Accessory installation guides or manuals—If you are using accessory
products, read the terminal block and cable assembly installation
guides. They explain how to physically connect the relevant pieces
of the system. Consult these guides when you are making your
connections.
About This Manual
Related Documentation
The following documents contain information you may find helpful:
• BNC-2140 User Manual
• National Instruments Application Note 025, Field Wiring and Noise
Considerations for Analog Signals
• PCI Local Bus Specification Revision 2.0
Customer Communication
National Instruments wants to receive your comments on our products
and manuals. We are interest ed in the applications you develop with our
products, and we want to help if you have problems with them. To make it
easy for you to contact us, thi s manual contains comment and conf iguration
forms for you to complete. These forms are in Appendix C, Customer
Communication, at the end of this manual.
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National Instruments Corporation xi PCI-4451/4452 User Manual
Introduction
This chapter describes the PC I-445 1 and PCI -4452 d evices , lists what you
need to get started, explains how to unpack you r devices, and describes the
optional software and optional equipment.
The PCI-4451/4452 are high-performance, high-accuracy analog I/O
devices for the PCI bus. These de vices are members of the PCI-DSA series
and are specifically designed for demanding dynamic signal acquisition
applications. The PCI-4451 has two channels of 16-bit simultaneously
sampled input at 204.8 kS/s and two channels of 16-bit simultaneously
updated output at 51.2 kS/s, while the PC I-4452 has four chan nels of 16-bit
simultaneously sampled analog input at 204.8 kS/s. Inf ormation on anal og
output applies only to the PCI-4451, where as information on anal og input
applies to both the PCI-4451 and the PCI-4452.
Both the analog input and the analog output circuitry have oversampling
delta-sigma modulating converters. Delta-sigma converters are inherently
linear, provide built-in brick-wall anti-aliasing/imaging filters, and have
specifications that exceed other conventional technology for this
application with regard to THD, SNR, and amplitude flatness. You can use
these high-quality specifications and features to acquire or generate signals
with high-accuracy and fidelity without introducing n oise or out-of-band
aliases.
1
Applications include audio signal processing and analysis, acoustics and
speech research, sonar, audio frequency test and measurement, vibration
and modal analysis, or any application requ iring high-fidelity signal
acquisition with a bandwidth up to 95 kHz or signal generation with a
bandwidth up to 23 kHz.
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National Instruments Corporation 1-1 PCI-4451/4452 User Manual
Chapter 1 Introduction
What You Need to Get Started
To set up and use your PCI-4451 or PCI-4452, you will need the following:
❑ One of the following devices:
PCI-4451
PCI-4452
❑ PCI-4451/4452 Series User Manual
❑ You may have one or more of the following software packages and
documentation:
LabVIEW for Windows
LabWindows/CVI for Windows
NI-DAQ for PC Compatibles
VirtualBench-DSA
ComponentWorks
Measure
❑ Your co mputer
Unpacking
❑
SHC68-C68-A1
analog cable
❑ BNC-2140 accessory
Your PCI-4451/4452 is shipped in an antistatic plastic package to prevent
electrostatic damage to the device. Electrostatic discharge can damage
components on the instrument. To avoid such damage in handling the
device, take the following precautions:
• Ground yourself vi a a grounding strap or by hold ing a grounded obj ect.
• Touch the plastic package to a metal part of your computer chassis
before removing the device from the package.
• Remove the device from the package and inspect the device for loose
components or any other si gn of damage. Notify National In struments
if the device appears damaged in any way. Do not install a damaged
device into your computer.
• Never touch the exposed pins of connectors.
PCI-4451/4452 User Manual 1-2
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National Instruments Corporation
Software Programming Choices
There are several options to choose from to program and use your
National Instruments device. You can use LabVIEW for Windows,
LabWindows/CVI for Windows, VirtualBench-DSA, ComponentWorks,
and Measure.
