• • scr I 'by Winston Gayler w. oward S ms 0, 4300 WEST 62ND ST. INDIANAPOLIS, INDIANA48268 USA Copyright © 1983 by Howard W. Sams & Co., Inc. Indianapolis, IN 46268 FIRST EDITION FIRST PRINTING-1983 All rights reserved. No part ofthis book shall be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission from the publisher. No patent liability is assumed with respect to the use of the information contained herein. While every precaution has been taken in the preparation of this book, the publisher assumes no responsibility for errors or omissions. Neitherisanyliabilityassumedfordamagesresulting from the use of the information contained herein. International Standard Book Number: 0-672-21959~X Library of Congress Catalog Card Number: 82-61966 Edited by: Welborn Associates Illustrated by: D. B. Clemons Printed in the United States ofAmerica. Preface This book is a detailed circuit description of the Apple II® computer. Specifically, it covers the main logic board including all revision's from the earliest through the latest (Rev. 0 through RFI Rev. D). Also covered are the current two-piece keyboard and the older single-piece keyboard. The intended audience includes engineers, technicians, students, and hobbyists. An attempt has been made to appeal to most skill levels and backgrounds. Thisis done by dividing each chapter into two sections: Overview and Detailed'Circuit Analysis. You may choose to read one, the other, or both. The book consists ofeight chapters. Chapter 1 discusses rremenclature and sym bols used throughout the text and figures. This chapter alsocontains a glossary of terms. Chapter 2 presents a description of the Apple II computer at the block dia gram level. The detailed descriptions start in Chapter 3. Chapters 3 and 4 cover the system clocks and part of the video circuitry. Chapter 5 explains the memory system and Chapter 6 examines the 6502 microprocessor and the system bus. Chapters 5 and 6 contain overview sections dedicated to the 4116 ~AM and the 6502 microprocessor. Asa result, the reader need not have prior knowledge of these devices. The keyboard and other on-board I/O are discussed in Chapter 7. The video display (graphics and text) is the subject ofChapter 8. Much ofthe Apple's circuitry serves to generate a video signal. Due to the importance ofthis topic, Appendix A is included to provide an introduction to video techniques. Appendix.B is a gathering ofall known circuit revisions ofthe Apple II mother board and keyboard. While the body of the book describes the latest Apple II revi sion, Appendix B describes differences between this latest Apple and all earlier re visions. Appendix C contains a set ofmother board and keyboard schematics. These schematics cover all revisions.'The book concludes with a list of references. WINSTON D. GAYLER EDITOR'S NOTE: In order to present the itlustrations as large as 'possible many have been placed on the foldout pages at the back ofthe book. These illustrations are indicated with an asterisk(*) immediately following the figure number in the text, e.g., Fig. 3-4* indicates that Fig. 3-4 is located at the back of the book. I wish to thank fellow Apple enthusiast Dr.James Alinsky for his many suggestions and general inspiration during the research and writing of this book. I am very appreciative for his review, from the reader's viewpoint, ofthe complete manuscript. Thanks also go to the numerous employees of Apple Computer, Inc., who as sisted by providing documentation and answering questions.T appreciate the assis tance of Apple's engineering department in coordinating much.ofthis activity. Finally, I wish to acknowledge Stephen Wozniak who designed the Apple II, making it all possible. onten CHAPTE,R 1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9 The Audience-Chapter Organization-Trademarks, Patents, and Copyrights-What You Should K.now-Revisions-IC and Signal Nomenclature-Waveforms-Research-Glossary of Terms C AP E 2 THE ApPLE II BLOCK DIAGRAM 17 Basic Architecture and Buses-Memory-Input/Output-Video-Power Supply-Summary CH 3 CLOCK GENERATOR AND HORIZONTAL TIMING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24 Overview- Detailed Circuit Analysis- Summary C AP ER 4 VIDEO TIMING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 34 Overview-Detailed Circuit Analysis-Summary CHAP ER 5 MEMORY SYSTEM 41 The 4116-0verview-Detaiied Circuit Analysis-Summary CHAPTER 6502 AND SYSTEM Bus 58 ()verview-Detailed Circuit Analysis-c-Burnmary 8 Contents ON-BoARD 110 ··.................... 86 Overview-Detailed Circuit Analysis-Summary THE VIDEO DISPLAY , '..104 Overview- Detailed Circuit Analysis- Summary APPENDIX VIDEO TECHNIQUES 139 The Basic Video Display-Broadcast Standards-Color-Overscan Summary APPEN IX ApPLE'S REVISIONS ',. _ 149 Overview of Revisions-Detailed Circuit Analysis AP EN IX ApPLE II SCHEMATICS ' 162 Revisions- Symbols- Acknowledgments APPEN IX REFERENCES· 165 l""'t INDEX ~ 168 '0•••••••••••••••••••••••••••••••••••••••••••••