GPIB-BUF
User Manual
February 1994 Edition
Part Number 320125-01
© Copyright 1989, 1994 National Instruments Corporation.
All Rights Reserved.
MicroGPIB Products
National Instruments has developed the MicroGPIB product line to offer a
series of high performance, low cost IEEE 488 support items that are
packaged in small all-metal cases, capable of being rack mounted.
Limited Warranty
The GPIB-BUF is warranted against defects in materials and workmanship
for a period of two years 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.
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 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 A
PARTICULAR PURPOSE. CUSTOMER’S RIGHT 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 Instruments must be brought within one year after the cause of
action accrues. National Instruments shall not be liable for 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, including photocopying,
recording, storing in an information retrieval system, or translating, in
whole or in part, without the prior written consent of National Instruments
Corporation.
Trademarks
®
MicroGPIB is a trademark of National Instruments Corporation.
Product and company names listed are trademarks or trade names of their
respective companies.
Warning Regarding Medical and Clinical Use
of National Instruments Products
National Instruments products are not designed with components and testing
intended to ensure a level of reliability suitable for use in treatment and
diagnosis of humans. Applications of National Instruments products
involving medical or clinical treatment can create a potential for accidental
injury caused by product failure, or by errors on the part of the user or
application designer. Any use or application of National Instruments
products for or involving medical or clinical treatment must be performed by
properly trained and qualified medical personnel, and all traditional medical
safeguards, equipment, and procedures that are appropriate in the particular
situation to prevent serious injury or death should always continue to be
used when National Instruments products are being used. National
Instruments products are NOT intended to be a substitute for any form of
established process, procedure, or equipment used to monitor or safeguard
human health and safety in medical or clinical treatment.
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 the following two regulatory
agencies:
Federal Communications Commission
This device complies with Part 15 of the Federal Communications
Commission (FCC) Rules for a Class A digital device. Operation is subject
to the following two conditions:
1. This device may not cause harmful interference in commercial
environments.
2. This device must accept any interference received, including
interference that may cause undesired operation.
Canadian Department of Communications
This device complies with the limits for radio noise emissions from digital
apparatus set out in the Radio Interference Regulations of the Canadian
Department of Communications (DOC).
Le présent appareil numérique n’émet pas de bruits radioélectriques
dépassant les limites applicables aux appareils numériques de classe A
prescrites dans le règlement sur le brouillage radioélectrique édicté par le
ministère des communications du Canada.
Instructions to Users
These regulations are designed to provide reasonable protection against
harmful interference from the equipment to radio reception in commercial
areas. Operation of this equipment in a residential area is likely to cause
harmful interference, in which case the user will be required to correct the
interference at his own expense.
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 installed and 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.
Reorient or relocate 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.
Notice to user: Changes or modifications not expressly approved by
National Instruments could void the user’s authority to
operate the equipment under the FCC Rules.
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.
About This Manual ..........................................................................ix
Chapter 1
What Your Kit Contains............................................................. 1-2
Optional Equipment....................................................................1-2
Set Configuration Switches ........................... 2-4
Step 4. Connect the Cables ........................................2-6
Step 5. Power on the Unit ..........................................2-7
Operation ....................................................................................2-7
Chapter 3
Technical Information ....................................................................3-1
Power Up ....................................................................................3-1
Addressing ..................................................................................3-2
Data Transfers............................................................................. 3-2
EOI ............................................................................................. 3-3
IFC ..............................................................................................3-4
REN ............................................................................................3-4
Polling the GPIB-BUF ............................................................... 3-5
Special Note About Timeouts..................................................... 3-8
Multiline Command Group......................................................... 3-8
© National Instruments Corp.
vii
GPIB-BUF User Manual
Hardware Specifications ..............................................................A-1
Appendix B
Customer Communication ..........................................................B-1
Glossary............................................................................................... G-1
Figures
Figure 1-2. The GPIB-BUF Front Panel ................................................1-3
Figure 1-4. The GPIB Connector and Signal Designations ................... 1-5
Figure 3-1. Serial Poll Status Byte......................................................... 3-5
Tables
Table 1-1. LED Descriptions ................................................................1-3
Table 2-1. Configuration Parameters for Switches 1 through 3 ........... 2-4
Table 2-2. Configuration Parameters for Switches 4 through 8 ........... 2-5
Table 3-1. Parallel Poll Responses ....................................................... 3-7
Table A-1. Electrical Characteristics..................................................... A-1
Table A-2. Environmental Characteristics............................................. A-1
Table A-3. Physical Characteristics....................................................... A-2
GPIB-BUF User Manual
viii
© National Instruments Corp.
About This Manual
Introduction to the GPIB-BUF
The GPIB-BUF is one of National Instruments family of MicroGPIB
products. These products are high-performance, low-cost IEEE 488
support items, packaged in small all-metal cases, capable of being rack
mounted.
Organization of This Manual
This manual is organized as follows:
•
Chapter 1, Description of the GPIB-BUF, contains general information
about the National Instruments GPIB-BUF and lists components and
accessories.
•
•
Chapter 2, Installation and Operation, describes the procedures for
installing and operating the GPIB-BUF.
Chapter 3, Technical Information, contains a more detailed description
of the operation of the GPIB-BUF. The timing characteristics of the
parallel port are provided in this chapter.
