National Instruments GPIB-LPT User manual

© Copyright 1989, 1990 National Instruments Corporation.
All Rights Reserved.
GPIB-LPT
User Manual
October 1989 Edition
Part Number 320161-01

National Instruments Corporation
6504 Bridge Point Parkway
Austin, TX 78730-5039
[phone]
(800) IEEE-488
Fax: [phone]

Limited Warranty
The GPIB-LPT hardware is warranted against defects in materials and workmanship for a period
of two years from date of shipment from National Instruments or its authorized dealer. The
GPIB-LPT Diagnostic Package software media is furnished warranted to be free from defects in
materials and workmanship under normal use for a period of 90 days from date of shipment from
NI or its authorized dealer. National Instruments will repair or replace equipment which proves to
be defective during the warranty period. This warranty includes parts and labor. A Return
Material Authorization (RMA) number must be obtained from National Instruments before any
equipment is returned for repair. Faults caused by misuse are not covered under the warranty.
During the warranty period, the owner may return failed parts to National Instruments for repair.
National Instruments will pay the shipping costs of returning the part to the owner. All items
returned to National Instruments for repair must be clearly marked on the outside of the package
with an RMA number. Defects caused by misuse, abuse, or shipment are not covered.
The GPIB-LPT Diagnostic Package software program is provided "as is" without warranty of any
kind, either expressed or implied. No other warranty is expressed or implied. NI shall not be
liable or responsible for any kind of damages, including special, indirect, or consequential
damages, arising or resulting from its products, the use of its products, or the modification to its
products.
Important Notice
The material in this manual is subject to change without notice. National Instruments assumes no
responsibility for errors which may appear in this manual. National Instruments makes no
commitment to update, nor to keep current, the information contained in this document.
Copyright
Under the copyright laws, this manual may not be copied, photocopied, reproduced, translated, in
whole or in part, without the prior written consent of National Instruments Corporation.
Trademarks
IBM PC and AT are registered trademarks and PC XT is a trademark of International Business
Machines Corporation.
TI Professional Computer is a trademark of Texas Instruments.

FCC/DOC Radio Frequency Interference Compliance
This equipment generates and uses radio frequency energy and, if not installed and used in strict
accordance with the instructions in this manual, may cause interference to radio and television
reception. This equipment has been tested and found to comply with (1) the limits for a Class B
computing device, in accordance with the specifications in Subpart J of Part 15 of U.S. Federal
Communications Commission (FCC) Rules, and (2) the limits for radio noise emissions from
digital apparatus set out in the Radio Interference Regulations of the Canadian Department of
Communication (DOC). These regulations are designed to provide reasonable protection against
interference from the equipment to radio and television reception in commercial areas.
There is no guarantee that interference will not occur in a particular installation. However, the
chances of interference are much less if the equipment is used according to this instruction manual.
If the equipment does cause interference to radio or television reception, which can be determined
by turning the equipment on and off, one or more of the following suggestions may reduce or
eliminate the problem.
• Operate the equipment and the receiver on different branches of your AC electrical system.
• Move the equipment away from the receiver with which it is interfering.
• Relocate the equipment with respect to the receiver.
• Reorient the receiver's antenna.
• Be sure that the equipment is plugged into a grounded outlet and that the grounding has not
been defeated with a cheater plug.
If necessary, consult National Instruments or an experienced radio/television technician for
additional suggestions. The following booklet prepared by the FCC may also be helpful: How to
Identify and Resolve Radio-TV Interference Problems. This booklet is available from the U.S.
Government Printing Office, Washington, DC 20402, Stock Number 004-000-00345-4.

