These registers are used to access the system NAND and the inserted SD card. Both devices use the same interface. Despite the bus clock of the ARM9 being double of the DSi in 3DS mode the SDMMC controller has HCLK=33.513982 MHz.
|Yes||EMMC_CMD||0x10006000||2||Boot9, NewKernel9Loader, Process9|
3DS SDMC/NAND IO registers are located at 0x10006000 and apparently mirrored at 0x10007000. It seems the 0x10007000 mirror is never used on retail units.
|3||SD card removal flag (Set to 1 when SD card is removed)|
|4||SD card insertion flag (Set to 1 when SD card is inserted)|
|5||SD card insertion status (0 = missing, 1 = inserted)|
SD card insertion status
Assertion happens around 250 ms after SD card insertion and/or enabling the EMMC hardware (delay could possibly be due to an SD bus timeout?).