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−There are two ways in which a flashed firmware image may be booted, which we
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−call mode 0 and mode 1 - see the Flash-boot-modes write-up in the
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−freecalypso-tools repository for the details.  All TI official firmwares
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−including our TCS211 reference version have used flash boot mode 1, and the
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−present Magnetite firmware is unchanged in this regard.
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−
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−Some FCDEV3B boards have a non-understood hardware problem that causes flash
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−boot to fail (the visible symptom is a dead hang with even JTAG not working)
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−when the firmware image in flash uses boot mode 1.  It is not currently known
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−how many boards are affected by this problem; it is possible that the Mother's
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−S/N 001 board is the only one that exhibits this oddity.
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−
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−Once the discovery was made that the flash boot problem occurs only when the fw
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−image uses flash boot mode 1, a workaround became apparent: switch to using
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−flash boot mode 0.  Redesigning Magnetite fw to use interrupt and exception
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−vectors in the ROM branching to 0x80001C-0x800034 in IRAM is not in line with
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−the Mother's vision, but a surgical hack to make the Magnetite fw flash image
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−receive control from the boot ROM in mode 0, disable the boot ROM via the
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−FFFF:FB10 register and jump to 0 as if in mode 1 is quite doable, and it
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−accomplishes the job of producing a flash image of FC Magnetite that boots
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−without a hitch on the flash-boot-challenged FCDEV3B.
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−
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−The standard FC Magnetite build is unchanged and unaffected, i.e., the hack in
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−question is NOT applied by default.  However, if you have a board that has
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−trouble booting the regular Magnetite fwimage.bin that uses flash boot mode 1,
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−you can run 'make fwimage.mode0' in your build directory to get an image patched
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−with the flash boot mode 0 hack.