National Instruments GPIB-COM User manual

© Copyright 1989, 1991 National Instruments Corporation.
All Rights Reserved.
GPIB-COM
User Manual
June 1990 Edition
Part Number 320197-01

National Instruments Corporation
6504 Bridge Point Parkway
Austin, TX 78730-5039
[phone]
(800) IEEE-488 (toll-free U.S. and Canada)
Technical support fax: [phone]

Limited Warranty
The GPIB-COM is warranted against defects in materials and workmanship for a period of two
years from date of shipment. 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.
No other warranty is expressed or implied. National Instruments shall not be liable for
consequential damages. Contact National Instruments for more information.
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.
Trademark
IBM is a registered trademark of International Business Machines Corporation.

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 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
Communications (DOC). These regulations are designed to provide reasonable protection
against interference from the equipment to radio and television reception in residential 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-COM User Manual
Preface
Introduction to the GPIB-COM
The GPIB-COM is a high-performance talk/listen interface board that makes communication
possible between IEEE-488 devices and IBM personal computers and compatibles (hereafter
referred to as PCs) equipped with software that uses the serial ports.
Organization of This Manual
This manual is divided into the following sections:
Section One, Introduction, contains a brief description of the GPIB-COM including a listing of its
features, accessories, and components.
Section Two, Configuration and Installation, describes how to configure and install the GPIB-
COM into your system.
Section Three, Function Description, shows a block diagram of the GPIB-COM and describes the
functional components of the GPIB-COM.
Section Four, Running Diagnostic Tests, describes how to run the diagnostic tests that are shipped
with the GPIB-COM.
Section Five, Programming the GPIB-COM, presents a description of the GPIB-COM Serial Port
Emulator registers and information on programming the IBM serial adapter.
Appendix A, Specifications, lists the specifications of the GPIB-COM board.
Appendix B, Multiline Interface Command Messages, contains an ASCII chart and a list of the
corresponding GPIB messages.
Appendix C, Operation of the GPIB, describes GPIB terminology and protocol for users
unfamiliar with the GPIB.
Related Documents
The following documents contain information that may be helpful as you read this manual:
•ANSI/IEEE Std 488-1978, IEEE Standard Digital Interface for Programmable
Instrumentation
•IBM Options and Adapters Manual
•IBM PC Technical Reference Manual
•IBM Disk Operating System Manual
•INS8250A Data Sheet, National Semiconductor

Preface
GPIB-COM User Manual vi © National Instruments Corporation
Abbreviations Used in This Manual
The following abbreviations are used in the text of this manual.
≤is less than or equal to
≥is greater than or equal to
±plus or minus
A ampere
C Celsius
hex hexadecimal
in. inch
I/O input/output
kbyte 1000 bytes
m meter
Mbyte megabyte
MHz megahertz
msec millisecond
r read
r/w read/write
sec second
V volt
VDC volts direct current
w write

© National Instruments Corporation vii GPIB-COM User Manual
Contents
Section One
Introduction..........................................................................................................................1-1
GPIB-COM Characteristics............................................................................................1-1
What Your Kit Should Contain......................................................................................1-2
Optional Equipment........................................................................................................1-3
Section Two
Configuration and Installation......................................................................................2-1
Configuration..................................................................................................................2-1
Switch and Jumper Settings................................................................................2-3
Base I/O Address and Interrupt Selection...........................................................2-3
Talk/Listen Modes..............................................................................................2-4
Talk/Listen Address and Special Function Selection...........................................2-5
Installation.......................................................................................................................2-7
Special Considerations When Using the GPIB-COM....................................................2-8
Section Three
Function Description........................................................................................................3-1
The GPIB-COM Interface..............................................................................................3-1
GPIB-COM Components...............................................................................................3-3
Address Decoding..............................................................................................3-3
Configuration Jumpers.......................................................................................3-3
INS8250A Compatible Registers.......................................................................3-3
GPIB Acceptor and Source Handshaking...........................................................3-3
Mode Control Logic............................................................................................3-3
Interrupt Control Logic.......................................................................................3-3
Direction Buffers................................................................................................3-4
GPIB Transceivers..............................................................................................3-4
Section Four
Running Diagnostic Tests...............................................................................................4-1
The GPIB-COM Test Commands..................................................................................4-1
-1 printer test.......................................................................................................4-1
-2 plotter test.......................................................................................................4-2
-c change COM configuration.............................................................................4-3
-q quit..................................................................................................................4-3
Section Five
Programming the GPIB-COM......................................................................................5-1
The GPIB-COM Registers.............................................................................................5-1
Transmitter Holding Register..............................................................................5-2
Receive Buffer Register......................................................................................5-3
Divisor Latch Least Significant Byte (LSB) Register..........................................5-4
Divisor Latch Most Significant Byte (MSB) Register........................................5-4
Interrupt Enable Register....................................................................................5-5
Interrupt Identification Register...........................................................................5-7

