The MCP23X18 device provides 16-bit, general purpose parallel I/O expansion for I2C bus or SPI applications. The two devices differ only in the serial interface.
• MCP23018 - I2C interface
• MCP23S18 - SPI interface
The MCP23X18 consists of multiple 8-bit configuration registers for input, output and polarity selection. The system master can enable the I/Os as either inputs or outputs by writing the I/O configuration bits. The data for each input or output is kept in the corresponding input or output register. The polarity of the input port register can be inverted with the polarity inversion register. All registers can be read by the system master.

  16-bit remote bidirectional I/O port

  Open-drain outputs:

  5.5V tolerant

  25 mA sink

  400 mA total current out

  Low standby current as low as 1 µA

  High-speed I2C™ interface up to 3.4MHz

  Single hardware address pin: Voltage input to allow up to eight devices on the bus

  Configurable interrupt output pins: Configurable as active-high, active-low or open-drain

  Low standby current:1 µA (typ.)