National Instruments GPIB-130 User manual

National Instruments GPIB-130 Manual
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© Copyright 1991, 1994 National Instruments Corporation.
All Rights Reserved.
GPIB-130
User Manual
November 1993 Edition
Part Number 370897A-01

National Instruments Corporate Headquarters
6504 Bridge Point Parkway
Austin, TX 78730-5039
[phone]
Technical support fax: [phone]
[phone]
Branch Offices:
Australia [phone], Austria [phone], Belgium 02/757.00.20, Canada (Ontario) [phone],
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Germany 089/741 31 30, Italy 02/48301892, Japan [phone], Netherlands 03480-33466, Norway 32-848400,
Spain (91) 640 0085, Sweden 08-730 49 70, Switzerland 056/20 51 51, U.K. 0635 523545

Limited Warranty
The GPIB-130 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
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’émiet pas de bruits radioélectriques dépassant les limites applicables aux appareils
numériques de classe A prescrites dans le réglement sur le brouillage radioélectrique édicté par le ministére 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.

© National Instruments Corporation v GPIB-130 User Manual
Contents
About This Manual.............................................................................................................ix
Organization of This Manual.........................................................................................ix
Conventions Used in This Manual.................................................................................ix
Related Documentation..................................................................................................x
Customer Communication .............................................................................................x
Chapter 1
Introduction..........................................................................................................................1-1
Description of the GPIB-130 .........................................................................................1-1
What Your Kit Should Contain......................................................................................1-3
Optional Equipment.......................................................................................................1-4
Unpacking Your GPIB-130 ...........................................................................................1-4
Chapter 2
Connection.............................................................................................................................2-1
Connecting the GPIB-130..............................................................................................2-1
Connecting an External Power Supply ..............................................................2-2
Connecting to a Specially Configured GPIB Interface Board...........................2-2
Connecting to Hewlett-Packard Controllers......................................................2-3
Chapter 3
Configuration and Operation.........................................................................................3-1
Operating Modes............................................................................................................3-1
Unbuffered Mode...............................................................................................3-1
Buffered Mode...................................................................................................3-1
Setting the Operating Mode...............................................................................3-2
Parallel Poll Response (PPR) Modes.............................................................................3-2
Stored PPR Mode (Approach 1) ........................................................................3-3
Immediate PPR Mode (Approach 2)..................................................................3-3
Choosing the PPR Mode....................................................................................3-3
Setting the PPR Mode........................................................................................3-4
Operating the GPIB-130 System....................................................................................3-4
Power LED.........................................................................................................3-4
Link LED ...........................................................................................................3-5
Talk LED............................................................................................................3-5
Listen LED.........................................................................................................3-5
Chapter 4
Theory of Operation ..........................................................................................................4-1
Power-On (PON) State...................................................................................................4-1
System Controller Detection..........................................................................................4-2
Controller-In-Charge Detection.....................................................................................4-2
Source Handshake Detection.........................................................................................4-2
Parallel Poll Detection ...................................................................................................4-2
FIFO Controller..............................................................................................................4-2

Contents
GPIB-130 User Manual vi © National Instruments Corporation
Appendix A
Operation of the GPIB......................................................................................................A-1
Types of Messages.........................................................................................................A-1
Talkers, Listeners, and Controllers................................................................................A-1
The Controller-In-Charge and System Controller .........................................................A-2
GPIB Signals and Lines.................................................................................................A-2
Data Lines..........................................................................................................A-2
Handshake Lines................................................................................................A-2
Not Ready For Data (NRFD).................................................................A-2
Not Data Accepted (NDAC)..................................................................A-3
Data Valid (DAV)..................................................................................A-3
Interface Management Lines..............................................................................A-3
Attention (ATN).....................................................................................A-3
Interface Clear (IFC)..............................................................................A-3
Remote Enable (REN) ...........................................................................A-3
Service Request (SRQ) ..........................................................................A-3
End Or Identify (EOI)............................................................................A-3
Physical and Electrical Characteristics..........................................................................A-4
Configuration Requirements..........................................................................................A-7
Related Document..........................................................................................................A-7
Appendix B
Specifications........................................................................................................................B-1
System Configuration ....................................................................................................B-1
Performance Characteristics ..........................................................................................B-1
Operating Characteristics...............................................................................................B-2
Electrical Characteristics................................................................................................B-2
Environmental Characteristics.......................................................................................B-2
Physical Characteristics .................................................................................................B-2
Appendix C
Cable Assembly Wire List ...............................................................................................C-1
Appendix D
Multiline Interface Messages..........................................................................................D-1
Appendix E
Customer Communication...............................................................................................E-1
Glossary......................................................................................................................Glossary-1

