The UART is used in personalcomputers( PC) to convert parallel data into serial data streams, which are then available at the serial interfaces( COM, LPT, IDE, etc.) for the connected peripheral devices and for data transmission via modems. The UART data set consists of 11 bits, a start bit, eight data bits, a parity bit and a stop bit. The UART itself consists of two FIFO buffers, which buffer the incoming and outgoing data signals on the transmitting and receiving sides. Depending on the width of the data bus, there are converters for 8-bit and 16-bit with transmission rates of 19.2 kbit/s, 56 kbit/s (UART16450) and 128 kbit/s (UART16650D).
One of the better known UARTs is the UART 16550A for secure data transmission at data rates of 256 kbit/s. Another well-known UART is the 16850, which contains a 128- byte FIFO that provides much higher data transfer rates without loading the central processing unit compared to the 16550. The corresponding synchronous operating circuit is the Universal Synchronous Receiver/Transmitter( USRT).