[U-Boot-Users] Question about U-Boot in general and the AT91RM9200 in particular

Sascha Erlacher sascha.erlacher at philips.com
Thu Jan 4 15:16:16 CET 2007

>thus in any way you must use a small (<12Kb) initial bootloader, which
>in turn loads u-boot from dataflash or NOR flash in SDRAM.

Hello Ivan,
this is not correct. As Wolfgang points out you can boot directly from NOR

It depends on the BootModeSelect (BMS) pin state of the AT91RM9200.
The datasheet states:

"Depending on the BMS pin state at reset and as a function of the remap
 command, the memory
mapped at address 0x0 is different. Before execution of the remap command
the on-chip ROM
(BMS = 1) or the 16-bit non-volatile memory connected to external chip
select zero (BMS = 0) is
mapped into Internal Memory Area 0."

When setting BMS=0 the AT91RM9200 internal boot rom code is not executed.
If the external (NOR) flash contains a valid U-Boot image it will be
executed directly,
and, in case it properly initializes an external SDRAM, will be able to
relocate itself to SDRAM
without going through internal SRAM.

Best regards,

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