National Instruments MXIbus VME-AT2000 User manual

© Copyright 1991, 1994 National Instruments Corporation.
All Rights Reserved.
Getting Started with Your
VME-AT2000 and the NI-VXI™
Software for MS-DOS
bus
August 1994 Edition
Part Number 320332B-01

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[phone]
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Limited Warranty
The National Instruments MXIbus boards 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 manual 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
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Trademarks
LabVIEW®and NI-VXI™are trademarks of National Instruments Corporation.
Product and company names listed are trademarks or trade names of their respective companies.

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of National Instruments Products
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© National Instruments Corporation vii VME-AT2000/NI-VXI MS-DOS Getting Started
Contents
About This Manual............................................................................................................xi
How to Use the Documentation Set.................................................................................xi
Organization of This Manual...........................................................................................xi
Conventions Used in This Manual ..................................................................................xii
Related Documentation ...................................................................................................xii
Customer Communication...............................................................................................xiii
Chapter 1
Introduction..........................................................................................................................1-1
What You Need to Get Started ......................................................................................1-1
Optional Equipment.......................................................................................................1-2
Optional Software..........................................................................................................1-2
Chapter 2
Hardware Configuration and Installation.................................................................2-1
Step 1. Unpack the AT-MXI and VME-MXI Hardware...............................................2-1
Step 2. Configure the AT-MXI Hardware.....................................................................2-2
Switch and Jumper Settings...............................................................................2-3
Base I/O Address Selection................................................................................2-3
Interrupt Selection..............................................................................................2-6
DMA Channel Selection....................................................................................2-8
Master Mode Versus Slave Mode..........................................................2-8
Step 3. Install the AT-MXI Hardware ...........................................................................2-11
Step 4. Configure the VME-MXI Hardware..................................................................2-13
Front Panel Features...........................................................................................2-15
VMEbus System Controller...............................................................................2-15
VME Address.....................................................................................................2-16
VMEbus Request Level Selection.....................................................................2-16
VMEbus Timeout Value....................................................................................2-18
Step 5. Install the VME-MXI Hardware........................................................................2-19
Step 6. Connect the MXIbus Cable................................................................................2-20
Nonpolarized Cables..........................................................................................2-20
Polarized Cables.................................................................................................2-21
Chapter 3
NI-VXI Software Installation and Configuration...................................................3-1
NI-VXI Software Overview...........................................................................................3-1
Main Programs and Files...................................................................................3-1
Additional Programs and Files...........................................................................3-2
Installing the Software...................................................................................................3-5
Modifying the AUTOEXEC.BAT File..............................................................3-6
Configuring the NI-VXI Software.................................................................................3-7
Running VXIEDIT.............................................................................................3-7
Configuration Editor..........................................................................................3-9

Contents
VME-AT2000/NI-VXI MS-DOS Getting Started viii © National Instruments Corporation
Logical Address Configuration..............................................................3-9
Bus Configuration..................................................................................3-13
Device Configuration.............................................................................3-15
Non-VXI Device Editor.....................................................................................3-17
Exiting VXIEDIT and Reinitializing the Hardware ..........................................3-18
Developing Your Application Program.........................................................................3-18
Appendix A
Specifications........................................................................................................................A-1
Appendix B
Troubleshooting...................................................................................................................B-1
Problems with VXIINIT................................................................................................B-1
VXIINIT Error Messages...................................................................................B-1
VXIINIT Could Not Find the AT-MXI.................................................B-2
VXIINIT Could Not Find Specific Files................................................B-2
Error Writing Log File...........................................................................B-3
VXIINIT Causes System to Hang......................................................................B-3
Problems with RESMAN...............................................................................................B-4
Memory Area Used by Another Device ............................................................B-4
Memory Area Used by Expanded-Memory Manager or Emulator...................B-4
Problems with Mouse.....................................................................................................B-5
Problems with MXIbus Cable........................................................................................B-5
Appendix C
Customer Communication...............................................................................................C-1
Glossary......................................................................................................................Glossary-1

