Lpc2000

If your reset can go hi before the 1.8V supply has been stable long 
enough for the oscillator to stabilize, you will definitely have a 
problem.  Basically, the reset circuit must monitor the 1.8V supply, 
even though it must drive a 3.3V input on the processor.  (LPC213x 
series, with internal 1.8V regulator, does not have this problem.)

However, I still don't understand why a subsequent valid reset 
signal, after all supplies have long been stable, should not restore 
operation.  Since you are able to re-create the problem when running 
from debugger, you should be able to find the cause by single 
stepping.  Is there some register which is not at its "reset state", 
when you start execution from 0?  Typically, your code runs for a 
while before the JTAG grabs control - and your code may have modified 
some registers.  Personally, I find it good practice to explicitely 
set all registers to their "reset state" in the boot code.  Then you 
can start execution from 0, without worrying what came before - 
provided MEMMAP is set to properly (i.e.: not pointing to FLASH - 
which may not be initialized).

 

--- In lpc2000@yahoogroups.com, "moostieuk" <moostieuk@y...> wrote:
> 
> Lots of decoupling on all the rails.  I can't remember what the 
> reset time is, but it's much longer (like 10 times or something - 
> can't tell you as I'm not at work now!) than the spec says - 
> Although the reset chip driven from the 3.3V, so it's possible that 
> there is a problem there.  We'll check it out tomorrow.
> 
> --- In lpc2000@yahoogroups.com, Robert Adsett <subscriptions@a...> 
> wrote:
> > At 05:13 PM 1/19/05 +0000, you wrote:
> > >Check your power up reset signal length, it should be at least 
> 10ms
> > >(AFTER V18 is stable, check this).  If it is shorter than this 
the
> > >processor may enter an "unknown state".
> > 
> > Also what's your decoupling like?  Marginal decoupling could give 
> symptoms 
> > like this.
> > 
> > Robert
> > 
> > 
> > " 'Freedom' has no meaning of itself.  There are always 
> restrictions,
> > be they legal, genetic, or physical.  If you don't believe me, 
try 
> to
> > chew a radio signal. "
> > 
> >                          Kelvin Throop, III