A system and method communicates with one of two or more secure digital input output (SDIO) units that only one SDIO unit responds when it is being addressed. The SDIO unit has an SDIO clock input port, an SDIO data bus output port, and an SDIO bidirectional command port. Each SDIO unit has an address indicator within it associated with each SDIO unit. An SDIO unit will not respond to an SDIO command unless an SDIO unit address encoded in the SDIO command matches its address indicator.