For undergraduate students taking a Microcontroller or Microprocessor course, frequently found in electrical engineering and computer engineering curricula. This text provides the reader with fundamental assembly language programming skills, an understanding of the functional hardware components of a microcontroller, and skills to interface a variety of external devices with microcontrollers.

During the summer of 1992, the first author (D.P.) was first introduced to the family of Motorola 68HC 11 Microcontrollers as he was constructing an interface module between a Puma robot arm robot controller and a force-torque sensor. Since then, he has become aware of thepowerof microcontrollers and their unlimited applications. Fortunately, as a professor of electrical engineering at the U.S. Air Force Academy, he has had ample opportunities to share his microcontroller experience with students. In the fall of 1995 at the Academy, he met the second author (S.B.), a friend, mentor, and, at that time, his immediate boss. Soon after the first author's arrival at the Academy, S.B. started to share his expert knowledge on digital systems with D.P., and D.P. has benefited tremendously to this point. Over time, we decided to share our work in a more concrete form. That is when we decided to write a book on the 68HC 12. MOTIVATION One of the most compelling reasons to write 68HC12 Book is that Motorola is slowly phasing out the popular 68HC 11 microcontroller-based evaluation boards and replacing them with the 68HC 12. The 68HC 11 family of microcontrollers have been the preferred choice of educators due to their built-in input and output (I/O) capabilities, a variety of timer functions, and platforms for easy programming and interfacing. The 68HC 12 retained all the favorable features of the 68HC 11 (in fact, one can run any 68HC 11 code on the 68HC 12 with minor modifications) and increased the computational power while enhancing hardware and software components. Compared to its predecessor, the 68HC12 has reduced the interrupt latency time, increased the I/O capacity, added complex math operations, incorporated fuzzy logic functions, and improved the overall system performance by adapting a mechanism calledinstruction queuing,which is similar to the pipelining s6heme found in more powerful microprocessors. This book is about the 68HC 12; we show how to program and uncover the possibilities of 68HC 12 applications. INTENDED READERS This book is written for undergraduate students taking a microcontroller or microprocessor course, frequently found in electrical engineering and computer engineering curricula. These courses aim to teach students the fundamental knowledge of microcontrollers/microprocessors and techniques to interface them with external devices, pointing out the important role of embedded microcontroller systems in our modern society. The book is designed to assist instructors to fulfill such course objectives by combining both the theory and applications of microcontrollers. In particular, we chose the 68HC12 microcontroller since it is becoming the industry standard. We expect students to have taken an introductory logic course and a freshmen programming language course. For a quick review of digital logic, we included Appendix D. Having taken a computer language course will help students understand how assembly language programs are related to high-level language programs, but we expect students with a minimal exposure to computer programming will follow the text subjects without too much trouble. We must also address one other category of readers. Although the book is mainly designed for students learning the subject in an academic setting, it can be easily adopted by engineers who want to learn the subject on their own. Since the underlying concepts and functional components of two different types of microcontrollers are very similar to each other, the acquired knowledge of the 68HC12 can naturally be applied to other microprocessors and microcontrollers. Such knowledge is essential for electrical and computer engineering students as we live in a society where more and more engineering problems are solved by embedded microcontrollers. In fact, we find the scope of actual applications of microcontrollers expanding as new problems are encountered and solved by