Lpc2000

At 07:35 PM 3/1/05 +0200, Anton Erasmus wrote:

>On 28 Feb 2005 at 16:04, Robert Adsett wrote:
>
> >
> > At 10:15 PM 2/28/05 +0200, Anton Erasmus wrote:
> > >Does anyone have some example code for gcc for a nested timer
> > >interrupt ? I have googled a bit, and have found some discussion
> > >regarding the switching of modes from interrupt mode to system mode
> > >before re-enabling interrupts.
> >
> > Before you go too far make sure you've read the timer race conditions
> > errata.
>
>I am using the LPC2292, and there is no mention in the LPC2292 errata
>regarding timer problems.
>http://www.semiconductors.philips.com/acrobat/erratasheets/2292.pdf
>Can you maybe point me to the specific errata sheet that describes this ?

Take a look for Timer_issue.pdf in the files section (I'd post a link but 
that seems problematic).  I think this has not made the actual errata 
sheets yet and AFAIK has not been addressed in any of the new devices yet 
(that was certainly the case when I asked about the 213x).


>The idea is to set up a periodic interrupt of x milli-seconds. After the 
>interrupt
>has been acknowledged, interrupts are enabled again. If an overrun occurs, the
>interrupt routine will be interrupted, and I can then detect this and take 
>appropriate
>action as neccesary.

You expect the timer interrupt to take multiple milliseconds?  That's a 
pretty busy interrupt routine.  I'll take some measurements of the SPI 
interrupt I'm working on if you'd like a time comparison.

Hmm, I did some performance measurements on a polled timer for the 
lpc-newlib 
support. 
http://www.aeolusdevelopment.com/AppNotes/LPC210X/an-timerperformance.pdf

microsecond resolution, 12 microsecond minimum time, keeps track of time as 
long as it's polled at least once every few minutes.  The 12 microsecond 
time is the overhead required to deal with various overflow, underflow and 
scalings so it's doing a fair amount of work.  I wouldn't expect even a 
fairly busy timer routine to take the two orders of magnitude longer that 
would be required to overflow a multi-millisecond timer.

Robert

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