ther is done to transmit. A full-duplex system does have the ideal case in which data is transferred simultaneously in both directions but the disadvantage of this is that an extra data line must be run between the devices which may prove more costly than the electronic switching hardware that would be necessary to use half-duplex.4.RS-232 was introduced in 1960, and is currently the most widely used communication standard. It is simple, inexpensive to implement, and though relatively slow, it is more than adequate for most simple serial communication devices such as keyboards and mice. RS-232 is a serial data transmission system, which means that it uses a single wire for data transmission. Signals are processed by determining whether they are positive or negative when compared with a ground. RS-232 systems are recommended for communication over short distances (up to 50 feet) and at relatively slow data rates, (up to 20 kbps). Sometimes these limits can be exceeded for certain applications but these are the basic standards. RS-232 also defines the meaning of the different serial signals and their respective pin assignments on a standard 25-pin (DB-25) serial connector. These assignments are shown in the attached table.5.UART is an acronym that stands for Universal Asynchronous Receiver/Transmitter. The UART chip is a computer component that handles asynchronous serial communications and manages all serial ports. All internal modems also contain a UART. Because the receiver and transmitter are independent in the chip, the UART can implement a full-duplex system. Although the UART is an asynchronous device, it still requires a clock signal to determine the transmission rate.6.When an asynchronous system is idle, the output is a high or a “1”. The start bit is the first bit that is sent and it is a low or “0”. This indicates that the next several bits (whatever the system is designed for) are going to be ...
