Measurement Extender 488HS User Manual

the smart approach to instrumentation

™

IOtech, Inc.

25971 Cannon Road Cleveland, OH 44146 Phone: (440) 439-4091 Fax: (440) 439-4093 E-mail: sales@iotech.com Internet: http:/www.iotech.com

Extender 488HS User’s Manual

p/n EXT488/HS-901, Rev. 2.0

1996-1997 by IOtech, Inc. Part No.EXT488/HS-901, Rev. 2.0

Printed in the United States of America

Warranty Information

Your IOtech warranty is as stated on the product warranty card. You may contact IOtech by phone, fax machine, or e-mail in regard to warranty-related issues. Phone: (440) 439-4091, fax: (440) 439-4093, e-mail: sales@iotech.com

Limitation of Liability

IOtech, Inc. cannot be held liable for any damages resulting from the use or misuse of this product.

All IOtech documentation, software, and hardware are copyright with all rights reserved. No part of this product may be copied, reproduced or transmitted by any mechanical, photographic, electronic, or other method without IOtech’s prior written consent. IOtech product names are trademarked; other product names, as applicable, are trademarks of their respective holders. All supplied IOtech software (including miscellaneous support files, drivers, and sample programs) may only be used on one installation. You may make archival backup copies.

FCC Statement

IOtech devices emit radio frequency energy in levels compliant with Federal Communications Commission rules (Part 15) for Class A devices. If necessary, refer to the FCC booklet How To Identify and Resolve Radio-TV Interference Problems (stock # 004-000-00345-4) which is available from the U.S. Government Printing Office, Washington, D.C. 20402.

CE Notice

Many IOtech products carry the CE marker indicating they comply with the safety and emissions standards of the European Community. As applicable, we ship these products with a Declaration of Conformity stating which specifications and operating conditions apply.

Warnings, Cautions, Notes, and Tips

Refer all service to qualified personnel. This caution symbol warns of possible personal injury or equipment damage under noted conditions. Follow all safety standards of professional practice and the recommendations in this manual. Using this equipment i n ways other than described in this manual can present serious safety hazards or cause equipment damage.

This ESD caution symbol urges proper handling of equipment or components sensitive to damage from electrostatic discharge. Proper handling guidelines include the use of grounded anti-static mats and wrist straps, ESD-protective bags and cartons, and related procedures.

Specifications and Calibration

Specifications are subject to change without notice. Significant changes will be addressed in an addendum or revision to the manual. As applicable, IOtech calibrates its hardware to published specifications. Periodic hardware calibration is not covered under the warranty and must be performed by qualified personnel as specified in this manual. Improper calibration procedures may void the warranty.

Quality Notice

IOtech has maintained ISO 9001 certification since 1996. Prior to shipment, we thoroughly test our products and review our documentation to assure the highest quality in all aspects. In a spirit of continuous improvement, IOtech welcomes your suggestions.

Section

Section 2 Getting Started ...........................................................................................................................................2.1

Section 3 IEEE 488 Primer..........................................................................................................................................3.1

1 Introduction 1.1

1.1 Description 1.1

1.2 Available Accessories 1.2

1.3 Specifications 1.2

1.4 Abbreviations 1.4

2.1 Inspection ..................................................................................................................................................2.1

2.2 Extender488/HS Configuration.................................................................................................................2.1

2.3 Front Panel Indicators................................................................................................................................2.3

2.4 Line Voltage Selection ..............................................................................................................................2.4

2.5 Hardware Installation.................................................................................................................................2.6

2.6 Operation...................................................................................................................................................2.7

2.7 Speed Considerations ................................................................................................................................2.8

3.1 History.......................................................................................................................................................3.1

3.2 General Structure.......................................................................................................................................3.1

3.3 Send It To My Address..............................................................................................................................3.4

3.4 Bus Management Lines.............................................................................................................................3.4

3.4.1 Attention (ATN) ....................................................................................................................3.4

3.4.2 Interface Clear (IFC)..............................................................................................................3.4

3.4.3 Remote Enable (REN)...........................................................................................................3.5

3.4.4 End or Identify (EOI).............................................................................................................3.5

3.4.5 Service Request (SRQ)..................................................................................................... .....3.5

3.5 Handshake Lines........................................................................................................................................3.5

3.5.1 Data Valid (DAV)..................................................................................................................3.5

3.5.2 Not Ready for Data (NRFD)..................................................................................................3.6

3.5.3 Not Data Accepted (NDAC)..................................................................................................3.6

3.6 Data Lines 3.7

3.7 Multiline Commands.................................................................................................................................3.7

3.7.1 Go To Local (GTL)................................................................................................................3.7

3.7.2 Listen Address Group (LAG)................................................................................................3.7

3.7.3 Unlisten (UNL)......................................................................................................................3.7

3.7.4 Talk Address Group (TAG)...................................................................................................3.7

3.7.5 Untalk (UNT).........................................................................................................................3.7

