Lpc2000

At 04:38 AM 4/15/06 +0000, jayasooriah wrote:
>--- In lpc2000@yahoogroups.com, "John Heenan" <l10@...> wrote:
> > Interrupts can be disabled without interworking on the LPC2xxx
> > through the VIC registers while in Thumb mode. I have brief notes in
> > preperation to be submitted as a file to the group.
>
>Yes but there are costs.  The first (and prohibitive as I have argued)
>is that the implementation of VIC on the LPC family (based on PL190
>design) causes spurious interrupts to be generated when you do this.
>
>The second (probably more insidious) is that the distinction between
>of user and system modes appear to have been lost in the process.

Is this distinction actually useful?  If user mode actually provided memory 
protection or I/O protection mechanisms I could see a use.  As it is the 
only real use I see for the mode distinctions is the register 
saving/shadowing on interrupts.  The inability to manipulate the interrupt 
flags appears to just be an annoyance/relic held over from ARM's larger 
general purpose computer roots.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/