E M : C,r * « M II p^PET and the IEEE 488 Bus (GPIB) Eugene Fisher -C.W.Jensen PET and the IEEE 488 Bus (GPIB) Eugene Fisher - C.W. Jensen OSBORNE/McGraw-Hill Berkeley, California Published by OSBORNE/McGraw-Hill 630 Bancroft Way Berkeley, California 94710 U.S.A For information on translations and book distributors outside of the U.S.A., please write OSBORNE/McGraw-Hill. PET AND THE IEEE 488 BUS (GPIB) Copyright ® 1 980 McGraw-Hill, Inc. All rights reserved. Printed in the United States of America. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publishers, with the exception that the program listings may be entered, stored, and executed in a computer system, but they may not be reproduced for publication. 1234567890 DODO 89876543210 ISBN 0-931988-31-4 Cartoons by Bruce Mishkin. In recognition of their understanding and support in this project, we dedicate this work to our families — the Fishers and the Jensens — for in a large sense, it's a family affair. Melissa, Christine and Randy Fisher Mary Belle, Tom, Carl, Reg, and Edna Jensen Thank you all Gene Bill Contents Preface 1. Layman's Introduction to the GPIB 1 Development of the IEEE Std 488 Bus 5 Evolution of Digital Interface Systems 5 Perspectives for Interface Design 6 2. GPIB Lines and Signals 9 The Bus Structure 10 Control Lines 12 Data Bus Lines 16 Data Transfer 16 The Handshake Procedure 20 How the Handshake Procedure Works — A Simplified Version 20 Handshake Sequence for the PET as a Controller/Talker 22 Handshake Sequence for the PET as a Controller/Listener 25 Accessing the GPIB from PET I/O Memory 28 Data Lines 28 Control Lines 30 viii Contents 3. Hardware 37 The PET-GPIB Interface 37 Data Bus Interface Circuits 37 Control Line Interface Circuits 40 Electrical Features 42 Data Rate 42 Number of Devices and Cable Length 42 Bus Receivers and Drivers 42 Typical Bus-Device Interface 43 Mechanical Features 44 Complete Cable Assemblies 44 Custom Cable Assemblies 44 Methods of Interfacing — Daisy Chain and Star 49 Interconnecting the PET with IEC Standard Instruments 52 Setting Up and Testing Bus Connections 55 4. Sample Bus Transactions 57 Programming the PET for the IEEE 488 Bus 57 Parameters 58 Transaction Codes (ASCII) 63 Address and Command Codes 65 Example Programs 68 GPIB PRINT Transactions — Immediate Mode 68 GPIB PRINT Transactions — Run Mode 69 GPIB OPEN/CLOSE Transactions — Immediate Mode 70 GPIB "Combination" Transactions 71 GPIB Multiple OPEN/PRINT Transactions 75 5. Execution and Timing Sequences 77 Timing Signals for the OPEN Statement 78 Timing Signals for the PRINT Statement 84 Timing Signals for the CMD (Command) Statement 92 Timing Signals for the SAVE Command 99 Timing Signals for the INPUT Statement 107 The LOAD Command 115 Timing Signals for the GET Statement 119 Timing Signals for the CLOSE Statement 126 6. Interfacing the GPIB with a Non-Standard Bus Device 1 29 Non-Standard Device Interfacing 129 Fast Non-Standard Device 134 Slow Non-Standard Device 134 IEEE 488 Functions Not Implemented by the PET 135 Concerning Speed 136 IEEE Bus Handshake Routine in Machine Language 136 Contents ,x 7. Applications 139 Digital Voltmeter, Hewlett-Packard Model 3455A 139 Data Output 140 Addressing 141 Programming the HP Model 3455A 141 Open File 142 Command Structure 142 Read Data 144 Close File 145 Sample Program 146 Frequency Counter, Systron-Donner Model 6043A 149 Front Panel and Address Switches 149 Program Control 150 Programming the Counter 151 Counter Output Sequence 152 Implementation 153 Line Printer, Centronics Model P1 Microprinter 155 Features of the Model P1 155 Interfacing 156 Implementation 158 Interface Fabrication 159 Printer Modification 159 Logic Analyzer, Tektronix Model 7D01 and Display Formatter, Tektronix Model DF2 162 Connecting the Display Formatter to the GPIB 164 Installation of the GPIB Adapter 167 Set-up for Data Analysis Display 168 488 Bus Interface Coupler, ICS Model 4880 175 PET Service Request (SRQ) Program 177 Other Implementation Notes 179 8. A GPIB Diagnostic Test 181 The System Doesn't Work — Now What? 181 Diagnostic Program Description 182 Appendices A. Companies and their GPIB Products 185 B. Bibliography 195 C. IEEE Std Definitions 203 D. ASCII Definitions 209 E. IEEE Bus Handshake Routine 211 F. Conversion Tables 217 G. ASCII-IEEE 488 Hex Codes 227 1 1 X Contents FIGURES 2-1 Block diagram of the PET and the IEEE 488 Bus (GPIB) 1 2-2 GPIB data bus 19 2-3 Simplified GPIB handshake timing diagram 21 2-4 Flowchart and handshake timing diagram for the PET as a controller/talker 23 2-5 Flowchart and handshake timing diagram for the PET as a controller/listener 27 3- 1 GPIB component locations on the PET PC board 38 3-2 