Lpc2000

At 02:06 AM 5/1/2006 +0000, jayasooriah wrote:
>--- In lpc2000@yahoogroups.com, Robert Adsett <subscriptions@...> wrote:
>
> > I prefer that the device get back to a known good state as soon as
> > possible.  Keeping the output in the (possibly bad) state it was in is
> > definitely the last thing I want in that eventuality.  That can be
>done in
> > SW but it does increase the latency.
>
>If your software is in deadlock, and output is in bad state, and you
>want to set it back, it would take you no more than a few microseconds.
>
>What is your watchdog timeout?  Milliseconds?  Seconds?  What is a few
>microsecond latency in comparision?
>
>Would you still say latency is an issue?

Seconds is way too long.  Mostly I agree with you but there is a certain 
comfort in not having to rush around resetting I/O but instead deal with 
other setup issues.  As I said earlier it's unlikely this would be a 
deciding factor for me in choosing micros.

>As for other processers doing this, sure it is okay to do this if
>there are no ill side effects.  In the case of LPC we know there are
>ill side effects.

Only if you use a variant with an external bus and try to use boot0 and 
boot1 as I/O. I don't think using the boot lines as I/O is a good idea, but 
that doesn't make the watchdog bad.  You do have the choice here as how to 
implement the system  It's up to you to do so and part of that is handling 
the reset sources properly including dealing with how I/O is dealt 
with.  Yes there could be a few more warnings in the user manual and data 
sheets.

>I had to use watchdog on COP8 processor once in telephone hardare to
>meet failsafe requrements.  It was not acceptable if the current call
>in progress was interrupted by a failsafe recovery triggered by the
>watchdog timer.

Different system, different requirements.

>Any procesor that does a full reset will not meet such requirements.

Which means that the LPC, the ST10 and many other processors won't meet 
those requirements.  In those circumstances you choose a different micro.

I'm not saying the LPC is a paragon among microcontrollers but neither is 
it irredeemable.  Most of the features you are spending so much energy 
decrying are commonplace on other microcontrollers. Dealing with them is 
common practice in this field.

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
http://www.aeolusdevelopment.com/