RE: How to handle very fast repeating interrupts?

["Chris Zimman" <czimman@bloomberg.com>]

>  i'm using a lpx2214 board which is running with 60MHz.
> Now I have an interrupt every 12us (so 80k per second.)
> The Interrupt handler is very short. It has to read one
> word from the external memeory interface and store it into a
> buffer. This has to happen until the next interrupt will occure
> because otherwise data would be lost.
> Because it has to do so little but so often I'd like to
> avoid the whole interrupt management/routing eCos implements.
> I'd like to configure this interrupt as a FIQ and just want
> to jump to my ISR routine. What do I have to pay attention
> on when doing so?
> I'd write the routine in ASM and store the register I use
> to the stack. (Which stack will I use. The one of the current
> process?)

Not to get of topic, but are you running eCos w/o the scheduler?  Because if
you're not, I don't see how you are going to be able to keep up with the time
interval that you need.

Figuring 1.1 DMIPS/MHz, you have 0.015151515 us/instruction, giving you about
792 instructions per 12us interrupt period, without including any bus wait
states etc. or other losses in time.  Even one context switch from eCos for
whatever reason may cause you to lose data if you really do need to service
it every 12uS.

That said, I would suggest just pointing the FIQ vector directly, and
managing your own stack.  You could just carve out a piece of memory for
yourself (many ways to do this, depending on your application) and use that.

--Chris