Lpc2000

Bill Knight wrote:

> Kris
>   Thanks for spotting this.  It's the old spurious interrupt problem.
> The fix is to disable global interrupts around the first read-modify-write
> instruction.  Doing the direct write (U0IER = xxx) can still allow the 
> problem
> to happen.  What happens is the interrupt occurs and is recognized while
> the masking instruction is executing but before it has completed.  Then
> when the instruction does complete, the interrupt can't find the vector
> so uses the default.  So to fix:
>
[snip]

    Why should the direct write cause this problem?  The issue with 
read-modify-write makes perfect sense, but the write should be an atomic 
operation.  How would you get an interrupt between <nothing> and the write?

    --jc