National Instruments GPIB-140A User manual

GPIB
GPIB-140A User Manual
GPIB-140A User Manual
February 2013
373124B-01

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The GPIB-140A and GPIB-140A/2 are warranted against defects in materials and workmanship for a period of one year from
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Compliance
Electromagnetic Compatibility Information
This hardware has been tested and found to comply with the applicable regulatory requirements and limits
for electromagnetic compatibility (EMC) as indicated in the hardware’s Declaration of Conformity (DoC)1.
These requirements and limits are designed to provide reasonable protection against harmful interference
when the hardware is operated in the intended electromagnetic environment. In special cases, for example
when either highly sensitive or noisy hardware is being used in close proximity, additional mitigation
measures may have to be employed to minimize the potential for electromagnetic interference.
While this hardware is compliant with the applicable regulatory EMC requirements, there is no guarantee
that interference will not occur in a particular installation. To minimize the potential for the hardware to
cause interference to radio and television reception or to experience unacceptable performance degradation,
install and use this hardware in strict accordance with the instructions in the hardware documentation and
the DoC1.
If this hardware does cause interference with licensed radio communications services or other nearby
electronics, which can be determined by turning the hardware off and on, you are encouraged to try to correct
the interference by one or more of the following measures:
• Reorient the antenna of the receiver (the device suffering interference).
• Relocate the transmitter (the device generating interference) with respect to the receiver.
• Plug the transmitter into a different outlet so that the transmitter and the receiver are on different branch
circuits.
Some hardware may require the use of a metal, shielded enclosure (windowless version) to meet the EMC
requirements for special EMC environments such as, for marine use or in heavy industrial areas. Refer to
the hardware’s user documentation and the DoC1for product installation requirements.
When the hardware is connected to a test object or to test leads, the system may become more sensitive to
disturbances or may cause interference in the local electromagnetic environment.
Operation of this hardware in a residential area is likely to cause harmful interference. Users are required to
correct the interference at their own expense or cease operation of the hardware.
Changes or modifications not expressly approved by National Instruments could void the user’s right to
operate the hardware under the local regulatory rules.
1 The Declaration of Conformity (DoC) contains important EMC compliance information and instructions
for the user or installer. To obtain the DoC for this product, visit ni.com/certification, search by
model number or product line, and click the appropriate link in the Certification column.

© National Instruments |vii
Contents
About This Manual
Conventions ...................................................................................................................... ix
Related Documentation .................................................................................................... ix
Chapter 1
Introduction
What Your Kit Should Contain ........................................................................................ 1-1
Optional Equipment.......................................................................................................... 1-1
Hardware Overview.......................................................................................................... 1-2
Time-Saving Development Tools..................................................................................... 1-3
Chapter 2
Connecting Your Hardware
Step 1. Verify the DIP Switch Setting.............................................................................. 2-1
Step 2. Connect the Cables ............................................................................................... 2-2
Step 3. Switch On Your GPIB Extender .......................................................................... 2-2
Step 4. Verify the Connection .......................................................................................... 2-2
Chapter 3
Configuring and Using Your Hardware
Data Transfer Modes ........................................................................................................ 3-1
Selecting a Data Transfer Mode ............................................................................... 3-1
Unbuffered Mode ............................................................................................. 3-1
Buffered Mode.................................................................................................. 3-1
Setting the Data Transfer Mode................................................................................ 3-2
HS488 Mode..................................................................................................................... 3-2
Selecting an HS488 Mode ........................................................................................ 3-2
HS488 Disabled................................................................................................ 3-2
HS488 Enabled ................................................................................................. 3-2
Setting the HS488 Mode........................................................................................... 3-2
Parallel Poll Response Modes .......................................................................................... 3-3
Immediate PPR Mode............................................................................................... 3-3
Latched PPR Mode................................................................................................... 3-3
Selecting a PPR Mode .............................................................................................. 3-4
Setting the PPR Mode............................................................................................... 3-4
Using Your Extension System.......................................................................................... 3-5