•
•
•
Appendix A, Hardware Specifications, contains tables which specify
the electrical, environmental, and physical characteristics of the
GPIB-BUF.
Appendix B, 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 a description of terms
used in this manual, including abbreviations, acronyms, metric
prefixes, mnemonics, and symbols.
© National Instruments Corp.
ix
GPIB-BUF User Manual
About This Manual
Conventions Used in This Manual
The following conventions are used in this manual.
italic
Italic text denotes emphasis, a cross reference,
or an introduction to a key concept.
bold italic
bold
Bold italic text denotes a note, caution, or
warning.
Bold text denotes the name of light-emitting
diode (LED).
Abbreviations, acronyms, metric prefixes, mnemonics, symbols, and terms
are listed in the Glossary.
Related Documentation
The following document contains information that you may find helpful as
you read this manual.
•
ANSI/IEEE Standard 488.1-1987, IEEE Standard Digital Interface for
Programmable Instrumentation
•
ANSI/IEEE Standard 488.2-1987, IEEE Standard Codes, Formats,
Protocols, and Common Commands.
Customer Communication
National Instruments wants to receive your comments on our products and
manuals. We are interested in the applications you develop with our
products, and we want to help if you have problems with them. To make it
easy for you to contact us, this manual contains comment and configuration
forms for you to complete. These forms are in Appendix B, Customer
Communication, at the end of this manual.
GPIB-BUF User Manual
x
© National Instruments Corp.
Chapter 1
Description of the GPIB-BUF
This chapter contains general information about the National Instruments
GPIB-BUF and lists components and accessories.
Introduction
The GPIB-BUF, shown in Figure 1-1, is an IEEE 488 (GPIB) data buffer
which increases GPIB performance by isolating a slow GPIB data acceptor
from the rest of the GPIB system. This increase in performance is reflected
both in an increase in the GPIB bandwidth and a quicker release of the
GPIB talker from the task of transferring data to a slow GPIB device. In
most cases, the GPIB talker is a computer with other tasks to perform. The
faster it transfers data, the sooner it can perform its next task.
Figure 1-1. The GPIB-BUF
© National Instruments Corp.
1-1
GPIB-BUF User Manual
Description of the GPIB-BUF
Chapter 1
The GPIB-BUF has two isolated GPIB ports and is placed in-line between a
GPIB system and a single, slower GPIB device (usually a printer or plotter).
The GPIB-BUF automatically buffers all device-dependent data sent to the
slower device. Because the GPIB-BUF can talk or listen on either port at
any time, the GPIB-BUF provides fully transparent bi-directional data
transfers. The target GPIB device appears to be connected directly to the
IEEE 488 bus.
What Your Kit Contains
Your kit should contain the following components:
Component
Part Number
One of the following boxes:
•
•
•
•
GPIB-BUF (256 KB RAM - 115 VAC)
GPIB-BUF (1 MB RAM - 115 VAC)
GPIB-BUF (256 KB RAM - 230 VAC)
GPIB-BUF (1 MB RAM - 230 VAC)
776226-02
776226-03
776226-32
776226-33
•
GPIB-BUF User Manual
320125-01
Optional Equipment
Component
Part Number
Rack Mount Kit:
Single (1 unit)
Dual (2 units)
180480-01
180480-02
Double-Shielded GPIB Cables:
GPIB Type X2 Cable – 1 m
GPIB Type X2 Cable – 2 m
GPIB Type X2 Cable – 4 m
763061-01
763061-02
763061-03
GPIB-BUF User Manual
1-2
© National Instruments Corp.
Chapter 1
Description of the GPIB-BUF
The GPIB-BUF Front Panel
The power switch and six Light Emitting Diodes (LEDs) are mounted on
the GPIB-BUF front panel. Figure 1-2 shows the front panel of the
GPIB-BUF.
NATIONAL
INS TRUMENTS
GPIB-BUF
IEEE-488 BUFFER
IEEE-488
POWER READY TALK LISTEN EMPTY FULL
Figure 1-2. The GPIB-BUF Front Panel
The LEDs show the current status of the GPIB-BUF at all times. The
following table describes each LED.
Table 1-1. LED Descriptions
LED
Indication
POWER
Indicates that power to the unit has been applied and the
ON/OFF switch is in the ON position.
READY
Indicates that the unit is running its power-on self-test
(blinking), has passed its power-on self-test and is ready to
operate (steady on), or has failed the power-on self-test
(steady off).
TALK
Indicates that the GPIB-BUF is configured as a GPIB
Talker.
LISTEN
EMPTY
FULL
Indicates that the GPIB-BUF is configured as a GPIB
Listener.
Indicates that the internal data buffer of the GPIB-BUF is
empty.
Indicates that the internal buffer of the GPIB-BUF is full.
© National Instruments, Corp.
1-3
GPIB-BUF User Manual
Description of the GPIB-BUF
Chapter 1
The GPIB-BUF Rear Panel
Figure 1-3 shows the power cable and the GPIB cables connected to the rear
panel of the GPIB-BUF.
Figure 1-3. The GPIB-BUF Rear Panel
The GPIB Connectors
The GPIB-BUF has two GPIB connectors labeled GPIB IN and GPIB OUT.
