Short for Universal Asynchronous Receiver-Transmitter, UART is a chip used to manage computer hardware devices which require timing. These devices include computer serial ports, disk drive interrupts, and screen refresh cycles. With a serial port transmission, UART converts the bytes into serial bits and transmits them through an asynchronous transmission, stripping out the start and stop bits for each character. Below is a listing of various UART chips. The 16550 chip series is the most commonly used UART.
- 8250 UART was the original UART and was capable of speeds up to 9600 bps with a 1-byte FIFO.
- 8250A UART was a revised version of the 8250 with an additional register that allowed software to verify it was a 8250 UART.
- 16450 UART Slightly faster than earlier UARTs.
- 16540 UART capable of speeds up to 9600 bps.
- 16550 UART has a 16-byte FIFO.
- 16550A UART had same features as previous 16550 UART with new fixes.
- 16550AF UART had same features as previous 16550 UART with faster capabilities.
- 16550AFN UART had same features as previous 16550 UART except was a ceramic chip.
- 16650 UART has a 32-byte FIFO.
- 16750 UART has a 64-byte FIFO.
- 16950 UART has a 128-byte FIFO.