SPRUIM2H May 2020 – October 2023 AM2431 , AM2432 , AM2434 , AM6411 , AM6412 , AM6421 , AM6422 , AM6441 , AM6442
SD Card boot is only available on Port 1 of the MMCSD controller (MMCSD1). The IOs on this port support both 1.8V and 3.3V operation, as well as dynamic voltage change. Thus, this port can support initial operation at 3.3V and remain at this voltage for legacy SD Cards, or support initial operation at 3.3V and change to 1.8V after ROM boot for UHS-I SD Cards.
The ROM will boot from SD cards using one of these methods:
The ROM is capable of booting from any size SD card because the MMCSD controller is responsible for addressing. Only single data rate with backward compatible interface timing is supported.
The MMCSD module depends on proper voltage level on the SD card detect signal (SDCD). If SDCD=1, the ROM will assume the card is not present and will fail the boot mode.The SDCD must be 0 for the ROM to continue to attempt to boot. Card detect using DAT3 is not supported. If the card is detected, the initial discovery phase is performed:
The ROM Code will start reading from the MMCSD memory boot sector, or filesystem, as specified by the BOOTMODE pins. Only FAT32 and FAT16 formats are supported in filesystem mode. It will continue reading data from the memory and storing it in internal RAM until a complete image has been read. In RAW mode only, the ROM supports a redundant image at offset 0x400000 in case the initial image fails to be recognized. When the complete image has been read and found in good integrity, the ROM Code will branch to the address defined in the Boot Info field of the boot header.
When SD Card boot is used as a backup boot option, only User Data Area (UDA) in filesystem mode is supported. Raw mode is not supported. Additionally, boot will only occur in 1-bit mode during backup booting.