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Unformatted text preview: C H A P T E R 1 Embedded Electronic Systems and Microcontrollers This chapter provides a short introduction to embedded electronic systems, where they are used, and ways in which they can be implemented. Microcontrollers were originally developed from microprocessors for use in embedded electronic control systems, as their name implies. They include a processor and most or all of the memory, clock, and other systems needed to support it. Everything is inside a single package, which is why a microcontroller is often described as a computer on a chip. I review the main features of a typical small microcontroller before setting the scene for the rest of the book with the MSP430. 1.1 What (and Where) Are Embedded Systems? Suppose that you asked people in the developed world to show you the products in their house that contained computer chips. (Admittedly, this term is deliberately vague.) Probably they would point to a personal computer and stop there. If you tried harder, you might be offered a game console or personal digital assistant. It is unlikely that they would mention cellular phones, which contain a startling degree of processing power just for communication, to say nothing of taking photographs and playing games. There is hardly an electrical consumer product nowadays that does not rely on digital control. This seems reasonable for washing machines and video recorders, but one might wonder why a toaster or a kettle needs any digital electronics. These products contain embedded electronic systems: The processor supports the operation of the product but is not the main reason for purchasing it. There are said to be about 100 embedded processors for each computer, so high-profile, leading-edge microprocessors make up a small part of the market in terms of www.newnespress.com 2 Chapter 1 volume. Fancy modern cars have approaching 100 processors and even a personal computer has embedded processors in its keyboard, mouse, screen, disk drives, and so on. The snag for an engineer is that embedded seems synonymous with invisible and few people appreciate the extent to which they rely on electronics. Embedded systems encompass a broad range of computational power. A crude classification is given by the number of bits that can be manipulated at a time. Many processors perform very simple tasks, for which 8 or even 4 bits are sufficient. For example, I have an electric toothbrush that pauses briey every 30 s to remind me to move on to the next quarter of my mouth. The electronics in a remote control, kettle, or toaster need not be very sophisticated either. A bigger device that can handle 8 bits is needed for something like a washing machine. These may be comparable in power with the processors used in the first personal computers and, in fact, the descendents of the microprocessors of those days are still widely used. Digital control has been employed in car engines for many years, since the first legislation was introduced to reduce pollution...
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This document was uploaded on 02/06/2012.
- Winter '09