Both GPIB connectors are standard 24-pin shielded AMP CHAMP female
connectors with metric screwlock hardware. As you face the rear panel, the
GPIB IN connector is the right-most GPIB connector. The GPIB OUT
connector is located on the left.
Notice that although these GPIB ports are labeled GPIB IN and GPIB OUT,
both are able to transfer data in either direction. The notations GPIB IN and
GPIB OUT are used in order to differentiate the ports since the GPIB IN
port, under normal circumstances, receives data while the GPIB OUT port
normally sends data to the GPIB target device.
GPIB-BUF User Manual
1-4
© National Instruments Corp.
Chapter 1
Description of the GPIB-BUF
The port labeled GPIB IN is intended to be connected to a GPIB system that
includes one or more GPIB devices which send data to the GPIB target
device. All data received via the GPIB IN port is transferred into the
Random Access Memory (RAM) buffer of the GPIB-BUF using the on-
board Direct Memory Access (DMA) controller. The port labeled GPIB
OUT should be connected to the GPIB target device. This port has GPIB
controller capabilities and addresses the GPIB target device when required.
All data input to the internal GPIB-BUF RAM buffer is output via the GPIB
OUT port. Under normal operating conditions, you should only connect
one device (your GPIB target device) to the GPIB OUT port.
Figure 1-4 shows a diagram of one of the GPIB connectors and the signal
designations. Only one GPIB connector is shown since both connectors
have the same signal and pin descriptions. A * suffix indicates that the
signal is active low.
13
14
15
16
17
18
19
20
21
22
23
24
DIO5*
DIO6*
DIO7*
DIO8*
DIO1*
DIO2*
DIO3*
DIO4*
EOI*
DAV*
NRFD*
NDAC*
IFC*
1
2
3
4
5
6
7
8
9
REN*
GND (Twisted Pair with DAV*)
GND (Twisted Pair with NRFD*)
GND (Twisted Pair with NDAC*)
GND (Twisted Pair with IFC*)
GND (Twisted Pair with SRQ*)
GND (Twisted Pair with ATN*)
SIGNAL GROUND
SRQ*
ATN*
SHIELD
10
11
12
Figure 1-4. The GPIB Connector and Signal Designations
© National Instruments, Corp.
1-5
GPIB-BUF User Manual
Chapter 2
Installation and Operation
This chapter describes the procedures for installing and operating the
GPIB-BUF.
Figure 2-1 shows an example of a GPIB-BUF connected to a GPIB system.
This example shows a GPIB-BUF placed in a GPIB system with a GPIB
Talker/Controller, such as an IBM-PC with a National Instruments
GPIB-PCII Controller board installed, and a slow GPIB data acceptor, such
as an HP 7475A Color Plotter. Notice that the GPIB-BUF is placed in-line
between the existing GPIB system and the GPIB target device.
GPIB Cable
NATIONAL
INS UMENT S ®
GPIB-BUF
IEEE 488 IEEE 488 BUFFER
T
R
GPIB Cable
POWER
READY
TALK
LISTEN
EMPTY
FULL
Figure 2-1. GPIB-BUF System Setup Example
© National Instruments Corp.
2-1
GPIB-BUF User Manual
Installation and Operation
Chapter 2
Installation
Install the GPIB-BUF according to the following procedure.
1. Inspect the GPIB-BUF.
2. Verify the voltage requirement.
3. Configure the operating parameters.
4. Connect the cables.
5. Power on the unit.
These steps are described in more detail in the following subsections.
Step 1. Inspect the GPIB-BUF
Before you install the GPIB-BUF, 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 reshipment.
If the equipment appears to be damaged, do not attempt to operate it.
Contact National Instruments for instructions.
Step 2. Verify the Voltage Requirement
The GPIB-BUF is shipped from the factory with either a 115 V or 230 V
wall-mount power supply.
Verify that the voltage on the power supply matches the voltage that is
supplied in your area.
Warning: Operating the unit at any voltage other than the one specified
could damage the unit.
GPIB-BUF User Manual
2-2
© National Instruments Corp.
Chapter 2
Installation and Operation
Step 3. Configure the Operating Parameters
The GPIB-BUF is shipped from the factory configured to operate at a GPIB
primary address of 5 with the SRQ-on-empty function disabled and device
clear recognition and pass through enabled.
The address specified on the configuration switches should match the GPIB
address of your target device. If the addresses do not match, you must
either change the primary address of your target device or change the
primary address of the GPIB-BUF so that they correspond.
To change the primary address of your target device, refer to the user
manual of the device.
To change the GPIB-BUF primary address, the SRQ-on-empty function, or
the device clear response method, you must open the unit and change the
configuration switches. The following steps describe how to change the
configuration switches.
1. Disconnect power to the GPIB-BUF and disconnect any cables attached
to the rear panel.
2. Remove the two screws on the opposite sides of the rear panel.
Warning: Most of the circuitry in the GPIB-BUF uses advanced
CMOS technology and can be damaged by static electricity.
Avoid touching any of the components and take any
necessary CMOS handling precautions.
3. Grasp the rear panel bezel and pull it straight away from the rest of the
unit. The board should slide out the back of the enclosure.
4. Locate the configuration DIP switch (U38) on the printed circuit board.
5. Set the switches for the desired configuration, as described in the
following section, Set Configuration Switches.
6. Close the unit and reinsert the rear panel screws.
© National Instruments Corp.