Contents
© National Instruments Corporation vii GPIB-130 User Manual
Figures
Figure 1-1. The Model GPIB-130 Bus Extender.................................................................1-1
Figure 1-2. Typical GPIB-130 Extension System (Physical Configuration)......................1-2
Figure 1-3. Typical GPIB-130 Extension System (Logical Configuration)........................1-2
Figure 2-1. GPIB-130 Side View........................................................................................2-1
Figure 3-1. Switch Setting for Operating Mode..................................................................3-2
Figure 3-2. Switch Setting for Parallel Poll Response (PPR) Mode...................................3-4
Figure 4-1. GPIB-130 Block Diagram ................................................................................4-1
Figure A-1. GPIB Connector and the Signal Assignment....................................................A-4
Figure A-2. Linear Configuration ........................................................................................A-5
Figure A-3. Star Configuration ............................................................................................A-6
Table
Table C-1. Cable Assembly Wire List................................................................................C-1

© National Instruments Corporation ix GPIB-130 User Manual
About This Manual
This manual describes how to use the National Instruments GPIB-130 bus extender.
Organization of This Manual
This manual is organized as follows:
• Chapter 1, Introduction, contains a description of the GPIB-130, lists the contents of your
GPIB-130 kit, lists optional equipment, and explains how to unpack the GPIB-130.
• Chapter 2, Connection, contains information for connecting your GPIB-130.
• Chapter 3, Configuration and Operation, describes how to configure and operate a GPIB-130
system.
• Chapter 4, Theory of Operation, describes how the GPIB-130 circuitry operates.
• Appendix A, Operation of the GPIB, describes GPIB terminology and protocol for users
unfamiliar with the GPIB.
• Appendix B, Specifications, lists the specifications of the GPIB-130.
• Appendix C, Cable Assembly Wire List, contains the listing of wire connections for the
GPIB-130 transmission cable.
• Appendix D, Multiline Interface Messages, contains an ASCII chart with a list of the
corresponding GPIB messages and hex values.
• Appendix E, Customer Communication, contains forms for you to complete to facilitate
communication with National Instruments concerning our products.
• The Glossary contains an alphabetical list and description of terms used in this manual,
including abbreviations, acronyms, metric prefixes, mnemonics, and symbols.
Conventions Used in This Manual
Throughout this manual, the following convention is used to distinguish elements of text:
italic Italic text denotes emphasis, a cross reference, or an introduction to a key
concept.

About This Manual
GPIB-130 User Manual x © National Instruments Corporation
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
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 to you complete. These forms are located in Appendix E, Customer
Communication, at the end of this manual.

© National Instruments Corporation 1-1 GPIB-130 User Manual
Chapter 1
Introduction
This chapter contains a description of the GPIB-130, lists the contents of your GPIB-130 kit, lists
optional equipment, and explains how to unpack the GPIB-130.
The GPIB-130 is a high-speed bus extender with the following features:
• It extends the maximum GPIB cable length to 300 m.
• It expands the GPIB to interface up to 28 devices.
• It performs high-speed parallel transmissions, with rates up to 900 kbytes/sec.
• It has a switch to select buffered transfers for high performance or normal GPIB transfers
with interlocked handshaking.
• It has a switch to select immediate parallel poll mode, for cable lengths of 60 m or less, or
stored parallel poll mode, for longer distances.
Description of the GPIB-130
The high-speed GPIB-130 bus extender (shown in Figure 1-1) is used in pairs with a special
parallel data transmission cable to connect two separate GPIB (IEEE 488) bus systems in a
functionally transparent manner.
Figure 1-1. The Model GPIB-130 Bus Extender

