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into circuits. A converter can convert between USB and RS-232, RS-485, TTL serial, or even a parallel interface. вЂў Internal modems that interface to phone lines. вЂў Serial ports on network serial-server modules. For USB virtual COM-port devices, Windows includes a driver for USBвЂ™s communication devices class CDC . For improved performance, some converters use vendor-specific drivers in place of the provided Windows drivers. Computer Types Computers that communicate via serial ports donвЂ™t have to be all the same type. Tiny microcontrollers can talk to the latest PCs as long as both ends of the link use compatible interfaces and protocols. The PC examples in this book are for the family of computers that has evolved from the IBM PC, including desktop 5 Chapter 1 and notebook PCs. Other computer types also have serial ports that are built in or available via converters or expansion cards. An embedded system is a computer-controlled device dedicated to performing a single task or a set of related tasks. Embedded systems are typically built into, or embedded in, the devices they control. For example, a modem is an embedded system that handles tasks of data communications over the phone system. Some embedded systems are one-of-a-kind or small-quantity projects. Many involve monitoring or control tasks. Embedded systems often use microcontrollers, which contain a CPU and I/O hardware such as UARTs. Microcontroller chips can be classified by data-bus width: 8-bit chips have an 8-bit data path and are popular in monitoring and control applications. Chips with 4-, 16-, and 32-, and 64-bit data buses are also available. Different chips have different combinations of features and abilities, including asynchronous and synchronous serial ports, USB controllers, type and amount of memory for storing programs and data, and support for power-saving modes. The Physical Link The physical link between computers consists of the wires or other medium that carries information from one com prom-electric.ru