2-3
GPIB-BUF User Manual
Installation and Operation
Chapter 2
Set Configuration Switches
Use the DIP switch at location U38 on the printed circuit board to configure
the GPIB primary address and operating modes of the GPIB-BUF. The DIP
switch has eight configuration switches. Figure 2-2 shows the factory
default setting.
Key
= depressed side of switch handle
1
2
3
4
5
6
7
8
O
N
O
F
F
Figure 2-2. Factory Default Switch Settings
Table 2-1 and Table 2-2 detail the possible configurations of the eight
switches and what each configuration indicates. For more information on
the different operating modes configured by the switches, refer to
Chapter 3, Technical Information.
Default settings are in shaded rows.
Table 2-1. Configuration Parameters for Switches 1 through 3
Switch
Position
OFF
Indication
1
Enables device clear recognition
Disables device clear recognition
ON
2
3
OFF
Sends DCL to the target and resets the
GPIB-BUF
ON
OFF
ON
Sends DCL to the target
Disables SRQ on buffer empty
Enables SRQ on buffer empty
GPIB-BUF User Manual
2-4
© National Instruments Corp.
Chapter 2
Installation and Operation
Table 2-2. Configuration Parameters for Switches 4 through 8
Switches
6
Indication
4
5
7
8
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
OFF
OFF
OFF
OFF
ON
OFF OFF
OFF ON
Sets GPIB primary address 0
Sets GPIB primary address 1
Sets GPIB primary address 2
Sets GPIB primary address 3
Sets GPIB primary address 4
Sets GPIB primary address 5
Sets GPIB primary address 6
Sets GPIB primary address 7
Sets GPIB primary address 8
Sets GPIB primary address 9
Sets GPIB primary address 10
Sets GPIB primary address 11
Sets GPIB primary address 12
Sets GPIB primary address 13
Sets GPIB primary address 14
Sets GPIB primary address 15
Sets GPIB primary address 16
Sets GPIB primary address 17
Sets GPIB primary address 18
Sets GPIB primary address 19
ON
ON
OFF
ON
OFF OFF
OFF ON
ON
ON
ON
ON
OFF
ON
ON
OFF
OFF
OFF
OFF
ON
OFF OFF
OFF ON
ON
ON
ON
ON
OFF
ON
ON
ON
OFF OFF
OFF ON
ON
ON
ON
ON
ON
ON
OFF
ON
ON
ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF OFF
OFF ON
ON
ON
ON
ON
OFF
ON
ON
(continues)
© National Instruments Corp.
2-5
GPIB-BUF User Manual
Installation and Operation
Chapter 2
Table 2-2. Configuration Parameters for Switches 4 through 8 (Continued)
Switches
Indication
4
5
6
7
8
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
ON
ON
ON
ON
OFF OFF
OFF ON
Sets GPIB primary address 20
Sets GPIB primary address 21
Sets GPIB primary address 22
Sets GPIB primary address 23
Sets GPIB primary address 24
Sets GPIB primary address 25
Sets GPIB primary address 26
Sets GPIB primary address 27
Sets GPIB primary address 28
Sets GPIB primary address 29
Sets GPIB primary address 30
Sets listen-only operation
ON
ON
OFF
ON
OFF OFF
OFF ON
ON
ON
OFF
ON
OFF OFF
OFF ON
ON
ON
OFF
ON
Step 4. Connect the Cables
Connect the cables as follows:
1. Connect the power jack of the wall-mount power supply to the power
receptacle on the back panel of the GPIB-BUF, then plug the supply
into an AC outlet of the correct voltage.
2. Connect a GPIB cable from the target device to the GPIB OUT port on
the rear panel of the GPIB-BUF.
3. Connect another GPIB cable from the GPIB IN port on the rear panel
of the GPIB-BUF to the remaining GPIB devices in your system.
Note: In steps 2 and 3, be sure to obey all IEEE 488 cabling
restrictions, and tighten all lock screws on the GPIB connectors.
GPIB-BUF User Manual
2-6
© National Instruments Corp.
Chapter 2
Installation and Operation
Step 5. Power on the Unit
Power on your target device then power on your GPIB-BUF by using the
front panel rocker switch. The POWER LED should light immediately and
the READY indicator should blink while the unit executes its power-on
self-test. The READY indicator should stop blinking and remain on when
the GPIB-BUF has passed its power-on self-test indicating the unit is ready
for operation.
If the READY indicator does not start to blink immediately or continues to
blink for more than 7 s for the 256 KB model or 20 s for the 1 MB model
after the unit is powered on, recheck all connections and switch settings and
retry the power-on sequence. If the READY light still fails to come on or
continues to blink longer than the specified time limits, contact National
Instruments for further instructions.
Operation
The GPIB-BUF is now ready to operate. When the GPIB-BUF is powered
on, it asserts the Interface Clear (IFC*) line on the GPIB OUT port to
initialize the GPIB link to the target device; therefore, ensure that the GPIB
target device is powered on before the GPIB-BUF.
When the GPIB-BUF is addressed to listen, all data sent to the unit via the
GPIB IN port is input directly to memory by the on-board DMA controller
at speeds up to 900 kbytes/s and is stored in the internal data buffer. The
actual speed depends on the speed of the GPIB talker as well as the speed of
other GPIB devices that are addressed to listen along with the GPIB-BUF.