Contents
© National Instruments Corporation ix VME-AT2000/NI-VXI MS-DOS Getting Started
Figures
Figure 2-1. AT-MXI Parts Locator Diagram.........................................................................2-2
Figure 2-2. Base I/O Address Switch Settings.......................................................................2-4
Figure 2-3. Board and MXIbus Interrupt Jumper Settings ....................................................2-7
Figure 2-4. DMA Channel Settings .......................................................................................2-10
Figure 2-5. AT-MXI Installed in a Computer........................................................................2-12
Figure 2-6. VME-MXI Parts Locator Diagram......................................................................2-13
Figure 2-7. VME-MXI with INTX Parts Locator Diagram...................................................2-14
Figure 2-8. VMEbus System Controller Selection................................................................ 2-15
Figure 2-9. VME-MXI VMEbus Requester Jumper Settings................................................2-17
Figure 2-10. VMEbus Timeout Value Selection......................................................................2-18
Figure 2-11. MXIbus Single-Ended Cable Configuration.......................................................2-20
Figure 2-12. MXIbus Dual-Ended Cable Configuration..........................................................2-21
Figure 3-1. VXIEDIT Main Menu.........................................................................................3-8
Figure 3-2. AT-MXI Logical Address Configuration Editor.................................................3-9
Figure 3-3. AT-MXI Bus Configuration Editor.....................................................................3-13
Figure 3-4. AT-MXI Device Configuration Editor................................................................3-15
Figure 3-5. Non-VXI Device Editor......................................................................................3-17
Tables
Table 2-1. AT-MXI Factory Default Settings and Optional Configurations........................2-3
Table 2-2. Possible Base I/O Address Settings for the AT-MXI..........................................2-5
Table 3-1. Logical Address Configuration Characteristics ..................................................3-10
Table 3-2. Bus Configuration Characteristics.......................................................................3-14
Table 3-3. Device Configuration Characteristics .................................................................3-16

© National Instruments Corporation xi VME-AT2000/NI-VXI MS-DOS Getting Started
About This Manual
This manual contains instructions for installing and configuring the National Instruments
VME-AT2000 interface kit. This manual is meant to be used with the NI-VXI C Software
Reference Manual for VME, the NI-VXI Software Reference Manual for BASIC, and the NI-VXI
DOS Utilities Reference Manual.
How to Use the Documentation Set
Begin by reading this manual to guide you through the installation and configuration of the
hardware and software. The software configuration requires that you first complete the
installation and configuration of the hardware.
When you are familiar with the material in this manual, you can begin to use the NI-VXI
C Software Reference Manual for VME. Chapter 1, Introduction to NI-VXI for VME, and
Chapter 2, Introduction to the NI-VXI Functions for VME, present the concepts of using the
NI-VXI software for programming VME systems and prepare you for detailed explanations of
the NI-VXI functions. Study the descriptions of each function given in Chapters 3 through 9
to fully understand the purpose and syntax of each function. The NI-VXI Software Reference
Manual for BASIC covers the same material but with BASIC syntax. Refer to the NI-VXI
DOS Utilities Reference Manual to learn more about the VIC and VXIEDIT programs. The
LabWindows VXI Library Reference Manual, part number 320318-01, explains how to install
and use the optional LabWindows VXI Library for the AT-MXI.
Organization of This Manual
Getting Started with Your VME-AT2000 and the NI-VXI Software for MS-DOS is organized as
follows:
• Chapter 1, Introduction, describes the VME-AT2000 interface kit, lists what you need to get
started, and lists optional equipment and software.
• Chapter 2, Hardware Configuration and Installation, contains the instructions to configure
and install the VME-AT2000 interface kit.

