1.3.2. Flash Memory Devices for Booting
The memory controllers and devices that contain the boot loader image have configuration requirements for proper boot from flash.
On all flash devices, there is an area of memory, called the boot area that contains up to four second-stage boot loader images. For the QSPI and SD/MMC devices, the boot area is 1 MB in size. For NAND devices the boot area is four device blocks in size and may be larger than 1 MB if the NAND erase block is larger than 256 KB.
The SD/MMC, Quad SPI and NAND flash devices all support raw and MBR (partition) mode. In raw mode, the boot image is located at the start of the flash memory device, at offset 0x0. In MBR mode:
- The boot image is read from a custom partition (0xA2)
- The first image is located at the beginning of the partition, at offset 0x0
- Start address = partition start address