Contents
viii |ni.com
Chapter 4
Theory of Operation
Message Interpreter Layer ................................................................................................4-2
Packet Translation Layer ..................................................................................................4-2
Link Management Layer...................................................................................................4-2
Parallel-to-Serial Conversion Layer .................................................................................4-2
Physical Layer................................................................................................................... 4-2
Appendix A
GPIB Basics
Appendix B
Introduction to HS488
Appendix C
Multiline Interface Messages
Appendix D
Specifications
Appendix E
Technical Support and Professional Services
Glossary

© National Instruments |ix
About This Manual
This manual describes how to install, configure, and operate the National Instruments GPIB-140A
or GPIB-140A/2 bus extender.
Conventions
The following conventions appear in this manual:
This icon denotes a note, which alerts you to important information.
This icon denotes a caution, which advises you of precautions to take
to avoid injury, data loss, or a system crash.
bold Bold text denotes the names of LEDs.
GPIB-140A GPIB-140A refers to a National Instruments GPIB extender that
extends the GPIB to a maximum distance of 1 km.
GPIB-140A/2 GPIB-140A/2 refers to a National Instruments GPIB extender that
extends the GPIB to a maximum distance of 2 km.
GPIB extender GPIB extender refers to the GPIB-140A and the GPIB-140A/2.
IEEE 488 and IEEE 488 and IEEE 488.2 refer to the ANSI/IEEE Standard 488.1-1987
IEEE 488.2 and the ANSI/IEEE Standard 488.2-1992, respectively, which define
the GPIB.
italic Italic text denotes variables, emphasis, a cross-reference, or an
introduction to a key concept. Italic text also denotes text that is a
placeholder for a word or value that you must supply.
monospace Text in this font denotes text or characters that you should enter from
the keyboard, sections of code, programming examples, and syntax
examples. This font is also used for the proper names of disk drives,
paths, directories, programs, subprograms, subroutines, device names,
functions, operations, variables, filenames and extensions, and code
excerpts.
Related Documentation
The following documents contain information that you might find helpful as you read this manual:
• ANSI/IEEE Standard 488.1-1987, IEEE Standard Digital Interface for Programmable
Instrumentation
• ANSI/IEEE Standard 488.2-1992, IEEE Standard Codes, Formats, Protocols, and
Common Commands

© National Instruments |1-1
1
Introduction
This chapter lists the kit contents and briefly describes the GPIB-140A bus extender.
What Your Kit Should Contain
Before you connect your GPIB-140A or GPIB-140A/2, make sure you have all of the following
items:
One of the following GPIB-140A or GPIB-140A/2 bus extenders:
– U.S. 100-120 VAC
– Switzerland 220-240 VAC
– Australia 220-240 VAC
– Universal European 220-240 VAC
– North American 220-240 VAC
– U.K. 220-240 VAC
– Japan 100 VAC
One of the following standard 3-wire power cables:
– 100-120 VAC
– 220-240 VAC
Optional Equipment
One of the following transmission cables, which you can purchase from National
Instruments:
– Type T7 fiber-optic cable—up to 1 km (used with GPIB-140A)
– Type T8 fiber-optic cable—up to 2 km (used with GPIB-140A/2)
Caution To meet FCC emission limits for this device, you must use a shielded
GPIB cable. If you operate this equipment with a non-shielded cable, it may interfere
with radio and television reception.
A Type X2 double-shielded cable (1, 2, or 4 m), which you can purchase from National
Instruments.

1-2 |ni.com
Chapter 1 Introduction
Hardware Overview
Note You cannot use the GPIB-140A or GPIB-140A/2 bus extenders to
communicate with either a GPIB-140 or GPIB-140/2 bus extender. The GPIB-140A
and GPIB-140A/2 bus extenders use a different protocol to communicate with each
other across the fiber optic cable.
The GPIB-140A and GPIB-140A/2 are high-speed bus extenders that you can use in pairs with
fiber-optic cable to connect two separate GPIB systems in a functionally transparent manner.
Although the two bus systems are physically separate, as shown in Figure 1-1, devices logically
appear to be located on the same bus, as shown in Figure 1-2.
Figure 1-1. Typical Extension System (Physical Configuration)
Figure 1-2. Typical Extension System (Logical Configuration)
POWER
LINK ERROR
GPIB-140
FUS
Printer
(Listener)
GPIB Cable
Computer
(System Controller,
Talker, and Listener)
GPIB Cable
Fiber-Optic Cable
Signal Generator
(Listener) Unit Under Test
Multimeter
(Talker and Listener)
GPIB-140A or
GPIB-140A/2
GPIB-140A or
GPIB-140A/2
GPIB Cable
POWER LINK ERROR
GPIB-140
FUS
Computer
(System Controller,
Talker, and Listener)
Printer
(Listener)
GPIB
Multimeter
(Talker and Listener)
Signal Generator
(Listener)
Unit Under Test

