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It also turns out that there are 8 bytes of external
RAM that peek through at addresses 0xff80-0xff87.
Writes to these locations also affect the motor
control register. I suppose there's a small advantage
in using these registers to control the motor since
accesses to these locations can use the processor's
8 bit addressing modes. And, because of the
"shadowing" by the RAM, the various bit instructions
seem to work fine. I bet the H8 designers left this
little hole just so these instructions could be used
on external devices.
Mark
"Kekoa Proudfoot" <kekoa@graphics.stanford.edu> wrote:
> Mark Riley <markril@hotmail.com> wrote:
> > So, I wrote a little test program that wrote a unique
> > pattern to all memory in the range 0xf000-0xfb7f.
> > I then inspected the memory, and sure enough the
> > entire pattern was intact. It turns out that the entire
> > range is RAM, even the address 0xf000!
>
> This is interesting. It makes sense that the memory backing these
> locations still works, but I never would have thought to try to use it. I
> will make a note of this on my pages.
>
> -Kekoa
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