About This Manual
VME-AT2000/NI-VXI MS-DOS Getting Started xii © National Instruments Corporation
• Chapter 3, NI-VXI Software Installation and Configuration, lists all the programs and files
located on the NI-VXI distribution diskette(s), contains step-by-step instructions for
installing and configuring the NI-VXI software for MS-DOS for VME, and contains a
description of the VXIEDIT configuration editor.
• Appendix A, Specifications, lists various module specifications of the AT-MXI and
VME-MXI, such as physical dimensions and power requirements.
• Appendix B, Troubleshooting, addresses certain problems you may encounter when using the
NI-VXI bus interface software on the AT-MXI platform.
• Appendix C, Customer Communication, contains forms you can use to request help from
National Instruments or to comment on our products and manuals.
• The Glossary contains an alphabetical list and description of terms used in this manual,
including abbreviations, acronyms, metric prefixes, mnemonics, and symbols.
Conventions Used in This Manual
The following conventions are used to distinguish elements of text throughout this manual:
bold Bold text denotes menus or menu items.
italic Italic text denotes emphasis, a cross reference, or an introduction to a
key concept.
monospace Text in this font denotes text or characters that are to be literally input
from the keyboard, the proper names of disk drives, paths, directories,
programs, subprograms, device names, filenames and extensions, and
for statements and comments taken from program code.
bold monospace Bold text in this font denotes the messages and responses that the
computer automatically prints to the screen.
bold italic Bold italic text denotes a note, caution, or warning.
<> Angle brackets enclose the name of a key on the keyboard–for
example, <Esc>.
Abbreviations, acronyms, metric prefixes, mnemonics, symbols, and terms are listed in the
Glossary.

About This Manual
© National Instruments Corporation xiii VME-AT2000/NI-VXI MS-DOS Getting Started
Related Documentation
The following documents contain information that you may find helpful as you read this manual:
•IEEE Standard for a Versatile Backplane Bus: VMEbus, ANSI/IEEE Standard 1014-1987
•Multisystem Extension Interface Bus Specification, Version 1.2
•NI-VXI Software Reference Manual for C (for VXI systems), National Instruments
Corporation
•VME-MXI User Manual, Instruments Corporation
• VXI-1, VXIbus System Specification, Rev. 1.4, VXIbus Consortium
• VXI-6, VXIbus Mainframe Extender Specification, Rev. 1.0, VXIbus Consortium
Customer Communication
National Instruments wants to receive your comments on our products and manuals. We are
interested in the applications you develop using our products, and we want to help if you have
problems with them. To make it easy for you to contact us, this manual contains comment and
configuration forms for you to complete. These forms are in Appendix C, Customer
Communication, at the end of this manual.

© National Instruments Corporation 1-1 VME-AT2000/NI-VXI MS-DOS Getting Started
Chapter 1
Introduction
This chapter describes the VME-AT2000 interface kit, lists what you need to get started, and
lists optional equipment and software.
The VME-AT2000 is an interface kit that links any IBM Personal Computer AT or compatible
computer (hereafter referred to as the PC AT) directly to the VMEbus. A PC AT equipped
with a VME-AT2000 can function as a VME master and/or slave device. The VME-AT2000
makes the PC AT appear as though it were an embedded CPU plugged directly into the VME
backplane, or as though it has internal VME slots for plug-in boards. The driver software for
the VME boards must, of course, be ported to run on the PC AT with the VME-AT2000 kit.
What You Need to Get Started
MS-DOS version 5.0 (or equivalent) or higher installed on your computer
AT-MXI interface board
Standard VME-MXI interface module
or
Enhanced VME-MXI interface module with INTX option
NI-VXI distribution disks for the AT-MXI and MS-DOS
You received both 3.5 in. disks and 5.25 in. disks in your kit.
2 m Type M1 MXIbus cable
Note: The 2 m Type M1 MXIbus cable is included in your kit unless you specified
otherwise in your order. You may have ordered your kit without this cable so that
you could order a different type or length of MXIbus cable. Refer to the Optional
Equipment section.

