Lpc2000

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@...] 
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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