SPRABA5D January 2014 – January 2019 AM1802 , AM1802 , AM1806 , AM1806 , AM1808 , AM1808 , AM1810 , AM1810
The MultiMedia Card/Secure Data (MMC/SD) boot mode is compliant with version 2.0 of the SD specification and version 4.2 of the enhanced MultiMedia Card (eMMC) specification. The boot loader and MMC/SD peripheral does not support features of the eMMC 4.3 or 4.4 specifications related to boot (no boot operation mode and no support for boot partitions). The AIS boot image is expected to be in the user data area of the memory device, written to address 0 of that region. The bootloader detects the AIS image by checking for the magic word (0x41504954). If the magic word is not found, the bootloader increments the starting address by 0x200 and tries again. The bootloader fails if the magic word is not found within the first 2 MB of the memory card.
Typically, the ROM boot loader will first try to detect an SD card. If that fails (a timeout occurs), the boot loader will then attempt to find an MMC or eMMC device. In cases where it is known that an SD card will never be present (for example, a memory card slot is not used and an eMMC device is placed on the PCB), the BOOT[5] pin of the SoC device should be pulled high to force the bootloader to skip the SD detection. This will guarantee the quickest boot in these circumstances. For further details, see Section 9.