© National Instruments Corporation v GPIB-LPT User Manual
Preface
This manual is divided into the following sections.
Section One, Introduction, contains a brief description of the GPIB-LPT including its features,
components, and accessories.
Section Two, Configuration and Installation, describes how to configure and install the GPIB-
LPT into your system.
Section Three, Function Description, shows a block diagram of the GPIB-LPT and describes the
functional components of the GPIB-LPT.
Section Four, Running Diagnostic Tests, describes how to run the diagnostic tests that are shipped
with the GPIB-LPT.
Section Five, Programming the GPIB-LPT, contains specific information about the GPIB-LPT
registers along with software examples.
Appendix A, Operation of the GPIB, describes GPIB terminology and protocol for users
unfamiliar with the GPIB.
Appendix B, Multiline Interface Messages, contains an ASCII chart and a list of the corresponding
GPIB messages.
Abbreviations Used in This Manual
The following abbreviations are used in the text of this manual.
A ampere
hex hexadecimal
kbytes 1,000 bytes
m meter
Mbytes 1,000,000 bytes
µsec microsecond
sec second
V volt
VDC Volts direct current

Preface
GPIB-LPT User Manual vi © National Instruments Corporation
Related Documents
The following documents are references that cover in greater detail specific topics introduced in
this manual:
•ANSI/IEEE Standard 488-1978, IEEE Standard Digital Interface for Programmable
Instrumentation
•IBM Options Adapters Manual

© National Instruments Corporation vii GPIB-LPT User Manual
Contents
Section One
Introduction .................................................................................................................1-1
Features............................................................................................................................1-1
What Your Kit Should Contain ...................................................................................... 1-3
Optional Equipment ........................................................................................................1-3
Section Two
Configuration and Installation
..................................................................2-1
Configuration .................................................................................................................. 2-2
Switch and Jumper Settings ................................................................................2-3
Base I/O Address and Interrupt Selection ...........................................................2-3
Listen Address and Control Function Selection ..................................................2-5
Installation........................................................................................................................2-8
Section Three
Function Description
...........................................................................................3-1
Address Decoding ..........................................................................................................3-2
Configuration Jumpers ...................................................................................................3-2
Data and Control Latches ................................................................................................ 3-2
Data Transceivers ............................................................................................................3-2
Data Wrap, Control Wrap and Status Buffers ................................................................3-2
External Device Listen Address Switch .......................................................................... 3-2
GPIB Handshaking ......................................................................................................... 3-3
GPIB Addressing ........................................................................................................... 3-3
Section Four
Running Diagnostic Tests
................................................................................4-1
The GPIB-LPT Test Commands .................................................................................... 4-1
-1 printer test .......................................................................................................4-1
-2 plotter test .......................................................................................................4-2
-c change LPT configuration ............................................................................... 4-3
-q quit ..................................................................................................................4-3
Section Five
Programming the GPIB-LPT
.......................................................................5-1
The GPIB-LPT Registers ................................................................................................ 5-1
Data Register (DATA) ........................................................................................ 5-2
Status Register (STAT) .......................................................................................5-3
Control Register (CTRL) .................................................................................... 5-5
Programming Considerations .........................................................................................5-6
Using the GPIB-LPT with the DOS Operating System .....................................5-6
Using the GPIB-LPT with C and BASIC ...........................................................5-6
Acessing the Parallel Port in C ................................................................5-7
Acessing the Parallel Port in BASIC ...................................................... 5-7

Contents
GPIB-LPT User Manual viii © National Instruments Corporation
Writing a GPIB-LPT Driver ...............................................................................5-7
Setup and Initialization ............................................................................5-8
Interrupt Handler Routine .......................................................................5-8
PRINT Routine ........................................................................... 5-8
Timing Constraints.................................................................................. 5-9
Appendix A
Operation of the GPIB
.......................................................................................A-1
History of the GPIB .......................................................................................................A-1
Types of Messages ........................................................................................................A-1
Talkers, Listeners, and Controllers .................................................................................A-1
System Controller and Active Controller .......................................................................A-2
GPIB Signals .................................................................................................................A-2
Data Lines ......................................................................................................................A-3
Handshake Lines ............................................................................................................A-3
NRFD (not ready for data) .................................................................................A-3
NDAC (not data accepted) .................................................................................A-3
DAV (data valid) ...............................................................................................A-3
Interface Management Lines ..........................................................................................A-4
ATN (attention) ..................................................................................................A-4
IFC (interface clear) ...........................................................................................A-4
REN (remote enable) .........................................................................................A-4
SRQ (service request) ........................................................................................A-4
EOI (end or identify) .........................................................................................A-4
Physical and Electrical Characteristics ...........................................................................A-5
Configuration Restrictions .............................................................................................A-7
Appendix B
Multiline Interface Messages
........................................................................B-1
Appendix C
Specifications
...............................................................................................................C-1

