NI SCXI-1120/D User manual

SCXI™
SCXI-1120/D User Manual
Eight-Channel Isolated Analog Input Module and
Eight-Channel Wide Band Isolated Analog Input Module
for Signal Conditioning
SCXI-1120/D User Manual
September 1999 Edition
Part Number 320425D-01

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©Copyright 1992, 1999 National Instruments Corporation. All rights reserved.

Important Information
Warranty
The SCXI-1120 and SCXI-1120D are warranted against defects in materials 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 work. National Instruments will pay the shipping costs of
returning to the owner parts which are covered by warranty.
National Instruments believes that the information in this document is accurate. The document has been carefully reviewed
for technical accuracy. In the event that technical or typographical errors exist, National Instruments reserves the right 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.
EXCEPT AS SPECIFIED HEREIN, NATIONAL INSTRUMENTS MAKES NO WARRANTIES, EXPRESS OR IMPLIED, AND SPECIFICALLY DISCLAIMS ANY
WARRANTY OF MERCHANTABILITY OR FITNESS FOR APARTICULAR PURPOSE. CUSTOMER’SRIGHT TO RECOVER DAMAGES CAUSED BY FAULT
OR NEGLIGENCE ON THE PART OF NATIONAL INSTRUMENTS SHALL BE LIMITED TO THE AMOUNT THERETOFORE PAID BY THE CUSTOMER.
NATIONAL INSTRUMENTS WILL NOT BE LIABLE FOR DAMAGES RESULTING FROM LOSS OF DATA, PROFITS, USE OF PRODUCTS, OR INCIDENTAL
OR CONSEQUENTIAL DAMAGES, EVEN IF ADVISED OF THE POSSIBILITY THEREOF. This limitation of the liability of National Instruments
will apply regardless of the form of action, whether in contract or tort, including negligence. Any action against National
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any delay in performance due to causes beyond its reasonable control. The warranty 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; owner’s abuse, misuse, or negligent acts; and power failure
or surges, fire, flood, accident, actions of third parties, or other events outside reasonable control.
Copyright
Under the copyright laws, this publication may not be reproduced or transmitted in any form, electronic or mechanical,
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Trademarks
ComponentWorks™, CVI™, LabVIEW™, Measure™, natinst.com™, National Instruments™, NI-DAQ™, SCXI™,
and VirtualBench™are trademarks of National Instruments Corporation.
Product and company names mentioned herein are trademarks or trade names of their respective companies.
WARNING REGARDING USE OF NATIONAL INSTRUMENTS PRODUCTS
(1) NATIONAL INSTRUMENTS PRODUCTS ARE NOT DESIGNED WITH COMPONENTS AND TESTING
FOR A LEVEL OF RELIABILITY SUITABLE FOR USE IN OR IN CONNECTION WITH SURGICAL IMPLANTS
OR AS CRITICAL COMPONENTS IN ANY LIFE SUPPORT SYSTEMS WHOSE FAILURE TO PERFORM CAN
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(2) IN ANY APPLICATION, INCLUDING THE ABOVE, RELIABILITY OF OPERATION OF THE SOFTWARE
PRODUCTS CAN BE IMPAIRED BY ADVERSE FACTORS, INCLUDING BUT NOT LIMITED TO FLUCTUATIONS
IN ELECTRICAL POWER SUPPLY, COMPUTER HARDWARE MALFUNCTIONS, COMPUTER OPERATING
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AN APPLICATION, INSTALLATION ERRORS, SOFTWARE AND HARDWARE COMPATIBILITY PROBLEMS,
MALFUNCTIONS OR FAILURES OF ELECTRONIC MONITORING OR CONTROL DEVICES, TRANSIENT
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AS THESE ARE HEREAFTER COLLECTIVELY TERMED “SYSTEM FAILURES”). ANY APPLICATION WHERE A
SYSTEM FAILURE WOULD CREATE A RISK OF HARM TO PROPERTY OR PERSONS (INCLUDING THE RISK OF
BODILY INJURY AND DEATH) SHOULD NOT BE RELIANT SOLELY UPON ONE FORM OF ELECTRONIC SYSTEM
DUE TO THE RISK OF SYSTEM FAILURE. TO AVOID DAMAGE, INJURY, OR DEATH, THE USER OR
APPLICATION DESIGNER MUST TAKE REASONABLY PRUDENT STEPS TO PROTECT AGAINST SYSTEM
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WITHOUT LIMITATION, THE APPROPRIATE DESIGN, PROCESS AND SAFETY LEVEL OF SUCH SYSTEM OR
APPLICATION.