National Instruments Application Software
LabVIEW and LabWindows/CVI are innovative program development
software packages for data acquisition and control applications. LabVIEW
uses graphical programming, whereas LabWindows/CVI enhances
traditional programing languages. Both packages include extensive
libraries for data acquisition, instrument control, data analysis, and
graphical data presentation.
LabVIEW features interactive graphics, a state-of-the-art user interface,
and a powerful graphical programming language. The LabVIEW Data
Acquisition VI Library, a series of VIs for using LabVIEW with National
Instruments device hardware, is included with LabVIEW. The LabVIEW
Data Acquisition VI Library is functionally equivalent to the NI-DAQ
software.
Chapter 1 Introduction
LabWindows/CVI features interactive graphics, a state-of-the-art user
interface, and uses the ANSI C programming language. The
LabWindows/CVI Data Acquisition, a series of functions for using
LabWindows/CVI with National Instruments device hardware, is included
with the NI-DAQ software kit. The LabWindows/CVI Data Acquisition
library is functionally equivalent to the NI-DAQ software.
VirtualBench is a suite of VIs that allows you to use your data acquisition
products just as you use stand-alone instruments, but you benefit from
processing, display, and storage capabilities of PCs. VirtualBench
instruments load and save waveform data to disk in the same forms used in
popular spreadsheet programs and word processors. A report generation
capability complements the raw data storage by adding timestamps,
measurements, user name, and comments.
The complete VirtualBench suite contains VirtualBench-Scope,
VirtualBench-DSA, VirtualBench-Function Generator, VirtualBench-FG,
VirtualBench-Arb, VirtualBench-AODC, VirtualBench-DIO,
VirtualBench-DMM, and VitualBench-Logger. Your PCI 4451/4452
comes with VirtualBench-DSA. VirtualBench-DSA is a turnkey
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National Instruments Corporation 1-3 PCI-4451/4452 User Manual
Chapter 1 Introduction
application you can use to make measurements as you would with a
standard dynamic analyzer.
ComponentWorks contains tools for data acquisition and instrument
control built on NI-DAQ driver software. ComponentWorks provides a
higher-level programming interface for building virtual instruments with
Visual Basic, V isual C++, Borland Delphi, and Microsoft Internet Explorer .
With Com ponentW orks, you can use al l of the configurat ion tools, resource
management utilities, and interactive control utilities included in NI-DAQ.
Measure is a data acquisition and instrument control add-in for Microsoft
Excel. With Measure, you can acquire data directly from plug-in DAQ
boards, GPIB instruments, or serial (RS-232) devices. Measure has
easy-to-use dialogs for configurin g your measurements. Your data is placed
directly into Excel worksheet cells, from which you can perform your
analysis and report generations using the full power and flexibility of Excel.
Optional Equipment
National Instruments offers a variety of products to use with your
PCI-4451/4452 series devices, including cables and connector blocks as
follows:
•
SHC50-68 digital cable
•
Shielded and DIN rail mountable 68-pin connector blocks
•
RTSI cables
Custom Cabling
National Instruments offers cable s of different l engths and the BNC-2140
DSA accessory to connect your analog I/O to the PCI-4451/4452. National
Instruments recommends you do not develop your own cabling solution
due to the difficulty of working with the high-density connector and the
need to maintain high signal integrity . Howeve r, if your application
requires that you develop your own cable use the following guidelines:
• Use shielded twisted-pair wires for each differential analog input or
output channel pair. Since the signals are differential, using this type
of wire yields the best results.
• When connecting the cable shields, be sure to connect the analog input
grounds to the AIGND pins and the analog output grounds to the
AOGND pins. For a conne ctor pin assignment, refer to Table 4- 1,
Analog I/O Connector Pin Assignment.
PCI-4451/4452 User Manual 1-4
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National Instruments Corporation
Chapter 1 Introduction
• To create your own accessories, you can use an AMP 68-pin
right-angle PWB receptacle header, part number 787254-1.
