10.6 GPIOs

The ten General Purpose Input/Output (GPIO) pins, labeled GPIO 0, GPIO 3-4, GPIO 7-8 and GPIO 17-21, are allowed to perform specific functions of an application. Each GPIO pin can be programmed as an input (the value of the pin can be read by the Host or internal processor) or as an output (the output values can be programmed by the host or internal processor), where the default mode after power-up is input. GPIOs 7 and 8 are only available when the Host does not use the SDIO interface, which shares two of its pins with these GPIOs. Therefore, for SDIO-based applications, eight GPIOs (0, 3-4 and 17-21) are available.