>(1). Could somebody tell me what's different for SYSTEM mode and SUPERVISOR
mode
>for ARM7TDMI?
System mode is like user mode except all operations are permitted.
Alternatively,
System mode is like supervisor mode except you work with user mode
registers.
System mode is usually what supervisor mode falls into when it needs to
change
something in the user mode (because you can go back to supervisor mode
from
system mode. If you went to user mode, you'd be stuck there as user mode
can't change the mode back to supervisor).
(this is valid for any ARM core, by the way)
>(2). Does ARM7TDMI mplement a hardware mechanism to detect memory violation?
> I mean if I have a program that run in user mode nad the
program try
>to access the system mode's data.
> Can hardware tell me memory violation? Or I must have a mechanism
>in software to access the violation?
I am not sure you can implement any kind of protection that would be
purely
software. Anyway, all ARM7 cores have some sort of protection mecanisms.
The
details depend on the actual core (some have full fledged MMU, others
only
a basic protection unit). You should be able to find details on the
memory system for your particular core on ARM's site.
Cheers,
Y.
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