©National Instruments Corporation v SCXI-1120/D User Manual
Contents
About This Manual
Conventions ...................................................................................................................ix
National Instruments Documentation............................................................................x
Chapter 1
Introduction
About the SCXI-1120/D................................................................................................1-1
What You Need to Get Started ......................................................................................1-2
Unpacking......................................................................................................................1-3
Software Programming Choices....................................................................................1-3
National Instruments Application Software....................................................1-3
NI-DAQ Driver Software................................................................................1-4
Optional Equipment.......................................................................................................1-5
Chapter 2
Configuration and Installation
Module Configuration....................................................................................................2-1
Digital Signal Connections..............................................................................2-4
Using Jumpers W42 and W43 ..........................................................2-5
Using Jumper W44 on Revisions A and B of the SCXI-1120..........2-6
Using Jumper W44 on Revision C of the SCXI-1120 and
All Revisions of the SCXI-1120D .................................................2-6
Analog Configuration......................................................................................2-8
Grounding, Shielding, and Reference-Mode Selection ....................2-8
Direct Temperature Connection........................................................2-10
Gain Jumpers for the SCXI-1120/D..................................................2-10
SCXI-1120 Filter Jumpers ................................................................2-12
SCXI-1120D Filter Jumpers .............................................................2-13
Hardware Installation.....................................................................................................2-14
Chapter 3
Signal Connections
SCXI-1120/D Front Connector......................................................................................3-3
Front Connector Signal Descriptions.............................................................................3-4
Analog Input Channels....................................................................................3-5
Temperature Sensor Connection .....................................................................3-7
SCXI-1120/D Rear Connector.......................................................................................3-8

Contents
SCXI-1120/D User Manual vi www.natinst.com
Rear Connector Signal Descriptions .............................................................................3-9
Analog Output Signal Connections.................................................................3-10
Chapter 4
Theory of Operation
Functional Overview.....................................................................................................4-1
Power-Up State ............................................................................................... 4-2
SCXIbus Connector and Digital Interface.....................................................................4-3
Digital Control Circuitry ...............................................................................................4-4
Analog and Timing Circuitry ........................................................................................4-5
Analog Input Channels....................................................................................4-6
Analog Output Circuitry...................................................................4-9
Chapter 5
Calibration
Calibration Equipment Requirements ...........................................................................5-1
Offset Null Adjust .........................................................................................................5-1
Appendix A
Specifications
Appendix B
Technical Support Resources
Glossary
Index
Figures
Figure 1-1. The Relationship between the Programming Environment,
NI-DAQ, and Your Hardware...............................................................1-5
Figure 2-1. SCXI-1120/D Parts Locator Diagram...................................................2-2
Figure 2-2. Removing the SCXI Module Cover......................................................2-4
Figure 3-1. SCXI-1120/D Front Connector Pin Assignments.................................3-3
Figure 3-2. Ground-Referenced Signal Connection for the SCXI-1120/D
with High Common-Mode Voltage ...................................................... 3-5
Figure 3-3. Floating Signal Connection for the SCXI-1120/D Referenced to
Chassis Ground for Better Signal-to-Noise Ratio................................. 3-5