Contents
GPIB-COM User Manual viii © National Instruments Corporation
Line Control Register..........................................................................................5-8
Modem Control Register....................................................................................5-10
Line Status Register............................................................................................5-12
Modem Status Register.......................................................................................5-14
Programming the Serial Adapter....................................................................................5-16
Polling Method...................................................................................................5-16
Interrupt-Driven Method.....................................................................................5-16
The GPIB-COM Controller Function.............................................................................5-17
Appendix A
Specifications.......................................................................................................................A-1
Appendix B
Multiline Interface Command Messages..................................................................B-1
Appendix C
Operation of the GPIB......................................................................................................C-1
History of the GPIB........................................................................................................C-1
Types of Messages.........................................................................................................C-1
Talkers, Listeners, and Controllers..................................................................................C-1
System Controller and Active Controller........................................................................C-2
GPIB Signals..................................................................................................................C-2
Data Lines.......................................................................................................................C-3
Handshake Lines.............................................................................................................C-3
NRFD (not ready for data)..................................................................................C-3
NDAC (not data accepted)..................................................................................C-3
DAV (data valid)................................................................................................C-4
Interface Management Lines...........................................................................................C-4
ATN (attention)...................................................................................................C-4
IFC (interface clear)............................................................................................C-4
REN (remote enable)..........................................................................................C-4
SRQ (service request).........................................................................................C-4
EOI (end or identify)..........................................................................................C-4
Physical and Electrical Characteristics............................................................................C-5
Configuration Restrictions..............................................................................................C-7

Contents
© National Instruments Corporation ix GPIB-COM User Manual
Figures
Figure 1-1. GPIB-COM Board................................................................................................1-2
Figure 2-1. GPIB-COM Parts Locator Diagram......................................................................2-1
Figure 2-2. Possible Settings for GPIB-COM Jumpers...........................................................2-4
Figure 2-3. Jumper W1 Settings..............................................................................................2-4
Figure 2-4. Switch Setting for REN* OFF, IFC* ON, SRQ* ON, and Listen Address 5......2-5
Figure 2-5. Listen Address Setting for Listen Address 10 Hex................................................2-6
Figure 2-6. Switch Setting for REN* ON, IFC* OFF, and SRQ* OFF..................................2-7
Figure 3-1. Block Diagram of GPIB-COM.............................................................................3-2
Figure 4-1. Plotter Output.........................................................................................................4-2
Figure C-1. GPIB Cable Connector..........................................................................................C-3
Figure C-2. Linear Configuration of the GPIB Devices............................................................C-5
Figure C-3. Star Configuration of GPIB Devices.....................................................................C-6
Tables
Table 2-1. IBM PC Serial Port Adapters................................................................................2-3
Table 2-2. Factory Default Settings and Optional Configurations...........................................2-3
Table 5-1. GPIB-COM Registers...........................................................................................5-1
Table 5-2. Interrupt Types and Priorities.................................................................................5-7
Table 5-3. Word Length Select Bits........................................................................................5-9

© National Instruments Corporation 1-1 GPIB-COM User Manual
Section One
Introduction
This section contains a brief description of the GPIB-COM interface and a list of its characteristics
and components.
GPIB-COM Characteristics
The National Instruments GPIB-COM is a high-performance talk/listen interface that converts data
between a standard serial port format and IEEE-488 General Purpose Interface Bus (GPIB)
format for use with IEEE-488 printers and plotters. It can be used with any serial port software
on the PC. The GPIB-COM looks like a standard serial port to the IBM PC operating system and
software. It can be used to interface IEEE-488 devices to any PC software that uses the serial
ports.
The GPIB-COM has the following hardware features:
• emulates the standard PC serial adapter interface so that no additional software is needed
• can be configured as either COM1, COM2, COM3, or COM4
• compatible with any software using the serial ports on the IBM PC and its compatibles
• transparent addressing of unaddressed Talkers and Listeners
• choice of talk-only mode for use with listen-only printers and plotters
• choice of REN mode, which operates an instrument in the remote mode
• choice of SRQ enable, which allows monitoring of asynchronous service requests
• choice of IFC mode, which sends an interface clear when the computer is powered on

Introduction Section One
GPIB-COM User Manual 1-2 © National Instruments Corporation
Figure 1-1 shows the GPIB-COM interface board.
Figure 1-1. GPIB-COM Board
What Your Kit Should Contain
Your kit should contain the following components:
Item Part Number
GPIB-COM interface board 180750-01
GPIB-COM User Manual 320197-01
GPIB-COM Diagnostic Test Diskette 420212-45
Note: The GPIB-COM Diagnostic Test Diskette contains the com.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.