3.7.6 Local Lockout (LLO).............................................................................................................3.8

3.7.7 Device Clear (DCL)...............................................................................................................3.8

3.7.8 Selected Device Clear (SDC)............................................................................................... ..3.8

3.7.9 Serial Poll Disable (SPD)....................................................................................................... 3.8

3.7.10 Serial Poll Enable (SPE)....................................................................................................3.8

3.7.11 Group Execute Trigger (GET)...........................................................................................3.8

3.7.12 Take Control (TCT)...........................................................................................................3.8

3.7.13 Secondary Command Group (SCG)...................................................................................3.9

3.7.14 Parallel Poll Configure (PPC)............................................................................................3.9

3.7.15 Parallel Poll Unconfigure (PPU)........................................................................................3.9

3.8 More On Service Requests........................................................................................................................3.9

3.8.1 Serial Poll...............................................................................................................................3.10

3.8.2 Parallel Poll............................................................................................................................3.10

Table of Contents

Section 4 Service Information.....................................................................................................................................4.1

4.1 Factory Service..........................................................................................................................................4.1

4.2 Theory of Operation..................................................................................................................................4.1

4.3 Extender488/HS Cable Construction.........................................................................................................4.1

4.3.1 Cable Wiring Diagram...........................................................................................................4.2

Appendix A Character Codes and IEEE Multiline Messages ............................................................................................A.1

Section 1 Introduction

Introduction

1.1 Description

The Extender488/HS High Speed IEEE 488 Bus Extender enables IEEE 488 devices to be controlled at a distance of up to 1,000 meters from a host computer. The Extender488/HS overcomes the limit imposed by the IEEE 488 specification of 2 meters between any two devices. In addition, the Extender488/HS Bus Extender allows up to 27 devices to be on the bus (plus the controller and the two Extender488/HS Bus Extenders), versus the 14 device limit imposed by the IEEE standard.

Two bus extenders are required to perform bus extension. The bus connected to the host computer, or controller, is the "local" bus. The bus to which control is extended is the "remote" bus. One Extender488/HS Bus Extender is required on each bus to accomplish IEEE bus extension.

Communication between bus extenders is accomplished with parallel data transmission, using RS-422 data drivers and receivers within the Extender488/HS Bus Extender. This differential parallel data format provides high noise immunity, high speed, and long-distance capability using a special cable.

Operation of the Extender488/HS Bus Extender is completely transparent to the system. The controller can access both local and remote devices in exactly the same manner.

IEEE Controller

evices

EEE

Up to

13 IEEE

Devices

Up to 14 IEEE Devices

Extender488/HS

igh-Speed arallel Link

p to

000 meters

1.1

Section 1 Introduction

1.2 Available Accessories

The following accessories are available from IOtech for use with the Extender488/HS

Bus Extender:

CA-7-1 CA-7-2 CA-7-3 CA-7-2 CA-56-30

CA-56-10 CN-20

CN-48 CN-22 CN-23 MAN-116-0015

1.5 foot IEEE 488 cable 6 foot IEEE 488 cable 6 foot IEEE 488 cable; shielded 6 foot IEEE 488 cable; reverse entry

30 m. Shielded parallel cable with ma ting connectors for the Extender488/HS 10 m. Shielded parallel cable with ma ting connectors for the

Extender488/HS Right angle IEEE 488 adapter Extender488/HS cable adapter IEEE 488 multi-tap bus strip; 4 connectors in parallel

IEEE 488 panel mount feed-thru connector

Additional Manual

Refer to the IOtech catalog for those accessories not listed here.

1.3 Specifications

IEEE 488-1978

Implementation: Proprietary transparent con tr ol and data transfers.

PASS CONTROL is not supported.

Connector: Standard IEEE 488 connector with metric studs.

Parallel Interface

EIA RS-422A: Balanced voltage on all signal lines. Connector: 50-pin Centronics female. Max. Cable Length: 1000 meters.

1.2

Section 1 Introduction

General

Data Rates: Specifications apply to data transfers after

addressing has been established.

Cable Length m. (ft.) Data Rate (kB/s, avg) *

10 (32.8) 800 20 (65.6) 700 50 (164) 450 100 (328.1) 300 200 (656.2) 150 500 (1640.5) 75 1000 (3281.0) 40

* using a 500ns data settling delay

Indicators: LEDs for IEEE Talk, Listen, Local Extender, Remote

Extender, Connect, and Power. Power: 105-125V or 210-250V; 50-60 Hz, 30 VA Max. Dimensions: 425mm wide x 45mm high x 208mm deep

(16.75" x 1.75" x 8.20"). Weight: 2.1 kg. (4.6 lbs). Environment: 0° - 50°C; 0 to 90% R.H. Non-Condensing Controls: Power Switch (external),

Configuration switch (external).

Specifications subject to change without notice.

