The PI4IOE5V9557 provide 8 bits of General Purpose parallel Input/Output (GPIO) expansion for I2Cbus/SMBus applications. It includes the features such as higher driving capability, 5V tolerance, lower power supply, individual I/O configuration, and smaller packaging. It provides a simple solution when additional I/O is needed for ACPI power switches, sensors, push buttons, LEDs, fans, etc. The PI4IOE5V9557 consists of an 8-bit register to configure the I/Os as either inputs or outputs, and an 8- bit polarity register to change the polarity of the input port register. The data for each input or output is kept in the corresponding Input port or Output port register. All registers can be read by the system master.