====== ElCheapo SD 2.x (GB/GBC) programming ======


Stub (only covers SPI bus for storage).

===== Registers =====

==== $0000 (RAM enable) ====

Write $09 to unlock other registers.

==== $3F00 (SPI read) ====

Returns the last read value from the SPI bus.

==== $3F01 (SPI write) ====

Write to send and receive a bytre via the SPI bus from/to the SD card.