Introduction Chapter 1
VME-AT2000/NI-VXI MS-DOS Getting Started 1-2 © National Instruments Corporation
Optional Equipment
Contact National Instruments for ordering information for any of the following optional
equipment.
•VXI-MXI standard VXIbus mainframe extender kit
•VXI-MXI enhanced VXIbus mainframe extender kit
•VME-MXI standard VXIbus chassis extender kit
•VME-MXI enhanced VXIbus chassis extender kit
•MXIbus terminating pac (External)
•Type M1 MXIbus cables (straight point-to-point connectors)
•Type M2 MXIbus cables (straight point-to-right angle daisy-chain connectors)
•Type M3 MXIbus cables (right angle point-to-right angle daisy-chain connectors)
The Type M1, M2, and M3 MXIbus cables are available in the following lengths:
•1 m
•2 m
•4 m
•8 m
•20 m
Optional Software
If you want to use LabWindows with your VME-AT2000 system, you can order the
LabWindows for DOS, VXI Development System. It contains the following components:
•LabWindows for DOS Full Develoment System
•LabWindows for DOS VXI Libraries
•LabWindows for DOS VXI Instrument Library
If you want to use LabVIEW with your VME-AT2000 system, you must order NI-VXI Windows
Software for the AT-MXI and the LabVIEW for Windows VXI Development System. It
contains the following components:
•LabVIEW for Windows Full Development System
•LabVIEW for Windows VXI Library
•LabVIEW for Windows/Sun VXI Instrument Library

© National Instruments Corporation 2-1 VME-AT2000/NI-VXI MS-DOS Getting Started
Chapter 2
Hardware Configuration and Installation
This chapter contains the instructions to configure and install the VME-AT2000 interface kit.
The instructions are given in the order that you should perform them. A summary of the steps is
as follows:
1. Unpack the AT-MXI and VME-MXI hardware.
2. Configure the AT-MXI hardware.
3. Install the AT-MXI hardware.
4. Configure the VME-MXI hardware.
5. Install the VME-MXI hardware.
6. Connect the MXIbus cable.
Step 1. Unpack the AT-MXI and VME-MXI
Follow these steps when unpacking your AT-MXI board and VME-MXI module:
1. Before attempting to configure or install the AT-MXI and VME-MXI, inspect the shipping
container and its contents for damage. If damage appears to have been caused in shipment,
file a claim with the carrier. Retain the packing material for possible inspection and/or for
reshipment.
2. Verify that the pieces contained in the package you received match the kit parts list. Do not
remove the boards from their plastic bags at this point.
3. Your AT-MXI board and VME-MXI module are shipped packaged in antistatic plastic bags
to prevent electrostatic damage. Some of the circuitry on the AT-MXI and VME-MXI use
CMOS technology and can be damaged by electrostatic discharge. Before removing the
boards from their antistatic bags, touch the bags to a metal part of your computer chassis.
4. As you remove the AT-MXI and VME-MXI from their bags, be sure to handle them only by
their edges. Avoid touching any of the IC components or connectors. Inspect them for loose
components or any other sign of damage. Notify National Instruments if either board
appears damaged in any way. Do not install equipment that appears to be damaged.

Hardware Configuration and Installation Chapter 2
VME-AT2000/NI-VXI MS-DOS Getting Started 2-2 © National Instruments Corporation
Step 2. Configure the AT-MXI Hardware
Figure 2-1 shows the location of the AT-MXI configuration jumpers and switches.
Figure 2-1. AT-MXI Parts Locator Diagram
Art not available in PDF version of document.