• Recommended manufacturer part numbers for the 68-pin mating
connector for the cable assembly are as follows:
– AMP 68-position straight cable plug, part number 787131-3
– AMP 68-position backshell with jackscrews, part number
787191-1
National Instruments also offers cables of differ ent lengths and accessories
to connect your digital I/O si gn als to th e PC I-4451/4452. To develop your
own cable, the mating connector for the digital I/O is a 50-position
receptacle. For a connector pinout assignment, refer to Table 4-3, Digital
I/O Connector Pin Assignment. Recommended manufacturer part numbers
for this mating connector are as follows:
• 50-position straight cable plug, part number 787131-1
• 50-position backshell with jackscrews, part number 787233-1
Refer to Appendix B, Pin Connections , for pin assign ments of digital
accessories and cables.
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National Instruments Corporation 1-5 PCI-4451/4452 User Manual
Installation and Configuration
This chapter explains how to install and configure your PCI-4451/4452
device.
Software Installation
2
Note
Install your software before you install your PCI-4451/4452 device.
If you are using NI-DAQ, refer to your NI-DAQ release notes. Find the
installation section for your operating system and follow the instructions
given there. If you are using LabVIEW, LabWindows/CVI, or other
National Instruments application software, refer to the appropriate release
notes. After you have installed your application software, refer to your
NI-DAQ release notes and follow the instructions given there for your
operating system and application software package.
Hardware Installation
You can install the PCI-4451/4452 device in any available PCI expansion
slot in your computer. However, to achieve the best noise performance,
leave as much room as possible between the PCI-4451/4452 device and
other devices and hardware. The following are general installation
instructions, but consult your computer user manual or techn ical reference
manual for specific instructions and warnings:
1. Write down the PCI-4451/4452 device serial number in the
PCI-4451/4452 Hardware and Software Configuration Form in
Appendix C, Customer Communication, of this manual.
2. Turn off and unplug your computer.
3. Remove the top cover or access port to the I/O channel.
4. Remove the expansion slot cover on the back panel of the computer.
5. Insert the PCI-4451/4452 device into a 5 V PCI slot. It should fit
snugly, but do not force the device into place.
6. Screw the mounting bracket of the PCI-4451/4452 device to the back
panel rail of the computer.
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National Instruments Corporation 2-1 PCI-4451/4452 User Manual
Chapter 2 Installation and Configuration
7. Check the installation.
8. Replace the cover.
9. Plug in and turn on your computer.
The PCI-4451/4452 de vice is now installe d. Y ou are now ready t o configure
your software.
Device Configuration
The PCI-4451/4452 devices are completely software configurable.
However, you must perform two types of configuration—bus-related and
data acquisition-related.
The PCI-4451/4452 devices are fully compatible with the industry
standard PCI Local Bus Specification Revision 2.0. The PCI system
automatically performs all bus-related configurations and requires no
interaction from you. Bus-related configuration includes setting the device
base memory address and interrupt channel.
Data acquisition related configuration includes such setting s as an alog
input polarity and range, analog input mode, and others. You can modify
these settings through National Instruments application level software,
such as ComponentWorks, LabVIEW, LabWindows/CVI, and
VirtualBench or driver software such as NI-DAQ.
PCI-4451/4452 User Manual 2-2
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National Instruments Corporation
Hardware Overview
This chapter presents an overview of the hardware functions on your
PCI-4451/4452 device. Figure 3-1 shows a block diagram of the digital
functions. Figure 3-2 shows a block diagram of the analog functions.
The two function blocks connect through the analog mezzanine bus.
Analog Mezzanine Bus (to Analog Section)
Analog Mezzanine Control
3
Clock Generator
Digital I/O Bus
RTSI Bus
†
PCI-4451 only
Direct Digital
Synthesis
DAQ-STC
Clock Control
General Control
Functions
MITE
PCI Controller
PCI Bus
Figure 3-1.
