The XR17D1541 (D154) is a quad PCI Bus Universal Asynchronous Receiver and Transmitter (UART) with same package and pin-out as the Exar XR17C158, XR17D158 and XR17C154. The device is designed to meet today's 32-bit PCI Bus and high bandwidth requirement in communication systems. The global interrupt source register provides a complete interrupt status indication for all 4 channels to speed up interrupt parsing. Each UART is independently controlled and has its own 16C550 compatible 5G 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, IrDA (Infrared Data Association) encoder/ decoder, 8 multi-purpose inputs/outputs and a 16-bit general purpose timer/counter.