16-bit I2C-bus I/O port with interrupt

Description

NCA9555 is a 24-pin CMOS device designed to provide GPIO (General Purpose Input/Output) expansion for I2C-bus applications.

1. Functionality: The NCA9555 serves as a GPIO expansion solution for I2C-bus applications. It is used when additional I/O (Input/Output) ports are required for various purposes such as controlling ACPI power switches, sensors, buttons, LEDs, fans, and more.
2. Configuration and Operation: The NCA9555 has 16 bits of GPIO, organized as two 8-bit ports. It includes Configuration registers that allow you to specify whether each pin should function as an input or output. You can also configure the polarity of inputs and outputs, meaning you can set whether the GPIO operates as active HIGH or active LOW.
3. Input and Output Registers: For each GPIO pin, there are corresponding Input and Output registers where data can be read from or written to. The system master (likely a microcontroller or processor) can control these registers to manage the state of the GPIO pins.
4. Polarity Inversion: The Polarity Inversion register allows you to invert the polarity of the read register. This means that the logic level read from an input can be inverted, helping to accommodate situations where the default logic levels need to be adjusted.
5. Interrupt Output: The NCA9555 has an open-drain interrupt output that becomes active when the input state differs from the corresponding input port register state. This feature is used to indicate to the system master that a change in input state has occurred.
6. Power-On Reset: When the device is powered on, a power-on reset mechanism initializes the registers to their default values and sets the device state machine to a known state.
7. I2C-Bus Addressing: The device features three hardware pins (A0, A1, A2) that allow you to configure the I2C-bus address of the device. This allows you to have up to eight devices with different addresses share the same I2C-bus.