1.3

Section 1 Introduction

1.4 Abbreviations

The following IEEE 488 abbreviations are used throughout this manual.

addr ATN Attention line CA Controller Active CO Controller CR Car riage Return data Data String DCL Device Clear GET Group Execute Trigger GTL Go To Local LA Listener Active LAG Listen Address Group LF Line Feed LLO Local Lock Out MLA My Listen Address MTA My Talk Address PE Peripheral PPC Parallel Poll Configure PPU Parallel Poll Unconfigure SC System Controller SDC Selected Device Clear SPD Serial Poll Disable SPE Serial Poll E nable SRQ Service Request TA Talker Active TAD Talker Address TCT Take Control term Terminator UNL Unlisten UNT Untalk * Unasserted

IEEE bus address "n"

1.4

Section 2 Getting Started

Getting Started

2.1 Inspection

Your Extender488/HS IEEE 488 Bus Extender was carefully inspected, both mechanically and electrically, prior to shipment. When you receive the Extender488/HS Bus Extender, carefully unpack all items from the shipping carton and check for any obvious signs of physical damage which may have occurred during shipment. Immediately report any damage found to the shipping agent. Remember to retain all shipping materials in the event that shipment back to the factory becomes necessary.

Every Extender488/HS Bus Extender is shipped with the following:

Extender488/HS

•

MAN-116-0015

•

A-116-0001

•

Note: accessories ordered may be packaged and shipped separately

Instruction Manual

High Speed IEEE 488 Bus Extender Interface

Accessory Kit (includes power cable, fuse, and rack mounting hardware)

2.2 Extender488/HS Configuration

Two Extender488/HS IEEE Bus Extenders are required to accomplish bus extension, with one connected directly to the Local IEEE 488 bus, and the other connected to the Remote IEEE 488 bus.

CAUTION

Make sure that the Extender488/HS Bus Extender that is connected to the controller is set for Local Extender mode and the other Extender488/HS Bus Extender is set to Remote Extender mode before applying power. Failure to observe this caution will result in damage to both Extender488/HS Bus Extenders.

Both local and remote bus extenders are identical. Before either unit is powered on, switch #1 of the rear panel configuration DIP switch must be set to Local Extender Mode

2.1

Section 2 Getting Started

the Extender488/HS Bus Extender connected to the Local bus) or Remote

(for Extender Mode (for the Extender488/HS Bus Extender connected to the Remote bus).

When both units are on, the Local bus extender will monitor all local bus activity and transmit this activity to the Remote bus extend er. All activity d etected b y the Remote bus extender is also communicated back to the Local bus extender.

WARNING

Never open the Extender488/HS Bus Extender case while it is connected to the AC line. Failure to observe this warning may result in equipment failure, personal injury or death.

Not Used

1 0

12345678

Remote Extender

Mode

Not Used

1 0

12345678

Local Extender

Mode

Extender488/HS Configuration Selection

Note: Factory default setting is REMOTE

Switch

Side

View

DOT

2.2

Section 2 Getting Started

2.3 Front Panel Indicators

Six LEDs on the front panel of the Extender488/HS display the status of the bus

extender. The function of each indicator is described below.

Extender488/HS

HIGH SPEED BUS EXTENDER

LOCAL EXTENDER

REMOTE EXTENDER

CONNECT LISTEN POWERTALK

Front Panel Indicators

LOCAL ON when the Extender488/HS is configured as the Local EXTENDER

Extender.

REMOTE ON when the Extender488/HS is configured as the EXTENDER

Remote Extender.

CONNECT ON if both Extender488/HS Bus Extenders are powered

on and the interconnecting cable is functional.

TALK Remote Extender - On when a device on the Local bus (or the

controller) is talking to device( s) on the Remote bus. Local Extender - On except when a device on the Local bus (or the

controller) is talking to device( s) on the Remote bus.

LISTEN Local Extender - On when a device on the Local bus (or the controller)

is talking to device(s) on the Rem ote bus. Remote Extender - On except when a device on the Local bus (or the

controller) is talking to device( s) on the Remote bus.

POWER ON when power is applied to the Extender488/HS and the power

switch on the rear panel is in the ON position (depressed). OFF otherwise.

2.4 Line Voltage Selection

The line voltage is set by an internal switch (S3) located near the rear panel power supply

connector, next to the power switch. To change the operating voltage, it is necessary to open the enclosure

2.3

Section 2 Getting Started

and change the setting of S3. The 1/2 Amp fuse (IOtech part number FU-1-.5) that is used for 115 Volt operation must be replaced with a 1/4 Amp fuse (IOtech part number FU-1-.25) for 230 Volt operation..

Disconnect the power cord from the AC line and from the Extender488/HS Bus Extender.

Disconnect any IEEE cables prior to disassembly.

WARNING :

Power Connector

115V

LETHAL VOLTAGES MAY BE PRESENT

Extender488/HS Fuse and Line Voltage Switch Locations

WARNING Never open the Extender488/HS Bus Extender case while it is connected to the AC line. Internal voltage potentials exist which could cause personal injury or death.

