The XR17L1521 (L152) is a monolithic dual PCI Bus Universal Asynchronous Receiver and Transmitter (UART) in Exar's PCI Bus UART family. The device is designed to meet today's 32-bit PCI Bus and high bandwidth requirements in communication systems. The global interrupt source register provides a complete interrupt status indication for both channels to speed up interrupt parsing. Each UART is independently controlled and has its own 16C550 compatible 5G (Fifth Generation) register set, transmit and receive FIFOs of 64 bytes, fully programmable transmit and receive FIFO trigger levels, transmit and receive FIFO level counters, automatic hardware flow control with programmable hysteresis, automatic software (Xon/Xoff) flow control, automatic half-duplex control output, wireless IrDA (Infrared Data Association) infrared encoder/decoder, 8 multi-purpose definable inputs/outputs, and a 16-bit general purpose timer/counter. NOTE: 1 Covered by U.S. Patents #5,649,122, #5,949,787