====== M3DS Real (NDS) programming ======

Original research provided mostly by lifehackerhansol.

===== Control flags =====

  * KEY1 gap1 length: 0, 256 for SD write and/or multi-sector commands.
  * KEY1 gap2 length: 24
  * KEY2 encryption: Enabled for data and commands
  * Transfer clock rate: 6.7 MHz
  * Data block size: 4 bytes (512 bytes for SD commands)

===== Commands =====

==== Get card information (B0 ?? ?? ?? ?? ?? ?? ??) ====

==== SD multi-sector read request (B1 sd sc sb sa 00 00 00) ====

  * (MSB) sd sc sb sa (LSB) - sector address

==== SD multi-sector read next (B2 sd sc sb sa 00 00 00) ====

  * (MSB) sd sc sb sa (LSB) - sector address

==== SD multi-sector end (B3 ?? ?? ?? ?? ?? ?? ??) ====

==== SD multi-sector write start (B4 sd sc sb sa 00 00 00) ====

  * (MSB) sd sc sb sa (LSB) - sector address

==== SD multi-sector write next (B5 sd sc sb sa 00 00 00) ====

  * (MSB) sd sc sb sa (LSB) - sector address

==== SD multi-sector write status (B6 sd sc sb sa 00 00 00) ====

  * (MSB) sd sc sb sa (LSB) - sector address

==== SD read data (BA 00 00 00 00 00 00 00) ====

Returns the 512 bytes read via the "SD read start" command.

==== SD write status (BC sd sc sb sa 00 00 00) ====

  * (MSB) sd sc sb sa (LSB) - sector address

Returns zero if done, non-zero if ongoing.

==== SD read request (BD sd sc sb sa 00 00 00) ====

  * (MSB) sd sc sb sa (LSB) - sector address

Returns zero when data is ready to access, non-zero if ongoing.

==== SD write start (BE sd sc sb sa 00 00 00) ====

  * (MSB) sd sc sb sa (LSB) - sector address

Followed by 512 bytes of SD card data.

==== ? (C8 ?? ?? ?? ?? ?? ?? ??) ====

==== ? (CC ?? ?? ?? ?? ?? ?? ??) ====

==== ? Get cart region ? (CD ?? ?? ?? ?? ?? ?? ??) ====