IOtech Isolator488 User Manual
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IOtech Isolator488 User Manual

Ieee 488 bus isolator
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  • Page 1 sales@artisantg.com artisantg.com (217) 352-9330 | Visit our website - Click HERE...
  • Page 2 Isolator488 IEEE 488 Bus Isolator USER’S MANUAL IOtech, Inc. • 25971 Cannon Road • Cleveland, Ohio 44146 • (440) 439-4091...
  • Page 3 Copyright, Trademark, and Licensing Notice 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.
  • Page 4 Isolator488 Instruction Manual Part No. Isolator488-901 Revision 1.2 December 1991 IOtech, Inc. 25971 Cannon Road Cleveland, Ohio 44146 (440) 439-4091...
  • Page 5 Be sure to remove power from all devices in your system before handling IEEE 488 cables connected to the Isolator488. Failure to follow this warning may result in personal injury or death. IOtech, Inc. • 25971 Cannon Road • Cleveland, Ohio 44146 • (440) 439-4091...

  • Page 6: Table Of Contents

    Table of Contents Section 1 INTRODUCTION Page General Description Available Accessories Specifications Abbreviations Section 2 GETTING STARTED Page Inspection Configuration Modifications Line Voltage Selection Hardware Installations Operation 2.10 2.6.1 BusLoading 2.11 2.6.2 Cabling Length 2.11 2.6.3 Signal Line Direction 2.12 2.6.4 Parallel Polling 2.13...
  • Page 7 Section 3 (cont.) Page 3.7.1 Go To Local (GTL) 3.7.2 Listen Address Group (LAG) 3.7.3 Unlisten (UNL) 3.7.4 Talk Address Group (TAG) 3.7.5 Untalk (UNT) 3.7.6 Local Lockout (LLO) 3.7.7 Device Clear (DCL) 3.7.8 Selected Device Clear (SDC) 3.10 3.7.9 Serial Poll Disable (SPD) 3.10 3.7.10...

  • Page 8: Introduction

    15, including the controller, to 28 while also providing optical isolation between the system controller and devices on the isolated bus. Since the Isolator488 does not occupy a bus address, its operation is entirely transparent to the IEEE controller.

  • Page 9: Specifications

    Section 1 Introduction 1.3 SPECIFICATIONS PROPAGATION DELAYS: Local to Remote Talker Data Lines 85 nS typ., nS Max. Command Lines 90 nS typ., nS Max. Remote to Local Talker /ATN to Local Data 355 nS typ., nS Max. /ATN to Local DAV 155 nS typ., 2075 nS Max.

  • Page 10: Abbreviations

    Section 1 Introduction 1.4 Abbreviations The following IEEE 488 abbreviations are used throughout this manual. addr n IEEE bus address "n" Attention line Controller Active Carriage Return data Data String Device Clear Group Execute Trigger Go To Local Listener Active Listen Address Group Line Feed Local Lock Out...

  • Page 11: Getting Started

    2.2 Configuration Before using the Isolator488, you should be aware of the connections between the IEEE digital commons, the shield lines on each bus, and earth ground. The following information is provided so that you can determine if the factory configuration is appropriate for your application or if some changes need to be made prior to use.
  • Page 12 Pins 18, 19, 20, 21, 22, 23, and 24 of the Controller Port are all connected to Instrument Common. Controller Shield The Shield connection (Pin 12) on the Controller Port. Instrument Shield The Shield connection (Pin 12) on the Instrument Port The factory configuration of the Isolator488 is as follows:...
  • Page 13 Section 2 Getting Started...

  • Page 14: Modifications

    Place the Isolator488 on a flat surface. Remove the six screws on top of the case and remove the top cover. Located to the right of the Controller Port IEEE 488 connector are locations for C16, R4, and F2.
  • Page 15 Section 2 Getting Started...
  • Page 16 C59. Solder these components in place from the solder side of the circuit board using rosin core solder. The bottom panel or the Isolator488 will need to be removed in order to do this. Make note of these changes for later reference.

  • Page 17: Line Voltage Selection

    JPR2. Make note of this change for later reference. After making any changes to the Isolator488 internal circuitry, be sure to document your changes then carefully reassemble the unit. 2.4 Line Voltage Selection The Isolator 488 is designed to accept either 105 to 125 volt or 210 to 250 volt, 50 or 60 Hz, AC power.
  • Page 18 Place the Isolator488 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 S2 and fuse F1.

  • Page 19: Hardware Installations

    Getting Started 2.5 Hardware Installation Included with the Isolator488 Bus Isolator 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.