Contents
©National Instruments Corporation vii SCXI-1120/D User Manual
Figure 3-4. Floating AC-Coupled Signal Connection for the SCXI-1120...............3-6
Figure 3-5. AC-Coupled Signal Connection for the SCXI-1120 with
High Common-Mode Voltage...............................................................3-6
Figure 3-6. AC-Coupled Signal Connection for the SCXI-1120D with
High Common Mode Voltage...............................................................3-7
Figure 3-7. Floating AC-Coupled Signal Connection for the SCXI-1120D............3-7
Figure 3-8. SCXI-1120/D Rear Signal Connector Pin Assignments.......................3-8
Figure 4-1. SCXI-1120/D Block Diagram...............................................................4-1
Figure 4-2. Digital Interface Circuitry Block Diagram............................................4-3
Figure 4-3. SCXI-1120/D Digital Control ...............................................................4-4
Figure 4-4. Analog Input Block Diagram ................................................................4-6
Figure 4-5. Analog Output Circuitry........................................................................4-9
Tables
Table 2-1. Digital Signal Connections, Jumper Settings........................................2-7
Table 2-2. Jumper W46 Settings.............................................................................2-9
Table 2-3. Jumper W41 Settings.............................................................................2-10
Table 2-4. Gain Jumper Allocation.........................................................................2-10
Table 2-5. Gain Jumper Positions...........................................................................2-11
Table 2-6. SCXI-1120 Filter Jumper Allocation ....................................................2-12
Table 2-7. SCXI-1120D Filter Jumper Allocation .................................................2-13
Table 3-1. SCXI-1120/D Front Connector Signal Descriptions.............................3-4
Table 3-2. Rear Connector Signal Descriptions .....................................................3-9
Table 3-3. SCXIbus to SCXI-1120/D Rear Connector
to DAQ Device Pin Equivalencies........................................................3-11
Table 5-1. Calibration Potentiometers Reference Designators...............................5-2
Table A-1. Input Signal Range................................................................................A-5
Table A-2. System Noise RTI (0.1 Hz to 50 kHz) ..................................................A-6
Table A-3. Switching Supply Noise (approximately at 100 kHz)...........................A-7

©National Instruments Corporation ix SCXI-1120/D User Manual
About This Manual
This manual describes the electrical and mechanical aspects of the
SCXI-1120 and SCXI-1120D (SCXI-1120/D) modules and contains
information concerning their installation and operation.
The SCXI-1120 and SCXI-1120D are National Instruments Signal
Conditioning eXtensions for Instrumentation (SCXI) Series modules.
The SCXI-1120/D provides eight isolated input channels. Each channel
is independently configurable through jumpers.
The SCXI-1120 module is designed for low-cost signal conditioning of
thermocouples, volt sources, millivolt sources, and 4 to 20 mA sources
or 0 to 20 mA process-current sources where high common-mode
voltages exist.
The SCXI-1120D module is designed for low-cost signal conditioning
of volt, millivolt, and current sources that require a 20 kHz bandwidth
and where high common-mode voltages exist.
Conventions
The following conventions appear in this manual:
♦The ♦symbol indicates that the following text applies only to a specific
product, a specific operating system, or a specific software version.
This icon denotes a note, which alerts you to important information.
This icon denotes a caution, which advises you of precautions to take to
avoid injury, data loss, or a system crash.
italic Italic text denotes variables, emphasis, a cross reference, or an introduction
to a key concept. Thisfont also denotes text that is a placeholder for a word
or value that you must supply.
Lab/1200 Lab device refers to the Lab-LC, Lab-NB, Lab-PC, Lab-PC+,
Lab-PC-1200, and Lab-PC-1200AI.
PC PC refers to the IBM PC/XT, the IBM PC AT, and compatible computers.
SCXI-1120 SCXI-1120 refers to only the SCXI-1120 module.

About This Manual
SCXI-1120/D User Manual x www.natinst.com
SCXI-1120D SCXI-1120D refers to only the SCXI-1120D module.
SCXI-1120/D SCXI-1120/D refers to both the SCXI-1120D module and the SCXI-1120
module.
Slot 0 Slot 0 refers to the power supply and control circuitry in the SCXI chassis.
National Instruments Documentation
The SCXI-1120/D 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:
•Getting Started with SCXI—If you are using SCXI, this is the first
manual you should read. It gives an overview of the SCXI system and
contains the most commonly needed information for the modules,
chassis, and software.
• Your SCXI hardware user manuals—If you are using SCXI, read these
manuals next for detailed information about signal connections and
module configuration. They also explain in greater detail how the
module works and contain application hints.
• Your DAQ hardware documentation—This documentation has
detailed information about the DAQ hardware that plugs into or is
connected to your computer. Use this documentation for hardware
installation and configuration instructions, specification information
about your DAQ hardware, and application hints.
• 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 software documentation
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.
•SCXI Chassis Manual—If you are using SCXI, read this manual for
maintenance information on the chassis and installation instructions.