Chapter 2 Hardware Configuration and Installation
© National Instruments Corporation 2-3 VME-AT2000/NI-VXI MS-DOS Getting Started
Switch and Jumper Settings
You can configure three options on the AT-MXI board:
• Base I/O address
• Interrupt levels
• DMA channels
Table 2-1 shows the factory settings and optional configurations for the switches and jumpers on
the AT-MXI.
Table 2-1. AT-MXI Factory Default Settings and Optional Configurations
AT-MXI Default Optional
Base I/O Address (hex) 340 100 to 3E0, increments of 20 hex
Master DMA Channel 6 0, 1, 2, 3, 5, 6, 7, and Not Used
Slave DMA Channel 3 0, 1, 2, 3, 5, 6, 7, and Not Used
Board Interrupt Level 12 3, 4, 5, 6, 7, 9, 10, 11, 12, 14, and 15
MXIbus Interrupt Level 10 3, 4, 5, 6, 7, 9, 10, 11, 12, 14, 15,
and Not Used
The factory-configured settings of the base I/O address, the interrupt levels, and the Direct
Memory Access (DMA) channels are suitable for most computer systems. The following
sections describe under what conditions you would be required to change the configuration
switches and/or jumpers on the AT-MXI and how to make these changes.
Base I/O Address Selection
The base I/O address of the AT-MXI is the starting address of the AT-MXI configuration
registers in PC AT I/O space. The base I/O address is determined by the position of the five
switches at location U31, as shown in Figure 2-1. The switches are set at the factory for a base
I/O address of 340 hex. Because the AT-MXI requires 32 bytes of consecutive I/O space for
its internal registers, the factory configuration uses the I/O address space in the range of 340 to
35F hex.
Note: Check to determine that this space is not already used by other I/O interfaces
installed in your PC AT computer. If any equipment in your computer uses this I/O
address space, you must change either the base I/O address of the AT-MXI or the
I/O address space requirements of the other device. All PC AT devices must have a
unique partition of the system's I/O address space. If you change the base I/O
address of the AT-MXI, you must make a corresponding change to the AT-MXI
configuration software as described in the Configuring the NI-VXI Software section
of Chapter 3 of this manual.

Hardware Configuration and Installation Chapter 2
VME-AT2000/NI-VXI MS-DOS Getting Started 2-4 © National Instruments Corporation
Each switch in U31 (1 through 5) corresponds to one of the PC AT address lines (A5 through
A9). The first switch (1) corresponds to address line A5, the next switch (2) corresponds to
address line A6, and so on. The five least significant bits of the address (A4 through A0) are
used by the AT-MXI to select the appropriate AT-MXI register and cannot be changed;
therefore, bits A4 through A0 are always zeros when determining the base I/O address.
To change the base I/O address of the AT-MXI, press the side markedOFF to select a binary
value of 1 for the corresponding address bit. Press the ON side of the switch to select a binary
value of 0 for the corresponding address bit. Refer to Table 2-2.
Figure 2-2 shows two possible switch settings.
OFF
54321
U31
Binary Hex
0
0
0
0
0
ON=0
ON=0
ON=0
OFF=1
ON=0
a. Switch Set to Base I/O Address hex 100
0
0
1
OFF
54321
U31
Binary Hex
0
0
0
0
0
ON=0
OFF=1
ON=0
OFF=1
OFF=1
b. Switch Set to Default Setting
(Base I/O Address hex 340)
0
4
3
Figure 2-2. Base I/O Address Switch Settings

Chapter 2 Hardware Configuration and Installation
© National Instruments Corporation 2-5 VME-AT2000/NI-VXI MS-DOS Getting Started
Table 2-2 lists the 24 possible switch settings, the corresponding base I/O address, and the I/O
address space used for that setting. Notice that the base address settings that correspond to an
I/O address in the range from 0 to FF hex are not listed. These addresses are used by logic on the
PC AT motherboard and cannot be used by I/O adapter modules.
Table 2-2. Possible Base I/O Address Settings for the AT-MXI
Switch Setting Base I/O Address I/O Ports Used
A9 A8 A7 A6 A5 (hex) (hex)
0 1 0 0 0 100 100 - 11F
0 1 0 0 1 120 120 - 13F
0 1 0 1 0 140 140 - 15F
0 1 0 1 1 160 160 - 17F
0 1 1 0 0 180 180 - 19F
0 1 1 0 1 1A0 1A0 - 1BF
0 1 1 1 0 1C0 1C0 - 1DF
0 1 1 1 1 1E0 1E0 - 1FF
1 0 0 0 0 200 200 - 21F
1 0 0 0 1 220 220 - 23F
1 0 0 1 0 240 240 - 25F
1 0 0 1 1 260 260 - 27F
1 0 1 0 0 280 280 - 29F
1 0 1 0 1 2A0 2A0 - 2BF
1 0 1 1 0 2C0 2C0 - 2DF
1 0 1 1 1 2E0 2E0 - 2FF
1 1 0 0 0 300 300 - 31F
1 1 0 0 1 320 320 - 33F
1 1 0 1 0 340 (default) 340 - 35F
1 1 0 1 1 360 360 - 37F
1 1 1 0 0 380 380 - 39F
1 1 1 0 1 3A0 3A0 - 3BF
1 1 1 1 0 3C0 3C0 - 3DF
1 1 1 1 1 3E0 3E0 - 3FF

