The purpose in writing this book is to introduce you to the signals within the Apple II computer and to show you how these signals can be used to control external devices under the control of BASIC language programs. A general-purpose computer interface breadboard has been developed to speed your circuit design and testing so that you can easily perform the many interesting experiments that are included in the book. By using a design system such as the one described in this book, you will spend your time concentrating on the ·principles involved, rather than troubleshooting your circuits. However, you will have the opportunity to build and test many digital circuits, as well as circuits that use digital-to-analog and analogto-digital converters. We have chosen to use the Apple II computer with 16K of read/write memory, and the Applesoft BASIC interpreter program. This software provides a great deal of flexibility and it is worth having it available when you are using external interface circuits. The Applesoft BASIC interpreter has two general-purpose commands that can be used to transfer information to and from the computer. These instructions are easily mastered, without requiring a detailed understanding of the 6502 microprocessor integrated circuit (IC) that is used as the "heart" of the Apple II.
CHAPTER 1 6502 PROCESSOR Memory-Input/Output ( I/O) Devices-Software I/O Control Instructions CHAPTER 2 APPLE INTERFACING . I/O Device Address Decoding-Device Addressing CHAPTER 3 I/O DEVICE INTERFACING . Output Ports-Input Ports CHAPTER 4 FLAGS AND DECISIONS . I/O Device Synchronization-Logical Operations and Flags-FlagDetecting Software-Assembly-Language Logical Operations-Complex Flags-Flag Circuits-Multiple Flags-Interrupts-Final Words CHAPTER 5 BREADBOARDING WITH THE APPLE Basic Breadboard-Connections to the Apple-Other Considerations CHAPTER 6 APPLE INTERFACE EXPERIMENTS . Introduction to the Experiments-Use of the Logic Probe-Use of the Device Address Decoder-Using Device Select Pulses-Constructing an Input Port-Multibyte Input Ports-Input Port Applications-Input Port Applications (11)-Constructing an Output Port-Output Port and Input Port Interactions-Data Logging and Display-Simple Digital-to-Analog Converter-Output Ports, BCD and Binary Codes -Output Ports Traffic Light Controller-Logic-Device Tester-Simple Flag Circuits-A Simple Analog-to-Digital Converter CHAPTER 7 ON THE BUS Interface Control Signals-An Interfacing Example APPENDIX A LOGIC FUNCTIONS APPENDIX B PARTS REQUIRED FOR THE EXPERIMENTS APPENDIX C 6502 MICROPROCESSOR TECHNICAL DATA APPENDIX D APPLE INTERFACE BREADBOARD PARTS APPENDIX E PRINTED-CIRCUIT BOARD ARTWORK
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