Continous eeprom checksum microcontroller

Hans-Bernhard Broeker wrote:

> Vishal <vishalpatil_89@yahoo.co.in> wrote:
> 
>> Is it worth doing ??
> 
> The answer to this, like to all truly interesting questions, is: "It
> depends".
> 
> In the case at hand, it depends on things like:
> 
> 1) What's more likely: the EEPROM to fail in operation, but without
> triggering a watch-dog reset or other safeguards; or your EEPROM
> checking routine itself to fail, for some unrelated reason?
> 
> 2) Can you afford the extra CPU load for doing this?
> 
> 3) Does it pay?  Or is it even required, maybe?
> 
> And remember: be careful asking questions if you can't do anything
> about the answers.  In other words, if the only known cure is worse
> than the disease, it may not be worth diagnosing the disease.
> 
> --
> Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
> Even if all the snow were burnt, ashes would remain.

It can be useful to ask the question even if nothing can be done about the 
fault condition other than letting the system die (hopefully with the 
outputs all set to a safe state).

As for errors in the checking code, this should be simple enough that it 
remains within the scope of Fagan Inspections to find out if this is flawed 
or operating correctly. There are other sanity checking measures that can 
be taken to ensure the system is generally behaving too.

-- 
********************************************************************
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Thanks.am doing it.Cant afford to neglect a wrong calibration.
Thanks.
 


"Paul E. Bennett" <peb@amleth.demon.co.uk> wrote in message news:<cc9jtt$hvv$1$8300dec7@news.demon.co.uk>...
> Hans-Bernhard Broeker wrote:
> 
> > Vishal <vishalpatil_89@yahoo.co.in> wrote:
> > 
> >> Is it worth doing ??
> > 
> > The answer to this, like to all truly interesting questions, is: "It
> > depends".
> > 
> > In the case at hand, it depends on things like:
> > 
> > 1) What's more likely: the EEPROM to fail in operation, but without
> > triggering a watch-dog reset or other safeguards; or your EEPROM
> > checking routine itself to fail, for some unrelated reason?
> > 
> > 2) Can you afford the extra CPU load for doing this?
> > 
> > 3) Does it pay?  Or is it even required, maybe?
> > 
> > And remember: be careful asking questions if you can't do anything
> > about the answers.  In other words, if the only known cure is worse
> > than the disease, it may not be worth diagnosing the disease.
> > 
> > --
> > Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
> > Even if all the snow were burnt, ashes would remain.
> 
> It can be useful to ask the question even if nothing can be done about the 
> fault condition other than letting the system die (hopefully with the 
> outputs all set to a safe state).
> 
> As for errors in the checking code, this should be simple enough that it 
> remains within the scope of Fagan Inspections to find out if this is flawed 
> or operating correctly. There are other sanity checking measures that can 
> be taken to ensure the system is generally behaving too.

Hi, one more(i am getting lazy,cant dig out on my own ;) )
One of the generic requirement by my customer asks for a register
refresh on continuous basis again. I am using a hc12 micro. My que is
the same  .. is it worth it ?? never implemented such a thing
before...

"Paul E. Bennett" <peb@amleth.demon.co.uk> wrote in message news:<cc9jtt$hvv$1$8300dec7@news.demon.co.uk>...
> Hans-Bernhard Broeker wrote:
> 
> > Vishal <vishalpatil_89@yahoo.co.in> wrote:
> > 
> >> Is it worth doing ??
> > 
> > The answer to this, like to all truly interesting questions, is: "It
> > depends".
> > 
> > In the case at hand, it depends on things like:
> > 
> > 1) What's more likely: the EEPROM to fail in operation, but without
> > triggering a watch-dog reset or other safeguards; or your EEPROM
> > checking routine itself to fail, for some unrelated reason?
> > 
> > 2) Can you afford the extra CPU load for doing this?
> > 
> > 3) Does it pay?  Or is it even required, maybe?
> > 
> > And remember: be careful asking questions if you can't do anything
> > about the answers.  In other words, if the only known cure is worse
> > than the disease, it may not be worth diagnosing the disease.
> > 
> > --
> > Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
> > Even if all the snow were burnt, ashes would remain.
> 
> It can be useful to ask the question even if nothing can be done about the 
> fault condition other than letting the system die (hopefully with the 
> outputs all set to a safe state).
> 
> As for errors in the checking code, this should be simple enough that it 
> remains within the scope of Fagan Inspections to find out if this is flawed 
> or operating correctly. There are other sanity checking measures that can 
> be taken to ensure the system is generally behaving too.