Contents
© National Instruments Corporation ix GPIB-LPT User Manual
Figures
Figure 1-1. GPIB-LPT Board ..................................................................................................1-2
Figure 2-1. GPIB-LPT Parts Locator Diagram .......................................................................2-1
Figure 2-2. Possible Settings for GPIB-LPT Jumpers ............................................................2-4
Figure 2-3. Switch Setting for REN OFF, IFC ON, SRQ ON , and Address 5 .....................2-5
Figure 2-4. Setting for Address 6 hex .....................................................................................2-6
Figure 2-5. Switch Setting for REN ON, IFC ON, and SRQ OFF ........................................2-7
Figure 3-1. GPIB-LPT Block Diagram ...................................................................................3-1
Figure 4-1. Plotter Output ........................................................................................................4-2
Figure A-1. GPIB Cable Connector .........................................................................................A-3
Figure A-2. Linear Configuration of GPIB Devices .................................................................A-5
Figure A-3. Star Configuration of GPIB Devices ....................................................................A-6
Tables
Table 2-1. IBM PC Parallel Port Adapters ..............................................................................2-2
Table 2-2. Factory Default Settings and Optional Configurations ........................................... 2-3

© National Instruments Corporation 1-1 GPIB-LPT User Manual
Section One
Introduction
The National Instruments GPIB-LPT is a high-performance talk-only interface that converts data
sent to a standard parallel port into an IEEE-488 General Purpose Interface Bus (GPIB) format for
use with IEEE-488 printers and plotters. The GPIB-LPT looks like a standard parallel port for the
IBM PC operating system and software. It can be used to communicate with GPIB printers and
plotters with PC application programs, such as AutoCAD, that use parallel ports for printer and
plotter output.
Features
The GPIB-LPT has the following hardware features:
• emulates the standard PC parallel printer interface so that no additional software is needed
• can be configured as either LPT1 (PRN), LPT2, or LPT3
• compatible with any software using the parallel ports on the IBM PC compatibles
• small dimensions so that it fits into any slot of a personal computer
• transparent addressing of unaddressed listeners
• interrupt synchronization circuitry which holds off interrupts until the GPIB handshake is
complete
• choice of REN mode which operates an instrument in the remote mode
• choice of SRQ enable which monitors of asynchronous service requests
• choice of IFC mode which sends an interface clear when the computer is powered on

Introduction Section One
GPIB-LPT User Manual 1-2 © National Instruments Corporation
Figure 1-1 shows the GPIB-LPT interface board.
Figure 1-1. GPIB-LPT Board
The GPIB-LPT works in most true IBM-compatible computers. It does not work in the TI
Professional Computer because it uses a different Basic Input Output System (BIOS) than the
IBM compatibles.

Section One Introduction
© National Instruments Corporation 1-3 GPIB-LPT User Manual
What Your Kit Should Contain
Your kit should contain the following components:
Item Part Number
GPIB-LPT interface board 180742-01
GPIB-LPT User Manual 320161-01
GPIB-LPT Diagnostic Package Diskette 420211-43
Note: The GPIB-LPT Diagnostic Package Diskette contains the lpt.exe diagnostic test that is
described in Section Four, Running Diagnostic Tests.
Make sure each of these items is in your kit. If any item is missing, contact National Instruments.
Optional Equipment
Item Part Number
Double Shielded Cables*:
GPIB Type X2 Cable - 1 m 763061-01
GPIB Type X2 Cable - 2 m 763061-02
GPIB Type X2 Cable - 4 m 763061-03
* In order to meet FCC emission limits for a Class B device, you must use a double shielded
(Type X2) GPIB cable. Operating this equipment with a single shielded (Type X1) cable
may cause interference to radio and television reception in residential areas.