Section One Introduction
© National Instruments Corporation 1-3 GPIB-COM User Manual
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 shielded
GPIB cable. Operating this equipment with a non-shielded cable may cause interference
to radio and television reception in residential areas.

© National Instruments Corporation 2-1 GPIB-COM User Manual
Section Two
Configuration and Installation
This section contains information on how to configure and install the GPIB-COM into your
system.
Configuration
Figure 2-1 shows the locations of the GPIB-COM configuration jumpers and switches.
Figure 2-1. GPIB-COM Parts Locator Diagram

Configuration and Installation Section Two
GPIB-COM User Manual 2-2 © National Instruments Corporation
When installing the GPIB-COM you must determine which serial port the GPIB-COM board will
respond to and select the appropriate base address and interrupt level. The GPIB-COM can be
configured to one of four base addresses:
• 3F8 for Serial Port 1
• 2F8 for Serial Port 2
• 3E8 for Serial Port 3
• 2E8 for Serial Port 4
Note: DOS and BIOS only recognize base addresses 3F8 and 2F8.
The GPIB-COM is shipped from the factory set to 3F8. It must be reconfigured to another base
address if another device (such as a printer adapter card or a built-in serial port) is already at that
address.
DOS has reserved device names for the serial ports it finds in the system: COM1 and COM2.
The serial port adapters are named in the order in which they are found. When the computer is
powered on, DOS searches the serial port addresses for installed adapters. It first searches 3F8,
then 2F8. If only one device is installed, that device is named COM1 regardless of what its I/O
address is. If there is more than one serial device installed, the first one found is assigned COM1
and the second one found is assigned COM2.
Some communications software also recognizes COM3 (base address 3E8) and COM4 (base
address 2E8). If you wish to use COM3 or COM4, set the jumpers to the desired base address as
shown in Figure 2-2. DOS and BIOS do not recognize COM3 or COM4. Consult your software
documentation to see which interrupt level, if any, is required. If interrupts are not used, the
jumper can be removed or stored with only one side on a pin.
The GPIB-COM may need to be reconfigured if its interrupt level conflicts with another device. If
the base I/O address of the GPIB-COM does not conflict with any other device in your computer
and the GPIB-COM still does not work with your software package, reconfigure the GPIB-COM
to a different interrupt level.

Section Two Configuration and Installation
© National Instruments Corporation 2-3 GPIB-COM User Manual
Table 2-1 shows the standard base I/O address and interrupt level for each serial port.
Table 2-1. IBM PC Serial Port Adapters
Name of Port Base I/O Address (hex) Interrupt Level
Serial Port 1 3F8 4
Serial Port 2 2F8 3
Serial Port 3 3E8 Not Used
Serial Port 4 2E8 Not Used
Switch and Jumper Settings
Table 2-2 shows the factory settings and optional configurations for the switches and jumpers on
the GPIB-COM.
Table 2-2. Factory Default Settings and Optional Configurations
GPIB-COM Default Optional
Base I/O Address 3F8 2F8, 3E8, 2E8
Interrupt Level 4 3
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-COM are determined by the jumpers
located at positions W2 and W5. The jumpers are set at the factory for base I/O address 3F8 hex
and interrupt level 4.

Configuration and Installation Section Two
GPIB-COM User Manual 2-4 © National Instruments Corporation
Figure 2-2 shows the four possible combinations of jumper settings.
•
•
•
XF8
3X8
IRQ4
XE8
2X8
IRQ3
W5
W2
a. COM1: Jumpers Set to Base I/O Address
3F8 hex and Interrupt Level 4 (Default)
•
•
•
XF8
3X8
IRQ4
XE8
2X8
IRQ3
W5
W2
b. COM2: Jumpers Set to Base I/O Address
2F8 hex and Interrupt Level 3
•
•
•
XF8
3X8
IRQ4
XE8
2X8
IRQ3
W5
W2
c. COM3: Jumpers Set to Base I/O Address
3E8 hex (Interrupts Not Used)
• •
•
•
XF8
3X8
IRQ4
XE8
2X8
IRQ3
W5
W2
d. COM4: Jumpers Set to Base I/O Addres
s
2E8 hex (Interrupts Not Used)
•
Figure 2-2. Possible Settings for GPIB-COM Jumpers
Talk/Listen Modes
If you are using your GPIB-COM with a listen-only printer or plotter, you can configure the
GPIB-COM for a talk-only mode. In this mode, the GPIB-COM is always a Talker and never
sends any interface commands. To set the talk-only mode, change jumper W1 from T/L to T as
shown in Figure 2-3:
• •
W1 W1
T T
T/L T/L
a. Talk/Listen
(Default) b. Talk Only
Figure 2-3. Jumper W1 Settings

