On Mon, Aug 11, 2014 at 01:01:44AM -0700, William "Chops" Westfield wrote:
> On Aug 10, 2014, at 4:59 PM, James Cameron wrote:
>=20
> > I've brought up C Forth on the Teensy 3.1.
>=20
> Neat.  Is it able to write new words to its flash memory?  I've
> worked slightly with AMFORTH on AVR, and it manages to write flash
> "with some difficulty" due to the AVR flash writing capabilities.

It looks like it may be possible, but I haven't done it yet.

The device has a flash memory controller integrated with the RAM in
some strange way that I don't yet fully comprehend.  The family
reference manual K20P64M72SF1RM.pdf describes address spaces such as;

- the program flash (0x0000.0000 to 0x0003.ffff, 256 KB),

- FlexNVM (0x1000.0000 to 0x1000.7fff, 32 KB), and

- FlexRAM (0x1400.0000 to 0x1400.07ff, 2 KB).

The flash controller also has prefetch speculation, and a 4-way, 8-set
cache.  So executing from flash isn't much of a hindrance.

(This overall feature has already bitten me.  In other systems,
writing to an address in program flash by accident is quite harmless,
but on this device you get a bus error; because the capability _is_
there to write.)

--=20
James Cameron
http://quozl.linux.org.au/
--=20
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