© National Instruments |1-3
GPIB-140A User Manual
The GPIB-140A and GPIB-140A/2 bus extenders comply with the specifications of the
ANSI/IEEE Standard 488.1-1987 and the ANSI/IEEE Standard 488.2-1992, including the Find
Listeners protocol. With the GPIB extenders, you can overcome the following two configuration
restrictions imposed by IEEE 488:
• A cable length limit of 20 m total per contiguous bus or 2 m per each device on the bus,
whichever is smaller
• An electrical loading limit of 15 devices per contiguous bus
Each GPIB-140A system extends the GPIB to a maximum distance of 1 km, and each
GPIB-140A/2 system extends the GPIB to a maximum distance of 2 km. Both systems extend
the loading limit to 28 devices (including the GPIB extenders), without sacrificing speed or
performance. You can connect these point-to-point extension systems in series for longer
distances or in star patterns for additional loading.
Using the HS488 protocol, the maximum data transfer rate over the extension is greater than
2.8 Mbytes/s. The GPIB extenders use a buffered transfer technique with a serial extension bus,
which maximizes performance and minimizes the cabling cost. Furthermore, the extender does
not affect the transfer rate between devices on the same side of the extension. The GPIB extender
can also check for errors to make sure that the data transmitted successfully over the fiber-optic
link.
Because the GPIB-140A and GPIB-140A/2 are functionally transparent extenders, the GPIB
communications and control programs that work with an unextended system also work with an
extended system. However, the Parallel Poll Response Modes section in Chapter 3, Configuring
and Using Your Hardware, describes one exception to this transparency in conducting parallel
polls.
Time-Saving Development Tools
Your kit includes the GPIB-140A or GPIB-140A/2 bus extender. In addition, you can order the
NI-488.2, LabWindows™/CVI™, or LabVIEW software from National Instruments to speed
your application development time and make it easier to communicate with your instruments.
The NI-488.2 software supports the concurrent use of multiple types of GPIB hardware. For
example, you can communicate with GPIB devices through a PCI-GPIB, a PCMCIA-GPIB, and
a GPIB-ENET/100 in the same system at the same time. The NI-488.2 software, along with the
GPIB hardware, transforms your computer into a GPIB Talker/Listener/Controller with
complete communications and bus management capability.
LabVIEW is an easy-to-use, graphical programming environment you can use to acquire data
from thousands of different instruments, including IEEE 488.2 devices, VXI devices, serial
devices, PLCs, and plug-in data acquisition boards. After you have acquired raw data, you can
convert it into meaningful results using the powerful data analysis routines in LabVIEW.
LabVIEW also comes with hundreds of instrument drivers, which dramatically reduce software
development time, because you do not have to spend time programming the low-level control of
each instrument.

1-4 |ni.com
Chapter 1 Introduction
LabWindows/CVI is similar to LabVIEW, except that it combines an interactive, easy-to-use
development approach with the programming power and flexibility of compiled ANSI C code.
The GPIB Analyzer is another optional tool available from National Instruments that is useful
in troubleshooting a variety of IEEE 488 hardware and software problems. With its built-in
time-stamping capability, you can easily determine the throughput and overhead of your GPIB
systems. The GPIB Analyzer software for Windows works with the AT-GPIB/TNT+,
PCI-GPIB+, and NI PCIe-GPIB+ products, which provide GPIB Analyzer support along with
the functionality of a high-performance GPIB Controller.
For ordering information, or to request free demonstration software, contact National
Instruments.