Parallel <-> Serial
Converter
FIFO and DMA
Control
Digital Function Block Diagram
AI FIFO
AO FIFO
†
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National Instruments Corporation 3-1 PCI-4451/4452 User Manual
Chapter 3 Hardware Overview
Analog Bus
ENABLE0
ENABLE1
Output
Enable
DIFF
ATTEN
††
DAC0
ADC0
LP
DIFF
Gain
Filter
AMP
AMP
DIFF
ATTEN
††
DAC1
ADC1
LP
DIFF
Gain
Filter
AMP
AMP
†
ADC2
LP
Filter
DIFF
Gain
AMP
†
LP
DIFF
Gain
ADC3
Filter
AMP
Control
Attenuation
Calibration
Gain/Offset
Manager
DAC Clock
DAC Control
General Control
Serial Data Manager
Digital
Detect
Overrange
ADC Control
Calibration
Gain/Offset
Detect
Analog
Overrange
Gain
Control
ADC Clock
Manager
Trigger
EEPROM
Control
Analog Mezzanine Bus (to Digital Section)
MUX0
ATTEN
0 dB/20 dB
MUX0
AC/DC
Coupling
MUX0
INPUT/CAL
MUX1
ATTEN
0 dB/20 dB
MUX1
AC/DC
Coupling
MUX1
INPUT/CAL
MUX2
ATTEN
0 dB/20 dB
MUX2
AC/DC
Coupling
MUX2
INPUT/CAL
Analog Bus
Figure 3-2.
PCI-4451/4452 User Manual 3-2
MUX3
ATTEN
0 dB/20 dB
MUX3
AC/DC
Coupling
MUX3
INPUT/CAL
MUX
ATTEN
Control
MUX
AC/DC
Control
MUX
Control
INPUT/CAL
Analog Function Block Diagram
PCI-4451 only
††
PCI-4452 only
†
©
National Instruments Corporation
Analog Input
Input Mode
Input Coupling
Chapter 3 Hardware Overview
The analog input section of each PCI-4451/4452 device is software
configurable. You can select di fferent anal og input con figuratio ns through
application software. The following sections describe in detail each of the
analog input categories.
The PCI-4451/4452 devices use differential (DIFF) inputs. You can
configure the input as a referenced single ended (SE) channel using the
BNC-2140 DSA accessory. For more information, please refer to the
BNC-2140 Use r Manual. In DIFF mode, one line connects to the positive
input of the channel, and the other connects to the negative inp ut of the
same channel. You can connect the differential input to SE or DIFF signals,
either floating or ground-referenced. However, grounding the negative
input from floating sources may impr ove the measurement quality by
removing the common-mode noise.
The PCI-4451/4452 has a software-programmable switch that determines
whether a capacitor is placed in the signal path. If the switch is set for DC,
the capacitor is bypassed and any DC offset present in the source signal is
passed to the ADC. If the source has a significant amount of unwanted
offset (bias voltage), you must set the switch for AC coupling to place the
capacitor in the signal path and take full advantage of the input signal
range.
Input Polarity and Input Range
The PCI-4451/4452 devices operate in bipolar mode. Bipolar input
means that the input voltage range is between –V
The PCI-4451/4452 has a bipolar input range of 20 V (±10 V) for a
gain of 1.0 (0 dB).
You can program the range settings on a per channel basis so that you can
configure each input channel uniquely. The software-programmable gain
on these devices increases their overall flexibility by matching the input
signal ranges to those that the ADC can accommodate. With the proper gain
setting, you can use the full resolution of the ADC to measure the input
signal. Table 3-1 shows the overall input range and precision according to
the input range configuration and gain used.
©
National Instruments Corporation 3-3 PCI-4451/4452 User Manual
/2 and +V
ref
/2.
ref
Chapter 3 Hardware Overview
Table 3-1.
