2.9.1.5.2 e.MMC/SD Card Bootstrap Filename
To boot on a FAT32-formatted e.MMC or SD card, the bootstrap image must be named "boot.bin".
When Dual Boot mode is enabled, the secondary bootstrap image must be named "bootWXYZ.bin", where <WXYZ> is the suffix written in eMMC/SD MEM_CFGx[3].DUALBOOT_CFG. See SD Card/eMMC Memory Boot Configuration (Fourth Word).
These files must be written in the file system root directory. The file size must not exceed the maximum bootstrap size allowed.
In Secure Boot mode, the bootstrap image filename must be "boot.cip". When Dual Boot mode is enabled, the secondary bootstrap filename must be "bootWXYZ.cip”.