1. Place the Extender488/HS on a flat surface. Remove the six screws on top of the case and remove the top cover. Located next to the rear panel power connector is switch S3 and fuse F1.

2. Using a small screwdriver, insert the tip of the screwdriver into th e slot of the switch and move the switch to the left or right so that the desired line voltage selection appears on the switch. Make note of the new setting for later reference.

CAUTION Use the 1/2 Amp fuse, FU-1-.5 for 115 volt operation. Use the 1/4 Amp fuse, FU-1.25 for 230 volt operation. Failure to use the correct fuse could result in damage to the Extender488/HS Bus Extender.

2.4

Section 2 Getting Started

3. Replace the 1/2 Amp fuse, FU-1-.5 (115 volt operation), with the 1/4 Amp fuse (230 volt operation), part number FU-1-.25, that is included in the Extender488/HS-004 Accessory Kit.

4. Carefully reassemble the unit.

WARNING The Extender88/HS Bus Extender is intended for INDOOR USE ONLY. Failure to observe this warning could result in equipment failure, personal injury or death.

2.5

Section 2 Getting Started

2.5 Hardware Installation

Included with the Extender488/HS Bus Extender are accessories for rack or bench use. If rack mount installation is required, install the two rack ears using the enclosed screws. These ears can be installed so either the front or the rear of the unit faces the front of the rack fixture.

Enclosure

Top or Bottom View

Top View

Rack Ear

Screw

If bench installation is required, the rubber feet can be installed on the underside of the unit near each corner.

(2 per ear)

View of Enclosure showing Rack Hardware Installation

Enclosure

Bottom View

Top View

View of Enclosure Bottom Showing Feet Placement

2.6

Section 2 Getting Started

2.6 Operation

After configuring the Extender488/HS IEEE 488 Bus Extenders and connecting the

Extender488/HS cable, plug the power cable connector into the rear jack on the bus extender.

WARNING

The Extender488/HS Bus Extender is intended for INDOOR USE ONLY. Failure to observe this warning could result in equipment failure, personal injury or death.

The Extender488/HS Bus Extender makes its earth ground connection through the IEEE interface cable. Each bus extender must be connected to at least one IEEE device which is earth ground referred. Failure to do so may allow the Extender488/HS Bus Extender to float to a voltage away from ground. This could result in damage to the Extender488/HS Bus Extender, personal injury, or death.

CAUTION

After installing the power cable into th e bus ex tender , plu g the p ower cab le into th e AC line p ower. Place the rear panel power switches on both u nits in the ON [depressed] position. The CONNECT and POWER LEDs should light on both units. The REMOTE EXTENDER LED should be lit on the unit set for REMOTE EXTENDER operation and the LOCAL EXTENDER LED should be lit on the unit set for LOCAL EXTENDER operation. If the LOCAL unit is connected to an IEEE 488 controller and the controller is on, the LISTEN LED should be lit on the LOCAL unit and the TALK LED should be lit on the REMOTE unit. If any of the following LED conditions exist after power-on, a failure has occurred:

2.7

Section 2 Getting Started

SYMPTOM FAILURE

CONNECT LED off Extender488/HS cable defective

or not properly installed

No LEDs on Power not connected

If the CONNECT LED is not lit on either unit, make sure that the Extender488/HS cable is firmly seated in the rear panel connector. If the problem is unresolved, refer to the Service Information section of this manual.

If proper operation is obtained, turn-off the Extender488/HS power switch and connect the other IEEE devices to each of the Extender488/HS IEEE ports. Apply power to all devices in the system.

Once all IEEE devices have been connected and powered on, the Extender488/HS will allow the system controller to command up to 13 IEEE devices on its local bus (in addition to itself and the local bus extender), and up to 14 IEEE devices on the remote bus (in addition to the remote bus extender). The bus extenders have no address o f their own, and therefore will oper ate completely transparent to the system. Be careful not to have two IEEE devices with the same address connected to either remote or local buses. Failure to do so will result in the bus 'lockin g up' when one of the devices is accessed.

2.7 Speed Considerations

The Extender488/HS bus extenders operate transparently to most IEEE 488 applications. However, since there is an inverse relationship between the data transfer rate and the cable length, the response time for bus transactions may be affected. The following information is provided so that you can determine if some modifications may be needed to your application.

As the length of the cable linking the two b us extenders is increased, the data transfer rate will decrease. A graph showing the typical data transfer rate as a function of distance is shown on the next page.

2.8

Section 2 Getting Started

1000

100

10 100 1000

Length (Meters)

Extender488/HS Data Rate vs Cable Length

Since the IEEE 488 handshake is maintained across the entire link from the Local bus to the Remote bus, it is highly unlikely that data will be lost. The only IEEE 488 transaction that could be affected by long cable lengths is parallel poll (PPOL). If your application uses

parallel polling, you should be aware of the time delays that are introduced into your system when any type of bus extender (including the Extender488/HS) is installed.