Linear Gain Gain Input Range Precision
0.1 –20 dB ±42.4 V
Actual Range and Measurement Precision
2
3.0518 mV
1
2
0.316 –10 dB ±31.6 V 965.05 µV
1.0 0 dB ±10.0 V 305.18 µV
3.16 10 dB ±3.16 V 96.505 µV
10 20 dB ±1.00 V 30.518 µV
31.6 30 dB ±0.316 V 9.6505 µV
100 40 dB ±0.100 V 3.0518 µV
316 50 dB ±31.6 mV 965.05 nV
1000 60 dB ±10.0 mV 305.18 nV
1
The value of 1 LSB of the 16-bit ADC; that is, the voltage increment corresponding to a
change of one count in t h e ADC 16-bit count.
2
The actual input range is by design ±100 V; howe ver, the device is not tested or certified
to operate in this range.
See Appendix A,
Specifications
, for absolute ma ximum ratings.
All data read from the ADC is interpreted as two’s complement format. In
two’s complement mode, digital data values read from the analog input
channel are either positive or negative.
Considerations for Selecting Input Ranges
The input range you select depends on the expected range of the incoming
signal. A large input range can accommodate a large signal variation but
reduces the voltage resolution. Choosing a smaller input range improves
the voltage resolution but can result in the input signal going out of range.
For best results, match the input range as closely as possible to the expected
range of the input signal.
If the input range is not appropriately chosen, an input signal can be clipped
and introduce large errors that are easily identified in the frequency
spectrum. The PCI-4451/4452 is equipped with overrange detection
circuits in both the analog and digital sections of each input channel. These
circuits determine if an input signal has exceeded the selected input
voltage. Chapter 6, Theory of Analog Operation, provides a m ore in-depth
explanation of how overranges can occur.
PCI-4451/4452 User Manual 3-4
©
National Instruments Corporation
Chapter 3 Hardware Overview
Caution If you exceed the rated input voltages, you can damage the computer and the
!
connected equipment.
Analog Output
The analog output section of t he PCI-4451 device is software-con figurable.
You can select different analog output configurations through application
software designed to control the PCI-4451. The followi ng sections describe
in detail each of the analog output categories. Th e PCI-4451 device has two
channels of analog output voltage at the I/O connector.
Output Mode
The PCI-4451 device uses DIFF outputs. You can configure the outputs as
an SE channel using the BNC-21 40 DSA accessory. For more information,
please refer to the BNC-2140 User Manual. In DIFF mode, one line
connects to the positive input of the channel, and the other connects to the
negative input of that same channel. You can connect the differential output
to either SE or DIFF loads, either floating or gro und-referenced. Howev er,
grounding the ne gative output is recommended w hen driving floating
single-ended loads.
Output Polarity and Output Range
The PCI-4451 device operates in bipolar mode. Bipolar outp ut means that
the output voltage range is between –V
a bipolar output range of 20 V (±10 V) for an attenuation of 1.0 (0 dB).
You can program the range settings on a per channel basis so that you can
configure each output channel uniquely. The software-programmable
attenuation on these devices increases their overall flexibility by matching
the output signal ranges to the your application. Table 3-2 shows the overall
output range and precision according to the attenuation used.
©
National Instruments Corporation 3-5 PCI-4451/4452 User Manual
/2 and +V
ref
/2. The PCI-4451 has
ref
Chapter 3 Hardware Overview
Table 3-2.
Attenuation
Linear
Actual Range and Measurement Precision
Attenuation
dB
1.0 0 dB ±10.0 V 305.18 µV
10 20 dB ±1.00 V 30.158 µV
100 40 dB ±0.100 V 3.0518 µV
∞ ∞ dB 0 V 0 V
1
The value of 1 LSB of the 16-bit DAC; that is, the voltage increment corresponding to a
change of one count in the DAC 16-bit count.
