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OMAP-L138 On-chip RAM usage by ROM bootloader in SD/MMC bootmode

rperezti
Genius 12870 points

Other Parts Discussed in Thread: OMAP-L138

How much of the onchip RAM does the OMAP-L138 ROM bootloader use when bootloading in MMC/SD mode?  The bootloader appnote mentions the RAM usage in non-NAND modes as 2KB and in NAND-Boot mode as 8KB. 

"9.1 General Comments

• Non-NAND Memory Usage: The bootloader uses 2 KB of ARM local RAM starting from 0xFFFF0000. This memory should not be used by any initialized section of the user application."

"9.6 NAND-Boot Modes

• The bootloader uses 8 KB of ARM local RAM starting from 0xFFFF0000. This memory should not be

used by any initialized section of the user application."

However, we have confirmed through testing in MMC/SD-boot mode that the ROM bootloader is writing data at 0xFFFF1000 (4KB from start) which is not consistent with the document.

What is the actual range or onchip RAM that the bootloader may affect during MMC/SD boot mode?

  • 0
    TI__Guru** 116950 points

    Hi Ruben,

    Your are right the Bootloader application notes needs to corrected to reflect the information that SD/MMC uses the same amount of ARM RAM as NAND Boot Mode ie 8KB. I will file a lit bug for this and work on fixing it in the next revision.

    For NAND and SD/MMC, the ROM code defines a 4K size memory buffer at 0xffff1000 to temporarily store data read from NAND page/ MMC block. Here is the mapo file details of ARM RAM usage for your reference

      RAM_ARM_VECT          ffff0000   00000020  00000000  00000020  RWIX
      RAM_ARM_STACK         ffff0020   000006e0  00000000  000006e0  RWIX
      RAM_ARM_BL1           ffff0700   00000100  00000000  00000100  RWIX
      RAM_ARM_MISC          ffff0800   00000800  00000000  00000800  RWIX
      RAM_ARM_MEMBUFF       ffff1000   00001000  00000000  00001000  RWIX (Used only in NAND/SD boot)

    Regards,

    Rahul