Thus, the speed is no longer limited to the speed of the target device which
is now isolated from the rest of the GPIB system. The GPIB-BUF
addresses the target device to listen and sends the buffered data to the target
device at the maximum rate that the target device can receive the data.
When addressed to talk, the GPIB-BUF waits until it has emptied all the
data currently stored in its internal buffer, then addresses the target device
to talk. All data sent by the target device is passed directly through the
GPIB-BUF to the GPIB listener(s) on the GPIB system.
The addressing of the target device, as well as the routing and buffering of
data, is taken care of automatically by the GPIB-BUF. All data operations
are completely transparent, and the target device appears to be connected
directly to the GPIB bus. You should operate and control your target device
in the same manner you would if you did not have a GPIB-BUF.
© National Instruments Corp.
2-7
GPIB-BUF User Manual
Chapter 3
Technical Information
This chapter contains a more detailed description of the operation of the
GPIB-BUF. The timing characteristics of the parallel port are provided in
this chapter.
The GPIB-BUF is actually a powerful 8-bit microcomputer tailored for use
as an IEEE 488 data buffer. The operating system of the unit is contained in
Read-Only Memory (ROM) and can address up to 1 MB of dynamic
Random Access Memory (RAM). The GPIB-BUF microprocessor contains
an integrated Direct Memory Access (DMA) Controller for high-speed data
transfers from the GPIB circuitry. The processor also contains an integrated
memory management unit, a dynamic RAM Controller, a clock generator, a
programmable timer unit, a full duplex UART, and an interrupt Controller.
Two LSI GPIB Controller chips which are programmed and maintained by
the operating system provide all GPIB functionality. Both controller chips
are connected to their respective ports through GPIB transceivers which are
responsible for guaranteeing that the electrical characteristics of the
IEEE 488 specification are upheld.
Power Up
When powered on, the GPIB-BUF runs internal diagnostics to verify the
operation of all internal circuitry. Since the diagnostics can take as long as
20 s, the READY LED blinks during the test to indicate that the power-on
self-test is progressing successfully. If no errors are found, the GPIB-BUF
illuminates the READY and EMPTY LEDs which indicates that the
GPIB-BUF is ready to operate and its internal data buffer is empty. If the
GPIB-BUF is in listen-only mode, it also illuminates the LISTEN LED at
this time.
After the GPIB-BUF has successfully completed its power-on self-test, it
asserts the Interface Clear (IFC *) signal on the GPIB OUT port to initialize
the link between the GPIB-BUF and the target device, and to establish the
ability of the GPIB-BUF to address the target device. The GPIB-BUF then
reads the status of the configuration switches and initializes the rest of the
system.
© National Instruments Corp.
3-1
GPIB-BUF User Manual
Technical Information
Chapter 3
If the SRQ-on-empty feature is enabled, the GPIB-BUF asserts the Service
Request (SRQ*) signal on the GPIB IN port. The SRQ condition can be
used to signal the GPIB Controller that the GPIB-BUF is powered on and
ready to accept data.
Addressing
The five GPIB address switches (U38, switches 4 through 8) become the
GPIB primary address to which the GPIB IN port responds. These switches
are also used to determine the talk and listen addresses used by the
GPIB-BUF when addressing the target device attached to the GPIB OUT
port. Unless either the GPIB-BUF or the target device is operating in listen-
only mode, the target device must be set at the same GPIB address as the
GPIB-BUF.
If all the GPIB address switches are set to ON, the GPIB-BUF is configured
to operate in listen-only mode. In this mode, no addressing is required to
make the GPIB-BUF a GPIB Listener and it cannot be unaddressed to
listen. Therefore, all data transferred on the GPIB IN port is accepted by
the GPIB-BUF and output to the target device.
When operating in listen-only mode, the GPIB-BUF can neither return any
data from the target device nor respond to a serial poll request since it
cannot be addressed as a GPIB Talker. As a consequence, the SRQ feature
of the GPIB-BUF should not be enabled when operating in listen-only
mode.
When operating in listen-only mode, the GPIB-BUF sends all possible
listen addresses to the target device (via the GPIB OUT port) after it has
finished its power-on self-test. Since all listen addresses are sent out, the
target device need not be in listen-only mode. Instead, it can be at any valid
GPIB primary address. This mode can also be used to connect more than
one target device to the GPIB-BUF which allows multiple, simultaneous
copies of a document or drawing to be created.
Data Transfers
Upon being addressed to listen, the GPIB-BUF updates the front panel
address indicators by turning on the LISTEN indicator and turning off the
TALK indicator. The GPIB-BUF then begins to accept data from the GPIB
IN port using the onboard Direct Memory Access (DMA) Controller. The
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© National Instruments Corp.
Chapter 3
Technical Information
DMA Controller transfers the data directly to the internal data buffer
without processor intervention. Thus, GPIB transfer rates as high as 900
kbytes/s are possible. The GPIB-BUF turns off the EMPTY indicator as
soon as it starts receiving data from the host.
The buffered data is then sent to the target device connected to the GPIB
OUT port at the maximum acceptance rate of the target device. The GPIB
OUT port is interrupt-driven and is asynchronous with respect to any DMA
activity that is taking place on the GPIB IN port. Both events take place
concurrently and without user intervention.