See Appendix A,
Note The device boots in a m ode with the outputs disabled
Specifications
, for absolute ma ximum ratings.
Although these functions appear similar, they are quite distinct and are
implemented to protect your external equipment from startup transients.
When the DACs no longer have data written to them, they automatically
retransmit the last data point they received. If you are expecting the data to return
to 0 V or any other voltage level, you
append the data to make it do so.
MUST
All data written to the DACs are interpreted as two’s complement format.
In two’s complement mode, data values written to the analog output
channel are either positive or negative.
Range Precision
infinitely (∞) attenuated.
AND
1
Trigger
In addition to supporting internal software tri ggering and external digital
triggering to initiate a data acquisition sequence, the PCI-44 51/4452 also
supports analog level triggering. You can configure the trigger circuit to
monitor any one of the analog input channels to generate the level trigger.
Choosing an input channel as the level trigger channel does not influence
the input channel capabilities. The level trigger circuit compares the full
16 bits of the programmed trigger level with the digitized 16-bit sample.
The trigger-level range is identical to the analog input voltage range. The
trigger-level resolution is the same as the precision for a given input range.
Refer to Table 3-1.
The trigger circuit generates an internal digital trigger based on the input
signal and the user-defined trigger levels. Any of the timing sections of the
DAQ-STC can use th is level trigger, including the analog input, analog
output, RTSI, and general-purpose counter/timer sections. For example,
PCI-4451/4452 User Manual 3-6
©
National Instruments Corporation
Chapter 3 Hardware Overview
you can configure the analog input section to acquire a given number of
samples after the analog input signal crosses a specific threshold. As
another example, you can configure the analog output section to generate
an output waveform whenever the analog input signal crosses a specific
threshold.
Due to the nature of delta-sigma con v er ters, the triggering cir cuits o perate
on the digital output of the converter. Since the trigger is generated at the
output of the converter, triggers can occur only when a sample is actually
generated. Placing the triggering circuits on the digital side of the converter
does not affect most measurements unless an analog output is generated
based on the input trigger. In this case, you must be aware of the inheren t
delays of the finite impulse response (FIR) filters internal to the delta-sigma
conv erters and you must accoun t for the delays. The delay through th e input
converter is 42 sample periods, while the delay through the output converter
is 34.6 ±0.5 sample periods.
During repetitive sampling of a waveform, you may observe jitter due to the
uncertainty of where a trigger level falls compared to the actual digitized
data. Although this trigger jitter is never greater than one sample period, it
can seem quite bad when the sample rate is only twice the bandwid th of
interest. This jitter has no effect on the processing of the data, and you can
decrease this jitter by oversampling.
There are five analog level triggering modes available, as shown in
Figures 3-3 throug h 3-7. You can set lowValue and highValue
independently in the software.
In below-low-level triggering mode, shown in Figure 3-3, the trigger is
generated when the signal value is less than lowValue. HighValue is
unused.
lowValue
Trigger
Figure 3-3.
©
National Instruments Corporation 3-7 PCI-4451/4452 User Manual
Below-Low-Level Triggering Mode
Chapter 3 Hardware Overview
In above-high-level triggering mode, the trigger is generated when the
signal value is greater than highValue. LowValue i s unu sed .
highValue
Trigger
Figure 3-4.
Above-High-Level Triggering Mode
In inside-region triggering mode, the trigger is generated when the signal
value is between the lowValue and the highValue.
highValue
lowValue
Trigger
Figure 3-5.
Inside-Region Triggering Mode
In high-hysteresi s trigger ing mode, the trigger i s generated when the signal
value is greater than highValue, with the hysteresis specified by lowValue.
highValue
lowValue
Trigger
Figure 3-6.
PCI-4451/4452 User Manual 3-8
High-Hysteresis Triggering Mode
©
National Instruments Corporation
Chapter 3 Hardware Overview
In low-hysteresis triggering mode, the trigger is generated when the signal
value is less than lowValue, with the hysteresis specified by highValue.
highValue
lowValue
Trigger
RTSI Triggers
Figure 3-7.