©National Instruments Corporation 1-1 SCXI-1120/D User Manual
1
Introduction
This chapter describes the SCXI-1120/D; lists what you need to get started;
describes the optional software, optional equipment, and custom cables;
and explains how to unpack the SCXI-1120/D kit.
About the SCXI-1120/D
The SCXI-1120/D has eight isolated input channels. The SCXI-1120 is a
module for signal conditioning of thermocouples, volt sources, millivolt
sources, 4 to 20 mA current sources, and 0 to 20 mA process-current
sources. If external excitation is provided, thermistors, RTDs, and strain
gauges can also be measured. The SCXI-1120D is a module for signal
conditioning and isolating volt sources, millivolt sources, and current
sources that require a bandwidth of up to 20kHz. If you provide external
excitation, you can use strain gauges and other vibration sensors. The
SCXI-1120/D can operate in two output modes—in the parallel-output
mode with all eight input channels connected in parallel to eight DAQ
device channels, or in the multiplexed-output mode with all eight channels
multiplexed into a single DAQ device channel.
The SCXI-1120/D operates with full functionality with the National
Instruments MIO, 1200 Series, and Lab PC+ devices. You can use the
Lab-NB, the Lab-PC, the Lab-LC, and the PC-LPM-16/PnP devices with
the SCXI-1120/D, but these devices cannot scan the module when it is
configured in the multiplexed-output mode. These devices can perform
only single-channel reads in this mode. You can multiplex several
SCXI-1120/D modules into a single channel, thus greatly increasing the
number of analog input signals that can be digitized.
The addition of a shielded terminal block provides screw terminals for easy
signal attachment to the SCXI-1120/D. In addition, a temperature sensor
for cold-junction compensation (CJC) of thermocouples is included on the
terminal block. This cold-junction reference (CJR) is either multiplexed
along with the eight channels or connected by jumpers to a different
channel of the DAQ device.

Chapter 1 Introduction
SCXI-1120/D User Manual 1-2 www.natinst.com
With the SCXI-1120/D, the SCXI chassis can serve as a fast-scanning
signal conditioner for laboratory testing, production testing, and industrial
process monitoring.
Detailed specifications of the SCXI-1120/D are listed in Appendix A,
Specifications.
What You Need to Get Started
To set up and use your SCXI-1120/D, you will need the following items:
❑SCXI-1120 or SCXI-1120D module
❑SCXI-1120/D User Manual
❑One of the following chassis and your SCXI chassis manual:
– SCXI-1000
– SCXI-1000DC
– SCXI-1001
– SCXI-2000
❑An SCXI terminal block/connector assembly (optional)
❑DAQ device or SCXI-1200
❑Your computer

Chapter 1 Introduction
©National Instruments Corporation 1-3 SCXI-1120/D User Manual
Unpacking
Your SCXI-1120/D module is shipped in an antistatic package to prevent
electrostatic damage to the module. Electrostatic discharge can damage
several components on the module. To avoid such damage in handling the
module, take the following precautions:
• Ground yourself using a grounding strap or by holding a grounded
object.
• Touch the antistatic package to a metal part of your SCXI chassis
before removing the module from the package.
• Remove the module from the package and inspectthe module for loose
components or any other sign of damage. Notify National Instruments
if the module appears damaged in any way. Do not install a damaged
module into your SCXI chassis.
•Never touch the exposed pins of connectors.
Software Programming Choices
There are several options to choose fromwhen programming your National
Instruments plug-in DAQ and SCXI hardware. You can use LabVIEW,
LabWindows/CVI, NI-DAQ, ComponentWorks, Measure, VirtualBench,
or register-level programming.
National Instruments Application Software
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
through standard OLE controls and DLLs. With ComponentWorks, you
can use all of the configuration tools, resource management utilities, and
interactive control utilities included with NI-DAQ.
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 devices, is included with LabVIEW. The LabVIEW Data
Acquisition VI Library is functionally equivalent to the NI-DAQ software.