If very large amounts of data are sent to the GPIB-BUF (greater than the
amount of RAM in the system) and the target device is a very slow data
acceptor (such as a printer or plotter), the internal data buffer of the
GPIB-BUF can become full. If this happens, the FULL indicator on the
front panel illuminates. This is not an error condition, but an indication that
the GPIB transfer rate from the GPIB Talker to the GPIB-BUF has slowed
to approximately the same rate as that of the target device accepting the
data.
Upon being addressed to talk, the GPIB-BUF updates the front panel
address indicators by turning on the TALK indicator and turning off the
LISTEN indicator. The GPIB-BUF waits for all the data in its internal
buffer to be accepted by the target, and then addresses the target device to
talk. Any data sent from the target device to the GPIB-BUF is not buffered,
but is passed directly through the GPIB-BUF to the GPIB IN port. Since no
buffer space is required when the GPIB-BUF is addressed to talk, all the
RAM in the system can be dedicated to providing the largest possible buffer
space for data coming into the GPIB IN port.
EOI
The GPIB End Or Identify (EOI) signal is used by the GPIB Listener(s) to
determine when the GPIB Talker has finished sending data. Without it, the
GPIB Listener must either know in advance the exact amount of data that
the Talker will send or must know of some terminating character sequence
that the Talker will adhere to when sending data. EOI signal reception and
transmission is fully supported on the GPIB-BUF.
When sending data while addressed as a GPIB Talker, the GPIB-BUF
asserts EOI* on the GPIB IN port with any byte received from the target
device that has the EOI* signal line asserted.
© National Instruments Corp.
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GPIB-BUF User Manual
Technical Information
Chapter 3
When receiving data while addressed as a GPIB Listener, the GPIB-BUF
buffers the state of the EOI* signal line along with the data byte it
corresponds to using an additional on-board RAM module. Therefore, the
GPIB-BUF is able to maintain the EOI status with each byte received even
when the DMA Controller is transferring data directly to memory. In this
way, the GPIB-BUF can accept multiple occurrences of EOI bytes at full
speed without loss of performance due to special EOI handling techniques.
IFC
Interface Clear (IFC) is used by a GPIB Controller to place an interface
system in a known, quiescent state. The function of the IFC* signal is to
halt current operations on the bus by unaddressing all Talkers and Listeners,
and disabling serial polls.
The GPIB-BUF asserts IFC* on the GPIB OUT port once at power-up for
500 µs. The action of asserting IFC* for at least 100 µs initializes the GPIB
link to the target device and establishes the ability of the GPIB-BUF
to address the target device. Any other response to IFC* is not defined by
the IEEE 488 specification and is specific to the target device.
If the GPIB-BUF detects IFC* asserted on the GPIB IN port, it immediately
unaddresses itself (unless it is in listen-only mode) and stops accepting data.
IFC* does not clear the GPIB-BUF data buffer or assert IFC* on the GPIB
OUT port since either of these operations aborts any current data transfer
taking place to the target device. Device CLear (DCL) or Selected Device
Clear (SDC) should be used to terminate an ongoing data transfer to the
target device.
REN
Remote Enable (REN) is asserted by the system Controller and is used to
enable GPIB devices to be placed in the remote programming mode
(programmable via the GPIB). The GPIB-BUF always asserts REN* on the
GPIB OUT port. REN* need not be asserted on the GPIB IN port for the
GPIB-BUF to operate.
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© National Instruments Corp.
Chapter 3
Technical Information
Polling the GPIB-BUF
The GPIB-BUF can return status information to the GPIB Controller
through the serial poll response byte as shown in Figure 3-1. This byte
contains two bits of information that reflect the current condition of the
GPIB-BUF data buffer and whether the GPIB-BUF is asserting the SRQ*
signal on the GPIB IN port. The serial poll status byte is returned as
follows:
bit
7
6
5
4
3
2
1
0
0
SRQ
0
0
0
0
empty
0
0 = not asserting SRQ*
1 = asserting SRQ*
0 = buffer is not empty
1 = buffer is empty
Figure 3-1. Serial Poll Status Byte
The empty bit always reflects the current status of the buffer while the SRQ
bit only returns a 1 if the GPIB-BUF is asserting the SRQ* signal line. The
GPIB-BUF asserts the SRQ* signal if the buffer is currently empty and the
SRQ-on-empty function is enabled by Switch 3 of U38. The GPIB-BUF
unasserts the SRQ* signal when the buffer is no longer empty or when the
GPIB Controller serial polls the GPIB-BUF. Although serial polls are
usually in response to an SRQ condition, the GPIB-BUF can be serial
polled at any time for any reason.
Note: The GPIB-BUF cannot return a serial poll status byte if it is in
listen-only mode.
© National Instruments Corp.
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GPIB-BUF User Manual
Technical Information
Chapter 3
The GPIB-BUF SRQ-on-empty feature and serial poll status byte are useful
for several reasons.
•
A remote Controller is able to tell when a data transfer to a plotter or
printer is completely finished.
•
A ready indicator is provided to a remote GPIB Controller signaling
that the GPIB-BUF has been powered on, has successfully completed
its self-test, and is ready to accept data.
•
A means is provided by which very large files can be transferred
without depleting the bandwidth of the GPIB Talker and the GPIB bus.
