SPRUHZ7K August 2015 – April 2024 AM5706 , AM5708 , AM5716 , AM5718 , AM5718-HIREL
The eMMC / SD cards can hold a file system that the ROM code reads. The image used by the booting procedure is taken from a booting file named MLO. This file must be in the root directory on an active primary partition of type FAT12/16 or FAT32.
An eMMC/SD card can be configured as floppy-like or hard-drive-like:
According to the MultiMediaCard FAT16 File System Specification from the MMCA Technical Committee, the card must always hold an MBR, except when using a floppy-like file system. However, depending on the operating system used, the eMMC / SD card is formatted with or without partitions (using an MBR). The ROM code supports both types: floppy-like or hard-drive-like. The ROM code retrieves a map of the booting file from the FAT. The booting file map is a collection of all FAT entries related to the booting file (a FAT entry points to a cluster holding part of the file). The booting procedure uses this map to access any 512-byte sector in the booting file without involving the ROM code FAT module. Figure 33-27 shows the complete process.