PET-GPIB interface diagram showing data lines 39 3-3 PET-GPIB interface diagram showing control lines 41 3-4 A typical GPIB-bus device interface 43 3-5 Belden IEEE GPIB cable 45 3-6 Rear view of 2001 Series computer 46 49 3-7 The PET J 1 edge connector 3-8 Two methods of interfacing devices on the GPIB 50 3-9 GPIB cable connectors showing the receptacle/plug combination 51 3-10 The GPIB connector showing pin designations 51 53 3-1 1 Cabling IEC Pub. 625-1 instruments to the PET via the GPIB 3-12 Connecting the PET in an lEC-compatible system 54 3-13 The PET 488 cable assembly manufactured by Pickles and Trout 55 5-1 Address timing for OPEN with primary and secondary address 80 5-2 Address timing for OPEN with primary address only 83 5-3 Address timing for PRINT with primary and secondary addresses 86 5-4 Address timing for PRINT with primary address only 87 5-5 Data burst timing for the PRINT statement 89 5-6 Untalk timing sequence for PRINT 90 5-7 Address timing for CMD with primary and secondary addresses 95 5-8 Address timing for CMD with primary address only 96 5-9 Data burst timing for the CMD statement 98 5-10 Address timing for SAVE with primary and secondary addresses 104 106 5-1 1 Data burst timing for the SAVE command 5-12 Address timing for INPUT with primary and secondary addresses 109 5-13 Address timing for INPUT with primary address only 1 1 5-14 Data burst timing for the INPUT statement 112 5-15 Unaddress timing sequence for the INPUT statement 114 5-16 Address timing for GET with primary and secondary addresses 122 5-17 Address timing for GET with primary address only 124 5-18 Unaddress timing sequence for GET 125 5- 19 Address timing for CLOSE with primary and secondary addresses 128 133 6- 1 Circuits for interfacing a non-standard device to the GPIB Figures xi FIGURES (Continued) 7-1 Hewlett-Packard Model 3455A Digital Voltmeter 140 7-2 The GPIB switches on the rear panel of the HP 3455A 141 7-3 Model 3455A operational verification flowchart 147 7-4 Model 3455A operational verification program 148 7-5 Systron-Donner Model 6043A Communication Systems Counter 149 7-6 Address switches on the Model 6043A counter 150 7-7 Equipment setup to measure frequencies under PET program control 153 7-8 Frequency Measurement Program 154 7-9 Display of frequency data when running Frequency Measurement Program 154 7-10 The Centronics Microprinter-P1 156 7-1 1 Interface necessary between the PET and a Centronics Microprinter-P1 157 7-12 Cable assembly to interface the PET and the Microprinter-P1 160 7-13 Interfacing method that will connect the Centronics printer with the PET and also allow standard IEEE 488 devices on the bus 160 7-14 Partial top inside view of the Microprinter-P1 161 7-15 Tektronix Model 7603 Oscilloscope with the 7D01 Logic Analyzer and DF2 Display Formatter 162 7-16 Model 7D01 Logic Analyzer display 163 7-17 Tektronix P.N. 103-029-00 Adapter 165 7-18 The GPIB connector and input combs 166 7-19 GPIB connector/Tektronix Logic Analyzer P6451 probe heads 167 7-20 The Tektronix 7D01 Logic Analyzer and DF2 Display Formatter connected to the PET 169 7-21 Triggering on any ATN message 170 7-22 Triggering on a message group 171 7-23 The image of the DF2 Display Formatter when the logic analyzer is triggered on the LAG 172 7-24 Typical DF2 tabular format of GPIB bus transactions 173 7-25 The Model 4880 Instrument Coupler 175 7-26 The PET and the 4880 Coupler in a typical application 176 7-27 Service Request (SRQ) program 178 7- 28 PET Group Execute Trigger program 179 8- 1 GPIB Diagnostic Test Program 184 Tables xii TABLES 2-1 Functions of the GPIB lines 15 2-2 Number conversions 17 2-3 PET hardware addresses for GPIB lines 28 42 3- 1 Specifications for GPIB line receivers and drivers 3-2 Cable assemblies 44 3-3 Manufacturer's receptacles for the PET J1 edge connector 45 3-4 Connections between the GPIB and PET connector J1 48 3-5 IEEE Std 488 (GPIB) standard bus connectors 48 3-6 IEEE Std 488-1 978/IEC Std 625-1 bus connector pin designations 52 4- 1 ASCII to hexadecimal and binary conversions 64 4-2 Address and command groups 66 4-3 PRINT transaction in immediate mode 68 4-4 PRINT transaction in run mode 69 4-5 OPEN/CLOSE transactions in immediate mode 70 4-6 Combination transactions 72 4-7 PET tokens for BASIC I/O statements 74 4-8 Multiple OPEN/PRINT transactions 75 78 5- 1 Sample bus transactions for the OPEN statement 5-2 The four types of GPIB device errors 81 5-3 Sample bus transactions for the PRINT statement with secondary address 84 5-4 Sample bus transactions for the PRINT statement without secondary address 84 5-5 Sample bus transactions for the CMD statement 93 5-6 Sample bus transactions for the SAVE