Provide two-way communication capabilities. Provide 3.3 -5V 1.8 - 3.3 v and other common level conversion capability. Serial communication interface compatible with UART/IIC/SPI port easy to connect. Widely used in the MCU and SD card MCU and serial devices MCU and 5V/3V module communiction. OE active high enable IO recommended by a low voltage side of the IO port.