Re: [f-cpu] Smooth Register backup issues...

[Martin Vahi <martinv@physic.ut.ee>]

>
> Or ARM. That's called swadow register. The problem with SRB is :
> - how do you handle nested interrupt ?
> - how do you "allocate" a new CMB ?
> - If saving is automatique even on very light it handler you must save all
> of the register.

  But would a "shadow stack" be a bad idea? Like, instead of
one shadow-register, there would be, let's say, 1000-level deep stack??
OK, it takes up some mount of silicon or some quantity of gates in the
FPGA case, but it should work somehow... And after the stack get's filled,
it's being automatically saved(and later retreived) to(from) some,
specially reserved region of the system's memory. All the housekeeping
would be the job for the memory management unit.
After all, the newest CPU's do have onboard
caches with sizes reaching atleast to 1MB. In the VHDL-code,
the ctack size can be stored in a variable, so, if anybody wants, he/she
set's it to 1, 10, 100, or what ever her/his hardware can afford.
  I'm a newby chip design's point of view, so, I hope You don't mind my
huge technical mistakes and I hope that my mistakes are getting
corrected.

Regards,
  Martin Vahi
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