The XL9535 is a 24-pin CMOS device that provides 16-bit universal parallel input/output (GPIO) extensions for most microcontroller families via the I²C bus /SMBus interface Serial Clock Line (SCL), Serial Data (SDA). These devices are designed for 2.3-V to 5.5-V Vcc operation. These improvements include higher drive capacity, 5V I/O tolerances, lower power supply currents, separate I/O configurations, and smaller packages. When powered on, I/O is configured as input. The system host can enable I/O as input or output by writing I/O configuration bits. Each input or output data is stored in the corresponding input or output register. The polarity of the input port register can be reversed using the polarity reversal register. All registers can be read by the system master. These device open interrupt (/INT) outputs are activated when any input state differs from its corresponding input port register state and are used to indicate to the system host that the input state has changed. In the case of time-out or other improper operations, the main system devices can be reset using the power-on reset function. Power-on reset sets the register to its default value and initializes the I²C/SMBus state machine. Three hardware pins (A0, A1, and A2) change the fixed I²C bus address and allow up to eight devices to share the same I²C bus /SMBus.