Hardware Configuration and Installation Chapter 2
VME-AT2000/NI-VXI MS-DOS Getting Started 2-6 © National Instruments Corporation
Interrupt Level Selection
The AT-MXI interface board can use either one or two of the eleven interrupt levels of the PC
AT I/O channel. Setting up an interrupt level for operation involves two steps. First you select
the interrupt level by arranging the jumpers on an array of pins. Next you enable the interrupt
level in the system software.
Note: You must enable the interrupt levels in the system software before they can
function. If you do not enable the interrupt level, that level will not be driven and
can be used by other devices, regardless of the positions of the jumpers.
Interrupt levels are selected by the position of two jumpers on the 3 by 11 array of pins labeled
W3, located above the I/O card-edge connector on the AT-MXI (refer to Figure 2-1). Use the
jumper farther from the card-edge connector to select the PC AT interrupt level that will convey
board status and error information. Remember to enable this level, or board interrupt, in the
system software for the AT-MXI to function properly. The factory default setting is level 12 and
is enabled on this level by the default configuration software.
Use the jumper on the W3 pin array closer to the I/O card-edge connector to select which PC AT
interrupt level corresponds to the MXIbus interrupt signal IRQ*. Because the MXIbus interrupt
is also one of the conditions covered by the other jumper, you normally do not need to use a
separate interrupt level for the MXIbus IRQ* signal; it is useful only if you want a different
interrupt vector or priority for MXIbus interrupts. This jumper is set at the factory to a default
level of 10.
Note: The AT-MXI does not have the ability to share interrupt levels with other devices.
If you select an interrupt level by placing a jumper on a particular level and enable
that level in software, no other device in the system can use that level. Make sure
that no other devices in your system use the interrupt level(s) selected and enabled
for use by the AT-MXI. If they do, change the interrupt level(s) of either the
AT-MXI or the other devices. If you change an AT-MXI interrupt level, make a
corresponding change to the AT-MXI configuration software as described in the
Configuring the NI-VXI Software section of Chapter 3.
The AT-MXI can use interrupt levels IRQ3, 4, 5, 6, 7, 9, 10, 11, 12, 14, and 15. Be careful when
re-assigning interrupt levels on the AT-MXI. Notice that most PC ATs use interrupt level 6 for
the diskette drive controller and interrupt level 14 for the hard disk drive controller. Other
interrupt levels might be used by standard logic devices on the motherboard so check your
computer documentation before changing interrupt levels.