Low-Hysteresis Triggering Mode
Y o u can use digital triggering through the RTSI bus and the external digital
50-pin connector using any one of the eight available programmable
function input (PFI) pi ns. PFI0/TRIG1 (EXT_TRIG) is the pin dedicated to
external digital triggering.
You can trigger the PCI-DSA devices from any other PCI-DSA device or
any National Instruments device that has the RTSI bus feature. You can
connect the devices through the RTSI bus cable. An external digital trigger
can also trigger multiple devices simultaneously by distributing that trigger
through the RTSI bus. You can select the polarity of the external digital
trigger.
The seven RTSI trigger lines on the RTSI bus provide a very flexible
interconnection scheme for any PCI-4451/4452 device sharing the RTSI
bus. These bidirectional lines can drive any of eight timing signals onto the
RTSI bus and can receive any of these timing signals. This signal
connection scheme is shown in Figure 3-8.
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National Instruments Corporation 3-9 PCI-4451/4452 User Manual
Chapter 3 Hardware Overview
Trigger 7
RTSI Bus Connector
Clock
RTSI Switch
switch
DAQ-STC
TRIG1
TRIG2
CONVERT*
UPDATE*
WFTRIG
GPCTR0_SOURCE
GPCTR0_GATE
GPCTR0_OUT
GPCTR1_SOURCE
GPCTR1_GATE
RTSI_OSC (20 MHz)
Figure 3-8.
RTSI Bus Signal Connection
Refer to the Chapter 4, Signal Connections for a des c ript i on of the signals
shown in Figure 3-8.
Digital I/O
The PCI-4451/4452 devices contain eight lines of digital I/O for
general-purpose use through the 50-pin connector. You can individually
software-configure each line for either input or output.
The hardware up/down control for general-purpose counters 0 and 1 are
connected onboard to DIO6 and DIO7, respectively. Thus, you can use
DIO6 and DIO7 to control the general-purpose counters. The up/down
control signals are input only and do not affect the operation of the DIO
lines.
Note At system power-on and reset, the hardware sets both the PFI and DIO lines to
high impedance. This means that the device circuitry is not actively driving the
output either high or low. F or example, DIO(0) will be in the high impedance state
after power on, and Table 4-4, Digital I/O Signal Summary, shows that there is a
50 kΩ pull-up resistor. This pull-up resistor sets the DIO(0) pin to a logic high
when the output is in a high-impedance state. Take careful consideration of the
power-on state of the system to prevent any damage to external equipment.
PCI-4451/4452 User Manual 3-10
©
National Instruments Corporation
Timing Signal Routing
The DAQ-STC provides a flexible interface for connecting timing signals
to other devices or to external circuitry. Your PCI-4451/4452 device uses
the RTSI bus to interconnect timing signals between devices, and uses the
PFI pins on the I/O connector to connect the device to external circuitry.
These connections enable the PCI-4 451/4452 device to both control and be
controlled by other devices and circuits.
There are a total of 13 timing signals internal to the DAQ-STC that you can
control by an external source. You can also control these timing signals by
signals generated internally to the DAQ-STC, and these selections are fully
software configurable. Many of these timing signals are also available as
outputs on the RTSI pins, as indicated in the RTSI Triggers section earlier
in this chapter, and on the PFI pins, as indicated in Chapter 4, Signal
Connections.
Programmable Function Inputs
The 10 PFIs are connected to the signal routing multiplexer for each timing
signal, and software can select one of the PFIs as the external source for a
given timing signal . It is im portant to note that you can use any of th e PFIs
as an input by any of the timing signals and that multiple timing signals can
use the same PFI simultaneously. This flexible routing scheme reduces the
need to change physical connections to the I/O connector for different
applications. You can also individually enable each of the PFI pins to
output a specific internal timing signal. For example, if you need the
GPCTR0_SOURCE signal as an output on the I/O connector, software can
turn on the output driver for the PFI8/GPCTR0_SOURCE pin.
