The MCP23X08 device provides 8-bit, general purpose, parallel I/O expansion for I2C bus or SPI applications. The two devices differ in the number of hardware address pins and the serial interface:
• MCP23008 – I2C interface; three address pins
• MCP23S08 – SPI interface; two address pins
The MCP23X08 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
• 8-bit remote bidirectional I/O port
- I/O pins default to input
• High-speed I2C™ interface (MCP23008)
- 100 kHz
- 400 kHz
- 1.7 MHz
• High-speed SPI interface (MCP23S08)
- 10 MHz
• Hardware address pins
- Three for the MCP23008 to allow up to eight devices on the bus
- Two for the MCP23S08 to allow up to four devices using the same chip-select
• Configurable interrupt output pin
- 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 (max.)
• Operating voltage:
- 1.8V to 5.5V @ -40°C to +85°C (I-Temp)
- 2.7V to 5.5V @ -40°C to +85°C (I-Temp)
- 4.5V to 5.5V @ -40°C to +125°C (E-Temp)

Packages
• 18-pin PDIP (300 mil)
• 18-pin SOIC (300 mil)
• 20-pin SSOP
• 20-pin QFN