The following paragraphs explain how this last point can be beneficial:
Suppose that you need to send a file to a plotter via the GPIB-BUF and the
file is larger than the available memory in the GPIB-BUF. Since the plotter
is a slow data acceptor and you are sending a large file, the GPIB-BUF
buffer will most likely become full. If this happens, the GPIB bus as well
as the GPIB Talker will bottleneck to the same speed as the plotter.
To avoid this problem, the SRQ-on-empty function can be enabled and the
GPIB Talker/Controller can send data amounts up to, but not exceeding the
GPIB-BUF buffer size. The Controller can then unaddress the GPIB-BUF
and allow other devices to use the GPIB while the GPIB-BUF is spooling
the file to the target device. The Controller also is now free to perform
other work while the file is being spooled. When the GPIB-BUF has
emptied its internal data buffer, it then requests service using SRQ* to
indicate that it is ready for additional data. The Controller can then
re-address the GPIB-BUF to listen and continue sending the rest of the file
in the above manner until all the data has been transferred.
Since the GPIB-BUF is a fully transparent, self-contained unit, the amount
of data buffering can also be increased by chaining multiple GPIB-BUF
units together.
Another means by which a Controller can determine if a device requires
service is by a parallel poll. During a parallel poll, each responding device
indicates its need for service by returning a status bit via one of the GPIB
data lines. GPIB data line assignments, as well as the level (high or low) of
the GPIB line, depend on the last parallel poll configuration command sent
to the device.
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© National Instruments Corp.
Chapter 3
Technical Information
Internally, the local Individual Status (ist) bit of the GPIB-BUF is reset to 0
when the internal data buffer is empty of data. It is set to 1 when the
internal data buffer is not empty.
Therefore, after the GPIB Controller configures the GPIB-BUF with a
Parallel Poll Enable (PPE) message from 60 to 67 hex, the GPIB-BUF,
during a parallel poll, drives the data line (which the Controller has
specified) active when the internal data buffer is empty. When data is
present in the GPIB-BUF, it drives the data line inactive. Likewise, after
the GPIB Controller configures the GPIB-BUF with a PPE message from
68 to 6F hex, the GPIB-BUF, during a parallel poll, drives the data line
(which the Controller has specified) active when the internal data buffer is
not empty of data. When the internal data buffer is empty, it drives the data
line inactive. The possible parallel poll responses from the GPIB-BUF are
summarized in Table 3-1.
Unlike serial polls, you can parallel poll the GPIB-BUF even when it is in
listen-only mode.
Table 3-1. Parallel Poll Responses
PPE
(hex)
GPIB Data Line Driven Active
in Response to Parallel Poll
Buffer Empty
Buffer Not Empty
60
61
62
63
64
65
66
67
68
69
6a
6b
6c
6d
6e
6f
DIO1
DIO2
DIO3
DIO4
DIO5
DIO6
DIO7
DIO8
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE
NONE
DIO1
DIO2
DIO3
DIO4
DIO5
DIO6
DIO7
DIO8
© National Instruments Corp.
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GPIB-BUF User Manual
Technical Information
Chapter 3
Special Note About Timeouts
If your current GPIB system relies on a timeout method to ensure a non-
functioning GPIB device does not hang the bus indefinitely, then it may be
necessary to adjust or disable the time limit to ensure that the target device
has enough time to respond to any requests for information.
For example, suppose that your current code sends a file to a plotter and
then prompts the plotter for its current status. If the file is large and GPIB
timeouts are in effect, the file is transferred to the GPIB-BUF followed
immediately by the plotter prompt. At this time, the Controller re-addresses
the GPIB-BUF to talk, starts its timeout timer, and waits for a response.
Since the GPIB-BUF is still spooling the data file to the plotter, which has
not yet received the prompt, the plotter cannot respond until the entire plot
is finished and the prompt is received. If the time required to finish the plot
and respond to the prompt are longer than the time limit of the Controller, a
timeout error will occur. This can be easily corrected by either increasing
or disabling time limits on GPIB operations of this type to very slow data
acceptors.
A more efficient way to handle responses after large file transfers is to wait
until the GPIB-BUF is empty before issuing the plotter request for
information. In this way, timeouts can remain in effect, and the GPIB
Talker can perform other useful work because it will not hang while waiting
for a plotter response. If SRQs are enabled, then the Controller need not
continually poll the GPIB-BUF, but can instead wait for an SRQ before
issuing the plotter request.
Multiline Command Group
When the GPIB-BUF receives either a GPIB Multiline Message SDC or
DCL via the GPIB IN port, it responds in one of several ways. The
response depends on the condition of switch 1 and 2 of the configuration
switch at location U38 on the printed circuit board.
If switch 1 is on, the GPIB-BUF ignores any SDC and DCL received and
takes no action. If switch 1 is off (default), the GPIB-BUF response
depends on the condition of switch 2.
If switch 2 is on, the GPIB-BUF immediately passes a DCL to the GPIB
target device when a DCL or SDC is received. If switch 2 is off (default),
the GPIB-BUF not only passes a DCL to the target device but also clears its
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© National Instruments Corp.
Chapter 3
Technical Information
internal data buffer. This mode can be used to prematurely abort a lengthy
plot or print.