In a system that does not use a bus extender, the following events occur when the controller

conducts a parallel poll:

1. Controller conducts parallel poll (asserts EOI and ATN).

2. Devices detect parallel poll state and respond by asserting a data line.

3. Controller reads parallel poll response from data bus.

In a system that uses bus extenders, the following delays are present when the controller conducts

a parallel poll:

1. Controller conducts parallel poll (asserts EOI and ATN)

2. Local extender detects parallel poll state and sends the message to the link port.

3. Message travels through the link cable and arrives at the remote extender after an amount

4. Remote unit receives parallel poll state and sends it to the remote IEEE 488 bus.

5. Devices on the remote bus detect the parallel poll state and respond by asserting a data

6. Response travels through remote extender to its link port.

7. Response travels through the link cable and arrives at the local extender after an amount

of time that depends on the length of the interconnecting cable.

line.

of time that depends on the length of the interconnecting cable.

2.9

Section 2 Getting Started

8. Local extender receives parallel poll response on the link port and sends it to the local IEEE 488 bus.

9. Controller reads parallel poll response.

Since most controllers read the parallel poll response shortly after asserting EOI and ATN (within 2 µs), the use of a bus extender may not provide the parallel poll response back to the controller in the allotted time. For applications that use the p arallel poll command, the interconnecting cable length should be such that time delays will not affect the parallel poll response. The following example may be used to help determine the response time to a parallel poll in your system.

If a cable length of 10 m. is used, the parallel poll response time would be calculated as shown below (from the previous parallel poll delay explanation):

Step Time Delay (approximate)

10 2 20 ns 3 59 ns (5.9 ns/meter) X (Interconnecting cable length) 4 20 ns 5 140 ns (device dependent) 6 20 ns 7 59 ns (5.9 ns/meter) X (Interconnecting cable length) 8 20 ns

Total 338 ns Total parallel poll response time

Since the IEEE 488 controller will wait 2 µs before reading the parallel poll response, the 338 ns response time is well within the required 2 µs response time. For distances greater than 150 meters, the parallel poll response may not be returned to the controller in the allotted time. The time is dependent on the response time of the instruments on the remote bus.

2.10

Section 3 IEEE 488 Primer

IEEE 488 Primer

3.1 HISTORY

IEEE 488

The Electronic Engineers in 1975 and revised in 1978. The designated

computer interfaces. This placed the burden of system hardware design on the end user. If his application required the products of several different manufacturers, then he might need to design several different hardware and software interfaces. The popularity of the

us or and control protocols. The use of the the interface to design of the high level software that is specific to the measurement application.

IEEE 488-1978

Prior to the adoption of this standard, most instrumentation manufacturers offered their own versions of

GPIB

) is due to the total specification of the electrical and mechanical interface as well as the data transfer

3.2 GENERAL STRUCTURE

bus is an instrumentation communication bus adopted by the Institute of Electrical and

Digital488

IEEE 488

interface (sometimes called the General Purpose Interface

standard has moved the responsibility of the user from design of

conforms to this most recent revision

The main purpose of the either be an instrument or a computer. Before any information transfer can take place, it is first necessary to specify which will do the talking (send data) and which devices will be allowed to listen (receive data). The decision of who will talk and who will listen usually falls o n the

Active Controller

System Controller

The speak at a time and the chairman is responsible for recognizing members and allowing them to have their say. On the bus, the device which is recognized to speak is the information transferred is to be clearly understood by all. The act of "giving the floor" to that device is called

Addressing to Talk

he can appoint an acting chairman to take control of the proceedings. For the

Active Controller

is similar to a committee chairman. On a well run committee, only one person may

. If the committee chairman can not attend the meeting, or if other matters require his attention,

GPIB

is to transfer information between two or more devices. A device can

Active Talker

3.1

System Controller

. There can only be one Talker at a time if the

which is, at power on, the

GPIB

, this device becomes the

Section 3 IEEE 488 Primer

At a committee meeting, everyone present usually listens. This is not the case with the commands all other devices to ignore what is being transmitted. A device is instructed to listen by being

Listener

GPIB

. The

. Devices which are to ignore the data message are instructed to

Active Controller

Addressed to Listen

selects which devices will listen and

. This device is then referred to as an

Unlisten

Active

The reason some devices are instructed to college instructor is presenting the day's lesson. Each student is told to raise their hand if the instructor has exceeded their ability to keep up while taking notes. If a hand is raised, the instructor stops his discussion to allow the slower students the time to catch up. In this way, the instructor is certain that each and every student receives all the information he is trying to present. Since there are a lot of students in the classroom, this exchange of information can be very slow. In fact, the rate of information transfer is no faster than the rate at which the slowest note-taker can keep up. The instructor, though, may have a message for one particular student. The instructor tells the rest of the class to ignore this messag e ( one student at a rate which he can understand. This information transfer can then happen much quicker, because it need not wait for the slowest student.

