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.

Features
• 16-bit remote bidirectional I/O port:
- I/O pins default to input
• Open-drain outputs:
- 5.5V tolerant
- 25 mA sink capable (per pin)
- 400 mA total
• High-speed I2C™ interface: (MCP23018)
- 100 kHz
- 400 kHz
- 3.4 MHz
• High-speed SPI interface: (MCP23S18)
- 10 MHz: 2.7V ≤ VDD ≤ 5.5V
• Single hardware address pin: (MCP23018)
- Voltage input to allow up to eight devices on the bus
• Configurable interrupt output pins:
- Configurable as active-high, active-low or open-drain
• Configurable interrupt source:
- Interrupt-on-change from configured defaults or pin change
• Polarity inversion register to configure the polarity
of the input port data
• External reset input
• Low standby current:
- 1 µA (-40°C ≤ TA ≤ +85°C)
- 6 µA (+85°C ≤ TA ≤ +125°C)
• Operating voltage:
- 1.8V to 5.5V