The I/O interface signals are described in the SD Flash Interfaces and eMMC Interface sections.
MIO Interface
Each I/O interface is routed separately through the PMC MIO or the PL EMIO. The interface is not available through the LPD MIO. The SD I/O interface signals includes 1 and 4-bit data with card detect, and write protect. The interface also includes signals to control an optional external voltage level shifter for interfacing to the devices at 3.3V and switching to 1.8V for higher speed, SD 3.0 functionality.