The XR16V25511 (V2551) is a high performance dual universal asynchronous receiver and transmitter (UART) with 16 byte TX and RX FIFOs. The device operates from 2.25 to 3.6 volts with 5 Volt tolerant inputs and is pin-to-pin compatible to Exar's XR16V2651 and XR16L2551. The device includes 2 additional capabilities over the XR16V2550: Intel and Motorola data bus selection and a "PowerSave" mode to further reduce sleep current to a minimum during sleep mode. It supports Exar's enhanced features of selectable FIFO trigger level, automatic hardware (RTS/CTS) and software flow control, and a complete modem interface. An internal loopback capability allows system diagnostics. Independent programmable fractional baud rate generators are provided in each channel to select data rates up to 16 Mbps at 3.3 Volt and 4X sampling clock. The V2551 is available in 48-pin TQFP and 32-pin QFN packages.