Lpc2000

--- In lpc2000@yahoogroups.com, "brendanmurphy37"
<brendanmurphy37@...> wrote:
>
> --- In lpc2000@yahoogroups.com, "jayasooriah" <jayasooriah@> 
> wrote:
> > The user (like you) can set everything back to the reset state if 
> they so wished. 
> 
> Maybe if you had experience of a peripheral that can't be reset by 
> software you'd have a different view.

I would not change my view.  I would move on to a processor chip that
does not have this type of nastiness.

> The UARTs in some members of 
> the NEC V850 familiy have this "feature": they can get locked into 
> modes that only a hardware reset can clear.

If NEC recommends that you needs to use the watchdog timer to recover
from UART lockups that cannot be recovered by software, my advice to
you is to move on to another vendor.  The market is full of alternatives.

> By definition (unless it's being used to implement something like 
> a "soft reset" feature), when a watchdog has expired the system is 
> in an unusual and unknown state.

This begs the question as to the purpose of the watchdog timer.  To
break deadlocks in hardware (CPU, UARTs, etc) or software?

If a manufacture tells you it is to break hardware deadlocks, my
advice is that you move on to one that does not.

> I'd much rather a system that the 
> watchdog is guaranteed to get it back into a known, initial state 
> than run the risk of being the first to discover the peripheral and 
> mode that can't be recovered by software.

If a peripheral locks up and cannot be recovered by re-initialisation,
it is time to move on.

Having to reset or power cycle such purposes is something most designs
will not tolerate.

> The Philips part (and most 
> others for that matter) gives this guarentee: a watchdog reset is 
> the same as a power-on or hard reset (other than the reset source 
> identifier). That's just the way I like it, thanks.

This "most others for that matter" is yet another ambit claim it
seems.  I looked at both SAM and OKI and these designs appear to have
put more thought into how one uses the watchdog.

I have already explained how OKI is different.  Here is an excerpt
from SAM user manual:

<quote>
The Watchdog Timer can be used to prevent system lock-up if the
software becomes trapped in a deadlock.
...
It can generate a general reset or a processor reset only.
</quote>

Considering Philips calls the LPC an alternative to SAM and OKI parts
whose hardware features they mimics by software, it makes sense to
compare limit comparisons with these.

Jaya