© National Instruments |2-1
2
Connecting Your Hardware
This chapter describes how to connect your GPIB extender and verify that it is working properly.
Step 1. Verify the DIP Switch Setting
The 3-bit DIP switch sets the operation mode of the GPIB extender. The default switch setting
is for unbuffered transfer mode, latched parallel poll response (PPR), and HS488 disabled mode,
as shown in Figure 2-1.
Figure 2-1. Default DIP Switch Setting
Verify that the DIP switches on your GPIB extender are in these default positions. If you need
to change these settings, refer to Chapter 3, Configuring and Using Your Hardware, for
instructions on how to set the operation mode for your application.
PARALLEL POLL IMMEDIATE
HS488 ENABLE
BUFFERED TRANSFER
OFF
ON

2-2 |ni.com
Chapter 2 Connecting Your Hardware
Step 2. Connect the Cables
To connect the cables to both GPIB extenders, complete the following steps:
1. Make sure that each GPIB extender is powered off.
2. Connect the two connectors on each end of the fiber-optic cable to your GPIB extenders, as
follows:
a. As shown in Figure 2-2, align the connector marked T (transmit) with the connector
marked TRANS on the side panel of the GPIB extender. Align the connector marked
R (receive) with the connector marked RCVR on the side panel of the GPIB extender.
Figure 2-2. Connecting the Fiber-Optic Cable to Both GPIB Extenders
b. Remove the caps on the connectors.
c. Align the notch on each cable connector to the slot of the fiber-optic connector on the
box.
d. Firmly push in the cable connector and rotate the sleeve clockwise until it locks on to
the side notch of the fiber-optic connector on the box.
3. Connect the end of the extender with the GPIB connector to your GPIB system. Make sure
that you follow all IEEE 488 cabling restrictions. For typical restrictions, refer to the
Configuration Requirements section in Appendix A, GPIB Basics.
4. Plug the utility power cord included with your GPIB extender into an AC outlet of the
correct voltage.
5. Plug the other end of the utility power cord into your GPIB extender.
Step 3. Switch On Your GPIB Extender
Power on each GPIB extender. The POWER LED should light immediately. If the POWER
LED does not light immediately, make sure that power is supplied to your GPIB extender.
The LINK LED lights only when both GPIB extenders are on and the fiber-optic cable is
properly connected between them.
GPIB-140A or
GPIB-140A/2
GPIB-140A or
GPIB-140A/2
Fiber-Optic Cable
T
TRANS
RCVRTRANS
RCVR
T
R
R

© National Instruments |2-3
GPIB-140A User Manual
Step 4. Verify the Connection
Each GPIB extender has a self test that determines whether the GPIB extender receivers,
transmitters, and packet transmission and reception circuitry are working properly.
To run the self test, complete the following steps:
1. Power off the GPIB extender.
2. Disconnect the fiber-optic cable from the GPIB extender.
3. Power on the GPIB extender.
The POWER LED lights, indicating that power is supplied to the extender. The LINK
LED remains off.
4. Connect the connector marked T (transmit) on one end of the fiber-optic cable to the
connector marked TRANS on the side panel of the GPIB extender.
5. Connect the connector marked R (receive) on the opposite end of the fiber-optic cable to
the connector marked RCVR on the side panel of the GPIB extender.
Figure 2-3. GPIB Extender Self-Test Configuration
The LINK LED lights, indicating that the cable is connected. The ERROR LED should
remain off, indicating that the GPIB extender is working properly.
6. If the ERROR LED does not remain off, complete the following steps to solve the problem:
a. Verify that the fiber-optic cable is connected to the GPIB extender, as described in
steps 4 and 5. If the problem persists, continue to the next step.
b. Repeat steps 4 and 5 using the unconnected ends of the fiber-optic cable. If switching
the fiber-optic cable connectors solves the problem, you need to replace your
fiber-optic cable. To order a new fiber-optic cable, contact National Instruments. If
switching the fiber-optic cable connectors does not solve the problem, continue to the
next step.
c. If possible, repeat steps 4 and 5 using a different fiber-optic cable. If the problem
persists, you might need to replace your GPIB extender. For more information, contact
National Instruments.
GPIB-140A or
GPIB-140A/2
Fiber-Optic
Cable
TRANS
RCVR
R
R
T
T

