MMC/SD

Some notes on the MMC/SD peripheral.

Initialisation

For voltage validation, the following procedure is advised:

1. Check for SDIO card.
2. Check for SDMEM card.
3. Check for MMC cards (up to 10 may be attached).

Commands

The MSC_CMD (command index) register indicates the issued command, with the MSC_ARG (command argument) register providing any necessary argument.