Lpc2000

In general, I'd say it is better to use global interrupt 
enable/disable than doing this in the VIC.

See http://www.arm.com/support/faqip/3677.html

IMHO, getting defualt IRQs is a way to clean up/detect spiruous 
activity rather than the normal way of doiing things.


--- In lpc2000@yahoogroups.com, "Curt Powell" <curt.powell@s...> 
wrote:
> Kris,
> 
> I added an assembler harness to accept the default irq, loaded up
> VICDefVectAddr with its address, and let it fly.  The default 
handler is
> being called periodically (it just prints a diagnostic and returns) 
so
> it appears to be working- I can't give a definitive answer until it 
runs
> for a couple of hours, but so far so good.  Thanks so much for your
> insight.
> 
> Curt
> 
> -----Original Message-----
> From: microbit [mailto:microbit@c...] 
> Sent: Monday, April 19, 2004 9:28 PM
> To: lpc2000@yahoogroups.com
> Subject: Re: [lpc2000] Disabling/enabling interrupt causing a data 
abort
> 
> 
> 
> > All,
> >
> > I have  a process receiving data from an rf modem (currently 
running 
> > at 4800 baud) using EXTINT2.  The data is clocked into a byte and 
> > complete bytes are placed into a temporary holding buffer.  The 
main 
> > thread periodically pulls the data from the holding buffer into a 
> > larger buffer in order to perform operations on it (bit shifts, 
etc.).
> 
> > I've been receiving data abort exceptions periodically on this 
> > process.  Turns out that I was disabling EXTINT2 prior to pulling 
data
> 
> > from the temp buffer and reenabling EXTINT2 immediately 
afterwards.  
> > This disabling/enabling is what is causing the exception, i.e. if 
I 
> > remove the disable/reenable the problem goes away as far as I can 
> > tell.  I am disabling by writing 0x10000 to VICIntEnClr 
(0xfffff014), 
> > enabling by writing 0x10000 to VICIntEnable (0xfffff010).
> >
> > Two questions:
> >
> > 1.  Is this the correct approach for disabling/reenabling EXTINT2? 
2.
> 
> > Can anyone venture a guess why disabling/enabling EXTINT2 would 
cause 
> > a data abort?
> 
> I had a similar thing happening with circular buffers for UART
> operation. When you're enabling/disabling INTs, the VIC apparently 
can
> produce "spurious" INTs, in that an interrupt can occur while it is
> being disabled - hence ...  Default_IRQ() has to handle it.
> 
> If you don't have a proper vector handler there that handles the
> interrupt going thru the default channel, your code might be causing
> execution to land in the land of lala, somewhere. (thus the Dabort) 
My
> suggestion (FWIW) : 1. check you have a proper default_IRQ handler
> present. 2. put then a breakpoint on it, and see if you're hitting 
the
> default IRQ. 3. Then you can either handle the exception in 
default_IRQ,
> or enable/disable INTs globally to avoid it.
> 
> Try that ?
> 
> Cheers,
> Kris
> 
> 
> 
> 
>  
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