POR and interrupt — two features that save firmware cycles
The power-on reset (POR) forces all registers to their default state when VDD rises, so the I/O pins start as inputs — no glitch on a relay coil or LED at power-up. The interrupt output (INT) asserts low when any input pin changes state relative to the last read. The host sees the interrupt, reads the input port register, and clears the flag. This beats polling 24 pins every loop, especially when the expander is on a slower I²C bus.
ROHS3 compliant.