Section Two Configuration and Installation
© National Instruments Corporation 2-5 GPIB-COM User Manual
Talk/Listen Address and Special Function Selection
The GPIB-COM interface board has eight onboard DIP switches you can use to configure the
GPIB controller responsibilities. In the talk/listen mode, the first five switches set the talk or listen
address of the external device(s) that will be attached to the GPIB-COM. In the talk-only mode,
the GPIB-COM does not send a talk or listen address.
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-COM. If enabled, the
GPIB-COM 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-COM
monitors the SRQ line through the Parity Error Bit (PE) in the Line Status Register.
When the switch is ON, the PE bit reflects the status of the SRQ line. When the
switch is OFF, the PE bit is always clear.
The GPIB-COM factory default switch configuration is for device listen address 5, REN* not
asserted, IFC* enabled, and SRQ* enabled. Figure 2-4 shows the factory default switch settings
for the GPIB-COM.
This side down for logic 0This side down for logic 1
Key
= side you must press down for default setting; Off = 1; On =
U13
1
2
4
8
16
REN
IFC
SRQ
12345678
OFF
Figure 2-4. Switch Setting for REN* OFF, IFC* ON, SRQ* ON, and Listen Address 5
(Default Setting)

Configuration and Installation Section Two
GPIB-COM User Manual 2-6 © National Instruments Corporation
Figure 2-5 shows the switch configuration needed when using a device with listen address 10 hex.
The listen address varies with each device so check the listen address of your device and set these
five bits accordingly.
Key
= side you must press down for Listen Address 10;
Off = 1; On = 0
This side down for logic 1 This side down for logic 0
U13
= used for setting REN* ON, IFC* ON, and SRQ* ON
1
2
4
8
16
REN
IFC
SRQ
123 45 67 8
OFF
Figure 2-5. Listen Address Setting for Listen Address 10 Hex

Section Two Configuration and Installation
© National Instruments Corporation 2-7 GPIB-COM User Manual
Figure 2-6 shows the switch configuration for REN* asserted, IFC* disabled, and SRQ* disabled.
Key
= side you must press down for REN* ON, IFC* OFF, and
SRQ* OFF; Off = 1; On = 0.
This side down for logic 1 This side down for logic 0
U13
= used for setting Listen Address
1
2
4
8
16
REN
IFC
SRQ
12 3 45 678
OFF
Figure 2-6. Switch Setting for REN* ON, IFC* OFF, and SRQ* OFF
Installation
Once you have changed, verified, and recorded the switches and jumper settings, you are ready to
install the GPIB-COM.
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-COM in an unused full-length 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.
6. Screw the right angle mounting bracket of the GPIB-COM to the back panel rail of your
computer.

Configuration and Installation Section Two
GPIB-COM User Manual 2-8 © National Instruments Corporation
7. Check the installation.
8. Replace the expansion slot cover of your computer.
9. Connect the GPIB cable to the GPIB-COM.
Special Considerations When Using the GPIB-COM
The GPIB-COM does not support XON/XOFF protocols. If your application software uses
XON/XOFF protocols, send your printer and plotter output to a file on disk. From DOS, send
your file to the GPIB-COM by using the DOS command:
copy
filename COM1:
copy
filename COM2:
The DOS MODE command is used to set the RS-232 parameters that will be used when COM1
and COM2 are accessed through DOS. Sometimes a timeout error may occur when writing
through the GPIB-COM to a slow device such as a printer or a plotter. If this happens, use the
MODE command to disable the timeout function by typing MODE COM1:12,,,,P. Some
software applications use the COM port baud rate setting to control the data transmission speed.
To obtain the fastest possible transfer rates, set the baud rate setting to 9600 baud. The Pat the end
disables the timeout. For more information on the MODE command, refer to the IBM Disk
Operating System Manual. This command can also be used in an autoexec.bat file to disable
timeouts when you start up the computer.