Chapter 1 Introduction
SCXI-1120/D User Manual 1-4 www.natinst.com
LabWindows/CVI features interactive graphics, a state-of-the-art user
interface, and uses the ANSI standard C programming language. The
LabWindows/CVI Data Acquisition Library, a series of functions for using
LabWindows/CVI with National Instruments DAQ hardware, is included
with your NI-DAQ software kit. The LabWindows/CVI Data Acquisition
Library is functionally equivalent to the NI-DAQ software.
VirtualBench features virtual instruments (VIs) that combine DAQ
products, software, and your computer to create a stand-alone instrument
with the added benefit of the processing, display, and storage capabilities
of your computer. VirtualBench instruments load and save waveform data
to disk in the same forms that can be used in popular spreadsheet programs
and word processors.
Using ComponentWorks, LabVIEW, LabWindows/CVI, or VirtualBench
software will greatly reduce the development time for your data acquisition
and control application.
NI-DAQ Driver Software
The NI-DAQ driver software is included at no charge with all National
Instruments DAQ hardware. NI-DAQ has an extensive library of functions
that you can call from your application programming environment. These
functions include routines for analog input (A/D conversion), buffered data
acquisition (high-speed A/D conversion), analog output (D/A conversion),
waveform generation, digital I/O, counter/timer operations, SCXI, RTSI,
self-calibration, messaging, and acquiring data to extended memory.
NI-DAQ also internally addresses many of the complex issues between the
computer and the plug-in device, such as programming interrupts and
DMA controllers. NI-DAQ maintains a consistent software interface
among its different versions so that you can change platforms with minimal
modifications to your code. Whether you are using conventional
programming languages, LabVIEW, or LabWindows/CVI, your
application uses the NI-DAQ driver software, as illustrated in Figure 1-1.

Chapter 1 Introduction
©National Instruments Corporation 1-5 SCXI-1120/D User Manual
Figure 1-1. The Relationship between the Programming Environment,
NI-DAQ, and Your Hardware
Optional Equipment
National Instruments offers a variety of products to use with your
SCXI-1120/D, as follows:
• Cables and cable assemblies, shielded and ribbon
• Shielded terminal blocks and connector-and-shell assemblies
• SCXI process current resistor kit
• SCXI modules and accessories for isolating, amplifying, exciting, and
multiplexing signals for relays and analog output. With SCXI you can
condition and acquire up to 3,072 channels.
For additional information about optional equipment available from
National Instruments refer to your National Instruments catalogue or
call the office nearest you.
LabWindows/CVI
(Windows 95, 3.1, NT,
or Sun)
LabVIEW
(Windows 95, 3.1, NT
Macintosh, or Sun)
ComponentWorks
(Windows 95, NT)
Conventional
Programming Enviroment
(Macintosh, or Sun)
Virtual Bench
(Windows 95, 3.1) NI-DAQ Driver Software
DAQ or
SCXI Hardware
Personal
Computer or
Workstation

©National Instruments Corporation 2-1 SCXI-1120/D User Manual
2
Configuration and Installation
This chapter describes how to configure the SCXI-1120/D jumpers and
how to install the SCXI-1120/D into the SCXI chassis.
Module Configuration
The SCXI-1120/D includes 46 jumpers that are shown in Figure 2-1.