Neither Group Execute Trigger (GET), Go To Local (GTL), nor Local
Lockout (LLO) have any effect on the GPIB-BUF.
The GPIB IN port on the GPIB-BUF can only act as a GPIB Talker or
Listener. It should not be passed control. If it is, the GPIB circuitry in the
GPIB-BUF will accept control and immediately assert ATN*. This is an
error condition that can lock up your system and, therefore, should be
avoided.
© National Instruments Corp.
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GPIB-BUF User Manual
Chapter 1
Description of the GPIB-232CV
Appendix A
Hardware Specifications
This appendix lists the electrical, environmental, and physical specifications of th
Table A-1. Electrical Characteristics
Characteristic
Specification
Power Supply Unit
Wall mount type, 115 VAC or 230 VAC,
50/60 Hz input, 9 VDC @ 1A max output
Voltage
Current
9 VDC regulated
700 mA typical; 1.0 A max
Table A-2. Environmental Characteristics
Characteristic
Specification
Operating Temperature
Storage Temperature
Relative Humidity
Noise Emissions
0° to 40° C
-20° to 70° C
10% to 90% noncondensing conditions
FCC Class A Verified
Hardware Specifications
Appendix A
Table A-3. Physical Characteristics
Characteristic
Specification
Case Size
1.6 in. by 5.7 in. by 8.4 in.
(40.6 mm by 144.8 mm by 213.4 mm)
Case Material
Rack Mounting
Weight
All metal enclosure
Single or dual kits available
28 oz. (796 gm) without power supply unit
Appendix B
Customer Communication
For your convenience, this appendix contains forms to help you gather the
information necessary to help us solve technical problems you might have as well
as a form you can use to comment on the product documentation. Filling out a
copy of the Technical Support Form before contacting National Instruments helps
us help you better and faster.
National Instruments provides comprehensive technical assistance around the
world. In the U.S. and Canada, applications engineers are available Monday
through Friday from 8:00 a.m. to 6:00 p.m. (central time). In other countries,
contact the nearest branch office. You may fax questions to us at any time.
Corporate Headquarters
(512) 795-8248
Technical support fax:
(800) 328-2203
(512) 794-5678
Branch Offices
Australia
Austria
Belgium
Denmark
Finland
France
Germany
Italy
Phone Number
(03) 879 9422
(0662) 435986
02/757.00.20
45 76 26 00
(90) 527 2321
(1) 48 14 24 00
089/741 31 30
02/48301892
(03) 3788-1921
03480-33466
32-848400
Fax Number
(03) 879 9179
(0662) 437010-19
02/757.03.11
45 76 71 11
(90) 502 2930
(1) 48 14 24 14
089/714 60 35
02/48301915
(03) 3788-1923
03480-30673
32-848600
Japan
Netherlands
Norway
Spain
Sweden
Switzerland
U.K.
(91) 640 0085
08-730 49 70
056/20 51 51
0635 523545
(91) 640 0533
08-730 43 70
056/20 51 55
0635 523154
Technical Support Form
Technical support is available at any time by fax. Include the information
from your configuration form. Use additional pages if necessary.
Name
Company
Address
Fax (
)
Phone (
)
Computer brand
Model
Processor
Operating system
Speed
MHz
RAM
MB
Display adapter
Mouse
yes
no
Other adapters installed
Hard disk capacity
Instruments used
MB
Brand
National Instruments hardware product model
Revision
Configuration
National Instruments software product
Version
Configuration
(continues)
The problem is
List any error messages
The following steps will reproduce the problem
Hardware Configuration Form
Record the settings and revisions of your hardware on the line to the right of
each item. Update this form each time you revise your hardware
configuration, and use this form as a reference for your current
configuration.
National Instruments Products
•
•
GPIB-BUF Revision
Switch Settings:
Other Products
•
•
•
•
•
Computer Make and Model
Microprocessor
Clock Frequency
Type of Monitor Card Installed
Application Programming Language (BASIC, C, Pascal, and so on)
Documentation Comment Form
National Instruments encourages you to comment on the documentation
supplied with our products. This information helps us provide quality
products to meet your needs.
Title: GPIB-BUF User Manual
Edition Date:
Part Number:
February 1994
320125-01
Please comment on the completeness, clarity, and organization of the
manual.
(continues)
If you find errors in the manual, please record the page numbers and
describe the errors.
Thank you for your help.
Name
Title
Company
Address
Phone
(
)
Mail to:
Technical Publications
National Instruments Corporation
6504 Bridge Point Parkway, MS 53-02
Austin, TX 78730-5039
Fax to:
Technical Publications
National Instruments Corporation
MS 53-02
(512) 794-5678
Glossary
Prefix
Meaning
micro
milli-
Value
-6
µ-
m-
10
-3
10
3
k-
kilo-
10
6
M-
mega-
10
°
%
degrees
percent
A
AC
amperes
alternating current
ANSI
C
EMI
FCC
GPIB
Hz
American National Standards Institute
Celsius
electromagnetic interference
Federal Communications Commission
General Purpose Interface Bus
hertz
IEEE
in.
KB
LED
m
Institute of Electrical and Electronic Engineers
inches
kilobytes of memory
light-emitting diode
meters
MB
oz
RAM
s
megabytes of memory
ounce
random-access memory
seconds
VAC
VDC
volts alternating current
volts direct current
|