Introduction Chapter 1
GPIB-130 User Manual 1-2 © National Instruments Corporation
While the two bus systems are physically separate, as shown in Figure 1-2, devices logically
appear to be located on the same bus as shown in Figure 1-3.
RS-422 Compatible
Transmission
Lines
Computer
(System Controller,
Talker, and Listener)
Printer
(Listener) Multimeter
(Talker and Listener) Signal Generator (Listener)
Unit Under Test
GPIB #2GPIB #1 GPIB-130 GPIB-130
Figure 1-2. Typical GPIB-130 Extension System (Physical Configuration)
Computer
(System Controller,
Talker, and Listener)
Printer
(Listener) Multimeter
(Talker and Listener) Signal Generator (Listener)
Unit Under Test
GPIB
Figure 1-3. Typical GPIB-130 Extension System (Logical Configuration)

Chapter 1 Introduction
© National Instruments Corporation 1-3 GPIB-130 User Manual
With the GPIB-130, it is possible to overcome the following two configuration restrictions
imposed by ANSI/IEEE Standard 488.1-1987:
• A cable length limit of 20 m total per contiguous bus or 2 m times the number of devices on
the bus, whichever is smaller
• An electrical loading limit of 15 devices per contiguous bus
Each GPIB-130 system extends the distance limit by 300 m and the loading limit to 30 devices
(including the extenders), without sacrificing speed or performance. These point-to-point
extender systems can be connected in series for longer distances or in star patterns for additional
loading.
The maximum data transfer rate over the extension is 900 kbytes/sec. Furthermore, there is no
speed degradation at all for transfers between devices on the same side of the extension.
Because the GPIB-130 is a functionally transparent extender, the same GPIB communications
and control programs that work with an unextended system can work unmodified with an
extended system. There is one minor exception to this transparency in conducting parallel polls,
as explained in Chapter 3 in the section Parallel Poll Response (PPR) Modes.
What Your Kit Should Contain
Your GPIB-130 kit should contain the following components:
Kit Component Part Number
GPIB-130 Bus Extender 181460-01
One of the following power supplies:
• 100-120 VAC (5V-regulated, 700mA)
or
• 220-240 VAC (5V-regulated, 1A)
181626-01
181626-31
GPIB-130 User Manual 320391-01

Introduction Chapter 1
GPIB-130 User Manual 1-4 © National Instruments Corporation
Optional Equipment
Equipment Part Number
Transmission Cables:
• Type T5 (NEC CL2 rated) – up to 50 m
• Type T2 (NEC CL2 rated) – 0 m to 300 m
• Type T6 (NEC CL2P-Plenum rated) – 0 m to 300 m
(xxx = length in meters)
181563-xxx
178056-xxx
181564-xxx
Type X1 GPIB Cable (Single-Shielded)*:
•1m
•2m
•4m
763001-01
763001-02
763001-03
Type X2 GPIB Cable (Double-Shielded)*:
•1m
•2m
•4m
763061-01
763061-02
763061-03
* To meet FCC emission limits for this Class A device, you must use a shielded (Type X1
or X2) GPIB cable. Operating this equipment with a non-shielded cable may cause
interference to radio and television reception in commercial areas.
Unpacking Your GPIB-130
Follow these steps when unpacking your GPIB-130.
1. Verify that the pieces contained in the package you received match the kit parts list given
earlier in this section.
2. Inspect the shipping container and contents for damage. If the container is damaged and the
damage appears to have been caused in shipment, file a claim with the carrier. If the
equipment is damaged, do not attempt to operate it. Contact National Instruments for
instructions. Retain the shipping material for possible inspection by carrier or reshipment of
the equipment.

© National Instruments Corporation 2-1 GPIB-130 User Manual
Chapter 2
Connection
This chapter contains information for connecting your GPIB-130.
Connecting the GPIB-130
Figure 2-1 shows a side view of the GPIB-130.
Figure 2-1. GPIB-130 Side View
The GPIB-130 may be powered on from either an external 5V regulated power supply or from a
specially configured National Instruments GPIB interface board.