GPIB

The

called

For data transfer on the

a) b) Designate who will c) Designate all the devices who are to

devices to

d) Indicate to all devices that the data transfer can take place.

transfers information in a similar way. This method of data tr ansfer is

handshaking

Unlisten

. More on this later.

IEEE 388

all devices to protect against eavesdroppers.

talk

listen

Active Controller

, the

addressing

Unlisten

a device to

listen

is quite simple. Suppose a

Unlisten

must …

talk

addressing

) and tells it to that

those

3.2

Section 3 IEEE 488 Primer

3.3

Section 3 IEEE 488 Primer

3.3 SEND IT TO MY ADDRESS

In the previous discussion, the terms

to Listen

one system. Each of these devices must have a unique address to avoid confusion. In a similar fashion, every building in town has a unique address to prevent one home from receiving another home's mail. Exactly how each device's address is set is specific to the product's manufacturer. Some are set by DIP switches in hardware, others by software. Consult the manufacturer's instructions to determine how to set the address.

Controller

(MTA),

were used. These terms require some clarification.

IEEE 488

The

Addresses are sent with

. These commands include

Talk Address Group

standard permits up to 15 devices to be configured within

universal (multiline

My Listen Address

(TAG), and

Listen Address Group

Addressed to Talk

) commands from the

(MLA),

(LAG).

Addressed

and

Active

My Talk Address

3.4 BUS MANAGEMENT LINES

Five hardware lines on the on these lines are often referred to as active low, i.e. a low voltage represents a logic "1" (asserted), and a high voltage represents a logic "0" (unasserted).

GPIB

are used for bus management. Signals

uniline

(single line) commands. The signals are

3.4.1 Attention (ATN)

ATN

is one of the most important lines for bus management. If Attention is asserted, then the information contained on the data lines is to be in terpreted as a multiline command. If it is not, then that information is to be interpreted as d ata for

Active Listener

the of this line.

Active Controller

s. The

is the only bus device that has control

3.4.2 Interface Clear (IFC)

IFC

The bus devices in a known state. Although device configurations vary, the command usually places the devices in the Talk and Listen Idle states (neither

Talker

nor

line is used only by the

Active Listener

System Controller

3.4

. It is used to place all

IFC

Active

Section 3 IEEE 488 Primer

3.4.3 Remote Enable (REN)

When the devices will respond to remote operation. Generally, the should be issued before any bus programming is attempted. Only the

System Controller

has control of the

sends the

Remote Enable

REN

command, bus

REN

line.

command

3.4.4 End or Identify (EOI)

EOI

The transfer. The device that is sending the data asserts of the last data byte. The the data may be indicated by some special character such as carriage return.

The by simultaneously asserting

line is used to signal the last byte of a multibyte data

EOI

during the transfer

EOI

signal is not always necessary as the end of

Active Controller

EOI

also uses

and

ATN

EOI

to perform a

Parallel Poll

3.4.5 Service Request (SRQ)

When a device desires the immediate attention of the

Controller

determine which device requested service. This is accomplished with a

Serial Poll

it asserts

or a

SRQ

. It is then the Controller's responsibility to

Parallel Poll

Active

3.5 HANDSHAKE LINES

GPIB

The got it" sequence. This handshake protocol assures reliable data transfer, at the rate determined by the slowest Listener. One line is controlled by th e Talker, while the other two are shared by all Active Listeners. The handshake lines, like the other

IEEE 488

lines, are active low.

uses three handshake lines in an "I'm ready - Here's the data - I've

3.5.1 Data Valid (DAV)

DAV

The

NDAC

is asserted (active low) which indicates that all Listeners have accepted

the previous data byte transferred. The

line is controlled by the

Talker

then outputs data on the bus and

3.5

. The

Talker

verifies that

Section 3 IEEE 488 Primer

waits until Listeners are ready to accept the information. When the proper state, the on the bus is valid.

NRFD

is unasserted (high) which indicates that all Addressed

NRFD

Talker

asserts

DAV

( active low) to indicate that the data

and

NDAC

are in

3.5.2 Not Ready for Data (NRFD)

This line is used by the are ready to accept new data. The unassert this line (high) which they will do at their own r a te wh en they are r eady for more data. This assures that all devices that are to accept the information are ready to receive it.

Listeners

Talker

must wait for each

to inform the

Talker

Listener

when they

3.5.3 Not Data Accepted (NDAC)

NDAC

The indicates to the information. Each device releases will not go high until the slowest Listener has accepted the data byte.

Talker

line is also controlled by the

that each device addressed to listen has accepted the

NDAC

(high) at its own rate, but the

Listeners

. This line

NDAC

3.6

Section 3 IEEE 488 Primer

3.6 DATA LINES

GPIB

The These eight data lines use the convention of binary designation of D0 to D7. The data lines are bidirectional and are active low.

provides eight data lines for a bit parallel/byte serial data tr ansfer.

