Boot strategies

A project log for SBC AT91RM9200

This is an open hardware SBC module around AT91RM9200 with 64MB SDRAM. It's built with nonBGA parts and is capable of running mainline Linux

Vadim RaduVadim Radu 05/14/2019 at 06:480 Comments

Boot mode is usually set using the BMS pin on the AT91SAM9 series processors. When pulled down, it boots a NAND flash on the EBI bus. As NAND is expensive and takes a considerable area on the board, the boot strategy was devised relaying on the internal BootROM and a small NVM memory attached to SPI0.

The U-Boot bootloader and a small Busybox are stored there ( for fallback puroposes). U-Boot tries to load the kernel and rootfs from microSD if present, or falls back to the NVM environment if not present.