The Philips Semiconductors SCN2651 PCI is a universal synchronous/asynchronous data communications controller chip designed for microcomputer systems. It interfaces directly to the Philips Semiconductors SCN2650 microprocessor and may be used in a polled or interrupt driven system environment. The SCN2651 accepts programmed instructions from the microprocessor and supports many serial data communication disciplines, synchronous and asynchronous, in the full or half-duplex mode.