4-Port, RS485/RS422 C Series Serial Interface Module—The NI‑9871 adds RS485/RS422 serial ports to CompactRIO systems. The serial ports are accessed directly from the FPGA to offer you flexibility in communicating with serial devices. The module has individual buffers on every port that save FPGA space and simplify programming. The NI‑9871 supports standard start bit, stop bit, and handshaking settings. It uses an external power to provide maximum compatibility and reliability under all serial port conditions.