The XR16C28521 (2852) is a dual universal asynchronous receiver and transmitter (UART). The device operates at 3.3V and 5V and is pin-to-pin compatible to Exar's ST16C2552 and XR16L2752. The 2852 register set is compatible to the ST16C2552 and the XR16C2752 enhanced features. It supports the Exar's enhanced features of 128 bytes of TX and RX FIFOs, programmable FIFO trigger level and FIFO level counters, automatic hardware (RTS/CTS) and software flow control, automatic RS-485 half duplex direction control output and a complete modem interface. Onboard registers provide the user with operational status and data error flags. An internal loopback capability allows system diagnotics. Independent programmable baud rate generators are provided in each channel to select data rates up to 3.125 Mbps at 5V. The 2852 is available in the 44-pin PLCC package.