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On Chip Memory Doubt

Japan Dave
Note: This was originally posted on 16th August 2010 at http://forums.arm.com

Hi,

          I want to know what kind of memory type BootROM having in any arm based processor (for example marvell kirkwood) and Why??
Why cant we boot the code residing in BootROM from external NAND flash????

What BootROM performs in embedded system exactly??? Can I see code inside that?
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  • Arm Employee Badge
    Note: This was originally posted on 16th August 2010 at http://forums.arm.com

    The boot ROM is on chip because somethign needs to configure the chip's memory interfaces so that they can see the outside world. If you have no code to initialize the memory controller, how are you supposed to access the external Flash?

    The usual approach is to have a very simple boot ROM which initializes the external memory interfaces, and then  have that load a secondary boot loaded from external Flash storage. This is very much like the BIOS on a PC loading GRUB from the HDD for booting Linux, for example.

    Other tasks for a ROM-based bootloader would include any security tasks (because the ROM cannot be changed, it can be more trusted than code loaded from external flash)

    >> Can I see code inside that?

    It depends on your device - talk to the manufacturer.
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  • Arm Employee Badge
    Note: This was originally posted on 16th August 2010 at http://forums.arm.com

    The boot ROM is on chip because somethign needs to configure the chip's memory interfaces so that they can see the outside world. If you have no code to initialize the memory controller, how are you supposed to access the external Flash?

    The usual approach is to have a very simple boot ROM which initializes the external memory interfaces, and then  have that load a secondary boot loaded from external Flash storage. This is very much like the BIOS on a PC loading GRUB from the HDD for booting Linux, for example.

    Other tasks for a ROM-based bootloader would include any security tasks (because the ROM cannot be changed, it can be more trusted than code loaded from external flash)

    >> Can I see code inside that?

    It depends on your device - talk to the manufacturer.
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