The 8-bit GPIO MCP23X08 family includes two devices, the MCP23008 has an I²C interface (1.7MHz max clock rate) and the MCP23S08 has an SPI interface (10MHz max clock rate). The 16-bit GPIO MCP23X17 family also includes two devices, the MCP23017 has an I²C interface (1.7MHz max clock rate) and the MCP23S17 has an SPI interface (10MHz max clock rate).