Chapter 3 Hardware Overview
Note
Two o f the 10 PF I pi n s are n ot avai l ab le for general-purpose input on the di git a l
connector . You can confi gure PFI2/C ONVERT * and PFI5 /UPD A TE * as output s
only.
Device and RTSI Clocks
Some PCI-4451/4452 device functions require a frequency timebase to
generate the necessary timing signals for controlling general-purpose
signals at the 50-pin digital I/O connector. You canno t use these signals for
the generating the frequency of sample rates or update rates. Refer to
Selecting Sample/Update Cl ock Freq uency section for information on
sample/update clock generation.
©
National Instruments Corporation 3-11 PCI-4451/4452 User Manual
Chapter 3 Hardware Overview
A PCI-4451/4452 device can use either its internal 20 MHz timebase or a
timebase received over the RTSI bus. In addition, if you configure the
device to use the internal timebase, you can pr ogram the de vi ce to dri v e its
internal timebase o ver the RTSI bus to anot her device that you program to
receive this timebase signal. The default configuration at startup is to use
the internal timebase without driving the RTSI bus timebase signal. This
timebase is software-selectable.
Selecting Sample/Update Clock Frequency
The two analog input channels of the PCI-4451 and the four inputs of the
PCI-4452 are simultaneously sampled at any software-programmable rate
from 5.0 kS/s to 204.8 kS/s in 190.7 µS/s increments (worst case). The
devices use direct digital synthesis (DDS) technology so that you can
choose the correct sample rate required for your application. All the input
channels acquire data at the same rate. One input channel cannot acquire
data at a different rate from another input channel.
The two analog output channels of the PCI-4451 are updated
simultaneously at any software programmable rate from 1.25 kS/s to
51.2 kS/s in 47.684 µS/s increments (worst case). The input sample rate
and output update rate on the PCI-4451 are synchronized and deri ved fro m
the same DDS clock. The input and output clocks may differ from each
other by a factor of 2 (1, 2, 4, 8, …, 128) while still maintaining their
synchronization as lon g as the lower bounds for update and sample rate are
maintained. All the output channels update data at the same rate. One
output channel cannot update data at a different rate from another output
channel.
The DDS clock signal and the synchronization start signal are transmitted
to other PCI-DSA devices via the RTSI bus. The PCI-4451/4452 can also
receive these signals to syn chronize the acquisition or wa veform generation
with other devices. In a multidevice system, a master device would drive
the clock and synchronization signal to other slave or receiving devices.
PCI-4451/4452 User Manual 3-12
©
National Instruments Corporation
Device Configuration Issues
Selecting a sample rate that is less than two times the frequency of a band
of interest can lead you to believe the board is functioning improperly. By
undersampling the signal, you could receive what appears to be a DC
signal. This situation is due to the sharp antialiasing filters that remove
frequency components above the sampling frequency. If you have a
situation where this occurred, simply increase the sample rate until it meets
the requirements of the Shannon Sampling Theorem. For more information
on the filters and aliasing, refer to Chapter 6, Theory of Analog Opera tio n.
Unlike other converter technologies, delta-sigma converters must be run
continuously and at a minimum clock rate. To operate within guaranteed
specifications, the A/D con verters should operate at a minimum sample rate
of 5.0 kS/s and the D/A converters should operate at a minimum update rate
of 1.25 kS/s. This minimum rate is required to keep the internal circuitry of
the converters running within specifications. You are responsible for
selecting sample and update rates that fall within the specified limits.
Failure to do so could greatly affect the specifications.
Chapter 3 Hardware Overview
©
National Instruments Corporation 3-13 PCI-4451/4452 User Manual
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