Continous eeprom checksum microcontroller

On Fri, 16 Jul 2004 00:54:44 -0700, Guy Macon
<http://www.guymacon.com> wrote:


>Paul Keinanen <keinanen@sci.fi> says...
>
>>These circuits are exercised each time any program executes, not just
>>when the checker routine is executed
>
>You think that a eeprom checksum task exercises the same circuits
>(registers, RAM, instruction decoders, EEPROM reading amplifiers...)
>that a do nothing task exercises?

Any system using interrupts will use quite a lot of the CPU resources.
In a RTOS you may have to run the scheduler after each interrupt to
see, if any high priority task became runnable due to the interrupt.

Thus, the job done by interrupts and scheduler is similar to that of
the EEPROM checker, even if the high priority tasks do nothing for a
long time.

I agree that the null task could be as trivial as a single
WaitForInterrupt instruction or a single branch to itself instruction,
which will exercise only a small part of the CPU, but this is not the
point.

Paul
    

Ignacio G.T. wrote:

[%X]

>>When you say that some systems have "no safe state" I am taking it that
>>you are speaking of individual sub-system modules that are one of a
>>redundant set so that failure of an individual sub-system module does not
>>have an impact on the overall safety of the whole system.
>
> I think the OP wouldn't agree on this definition (at least, I do not). One
> example of a system with a safe state is a railway interlocking, where the
> safe state is "all signals red, all points motionless": if a catastrofic
> error is diagnosed by a properly designed interlocking, you can always go
> to that state, where a minimum harm is guaranteed for trains and
> passangers.
> 
> On the contrary, an avionic system has not an evident safe state. Just
> imagine stopping the jets in case of panic...

I think you may have missed the point of my paragraph above. I am quite 
aware that no-one should tolerate things like an avionics system failing 
which is why I expect to see redundant sub-systems and voting mechanisms in 
such overall system structures. I do not consider avionics as one amorphous 
system but as a collection autonomous sub-systems withj back-up measures, 
reduncant sub-systems and compliance voting in a mesh that supports the 
full and continuing functioniung of the air/space craft.

As I stated, I have never worked in avionics but I try and stay abreast of 
techniques used there just to be aware of methods that may prove useful to 
me in my own domains (energy, transport and medical)..

-- 
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