Connection Chapter 2
GPIB-130 User Manual 2-2 © National Instruments Corporation
Connecting an External Power Supply
Caution: Not for installation in air ducts or plenums. For installation in other environmental
air handling spaces, use only with cable classified by U.L. Inc. as to fire and smoke
characteristics in accordance with section 725.2(B) of the National Electrical Code.
To connect an external power supply to the GPIB-130, complete the following steps.
Caution: Failure to follow these steps for installation may result in damage to your GPIB-130
and your system.
1. Make sure that the power switch on the side panel is in the off position.
2. Inspect the power supply to confirm that it is compatible with the line voltage available
from the wall outlet.
3. Push the phono-jack connector of the external power supply into the 5VDC jack of the
GPIB-130.
4. Turn the phono-jack connector so that it screws into the threading on the 5VDC jack.
5. Plug the power supply into the wall outlet.
6. Connect the transmission cable to both GPIB-130s.
7. Slide the power switch of both extenders to the on position.
The GPIB-130 extension is now operational.
Connecting to a Specially Configured GPIB Interface Board
To connect the GPIB-130 to a specially equipped National Instruments GPIB interface board,
complete the following steps.
Caution: Failure to follow these steps for installation may result in damage to your GPIB-130
and your system.
1. Make sure that the power switch on the side panel is in the off position.
2. Turn off the computer containing the interface board.
3. Unplug the power cord of the computer.
4. Push either phono-jack connector of the special power cord into the 5VDC jack of the
GPIB-130.
5. Turn the phono-jack connector so that it screws into the threading on the 5VDC jack on
the GPIB-130.

Chapter 2 Connection
© National Instruments Corporation 2-3 GPIB-130 User Manual
6. Push the other phono-jack connector of the special power cord into the 5VDC jack of the
National Instruments interface board.
7. Turn the phono-jack connector so that it screws into the threading on the 5VDC jack on
the interface board.
8. Plug in the power cord of the computer and turn on the computer.
9. Connect the transmission cable to both GPIB-130s.
10. Slide the power switch of both extenders to the on position.
The GPIB-130 extension is now operational.
Connecting to Hewlett-Packard Controllers
To achieve very high data transfer rates and long cable spans between devices, many HP
Controllers and computers, such as the 64000 series, use a preload technique on the unit
designated Master Controller. When preloaded, the GPIB lines of the Master Controller are
terminated to represent six device loads. HP has two types of preloading: Class A, in which all
16 GPIB lines are loaded, and Class B, in which all lines, except NRFD and NDAC lines, are
loaded.
Preloading increases ringing on signal transitions and can cause improper operation of the
GPIB-130s. If this happens, set all signals on the Master Controller to normal (1 unit) load. This
is done using a back panel switch on your HP Controller. In addition, you must also strictly
conform to the cabling rule of no more than two meters per device.

© National Instruments Corporation 3-1 GPIB-130 User Manual
Chapter 3
Configuration and Operation
This chapter describes how to configure and operate a GPIB-130 system.
Operating Modes
The GPIB-130 has two operating modes: Unbuffered mode and Buffered mode. The operating
mode determines how data is transmitted across the extension. Both units in the extension
system must be set to the same mode.
Unbuffered Mode
In Unbuffered mode, each data byte is transmitted using the GPIB double interlocked
handshaking protocol. For long data streams, transfers using Unbuffered mode are slower than
transfers using Buffered mode. However, the GPIB extension is transparent in Unbuffered
mode.
Buffered Mode
In Buffered mode, the GPIB-130 uses FIFOs to buffer data between the remote and local units.
For long data streams, you can obtain a much higher data throughput with Buffered mode than
with Unbuffered mode.
Consider the following situation: a GPIB device on the local side of the extension is addressed to
talk; another device on the remote side is addressed to listen. When the talking device sources
data bytes, the GPIB-130s accept the data bytes and store them in a FIFO. At the same time, the
GPIB-130s read data from the FIFO and source data bytes to the Listener. Whenever the FIFO
contains data, the number of bytes sourced by the Talker differs from the number of bytes
accepted by the Listener. A few applications may not operate properly in Buffered mode.
GPIB command bytes are not stored in the FIFOs; they are transmitted using the GPIB double
interlocked handshaking protocol.
In most applications, the GPIB-130s should be configured in Buffered mode.

