The Asynchronous Communications Adapter is more commonly known as the Serial Port . Two additional serial ports are supported but by sharing interrupts. The main component of the Serial Port is the UART . The UART converts the parallel digital data from the computer bus into an Asynchronous data stream on the transmitting side and from an asynchronous data stream back into parallel digital data on the recieving end. In this conversion each data byte is framed ie.
Synchronization is achieved for each character only.
The UART in the original IBM PC was the 8250. To increase data rates to 9600 bps, the UART in the IBM AT was upgraded from the 8250 to the 16450. BITS - 1, 1.5, or 2 stop bits. This conversion amplifies and inverts the signals. The EIA RS-232 interface transfers data between the DTE and DCE devices via the TD and RD lines.