Abstract: Circuitry and methods are provided for a standardized serial interface. The interface uses auxiliary port connector pin of a device conforming to the Personal Computer Memory Card International Association (PCMCIA) standard as a serial bus. Protocols are provided that allow a host computer to selectively connect to and communicate with either the PCMCIA based device or with devices connected to the serial bus. The circuitry and protocols support a daisy-chain of multiple devices from a single PCMCIA based device.