ABSTRACT
As shown in Fig. 23.1, the term embedded microcomputer system refers to a device that contains one or more microcomputers inside. To better understand the expression “embedded microcomputer system,” consider each word separately. In this context, the word embedded means “hidden inside so one cannot see it.” A computer is an electronic device with a processor, memory, and I/O ports. The processor executes software, which performs specific predefined operations. The processor includes registers (which are highspeed memory), an arithmetic logic unit or ALU (to execute math functions), a bus interface unit or BIU (which communicates with memory and I/O), and a control unit or CU (for making decisions.) Memory is a high-speed storage medium for software and data. Software consists of a sequence of commands that are usually executed in order. In an embedded system, we use read only memory (ROM) for storing the software and fixed constant data, and random access memory (RAM) for storing temporary information. The information in the ROM is nonvolatile, meaning the contents are not lost when power is removed. I/O ports allow information to enter via the input ports and exit via the output ports. The I/O devices (e.g., parallel ports, serial ports, timer, and ADC) are a crucial part of an embedded system because they
provide necessary functionality. The software together with the I/O ports and associated interface circuits give an embedded computer system its distinctive characteristics.
