ganssle, j. g. (1999). the art of designing embedded systems

THE The Art of Designing Embedded Systems The Art of Designing Embedded Systems Jack G. Ganssle Newnes BOSTON OXFORD AUCKLAND JOHANNESBURG MELBOURNE NEW DELHI Newnes is an imprint of Butterworth-Heinemann. Copyright 0 2000 by Butterworth-Heinemann A member of the Reed Elsevier group All rights reserved. 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 other- wise, without the prior written permission of the publisher. 130' Recognizing the importance of preserving what has been written, Butterworth-Heinemann prints its books on acid-free paper whenever possible. Butterworth-Heinemann supports the efforts of American Forests and the Global ReLeaf program in its campaign for the betterment of trees, forests. and our environment. Library of Congress Cataloging-in-Publication Data Ganssle, Jack G. The art of designing embedded systems I Jack G. Ganssle. ISBN 0-7506-9869-1 (hc. : alk. paper) 1. Embedded computer systems-Design. p. cm. I. Title. Tk7895.E42G36 1999 99-36724 004.16- dc2 1 CIP British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. The publisher offers special discounts on bulk orders of this book. For information, please contact: Manager of Special Sales Butterworth-Heinemann 225 Wildwood Avenue Woburn, MA 0 180 1-204 1 Tel: 781-904-2500 Fax: 78 1-904-2620 For information on all Butterworth-Heinemann publications available, contact our World Wide Web home page at: http://www.newnespress.com 109 8 7 65 4 3 Printed in the United States of America Dedicated to Graham and Kristy Acknowledgments Chapter 1 Introduction Chapter 2 Disciplined Development Chapter 3 Chapter 4 Chapter 5 Firmware Musings Chapter 6 Hardware Musings Chapter 7 Troubleshooting Tools Chapter 8 Troubleshooting Chapter 9 People Musings Appendix A A Firmware Standards Manual Appendix B A Drawing System Stop Writing Big Programs! Real Time Means Right Now i 5 35 53 87 109 133 165 187 203 223 Index 23 7 . THE The Art of Designing Embedded Systems The Art of Designing Embedded Systems Jack G. Ganssle Newnes BOSTON OXFORD AUCKLAND JOHANNESBURG MELBOURNE NEW DELHI. Ganssle, Jack G. The art of designing embedded systems I Jack G. Ganssle. ISBN 0-7506-9869-1 (hc. : alk. paper) 1. Embedded computer systems- Design. p. cm. I. Title. Tk7895.E4 2G3 6. create software. Under close questioning, though, the majority of these admit to applying their rules in a haphazard manner. 5 6 THE ART OF DESIGNING EMBEDDED SYSTEMS When the pressure