Lpc2000

At 01:34 PM 5/10/04 -0400, you wrote:
>I don't understand why I need to look at VICFIQStatus.  Can't I just put a 
>"mov pc,[pc,#-0xfec]" at address 0x1c? As long as my IRQ and FIQ interrupt 
>service routines know what to do, it seems like this should work without 
>having to go further to determine the source of the interrupt.

The  VICVectAddr register only gives the address of the highest priority 
IRQ, not the FIQ.

>In fact, in non-preemptive designs, I don't know why you wouldn't make 
>everything FIQ.

Well, you lose the benefits of the semi-vectoring you get with the 
IRQ.  Also the assumption of the FIQ is that you have one (or a few) 
interrupt(s) that you want to preempt the others on a high priority, low 
latency basis.  So the FIQ gets a higher priority response and several more 
shadow registers.

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