The SC16C650B is a Universal Asynchronous Receiver and Transmitter (UART) used for serial data communications. Its principal function is to convert parallel data into serial data, and vice versa. The UART can handle serial data rates up to 3 Mbit/s. The SC16C650B is pin compatible with the ST16C650A and it will power-up to be functionally equivalent to the 16C450. Programming of control registers enables the added features of the SC16C650B. Some of these added features are the 32-byte receive and transmit FIFOs, automatic hardware or software flow control and infrared encoding/decoding. The selectable auto-flow control feature significantly reduces software overload and increases system efficiency while in FIFO mode by automatically controlling serial data flow using RTS output and CTS input signals. The SC16C650B also provides DMA mode data transfers through FIFO trigger levels and the RXRDY and TXRDY signals. On-board status registers provide the user with error indications, operational status, and modem interface control. System interrupts may be tailored to meet user requirements. An internal loop-back capability allows on-board diagnostics.