Chapter 2 Configuration and Installation SCXI-1120/D User Manual 2-2 www.natinst.com
Figure 2-1. SCXI-1120/D Parts Locator Diagram
First-Stage
Gain Jumpers
Thumbscrew
Thumbscrew
Input Null
Adjust
Potentiometers
Output Null
Adjust
Potentiometers
Product Name,
Assembly Number,
and Serial Number
Front
Connector
Second-Stage
Filter Jumpers
Second-Stage
Gain Jumpers
First-Stage
Filter Jumpers
Digital
Jumpers
Rear
Signal
Connector
Connector
SCXIbus
Grounding
Screw
FRONT REAR
Connector
and Shell
Mounting
Holes
Terminal
Block
Mounting
Hole
Terminal
Block
Mounting
Hole

Chapter 2 Configuration and Installation
©National Instruments Corporation 2-3 SCXI-1120/D User Manual
The jumpers are used as follows:
• Fixed jumpers
– On Revision A and B SCXI-1120 modules, jumper W42 is unused
and should not be connected.
– Jumper W45 is reserved and should not be reconfigured.
– On Revision A and B SCXI-1120 modules, jumper W44 carries
the SLOT0SEL* signal from the rear signal connector, after
buffering, to the SCXIbus INTR* line and should be left in the
SCXI-1120 factory-default position (position 1). On all
SCXI-1120D modules and on Revision C and later SCXI-1120
modules, jumper W44 does not exist.
Note The revision letter is located on the National Instruments label located on the side of
each SCXI-1120/D module. The revision letter is found in the part number and is the letter
found in that part number.
• User-configurable jumpers
– Jumper W43 carries the SCXIbus MISO line, after buffering, to
the SERDATOUT signal on the rear signal connector.
– On all SCXI-1120D and on Revision C and later SCXI-1120
modules, jumper 42 connects a pullup resistor to the
SERDATOUT signal on the rear signal connector.
– Jumper W46 configures the guard, the analog output ground, and
enables the NRSE mode.
– JumpersW1 through W8 configurethe first-stagegainof channels
0 through 7, respectively.
– Jumpers W9 through W16 configure the second-stage gain of
channels 0 through 7, respectively.
– Jumpers W17 through W24 configure the first-stage filtering of
input channels 0 through 7, respectively.
– JumpersW25 throughW40configurethe second-stage filteringof
input channels 0 through 7, respectively.
– Jumper W41 directly connects the temperature sensor to the rear
signal connector. To do so, set jumper W46 in the AB-R2 or
AB-R0 position first.

Chapter 2 Configuration and Installation
SCXI-1120/D User Manual 2-4 www.natinst.com
Tables 2-1 to 2-2 list the description and configuration of the
user-configurable jumpers. To change the configuration of the module,
refer to Figures 2-1 and 2-2 as you perform the following steps:
1. Remove the grounding screw of the SCXI module top cover.
2. Snap out the top cover of the shield by placing a screwdriver in the
groove at the bottom of the module and pushing down.
3. Remove the jumpers you want to change and replace them on the
appropriate pins.
4. Snap the top cover back in place.
5. Replace the grounding screw to ensure proper shielding.
You must use software to further configure the module. Refer to your
software manual.
Figure 2-2. Removing the SCXI Module Cover
Digital Signal Connections
The four digital signal connection jumpers have position 1 marked on the
module. Position 3 is not marked explicitly on the module.
The SCXI-1120/D has three jumpers dedicated for communication
between the DAQ device and the SCXIbus. These jumpers are W42, W43,
and W44.
Grounding
Screw
Top of Module
Front Connector
Removable Cover