  • Page 20: Operation

    Service Information section (Section 4) of this manual. If proper operation is obtained, turn off the Isolator488 and connect the other IEEE 488 devices to each of the Isolator488 ports. Apply power to all devices in the system.

  • Page 21: Cabling Length

    2 meters (approx. 7 feet). The total worst case distance from the two furthest devices is not allowed to exceed 20 meters (approx. 70 feet). The addition of the Isolator488 does not increase this distance. 2.6.3 Signal Line Direction The signal lines and their direction include..

  • Page 22: Parallel Polling

    Section 2 Getting Started When ATN is unasserted, the Isolator488 asserts NDAC on both ports, for a minimum of 200 nanoseconds, while looking for an active talker. If the talker is detected on the CONTROLLER port, the NDAC lines are released and the data and handshake line directions remain unchanged.

  • Page 23: Ieee 488 Primer

    The IEEE 488 bus is an instrumentation communication bus adopted by the Institute of Electrical and Electronic Engineers in 1975 and revised in 1978. The Isolator488 conforms to this most recent revision designated IEEE 488-1978. Prior to the adoption of this standard, most instrumentation manufacturers offered their own versions of computer interfaces.
  • Page 24 Section 3 IEEE 488 Primer At a committee meeting, everyone present usually listens. This is not the case with the GPIB. The Active Controller selects which devices will listen and commands all other devices to ignore what is being transmitted. A device is instructed to listen by being Addressed to Listen.
  • Page 25 Section 3 IEEE 488 Primer To Other Devices Device 1 System Controller Able to Talk, Listen, and Control Data Bus Device 2 Able to Talk Data Byte and Listen Transfer Control Device 3 Printer Only Able to Listen General Interface Management Device 4 Frequency Counter...

  • Page 26: Send It To My Address

    Section 3 IEEE 488 Primer 3.3 SEND IT TO MY ADDRESS In the previous discussion, the terms Addressed to Talk and Addressed to Listen were used. These terms require some clarification. The IEEE 488 standard permits up to 15 devices to be configured within one system.

  • Page 27: Interface Clear (Ifc)

    Section 3 IEEE 488 Primer 3.4.2 Interface Clear (IFC) The IFC line is used only by the System Controller. It is used to place all bus devices in a known state. Although device configurations vary, the IFC command usually places the devices in the Talk and Listen Idle states (neither Active Talker nor Active Listener).

  • Page 28: Handshake Lines

    Section 3 IEEE 488 Primer 3.5 HANDSHAKE LINES The GPIB uses three handshake lines in an "I'm ready - Here's the data - I've got it" sequence. This handshake protocol assures reliable data transfer, at the rate determined by the slowest Listener. One line is controlled by the Talker, while the other two are shared by all Active Listeners.

  • Page 29: Data Lines

    Section 3 IEEE 488 Primer 1st Data Byte 2nd Data Byte DIO1-8 (composite) Valid Valid Source Valid Valid NRFD None None Ready Ready Ready Ready Acceptor None None NDAC Acceptor Accept Accept Accept Accept IEEE Bus Handshaking 3.6 DATA LINES The GPIB provides eight data lines for a bit parallel/byte serial data transfer.
  • Page 30 Section 3 IEEE 488 Primer 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.
  • Page 31 Section 3 IEEE 488 Primer 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) The SPD command disables all devices from sending their Serial Poll status byte.
  • Page 32 Section 3 IEEE 488 Primer 3.7.14 Parallel Poll Configure (PPC) This configures devices capable of performing a Parallel Poll as to which data bit they are to assert in response to a Parallel Poll. ($05) 3.7.15 Parallel Poll Unconfigure (PPU) This disables all devices from responding to a Parallel Poll.
  • Page 33 Section 3 IEEE 488 Primer 3.8.1 Serial Poll Suppose the Controller receives a service request. For this example, let's assume there are several devices which could assert SRQ. The Controller issues an SPE (Serial Poll enable) command to each device sequentially. If any device responds with DIO7 asserted it indicates to the Controller that it was the device that asserted SRQ.
  • Page 34 Service Information 4.1 FACTORY SERVICE IOtech maintains a factory service center in Cleveland, Ohio. If problems are encountered in using the Expander488 you should first telephone the factory. Many problems can be resolved by discussing the problems with our applications department.
  • Page 35 Appendix A Character Codes And IEEE Multiline Messages " & < > ACG = Addressed Command Group TAG = Talk Address Group UCG = Universal Command Group SCG = Secondary Command Group LAG = Listen Address Group...

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