The PCAL6524 is a 24-bit general purpose I/O expander that provides remote I/O expansion for most microcontroller families via the Fast-mode Plus (Fm+) I²C-bus interface. The ultra low-voltage interface allows for direct connection to a microcontroller operating down to 0.8 V. NXP I/O expanders provide a simple solution when additional I/Os are needed while keeping interconnections to a minimum, for example, in battery-powered mobile applications for interfacing to sensors, push buttons, keypad, etc. In addition to providing a flexible set of GPIOs, it simplifies interconnection of a processor running at one voltage level down to 0.8 V to I/O devices operating at a different voltage level 1.65 V to 5.5 V.