These registers are used to access the system NAND and the inserted SD card. Both devices use the same interface.
|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?).