[ECOS] EDB7312(ARM720T) interrupts

Gary Thomas gary@mlbassoc.com
Fri Nov 7 21:14:00 GMT 2003

On Fri, 2003-11-07 at 14:01, Aaron Case wrote:
> Hello,
> I have a question about implementing interrupts with the rich eCos interrupt
> API with the limited ARM interrupt vector table.
> >From my experience, and as mentioned in the Massa test, the ARM architecture
> has only two vectors for interrupts(FIQ and IRQ) and the eCos API is
> implemented more readily for architectures that have multiple entries in
> their vector tables.
> It is therefore up to the software to look at the INTSR1/2/3 registers to
> determine the source of the interrupt.
> So when I create my 23 different interrupts, where is the most advisable
> place to decode the source of the interrupt. Ive considered having all the
> IRQ's share an ISR and each have a unique DSR identifiable through the data
> argument of the cyg_interrupt_create() call.
> Having all the interrupts share an ISR to decode the interrupt source SEEMS
> to be more processing than the ISR was intended to handle.
> If the aforementioned approach is not in vogue(or feasible), than could
> someone out there who has done this before and would be able to point me to
> a post or document that describes how to approach this implementation best.

On the ARM architecture, we assume that your HAL has a function 
"hal_IRQ_handler()" which will interrogate your hardware and return
a unique value (typically 1..N) indicating which of those interrupts
has just occurred.  Then there can be a potentially different ISR
for each interrupt.

Look at some of the ARM HALs to see how this is done.

Gary Thomas <gary@mlbassoc.com>
MLB Associates

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