G. Jack Lipovski 
Introduction to Microcontrollers [PDF ebook] 
Architecture, Programming, and Interfacing for the Freescale 68HC12

Introduction to Microcontrollers is a comprehensive, introductory text/reference for electrical and computer engineers and students with little experience with a high-level programming language. It systematically teaches the programming of a microcontroller in assembly language, as well as C and C++. This books also covers the principles of good programming practice through top-down design and the use of data structures. It is suitable as an introductory text for a first course on microcomputers that demonstrates what a small computer can do. – Shows how a computer executes instructions;- Shows how a high-level programming language converts to assembler language;- Shows how a microcontroller is interfaced to the outside world;- Hundreds of examples, experiments, "brain-teasers" and motivators;- More than 20 exercises at the end of each chapter