Vishal <vishalpatil_89@yahoo.co.in> wrote:

> One of the generic requirement by my customer asks for a register
> refresh on continuous basis again. I am using a hc12 micro. My que is
> the same  .. is it worth it ?? 

They ask for it, they pay for it --- that's obviously worth something.

But to be sure, ask your customer.  If they thought of requesting such
a feature by themselves, odds are they have reasons.  

Seems your customer knows more about the project than you do --- this
might be a danger to your long-term business prospects if you don't
get up to speed fast.

Vishal <vishalpatil_89@yahoo.co.in> says...

>Hi, one more(i am getting lazy,cant dig out on my own ;) )
>One of the generic requirement by my customer asks for a register
>refresh on continuous basis again. I am using a hc12 micro. My que is
>the same  .. is it worth it ?? never implemented such a thing
>before...

I would ask for the justification behind the assumption that the
place where you get the data to be written to the register is less
likely to be corrupt than the data already in the register is. 

You might wish to look at my resume (see below) and then call me 
in for a one-day requirements review.

-- 
Guy Macon, Electronics Engineer & Project Manager for hire. 
Remember Doc Brown from the _Back to the Future_ movies? Do you 
have an "impossible" engineering project that only someone like 
Doc Brown can solve?  My resume is at http://www.guymacon.com/ 
  

OK , I will rephrase the question.Is the register area of a micro more
reliable than that of static RAM? I got this  guideline doc
(requirement doc as they call it)
which asks for reg refresh.Since the document is quite old , i was
wondering if it makes sense to do reg refresh.

Thanks.


Anton Erasmus <nobody@nowhere.net> wrote in message news:<o7ffe0tdpfv90820f3cfj4fsei440o7co9@4ax.com>...
> On 2 Jul 2004 21:34:16 -0700, vishalpatil_89@yahoo.co.in (Vishal)
> wrote:
> 
> >Hi, Anybody come across continous background checksum tests on
> >eeprom?? Is it worth doing ??
> 
> Hi,
> 
> The most important thing when asking if any sort of error checking is
> worthwhile, is what do you do if the answer is that there is a problem
> . If you cannot do something practical/realistic with the answer, then
> do not bother. 
> Anything that can actually be checked and realistically be used to
> improve reliability is worthwhile.
> 
> Regards
>    Anton Erasmus

> Is the register area of a micro more reliable than that of static RAM?
As data is continually changing there keeping a checksum 
is not practical. 

> I got this guideline doc which asks for reg refresh.
Some old and new mainframes have ECC errorcorrection for 1 or 2 bits
per word for the external RAM. A background task ( "scrub" ) is
reading & writing the memory thereby preventing 1 and 2 bit errors
that can be corrected building up to 3 bit errors that cannot
be corrected. 
For that "refresh" of external RAM one would have to implement 
the ECC in software. For registers in the controller 
not practical either. 

MfG JRD

On Tue, 06 Jul 2004 08:06:38 +0200, Rafael Deliano
<Rafael_Deliano@t-online.de> wrote:

>> Is the register area of a micro more reliable than that of static RAM?
>As data is continually changing there keeping a checksum 
>is not practical. 

It is fully practical (for the chip maker) and it has been used at
least in the past. On some ECL (Emitter Coupled Logic) processors,
which definitely are not sensitive to radiation, had parity bits on
internal data paths and internal scratch pad memories. 