© National Instruments |3-1
3
Configuring and Using
Your Hardware
This chapter describes how to configure and use your GPIB-140A or GPIB-140A/2 system.
Data Transfer Modes
The GPIB extender has two data transfer modes—unbuffered mode and buffered mode. The data
transfer mode determines how data is transmitted across the extension.
Selecting a Data Transfer Mode
To select a data transfer mode, refer to the following descriptions of each mode.
Unbuffered Mode
In unbuffered mode, each data byte is transmitted using the GPIB double-interlocked
handshaking protocol. For long data streams, transfers are slower than transfers using buffered
mode. However, the GPIB extension is transparent in unbuffered mode.
Buffered Mode
In buffered mode, the GPIB extenders use FIFO (first-in-first-out) buffers to buffer data between
the remote and local units. For long data streams, the data throughput is much higher than with
unbuffered mode.
However, a few applications may not operate properly in buffered mode. For example, 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 Talker sources data bytes, the GPIB extenders accept the data
bytes and store them in a FIFO buffer. At the same time, the GPIB extenders read data from the
FIFO buffer and source data bytes to the Listener. If the FIFO buffer contains data, the number
of bytes sourced by the Talker differs from the number of bytes accepted by the Listener.
GPIB command bytes are not stored in the FIFO buffers; they are transmitted using the GPIB
double-interlocked handshaking protocol.

3-2 |ni.com
Chapter 3 Configuring and Using Your Hardware
Setting the Data Transfer Mode
The two GPIB extenders in your extension system must use the same data transfer mode.
To use buffered mode, set DIP switch 1 to the ON position, as shown in Figure 3-1. To use
unbuffered mode, set DIP switch 1 to the OFF position.
Figure 3-1. DIP Switch Setting for Buffered Mode
HS488 Mode
The GPIB extender can handle data transfers using the HS488 protocol. HS488 transfers data
between two or more devices using a noninterlocked handshaking protocol. You can use HS488
to transfer data at rates higher than rates possible using the IEEE 488 protocol. For more
information about HS488, refer to Appendix B, Introduction to HS488.
Selecting an HS488 Mode
To select an HS488 mode, refer to the following descriptions of each mode.
HS488 Disabled
If you disable HS488, the GPIB extender sources and accepts data using a three-wire handshaking
protocol, even if both the Talker and Listener can transfer data using the HS488 protocol.
HS488 Enabled
After the Talker indicates that it wants to issue HS488 transfers, HS488 is enabled and the GPIB
extender accepts data using the HS488 protocol. Also, when talking, the GPIB extender always
tries to use the HS488 mode. In HS488 mode, FIFO buffers buffer data during HS488 transfers,
even if the data transfer mode is set to unbuffered. When you use the HS488 protocol with the
GPIB extender, you should set the GPIB cable length to 5 m for both the local and the remote
system. To do so, use your IEEE 488.2 software configuration utility.
Setting the HS488 Mode
The two GPIB extenders in your extension system do not need to use the same HS488 mode.
However, the system uses the maximum data transfer rate when both sides in your extension
system use HS488.
PARALLEL POLL IMMEDIATE
HS488 ENABLE
BUFFERED TRANSFER
= Not used to set datatransfer mode
OFF
ON

