INTRODUCTION 1 HARDWARE WATCHDOG TIMER 1 ANALOG TO DIGITAL CONVERTER 3 A/D Comparison Feature 4 A/D Modes of Operation 5 A/D Interrupt 5 A/D Converter Examples 5 Closed Loop Control with the A/D and PCA 7 CONTENTS PAGE SERIAL EXPANSION PORT 10 SEP Transmission or Reception ÀÀ 12 SEP Example 12 APPENDIX A COMPLETE CODE FOR 87C51GB TO XICOR 244 INTERFACE PROGRAM A-1 APPENDIX B HARDWARE SET UP FOR THE CODE FOR APPENDIX A B-1