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PXA25x Boot flash same as mass storage flash?

Discussion in 'Embedded' started by Guest, Oct 21, 2003.

  1. Guest

    Guest Guest


    I am about to start a design based on PXA255 and for economy I was
    thinking of using the very same flash (or flash pair) for both boot
    loader and general storage (kernel and file system), maybe using flash
    internal mechanisms (and perhaps some glue logic) for protecting boot
    blocks from accidental erasing. I have seen at least two PXA255 based
    boards that have a flash for RedBoot only and place kernel and file
    system in other flashes. Is there any mistake with my design? If not,
    why not using the same flash for boot loader and normal storage?

    Thank you very much for your advice.

    Guest, Oct 21, 2003
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  2. Guest

    Dave Tweed Guest

    The very high density flashes you want for filesystems do not support
    the random access needed for direct execution of firmware. I just did
    a PXA255 design and included two chips for boot flash (8M x 32 bits
    total) and two chips for filesystem flash (256M x 8 bits total).

    If you can get enough random-access flash into your system to meet your
    needs, then that's the only kind you need to have.

    -- Dave Tweed
    Dave Tweed, Oct 21, 2003
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  3. Guest

    Guest Guest

    Hmmm... I was thinking of Intel strata flash (28F320J3 or K3 - or
    their higher density siblings) and compatibles. A quick glance through
    the data sheet gave me the impression they can stand random access. I
    have to take a deeper look at it though.
    I need 8MB or 16MB at most.

    Thanks for the hints.

    Guest, Oct 22, 2003
  4. I am about to start a design based on PXA255 and for economy I was
    I've done this, though not on ARM-cored products. It worked out to be
    more expensive than using a tiny (16Kbyte) boot flash loading the main
    OS out of NAND flash, though. NAND flash is dirt cheap, and
    pin-compatible for sizes from 8Mb to 128Mb.
    Lewin A.R.W. Edwards, Oct 22, 2003
  5. Guest

    Guest Guest

    RedBoot requires 128KB at least. I am considering putting it into the
    same flash more for space saving than for cost though it also matters
    a lot. We've been asked to use TSOP instead of uBGA so only PXA255
    will be BGA and space may become an issue in this design.


    Guest, Oct 22, 2003
  6. I am about to start a design based on PXA255 and for economy I was
    Well, board space is board space... but what I wound up doing was using an
    OTP EPROM. *Everything* software-wise is on the NAND. The OTP only contains
    enough code to boot the OS out of NAND flash. The NAND is partitioned into
    "OS" and "data" areas using a wholly DOS-esque partition table. If I was
    using RedBoot, I would have had it on the NAND, compiled for RAM start-up
    (I'm assuming the terminology hasn't changed since I last used it).
    Lewin A.R.W. Edwards, Oct 23, 2003
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