© National Instruments |3-3
GPIB-140A User Manual
To enable HS488, set DIP switch 2 to the ON position, as shown in Figure 3-2. To disable
HS488, set DIP switch 2 to the OFF position.
Figure 3-2. DIP Switch Setting for Enabled HS488
Parallel Poll Response Modes
According to IEEE 488, devices must respond to a parallel poll within 200 ns after the
Controller-In-Charge (CIC) asserts the Identify (IDY) message—Attention (ATN) and End or
Identify (EOI). The CIC waits at least 2 µs 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. To solve this problem, use one of the following two
solutions in your application:
• If possible, specify in your application that the CIC must allow enough time to receive the
response. For more information, refer to the following section, Immediate PPR Mode. If
you are using the NI-488.2 software, you can use the NI-488.2 Configuration utility to set
the amount of time that the CIC waits.
• Execute two consecutive parallel polls and use the second response. For more information,
refer to the Latched PPR Mode section later in this chapter.
Immediate PPR Mode
In immediate PPR mode, the GPIB extenders do not use the internal PPR data register. When a
Controller on the local system asserts IDY, the local extender sends the IDY message to the
remote bus and the response is returned as fast as propagation delays permit. Your application
must allow enough time to receive the response.
Latched PPR Mode
In latched PPR mode, the GPIB extenders use an internal PPR data register. When a Controller
on the local system asserts IDY, the local extender sends the contents of the PPR data register to
the local data lines. At the same time, a parallel poll message is sent to the remote bus. When the
local system unasserts IDY, 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 systems, your application should execute two
consecutive parallel polls and use the second response.
= Not used to set HS488 mode
PARALLEL POLL IMMEDIATE
HS488 ENABLE
BUFFERED TRANSFER
OFF
ON

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Chapter 3 Configuring and Using Your Hardware
The software driver library of most Controllers contains an easy-to-use parallel poll function.
For example, if the function is called ibrpp and your application is written in BASIC, the
sequence to execute a poll in latched PPR mode might be similar to the following sequence:
CALL ibrpp (brd0%, ppr%)
CALL ibrpp (brd0%, ppr%)
IF ppr > 0 GOTO 300
Selecting a PPR Mode
To select a PPR mode, consider the type of Controller present in your GPIB system and the
length of cable between the GPIB-140A extenders. However, if your application does not use
parallel polls, you do not need to select a PPR mode.
Some Hewlett Packard GPIB Controllers remain in a parallel poll state with IDY asserted if they
are not performing another function. A change in the response interrupts the application. In some
Controllers, the IDY signal is toggled on and off, and you can change the duration of the signal
to accommodate delayed responses over extenders. If you are using these types of Controllers,
you should set the GPIB extender to immediate PPR mode.
Most other Controllers pulse the IDY signal for approximately 2 µs and expect a response within
that time. If you are using this type of Controller and if the cable between the extenders is longer
than 60 m, you should set the GPIB extender to latched PPR mode. For shorter cable distances,
use immediate PPR mode.
The two GPIB extenders in your extension system do not need to use the same PPR mode. Select
the PPR mode of the local GPIB extender based on the Controllers on the local GPIB system.
Likewise, select the PPR mode of the remote GPIB extender based on the Controllers on the
remote GPIB system. If no Controllers are physically connected to one of the GPIB extenders,
the PPR mode of that GPIB extender has no effect on your system.
Setting the PPR Mode
To use immediate PPR mode, set DIP switch 3 to the ON position, as shown in Figure 3-3. To
use latched PPR mode, set DIP switch 3 to the OFF position.
Figure 3-3. DIP Switch Setting for Immediate PPR Mode
= Not used to set Parallel Poll Response (PPR) mode
PARALLEL POLL IMMEDIATE
HS488 ENABLE
BUFFERED TRANSFER
OFF
ON

© National Instruments |3-5
GPIB-140A User Manual
Using Your Extension System
After you supply power to both extenders and connect the fiber-optic cable, you can use your
GPIB-140A or GPIB-140A/2 extension system.
Table 3-1 lists the three LEDs that indicate the operational status of each GPIB extender.
Table 3-1. GPIB-140A LEDs
LED Description
POWER Lights if power is supplied to the GPIB extender and the power
switch is in the on position.
LINK Lights if both GPIB extenders are powered on and the transmission
cable is properly connected to both extenders. During operation, the
LINK LED turns off if you disconnect the cable from the receiver of
the GPIB extender, or if you power off either GPIB extender.
ERROR Lights if the GPIB extender receives corrupted data. The ERROR
LED turns off after the GPIB extender starts re-transmission and has
received the first retransmitted data byte without error.