Even on some ALU operations it makes sense to calculate the parity.
For instance, on addition, count the parity on both the operands
separately, sum the two parity bits, calculate the parity of the
parity sum (full adder) and compare it with the parity calculated from
the ALU sum parity.
  
>> I got this guideline doc which asks for reg refresh.
>Some old and new mainframes have ECC errorcorrection for 1 or 2 bits
>per word for the external RAM. A background task ( "scrub" ) is
>reading & writing the memory thereby preventing 1 and 2 bit errors
>that can be corrected building up to 3 bit errors that cannot
>be corrected. 

This is currently used when cosmic radiation flips individual memory
cells in various satellites.

Paul

Vishal <vishalpatil_89@yahoo.co.in> says...

>OK , I will rephrase the question.Is the register area of a micro more
>reliable than that of static RAM? I got this  guideline doc
>(requirement doc as they call it)
>which asks for reg refresh.Since the document is quite old , i was
>wondering if it makes sense to do reg refresh.

It is the job of the person making the request to prove any reliability
differences between register and RAM. It is your job to indentify any
outdated requirements. A guideline is not a requirement and a requirement
is not a guideline. You really, really need an experienced embedded systems
engineer to do a one-day requirements review and later to do a one-day
design review. You are in dire need of help. The cost of an airplane ticket
and of hiring a consultant is cheap compared to the cost of project failure,
and I fear that project failure is where you are headed. Get help.

-- 
Guy Macon, Electronics Engineer & Project Manager for hire. 
Remember Doc Brown from the _Back to the Future_ movies? Do you 
have an "impossible" engineering project that only someone like 
Doc Brown can solve?  My resume is at http://www.guymacon.com/ 

I did some radiation effects testing on PIC's a while ago. From
memory on the particular PICs I tested, random singlebit errors 
(soft errors) were just as likely in SRAM as they are in registers.

PROM/EPROM is more reliable for soft errors; but they develop 
hard errors over time (but it took lot of exposure).

The test involved doing running checksum tests on program PROM,
registers, checkpoints to catch flipped PC bits, and testing
for watch dog resets. One version of the test also tested serial
EEPROM. The chips were put in a beam line and exposed until none
of them worked.

For high reliability applications, it's a good idea to program
very defensibly and use the watch dog reset. Bascially, expect
single bit errors in calculations, flipped bits in registers and
SRAM and the PC.

There was an article reference (I think slashdot or embedded.com),
that talked about the programming the space shuttle computer. Much
of the effort is lots of code reviews and talking about what ifs.
E.g. if I detect an error here, what do I do.

See ya, -ingo


In article <8c90af46.0407052018.18368ef@posting.google.com>,
Vishal <vishalpatil_89@yahoo.co.in> wrote:
>OK , I will rephrase the question.Is the register area of a micro more
>reliable than that of static RAM? I got this  guideline doc
>(requirement doc as they call it)
>which asks for reg refresh.Since the document is quite old , i was
>wondering if it makes sense to do reg refresh.
>
>Thanks.
>
>
>Anton Erasmus <nobody@nowhere.net> wrote in message
>news:<o7ffe0tdpfv90820f3cfj4fsei440o7co9@4ax.com>...
>> On 2 Jul 2004 21:34:16 -0700, vishalpatil_89@yahoo.co.in (Vishal)
>> wrote:
>> 
>> >Hi, Anybody come across continous background checksum tests on
>> >eeprom?? Is it worth doing ??
>> 
>> Hi,
>> 
>> The most important thing when asking if any sort of error checking is
>> worthwhile, is what do you do if the answer is that there is a problem
>> . If you cannot do something practical/realistic with the answer, then
>> do not bother. 
>> Anything that can actually be checked and realistically be used to
>> improve reliability is worthwhile.
>> 
>> Regards
>>    Anton Erasmus


-- 
/* Ingo Cyliax, cyliax@ezcomm.com, Tel: 812-391-0895 */