PCA9554ADB,118 is an 8-bit I²C-bus and SMBus I/O port with an interrupt 16-pin CMOS device. It provided 8 bits of general-purpose parallel input/output (GPIO) expansion for I²C-bus/SMBus applications and was developed to enhance the NXP Semiconductors family of I²C-bus I/O expanders. The improvements include higher drive capability, 5V I/O tolerance, lower supply current, individual I/O configuration, 400KHz clock frequency, and smaller packaging. I/O expanders provide a simple solution when additional I/O is needed for ACPI power switches, sensors, push buttons, LEDs, fans, and so on. The system can enable the I/Os as either inputs or outputs by writing to the I/O configuration bits. The data for each input or output is kept in the corresponding input port or output port register. The polarity of the read register can be inverted with the Polarity inversion register.