PCAL9535AHF,128 is a low-voltage 16bit general purpose input/output (GPIO) expander with interrupt and reset for I²C-bus/SMBus applications. NXP I/O expander provides a simple solution when additional I/Os are needed while keeping interconnections to a minimum, for example, in ACPI power switches, sensors, push buttons, LEDs, fan control, etc. In addition to providing a flexible set of GPIOs, the wide VDD range of 1.65V to 5.5V allows the interface with next-generation microprocessors and microcontrollers where supply levels are dropping down to conserve power. This mask default allows for a board bring-up free of spurious interrupts at power-up. The open-drain interrupt (INT) output is activated when any input state differs from its corresponding input port register state and is used to indicate to the system that an input state has changed.