© National Instruments Corporation 2-1 GPIB-LPT User Manual
Section Two
Configuration and Installation
Figure 2-1 shows the locations of the GPIB-LPT configuration jumpers and switches.
Figure 2-1. GPIB-LPT Parts Locator Diagram

Configuration and Installation Section Two
GPIB-LPT User Manual 2-2 © National Instruments Corporation
Configuration
When installing the GPIB-LPT you must determine which IBM PC parallel port adapter the
GPIB-LPT board will respond to and select the appropriate base address and interrupt level. The
GPIB-LPT can be configured to one of three base addresses:
• 3BC Monochrome adapter
• 378/37C Parallel Port 1
• 278/27C Parallel Port 2
It is shipped from the factory set to 278/27C. The GPIB-LPT needs to be reconfigured if there is
another device (such as a printer adapter card or a built-in parallel port) at the same address.
DOS has reserved device names for the parallel ports it finds in the system: LPT1 or PRN, LPT2,
and LPT3. The parallel port adapters are named in the order in which they are found. Whenever
the computer is turned on, it searches all three parallel port addresses for installed adapters. It first
searches 3BC (LPT1), then 378 (LPT2), then 278 (LPT3). If only one device is installed, that
device is named LPT1 regardless of what its I/O address is. If there is more than one parallel
device installed, the first one found is assigned LPT1, the second one found is assigned LPT2, and
so on.
The GPIB-LPT may need to be reconfigured if its interrupt level conflicts with another device. If
the base I/O address of the GPIB-LPT does not conflict with any other device in your computer
and the GPIB-LPT still does not work with your software package, reconfigure the GPIB-LPT to a
different interrupt level.
Table 2-1 shows the standard base I/O address and interrupt level for each parallel port.
Table 2-1. IBM PC Parallel Port Adapters
Name of Port Base I/O Address (hex) Interrupt Level
Monochrome Display 3BC 7
and Printer Adapter
Parallel Port 1 378 or 37C 7
Parallel Port 2 278 or 27C 5
The GPIB-LPT is shipped from the factory configured to operate as Parallel Port 2 (base I/O
address 278 or 27C). If your PC already has a device responding to Parallel Port 2, it is necessary
to reconfigure the GPIB-LPT board to another parallel port by changing the base I/O address and
interrupt level.

Section Two Configuration and Installation
© National Instruments Corporation 2-3 GPIB-LPT User Manual
Switch and Jumper Settings
Table 2-2 lists the factory settings and optional configurations for the switches and jumpers on the
GPIB-LPT.
Table 2-2. Factory Default Settings and Optional Configurations
GPIB-LPT Default Optional
Base I/O Address 278/27C 3BC and 378/37C
Interrupt Level 5 7
If you need to change the factory settings, continue on. If you do not need to change the factory
settings, skip to Installation later in this section.
Base I/O Address and Interrupt Selection
The base I/O address and interrupt line used by the GPIB-LPT are determined by the jumpers
located at positions W1 and W2. The jumpers are set at the factory for base I/O address 278/27C
hex and interrupt level 5.

Configuration and Installation Section Two
GPIB-LPT User Manual 2-4 © National Instruments Corporation
Figure 2-2 shows the three possible combinations of jumper settings.
Note: PA stands for Parallel Adapter and MA stands for Monochrome Adapter.
• •
• •
W2
I5
P2
I7
P1
• •
• •
W1
PA
MA
a. Jumpers Set to Base I/O Address 3BC hex and Interrupt Level 7.
(Monochrome Display and Printer Adapter)
• •
• •
W2
I5
P2
I7
P1
• •
• •
W1
PA
MA
b. Jumpers Set to Base I/O Address 378/37C hex and Interrupt Level 7
.
(Parallel Port 1)
• •
• •
W2
I5
P2
I7
P1
• •
• •
W1
PA
MA
c. Jumpers Set to Default Setting.
(Base I/O Address 278/27C hex and Interrupt Level 5)
(Parallel Port 2)
Figure 2-2. Possible Settings for GPIB-LPT Jumpers

