National Instruments Switch GPIB BUF User Manual

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. CUSTOMERS 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  
GPIB-BUF User Manual  
3-2  
© 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.  
3-3  
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.  
GPIB-BUF User Manual  
3-4  
© 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.  
3-5  
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.  
GPIB-BUF User Manual  
3-6  
© 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.  
3-7  
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  
GPIB-BUF User Manual  
3-8  
© 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.  
3-9  
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  
 
 

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