DIO1

through

DIO8

instead of the

3.7 MULTILINE COMMANDS

Multiline

bus with listen, Untalk and Unlisten.

ATN

(bus) commands are sent by the

asserted. These commands include addressing commands for talk,

Active Controller

over the data

3.7.1 Go To Local (GTL)

This command allows the selected devices to be manually controlled. ($01)

3.7.2 Listen Address Group (LAG)

There are 31 (0 to 30) listen addresses associated with this group. The 3 most significant bits of the data bus are set to 001 while the 5 least significant bits are the address of the device being told to listen.

3.7.3 Unlisten (UNL)

This command tells all bus devices to Unlisten. The same as Unaddressed to Listen. ($3F)

3.7.4 Talk Address Group (TAG)

There are 31 (0 to 30) talk addresses associated with this group. The 3 most significant bits of the data bus are set to 010 while the 5 least significant bits are the address of the device being told to talk.

3.7.5 Untalk (UNT)

This command tells bus devices to Untalk. The same as Unaddressed to Talk. ($5F)

3.7

Section 3 IEEE 488 Primer

3.7.6 Local Lockout (LLO)

Issuing the functions. ($11)

LLO

command prevents manual control of the instrument's

3.7.7 Device Clear (DCL)

This command causes all bus devices to be initialized to a pre-defined or power up state. ($14)

3.7.8 Selected Device Clear (SDC)

This causes a single device to be initialized to a pre-defined or power up state. ($04)

3.7.9 Serial Poll Disable (SPD)

SPD

The status byte. ($19)

command disables all devices from sending their Serial Poll

3.7.10 Serial Poll Enable (SPE

A device which is Addressed to Talk will output its Serial Poll status byte after

SPE

is sent and

ATN

)

is unasserted. ($18)

3.7.11 Group Execute Trigger (GET)

This command usually signals a group of devices to begin executing a triggered action. This allows actions of different devices to begin simultaneously. ($08)

3.7.12 Take Control (TCT)

This command passes bus control responsibilities from the current

Controller

to another device which has the ability to control. ($09)

3.8

Section 3 IEEE 488 Primer

3.7.13 Secondary Command Group (SCG)

These are any one of the 32 possible commands (0 to 31) in this group. They must immediately follow a talk or listen address. ($60 to $7F)

3.7.14 Parallel Poll Configure (PPC)

This configures devices capable of performing a which data bit they are to assert in response to a

Parallel Poll

as to

. ($05)

3.7.15 Parallel Poll Unconfigure (PPU)

This disables all devices from responding to a

Parallel Poll

. ($15)

3.8 MORE ON SERVICE REQUESTS

Most of the commands covered, both uniline and multiline, are the responsibility of the Most of these happen routinely by the interface and are totally transparent to the system programmer. Other commands are used directly by the user to provide optimum system control. Of the uniline commands, test system and the software designer has easy access to this line by most devices. Service Request is the method by which a bus device can signal to the that an event has occurred. It is similar to an interrupt in a microprocesso r based system.

Most intelligent bus peripherals have the ability to assert might assert it when its measurement is comp lete, if its input is overloaded or for any of an assortment of reasons. A power supply might limited. This is a powerful bus feature that removes the burden from the

Controller

says, "Do what I told you to do and let me know when you're done" or "Tell me when something is wrong."

to periodically inquire, "Are you done yet?". Instead, the

Active Controller

to send and the bus devices to recognize.

SRQ

is very important to the

Controller

SRQ

. A DMM

SRQ

if its output has current

System

Controller

SRQ

Since determine which device requested the service without additional information. This information is provided by the multiline commands for

is a single line command, there is no way for the

Serial Poll

3.9

Controller

Parallel Poll

and

Section 3 IEEE 488 Primer

3.8.1 Serial Poll

Suppose the

let's assume there are several devices which could assert

Controller

sequentially. If any device responds with DIO7 asserted it indicates to the

Controller

bits will indicate why the device wanted service. This

sequence, and any resulting action, is under control of the software designer.

issues an

that it was the device that asserted

Controller

SPE

receives a service request. For this example,

(Serial Poll enable) command to each device

SRQ

. Often times the other

Serial Polling

3.8.2 Parallel Poll

Parallel Poll

The device requested service. It provides the who but not necessarily the why. When bus devices are configured for Parallel Poll, they are assigned one bit on the data bus for their response. By using the Status bit, the logic level of the response can be programmed to allow logical OR/AND conditions on one data line by more than one device. When

Controller

must then analyze the eight bits of data received to determine the source of the request. Once the source is determined, a determine the why.

Of the two polling types, the

to determine the who and why. In addition, most devices support

(under user's software) conducts a

is another way the

Serial Poll

Controller

SRQ

Parallel Poll

Serial Poll

is the most popular due to its ability

can determine which

is asserted, the

SRQ

. The

Controller

. The

might be used to

Serial Poll

only.

