The OX16PCI954 is a single chip solution for PCI-based serial and parallel expansion add-in cards. It is a dual function PCI device, where function 0 offers four ultra-high performance OX16C950 UARTs, and function 1 is configurable to offer either an 8 bit Local Bus or a bidirectional parallel port. Serial port cards with up to 8 ports (or with 4 serial ports and a parallel port) can be designed without redefining any device or timing parameters. Each channel in the OX16PCI954, the fastest available PC-compatible UART, offers data rates up to 15Mbps and 128-deep transmitter and receiver FIFOs. Deep FIFOs reduce CPU overhead and allow utilisation of higher data rates. Each channel is software compatible with the widely used industry-standard 16C550 devices and compatibles as well as the OX16C95x family of high performance UARTs. In addition to increased performance and FIFO size, the UARTs also provide the full set of OX16C95x enhanced features including automated in-band flow control, readable FIFO levels etc. The efficient 32-bit, 33MHz target-only PCI interface is compliant with version 2.2 of the PCI Bus Specification and version 1.0 of PCI Power Management Specification. For applications that do not require the internal parallel port or the local Bus, card designers can assign a Subsystem Vendor ID and a Subsystem ID using 32 input pins. If the UARTs are not required, the Local Bus can be extended from 8-bit operation to a full 32-bit pass-through interface.