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Re: Few questions on embedded stuff

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capacitor,
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What does "4-digit improvement in soft error rate" mean?  Failure rate
1/3000 of comparison RAM?  What is the approximate failure rate of
conventional uncorrected SRAM?  of the new technology?  At what flux is
SRAM immune to radiation errors?  What is the safety margin with respect
to normal background radiation?  How does this compare to memories with
larger processes (not just previous 0.13 um)?

Thad

Re: Few questions on embedded stuff
Hi Ed,

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Absolutely agree. Even rad hard stuff will have a chance to fail. Not
using a WDT is like driving around without a safety belt. Some of us
might live to be 90 that way, others not. All it takes is a tire blowing
at 65mph.

What I don't like are designs that rely on WDT for regular operation.

Regards, Joerg

http://www.analogconsultants.com

Re: Few questions on embedded stuff
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OTOH, some of us drive 90mph and hope to reach 65.  ;-)

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Yes, and I think that's always the fear of using WDT's -- that they'll
be abused.  Also, one participant in this thread already noted that a
WDT is most useful if enough of the context is saved to be able to
forensically analyze what went wrong.  It's a technically sound comment,
but it's not always possible in the case that an external WDT is used
and tied to the microprocessor's reset line.  In many cases, the reset
itself wipes out all traces of evidence and makes diagnosis impossible.
  In such cases, and depending on the application, it may be preferable
for the device to fail visibly than to reset and continue quietly.  Like
most engineering, it requires an analysis of the tradeoffs for the
particular problem at hand...

Ed



Re: Few questions on embedded stuff
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It does not have to be a gamma ray.

In an ancient existence I used AMD87c521 (IIRC) devices and as I had
to keep UV erasing the parts and being a typical lazy recent graduate
could not be bothered to cover up the erase window.  The parts worked
fine through the start of the development but as the year went on I
started to get sone peculiar failures where the processor went off
with the faeries.  Turned out that the brighter sunlight in the summer
caused the device RAM to be corrupted during the run.  (Yes I worked
in a development lab with REAL WINDOWS ;-).  Bill hadn't even got
round to version 3.1 in those days :-D )

S-V

Re: Few questions on embedded stuff
On 29 Jun 2004 07:07:17 -0700, sacre snipped-for-privacy@hotmail.com (Sacre Vert)

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One of my previous colleagues told the story of where they proudly
demoed the first prototype of a fairly large Servo Amp for the client.
The device used a mcu with EPROM, and of course the window was
uncovered. Someone took a photo while it was being demoed, and the
flash caused the MCU to go haywire, and needless to say the whole
prototype went up in smoke with nice loud bangs.

Regards
   Anton Erasmus


Re: Few questions on embedded stuff
snipped-for-privacy@nowhere.net says...
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As I recall, the Motorola HC705P6 in the ceramic/windowed package would
not even blank check if the window was not covered and would do strange
things in operation if the window was not covered.  

         Jim

Re: Few questions on embedded stuff

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We once had an engineer who ran a phototransistor driving a 74HC input
off of a 12V supply with no series resistor.  He reasoned that the LED
could never provide enough light to saturate it enough to exceed the
current specs for the photoransistor or the input.

We replaced hundreds of units after users powered them up with the
cover off and sunlight coming in through a window...

--
Guy Macon, Electronics Engineer & Project Manager for hire.
Remember Doc Brown from the _Back to the Future_ movies? Do you
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Re: Few questions on embedded stuff
Anton, did you ever see it the other way around? Where an EPROM window
starts an orange glow beneath the glass? That was really spooky.

Regards, Joerg

http://www.analogconsultants.com

Re: Few questions on embedded stuff
$ snipped-for-privacy@newssvr27.news.prodigy.com:

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As I recall, I plugged in a 128KB UV EPROM backwards once, and it lit up
for a short while.  The amazing thing was that it still worked after that.
Mind you, I wouldn't place any bets on it's life expectancy.

--
Richard

Re: Few questions on embedded stuff

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http://groups.google.com/groups?selm38%0b33d4.322189483%40192.168.2.34&output=gplain

Regards,

                               -=Dave
--
Change is inevitable, progress is not.

Re: Few questions on embedded stuff
oN 29-Jun-04, Dave Hansen said:

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LOL! At best, if the wire was not damaged, I would expect some (or all)
of the operating parameters of any still-functioning parts to have been
affected.

--
Bill
Posted with XanaNews Version 1.16.3.1

Re: Few questions on embedded stuff

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You were lucky, that was really rare. Here, most EPROMs died with a
nice flashlight effect.

Andreas
--
You are not allowed to call yourself an engineer until you've "smoked"
at least 100 circuits *and* understand why they "smoked" ;-)
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Re: Few questions on embedded stuff

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I never tried to reprogram it, and did toss it out shortly afterwards,
but, at the time it was plugged in, it already contained our executable,
and when turned around, it did function, including passing the crc test
of the executable image.

--
Richard

Re: Few questions on embedded stuff
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You're right.  More usual is an alpha particle, but I wanted to sidestep
the issue of packaging material choices (e.g. solderless parts with less
  lead).

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I put a part backwards into my programmer and enjoyed the brief purplish
glow of sunset from behind the tiny erase window in my otherwise
windowless lab.  Thank you for putting the sunshine in.  ;-)

Ed


Re: Few questions on embedded stuff
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Wouldn't that mean that you have race condition(s) in your design,
and that you are relying on the automatic reboot to correct the
deficiency?

Re: Few questions on embedded stuff

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Yes it does, which is why all the remote robots have a WDT:
sometimes nature's timing is out of spec (or at least out of the
range that you thought was sensible to test!) - RM


Re: Few questions on embedded stuff
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  Missing in this discussion is an analysis of what SORT of WDOG to use :)
  I have worked on systems where a device reset pin was better called a
Reset-request (sic), and where a pin RESET was NOT enough to cause
system recovery from deliberate induce crashes.  These were NOT SW
lost-state failures, but were external electrical energy events.
  If you have a chip with a "reset-request" pin, then full power
removal/recycle is needed.
  I have also seen time-window watchdog devices, and also Wdogs with
boot-stretch timeouts .....
-jg


Re: Few questions on embedded stuff
On Mon, 28 Jun 2004 11:55:52 +1200, Jim Granville

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   What chips have a "reset-request" pin instead of reset?

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Re: Few questions on embedded stuff

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  It is, of course, not labeled as such, (and the IC manufacturers
will usually not clearly describe it as such!), but you can find hints
in the data, and aggressive testing (ESD and non-monotonic brown outs)
can readily show such devices.
  Quite often, digital chips have a simple, FET+CAP power on reset
internally, and that can deliver different reset signals from the RST pin.
-jg


Re: Few questions on embedded stuff
On Mon, 28 Jun 2004 14:03:18 +1200, Jim Granville

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   Oh, I see. I do recall chips that have the "feature" of being able
to differentiate an internally generated "power-on reset" from
"reset-pin reset."

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