Configuration and Operation Chapter 3
GPIB-130 User Manual 3-2 © National Instruments Corporation
Setting the Operating Mode
Both GPIB-130s in the extension system must be set to the same operating mode. Use switch
position 1 on the side of each GPIB-130 to set the operating mode. Slide the switch to the up
position to set Buffered mode; slide the switch down to set Unbuffered mode. See Figure 3-1.
On Off
. . . . . . . . . . . .
A. Buffered Mode
B. Unbuffered Mode
Key
= Buffer position
= PPoll position
On Off
. . . . . . . . . . . .
PPoll Im
PPoll St
Buffered
Unbuffered
PPoll Im
PPoll St
Buffered
Unbuffered
Figure 3-1. Switch Setting for Operating Mode
Parallel Poll Response (PPR) Modes
According to ANSI/IEEE Standard 488.1-1987, devices must respond to a parallel poll within
200 nsec after the Identify (IDY) message (Attention (ATN) and End Or Identify (EOI)) is
asserted by the Controller-In-Charge (CIC). The Controller then waits at least 2 µsec before
reading the Parallel Poll Response (PPR). In many cases, a remote device on an extended
system cannot respond to Parallel Polls this quickly because of cable propagation delays. The
GPIB-130s can solve this problem using one of the following two approaches:
Approach 1: Respond to IDY within 200 nsec with the results of the previous poll of the
remote bus.
Approach 2: Ignore the 200 nsec rule and assume that the Controller will wait long enough to
capture the response.

Chapter 3 Configuration and Operation
© National Instruments Corporation 3-3 GPIB-130 User Manual
Stored PPR Mode (Approach 1)
In the stored PPR mode, the GPIB-130s use an internal PPR data register. When a Controller on
the local GPIB system asserts IDY, the local GPIB-130 extender responds by outputting the
contents of the PPR data register to the local GPIB data lines. At the same time, a parallel poll
message is sent to the remote bus. When the local IDY signal is unasserted, the PPR from the
remote system is loaded into the internal PPR data register. Consequently, the register always
contains the response of the previous complete poll. To obtain the response of both local and
remote GPIB systems, the control program executes two parallel polls back-to-back and uses the
second response.
The software driver library of most Controllers contains an easy-to-use parallel poll function. If,
for example, the function is called ibrpp and the control program is written in BASIC, the
sequence to conduct a poll in Stored PPR mode might be similar to the following sequence:
.
.
.
CALL ibrpp (brd0%, ppr%)
CALL ibrpp (brd0%, ppr%)
IF ppr > 0 GOTO 300
.
.
.
Immediate PPR Mode (Approach 2)
In this mode, the GPIB-130s do not use the internal PPR data register. When a Controller on the
local GPIB system asserts IDY, the local GPIB-130 extender sends the IDY message to the
remote bus and the response is returned as fast as propagation delays permit. The Controller
must allow time to receive the response.
Choosing the PPR Mode
Choosing the right PPR depends on the type of Controllers present in the GPIB system and the
length of cable between the GPIB-130s. Of course, if the control program does not use parallel
polls, the PPR mode does not matter.
Many Hewlett-Packard GPIB Controllers remain in a parallel poll state with IDY asserted
whenever they are not performing another function. A change in the response causes an interrupt
of the control program. In other Controllers, the IDY signal is toggled on and off and the
duration of the signal can be varied to accommodate delayed responses over extenders. When
used with these types of Controllers, the GPIB-130 should be set to Immediate PPR mode.
Most other Controllers pulse the IDY signal for about 2 µsec and expect a response within that
time. When used with this type of Controller, the GPIB-130 should use the Stored PPR mode if
the cable between the extenders is longer than about 60 m. For shorter cable distances, using the
Immediate PPR mode is recommended.