3.10

Section 4 Service Information

Service Information

4.1 Factory Service

IOtech maintains a factory service center in Cleveland, Ohio. If problems are encountered in using the Extender488/HS Bus Extender, you should first telephone the factory. Many problems can be resolved by discussing the problem with our applications department. If the problem cannot be solved by this method, you will be instructed as to the proper return procedure.

4.2 Theory of Operation

The Extender488/HS Bus Extender is controlled by two programmable array logic integrated circuits. Each Extender488/HS monitors the control and handshake lines on each bus and the internal logic determines the correct direction for all data transceivers.

Communication between each Extender488/HS is accomplished using RS-422 transceivers. These transceivers as well as the IEEE 488 transceivers are controlled by the internal logic.

4.3 Extender488/HS Cable Construction

The following information is provided for users that want to make their own interconnecting cable for Extender488/HS. Shielded twisted pair cable must be used and the pairs must be connected as shown in the cable wiring diagram.

Shielded Male Connector: AMP 554953-2 (or equivalent) Cover: AMP 554946-2 (or equivalent) Cable: 24 AWG., 50 conductor

shielded cable (25 twisted pairs). Nominal capacitance between conductors for each pair must be less than 13 pF per foot.

4.1

Section 4 Service Information

4.3.1 Extender488/HS Cable Wiring Diagram

Pair Shielded Shielded

Male Connector Male Connector

1 11

26 26

2 22

27 27

3 33

28 28

4 44

29 29

5 55

30 30

6 66

31 31

7 77

32 32

8 88

33 33

9 99

34 34

10 10 10

35 35

11 11 11

36 36

12 12 12

37 37

13 13 13

38 38

14 14 14

39 39

15 15 15

40 40

4.2

Section 4 Service Information

Extender488/HS Wiring Diagram - Continued

Pair

16 16 16

17 17 17

18 18 18

19 19 19

20 20 20

21 21 21

22 22 22

23 23 23

24 24 24

25 25 25

Shielded Shielded Male Connector Male Connector

41 41

42 42

43 43

44 44

45 45

46 46

47 47

48 48

49 49

50 50

4.3

Appendix A Character Codes And IEEE Multiline Messages

$00 $10 $20 $30 $40 $50 $60 $70

NUL

$01 $11 $21 $31 $41 $51 $61 $71

SOH

GTL LLO $02 $12 $22 $32 $42 $52 $62 $72

STX

$03 $13 $23 $33 $43 $53 $63 $73

ETX

$04 $14 $24 $34 $44 $54 $64 $74

EOT

SDC DCL $05 $15 $25 $35 $45 $55 $65 $75

ENQ

PPC PPU $06 $16 $26 $36 $46 $56 $66 $76

ACK

$07 $17 $27 $37 $47 $57 $67 $77

BEL

$08 $18 $28 $38 $48 $58 $68 $78

GET SPE $09 $19 $29 $39 $49 $59 $69 $79

TCT SPD $0A $1A $2A $3A $4A $5A $6A $7A

$0B $1B $2B $3B $4B $5B $6B $7B

$0C $1C $2C $3C $4C $5C $6C $7C

$0D $1D $2D $3D $4D $5D $6D $7D

$0E $1E $2E $3E $4E $5E $6E $7E

$0F $1F $2F $3F $4F $5F $6F $7F

ACG UCG

ACG = Addressed Command Group UCG = Universal Command Group LAG = Listen Address Group

DC1

DC2

DC3

DC4

NAK

SYN

ETB

CAN

SUB

ESC

UNL

;

(

)

LAG TAG SCG

48 64 80 96 112

DLE

UNT

SCG

[

SCG

]

SCG

TAG = Talk Address Group SCG = Secondary Command Group

SCG

113

SCG

114

SCG

115

SCG

100

116

SCG

101

117

SCG

102

118

SCG

103

119

SCG

104

120

SCG

105

121

SCG

106

122

SCG

107

123

{

SCG

108

124

SCG

109

125

}

SCG

110

126

SCG

111

127

DEL

SCG

A.1

Measurement Extender 488HS User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Warranty Information

Warnings, Cautions, Notes, and Tips

Table of Contents

1.1 Description

1.3 Specifications

1.4 Abbreviations

2.1 Inspection

2.2 Extender488/HS Configuration

2.3 Front Panel Indicators

2.4 Line Voltage Selection

2.5 Hardware Installation

2.6 Operation

2.7 Speed Considerations

3.1 HISTORY

3.2 GENERAL STRUCTURE

3.3 SEND IT TO MY ADDRESS

3.4 BUS MANAGEMENT LINES

Remote Enable

3.5 HANDSHAKE LINES

3.6 DATA LINES

3.7 MULTILINE COMMANDS

3.8 MORE ON SERVICE REQUESTS

3.8.1 Serial Poll

3.8.2 Parallel Poll

4.1 Factory Service

4.2 Theory of Operation

4.3 Extender488/HS Cable Construction

4.3.1 Extender488/HS Cable Wiring Diagram