The XR16V25521 (V2552) 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 ST16C2552 and XR16L2552. The V2552 register set is compatible to the ST16C2552 and the XR16L2552. It supports the Exar's enhanced features of selectable FIFO trigger level, automatic hardware (RTS/CTS) and software (Xon/Xoff) flow control, and a complete modem interface. Onboard registers provide the user with operational status and data error flags. An internal loopback capability allows system diagnostics. Independent programmable baud rate generators are provided in each channel to select data rates up to 16 Mbps at 3.3 Volt with 4X sampling clock. The V2552 is available in 44-pin PLCC and 32-pin QFN packages.