The MCP23S17-E/SS is an integrated circuit expander manufactured by Microchip. It features a 16-bit input/output port with SPI communication, and is packaged in a SSOP28. It operates on a voltage range of 1.8 to 5.5VDC. The IC is ideal for device interfacing, LED display driving, and operating relays. It can also be used to interface microcontrollers to LCDs, or to expand GPIO pins.