Microprocessors and their microcontroller derivatives are a ubiquitous, if rather invisible, part of the infrastructure of our 21st century electronic 1 and communications society. In 1998 it was reckoned that hidden in ev ery home were about 100 microcontrollers and microprocessors; in the sillging birthday card, washing machine, microwave oven, television con troller, telephone, personal computer and so on. About 20 more lurked in the average family car. For example monitoring in-tire radio pressure sensors and displaying critical data through the car area network (CAN). Around 4 billion such devices are sold each year to implement the intelligence of these smart electronic devices, ranging from smart egg timers through aircraft management systems. The evolution of the mi croprocessor from the firstIntel device introduced 30 years ago in 1971 has revolutionised the structure of society, effectively creating the sec ond smart industrial revolution coming to fruition at the beginning of the 21st century. Although the microprocessor is better known in its guise of powering the ubiquitous PC, in which raw computing power is the goal, sales of such microprocessors as the Intel Pentium, represent only around 2% of total volume. The vast majority of sales are of low-cost microcontrollers embedded into a dedicated-function digital electronic device, such as the smart card. Here the emphasis is the integration of the core processor with memory and input/output resources in the one chip. This integrated computing system is known as a microcontroller.