Chapter 2 Configuration and Installation
©National Instruments Corporation 2-5 SCXI-1120/D User Manual
Using Jumpers W42 and W43
Leave jumpers W42 and W 43 in their factory-default settings if any one of
the following applies:
• The SCXI-1120/D is not cabled to a DAQ device
• The SCXI-1120/D is cabled to a DAQ device, and the SCXI chassis is
the only SCXI chassis cabled to that DAQ device
• The SCXI-1120/D is cabled to a DAQ device, and there are multiple
SCXI chassis cabled to that DAQ device with shielded cables
In the factory-default setting, jumper W43 connects, after buffering, the
SCXIbus Master-In-Slave-Out (MISO) line to the SERDATOUT pin of the
rear signal connector. In this setting, along with the proper setting of
jumper W42, the DAQ device can read the SCXI-1120/D Module ID
Register. See Chapter 3, Signal Connections, for the pin equivalencies of
the SCXI-1120/D rear signal connector and the DAQ device I/O connector.
Revisions A and B of the SCXI-1120
On Revision A and B SCXI-1120 modules, jumper W42 is not used. Set
jumper W43 as explained in the cases above, except in the case of a
multichassis ribbon cable system. In a multichassis ribbon cable system
with Revision A and B SCXI-1120 modules cabled to the DAQ device, you
can access the MISO line in only one chassis. Pick one of the chassis that
has the SCXI-1120 cabled to the DAQ device. Set jumper W43 on the
SCXI-1120 to position 1. On the SCXI-1120 modules that are in the other
chassis and cabled to the DAQ device, set jumper W43 to position 3.
Notice that you will only be able to access digital information from the
chassis that has the SCXI-1120 with jumper W43 set to position 1.
Revisions C and Later of the SCXI-1120 and All Revisions of
the SCXI-1120D
Jumper W42 in position 1 connects a 2.2 kΩpullup resistor to the
SERDATOUT line. Position 3 does not connect the pullup resistor to
the SERDATOUT line.
The SERDATOUT line is driven with an open-collector driver.
(An open-collector driver drives low or goes to a high-impedance state,
relying on a pullup resistor to make the signal line go high.)

Chapter 2 Configuration and Installation
SCXI-1120/D User Manual 2-6 www.natinst.com
When using a single chassis, leave W42 and W43 in position 1 on the
SCXI-1120/D that is connected to the DAQ device. In this setting, the
module drives MISO to SERDATOUT and connects the necessary pullup
resistor to the SERDATOUT line.
When using multiple chassis cabled to your DAQ device with shielded
cables, leave jumper W42 and W43 in position 1 on the SCXI-1120/D
modules that are connected to the DAQ device. In this setting, the module
drives MISO to SERDATOUT and connects the necessary pullup resistor
to the SERDATOUT line. All of the shielded adapters buffer and combine
the SERDATOUT from each chassis to the DAQ device.
When using multiple chassis cabled to your DAQ device with ribbon
cables, leave jumper W43 in position 1 on all of the SCXI-1120/D modules
that are cabled to the DAQ device. Set jumper W42 to position 1 on only
one of the SCXI-1120/D modules cabled to the DAQ device. All the other
SCXI-1120/D modules that are cabled to the DAQ device should have
jumper W42 in position 3. If too many pullup resistors are attached to the
SERDATOUT line, the drivers cannot drive the line low. See Table 2-1 for
the description and configuration of the jumper settings.
Using Jumper W44 on Revisions A and B of the
SCXI-1120
On Revision A and B SCXI-1120 modules, the jumper is in factory-default
position 1, which connects SLOT0SEL* to the SCXIbus INTR* line after
buffering. In this setting, the DAQ device controls the SCXIbus INTR*
line. See Chapter 3, Signal Connections, for the pin equivalences of the
SCXI-1120 rear signal connector and the DAQ device I/O connector.
Note Do not use position 3. It is reserved.
Using Jumper W44 on Revision C of the SCXI-1120
and All Revisions of the SCXI-1120D
On Revision C SCXI-1120 modules and all revisions of the SCXI-1120D
modules, jumper W44 is not loaded, and SLOT0SEL* is always buffered
to the INTR* line.

Chapter 2 Configuration and Installation
©National Instruments Corporation 2-7 SCXI-1120/D User Manual
Table 2-1. Digital Signal Connections, Jumper Settings
Jumper Description Configuration
W42 Position 1—Connects pullup
to SERDATOUT
(factory-default setting).
Applies only to SCXI-1120
Revisions C or later and all
SCXI-1120D modules.
W42 Position 3—Parking position
(notconnectedonRevisionsA
and B of the SCXI-1120).
W43 Position 1—Connects MISO
to SERDATOUT
(factory-default setting).
W43 Position 3—Parking position
1
2
3
1
2
3
1
2
3
1
2
3