Section Two Configuration and Installation
© National Instruments Corporation 2-5 GPIB-LPT User Manual
Listen Address and Control Function Selection
The GPIB-LPT interface board has eight onboard switches you can use to configure the GPIB
controller responsibilities. The lower five switches set the listen address of the external device(s)
that will be attached to the GPIB-LPT. This address is used to send a GPIB listen address to the
device(s) whenever the device(s) indicates that it is not a Listener. The three remaining switches
(REN, IFC, and SRQ) have the following special functions:
Note: An asterisk (*) after a signal name indicates that the signal is inverted (negative logic).
• REN* Asserts/unasserts the Remote Enable (REN) line that places an instrument in remote
mode. The ON position enables REN. The OFF position disables REN.
• IFC* Enables/disables the Interface Clear (IFC) option on the GPIB-LPT. If enabled, the
GPIB-LPT issues an IFC when it is initialized. The ON position enables IFC on
initialization. The OFF position holds IFC unasserted.
• SRQ* Enables/disables the Service Request (SRQ) option. If enabled, the GPIB-LPT
monitors the SRQ line through the Paper Error (PE) bit in the GPIB-LPT status
register. When the switch is positioned ON, the PE bit reflects the status of the SRQ
line. When the switch is positioned OFF, the PE bit is always low.
The GPIB-LPT factory default switch configuration is for device address 5, REN OFF, IFC ON,
and SRQ ON. Figure 2-3 shows the factory default switch settings for the GPIB-LPT.
Key
= side you must press down for default setting; Off = 1; On =
O F F O N
This side down for logic 0This side down for logic 1
REN
IFC
SRQ
1
2
4
8
16
U18
Figure 2-3. Switch Setting for REN OFF, IFC ON, SRQ ON, and Address 5
(Default Setting)

Configuration and Installation Section Two
GPIB-LPT User Manual 2-6 © National Instruments Corporation
Figure 2-4 shows the switch configuration when using a device with address 6 hex. The address
varies with each device so check the address of your device and set these lower five bits.
O F F O N
This side down for logic 0This side down for logic 1
REN
IFC
SRQ
1
2
4
8
16
U18
Key
= side you must press down for Listen Address 6; Off = 1; On =
0
= used for setting REN, IFC, and SRQ Options
Figure 2-4. Setting for Address 6 hex

Section Two Configuration and Installation
© National Instruments Corporation 2-7 GPIB-LPT User Manual
Figure 2-5 shows the switch configuration for REN* always asserted, IFC* enabled on GPIB-
LPT initialization, and PE always low.
O F F O N
This side down for logic 0This side down for logic 1
REN
IFC
SRQ
1
2
4
8
16
U18
Key
= side you must press down for REN ON, IFC ON,
= used for setting Listen Address
and SRQ OFF; Off = 1; On = 0
Figure 2-5. Switch Setting for REN ON, IFC ON, and SRQ OFF
In the space provided here, record the new settings for your GPIB-LPT so that you will have them
handy for future reference.
GPIB-LPT New Setting
Base I/O Address
Interrupt Level
REN Option
IFC Option
SRQ Option
Listen Address

Configuration and Installation Section Two
GPIB-LPT User Manual 2-8 © National Instruments Corporation
Installation
The GPIB-LPT can be installed in any unused expansion slot in your computer. Once you have
changed, verified, and recorded the switch and jumper settings, you are ready to install the GPIB-
LPT.
The following steps are general installation instructions. Consult the user manual or technical
reference manual of your personal computer for specific instructions and warnings.
1. Turn off your computer.
2. Remove the plug from its power source.
3. Remove the top cover or access port to the I/O channel.
4. Remove the expansion slot cover on the back panel of your computer.
5. Insert the GPIB-LPT in an unused slot with the IEEE-488 receptacle sticking out of the
opening of the back panel. It may be a tight fit, but do not force the board into place.
Note: The GPIB-LPT cannot be used in slot J8 of the IBM PC XT.
6. Screw the right angle mounting bracket of the GPIB-LPT to the back panel rail of your
computer.
7. Check the installation.
8. Replace the expansion slot cover of your computer.