Introduction

Abstract

Embedded systems are characterized by the presence of processors running application specific programs. They differ from traditional digital systems, in which most of the system functionality is implemented in hardware, such as in full custom logic, application specific integrated circuits (ASICs), or field programming gate arrays (FPGAs). In an embedded system, many of these functionalities (or tasks) are implemented in software running on one or more processors, leaving only the high performance functions implemented in hardware. Typical examples of embedded systems include printers, cellular phones and automotive engine controller units. Thus, an embedded system contains one or more processors, memories, and additional logic. This is similar in composition to a general-purpose computer. However, there is a key difference between an embedded system and a general-purpose computer. The software in the embedded system is part of the system specification. Embedded software is a key part of system design and is, in general, unchanged after the system is shipped to the end user. For this reason, embedded software is also referred to as firmware.