Chapter 2 Hardware Configuration and Installation
© National Instruments Corporation 2-7 VME-AT2000/NI-VXI MS-DOS Getting Started
Once you have chosen an interrupt level, place the jumper on the appropriate pins to select that
interrupt level. Use the two rows of pins farther from the card-edge connector to select the board
interrupt level, and the two rows of pins closer to the card-edge connector to select the MXIbus
interrupt level. Figure 2-3a shows the factory default interrupt jumper setting of the AT-MXI,
with board interrupt level 12 and MXIbus interrupt level 10.
a. Factory Default
Interrupt
Jumper Setting–
Board Interrupt Level 12,
MXIbus Interrupt Level 10
• • •
• • •
• • •
• • •
IRQ15
• • •
• • •
• • •
• • •
• • •
• • •
• • •
IRQ14
IRQ12
IRQ11
IRQ10
IRQ9
IRQ7
IRQ6
IRQ5
IRQ4
IRQ3
W3
To set MXIbus
Interrupt Level To set Board
Interrupt Level
b. Board Interrupt Level 5,
MXIbus Interrupt Level 10
• • •
• • •
• • •
• • •
IRQ15
• • •
• • •
• • •
• • •
• • •
• • •
• • •
IRQ14
IRQ12
IRQ11
IRQ10
IRQ9
IRQ7
IRQ6
IRQ5
IRQ4
IRQ3
W3
To set MXIbus
Interrupt Level To set Board
Interrupt Level
Figure 2-3. Board and MXIbus Interrupt Jumper Settings
To change to another interrupt level, remove the appropriate jumper from its current position and
place it on the new posts. Figure 2-3b shows the board interrupt level changed to IRQ5.

Hardware Configuration and Installation Chapter 2
VME-AT2000/NI-VXI MS-DOS Getting Started 2-8 © National Instruments Corporation
DMA Channel Selection
The AT-MXI interface board can use one, two, or none of the seven DMA channels of the
PC AT I/O channel. Setting up a DMA channel for operation involves two steps. First you
select the DMA channel by arranging the jumpers on an array of pins. Next you enable the
DMA channel in the system software.
Note: You must enable the DMA channels in the system software before they can
function. If you do not enable the DMA channel, that channel will not be driven
and can be used by other devices, regardless of the positions of the jumpers.
Select the DMA channels on the two 3 by 7 arrays of pins labeled W1 and W2, located above the
I/O card-edge connector on the AT-MXI (refer to Figure 2-1). Use the W1 array to select the
DMA request line(s), and use the W2 array to select the DMA acknowledge line(s). You must
position two jumpers to select a single DMA channel. The DMA ACKnowledge (DACKn) and
DMA ReQuest (DRQn) lines selected must have the same numeric suffix for proper operation.
Therefore, make sure that the jumper positions on the W1 array are identical to the jumper
positions on the W2 array.
Master Mode Versus Slave Mode
The AT-MXI can function as both a MXIbus master and a MXIbus slave. As a MXIbus master,
the AT-MXI circuitry determines whether a PC AT cycle is to be mapped into a MXIbus cycle
intended for some external MXIbus device such as a VMEbus backplane. As a MXIbus slave,
the AT-MXI circuitry determines whether an external device is attempting to access PC AT
memory or I/O resources.
Note: When allocating DMA channels for use by the AT-MXI, keep in mind that master-
mode and slave-mode operation are two distinct asynchronous functions and
require different DMA channels.
Although the master-mode DMA jumpers are set at the factory to use DMA channel 6, the
software statically disables the master-mode DMA channel with a setting of NONE and cannot be
changed. While the AT-MXI itself is capable of using DMA to perform high-speed block-mode
transfers to or from external MXIbus devices, the processor is able to transfer data at
significantly faster rates by using the movs (move string) instruction. DMA transfers offer
superior performance only in asynchronous function calls, which begin an operation and return
immediately, freeing the processor to do other useful work. However, because DMA transfers
would be applicable only for the VXImove function, which is not asynchronous, the software is
configured to ignore this option, making the hardware setting irrelevant. The field remains in the
VXIEDIT software configuration program for backward compatibility only.
The slave-mode DMA jumpers are set at the factory to use DMA channel 3. Although the
default software configuration enables this setting, several factors effectively disable the slave-
mode DMA channel. As a result, DMA channel 3 can be used by other devices if you do not
need to use slave-mode DMA with your AT-MXI.
The slave-mode DMA channel is necessary only for setting up shared access to PC AT resource
from external MXIbus devices. If you intend to communicate with VME devices using a shared