Lpc2000

--- In lpc2000@yahoogroups.com, "Lewin A.R.W. Edwards" <larwe@l...> 
wrote:
> 
> > I take it this came from the ARM2/3 days when there was one 
physical
> > IRQ to the CPU and a peripherial handled combining IRQs?
> 
> Huh? What do you mean "from the ARM2/3 days..."? There are still 
only
> two interrupts on the ARM7 (ARM4 core) - FIQ and IRQ. Vectoring of 
IRQs
> is handled by a peripheral.

The vectoring is handled by the VIC which is a peripheral yes, but 
the nature of how the VIC works, together with the way the core 
works, opens up some holes where there spurious interrupts can show 
up.

Whether this is a bad design is open to interpretation, but it comes 
down to being one of those compromises we encounter. ie. I'm sure the 
ARM folk could have added interlocking etc to prevent spurious 
interrupts from happening, but that would force a tighter coupling 
between the VIC and the core. It would probably also have caused 
performance implications (eg. pipeline flushing everytime there is an 
interrupt).

-- Charles