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Re: Robust configuration memory
Piotr Wyderski wrote:
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   Yes; use an ANALOG sum, the rest of that solution should be obvious.


Re: Robust configuration memory
On Sun, 18 Feb 2018 11:20:45 +0100, Piotr Wyderski

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It should be pretty simple with a CPLD.  You could also compare on a
bit-by-bit basis, which shouldn't be too difficult, even limited to
unit logic.  

Put the redundancy in the FPGA.  If a bit of the configuration memory
is in error, it's unlikely to be wrong in each of the redundant parts.

You could use the FPGA to verify the contents of the flash, after
configuration but before (application) enable.  

There are all sorts of possibilities but a lot depends on unspecified
requirements.

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Not enough information.

Re: Robust configuration memory
snipped-for-privacy@notreal.com wrote:

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Which, again, is nowadays based on flash. Vicious circle.
I don't want its configuration evaporate either.

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And this is the correct approach: bit-by-bit voting on a serial stream.
A single majority gate of still unknown implementation will suffice.

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What do you mean? An FPGA won't boot from a corrupt bitstream.
Do you mean many FPGAs?

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But the flash can die just before/during configuration.

    Best regards, Piotr

Re: Robust configuration memory
On Sun, 18 Feb 2018 16:46:30 +0100, Piotr Wyderski

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OK, what error in the "checker" is going to give you an almost-good
flash image for the target device?  What I'm suggesting is an
"equivalence" gate in the configuration stream.

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Not majority.  Just equal, if all you care about is "valid"/"not
valid" configuration.  If you want TMR, then you need voting, which is
a little more difficult.  But in this case, you probably need TMR in
the application, too.
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I thought this was your problem.  If it doesn't boot, problem solved.

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Sorry, I thought this was the desired outcome.

Re: Robust configuration memory
snipped-for-privacy@notreal.com wrote:

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OK, but no, the desired effect is to work correctly for as long
as possible, even knowing about memory errors. Hence the RAID5
reference. I assume a configured FPGA works correctly, the problem
is to provide it with a good bitstream, as I expect the flash chips
to be least durable. Putting 3 instead of 1 doesn't increase
complexity that much, but can greatly increase reliability.

 > If it doesn't boot, problem solved.

In that case, don't most FPGAs already have all the needed checksum  
circuitry inside?

    Best regards, Piotr

Re: Robust configuration memory
On Sun, 18 Feb 2018 17:50:53 +0100, Piotr Wyderski

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In that case, a CPLD should work.  If the CPLD doesn't configure
properly, there is little chance that it'll pass a configuration
stream with a proper checksum.
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OK, then use that fact.

Re: Robust configuration memory
On 18.2.18 17:36, snipped-for-privacy@notreal.com wrote:
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Using a FPGA is going to a circular definition: The FPGA has
some kind of semi-permanent memory for the configutarion.

I see two possibilities:

  - Create the voter from discrete gates,
  - Use a processor to handle the redundancy, and get a
    problem of the processor code.

I once had a customer with an instrument with calibration data
inside an EEPROM. It had the habit of losing the calibration
occasionally, so in the next generation, a triple redundancy
calibration store was made in the software. During years of
use of hundreds of instruments, there was not a single case
of redundancy correction. It was proven that the problems with
the old generation were from flaky software.

--  

-TV



Re: Robust configuration memory
Piotr Wyderski wrote:
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   Punched paper tape or cards?


Re: Robust configuration memory
On 20.2.18 08:22, Robert Baer wrote:
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They were prone to tearing. I still remember disassembling and
re-assembling one card reader with a hefty card jam.

--  

-TV


Re: Robust configuration memory
On Mon, 19 Feb 2018 22:22:43 -0800, Robert Baer

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I'll take plastic.

Re: Robust configuration memory
On Wednesday, February 21, 2018 at 8:17:04 AM UTC+11, snipped-for-privacy@notreal.com wrote:
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Not all plastics are created equal. Teflon (PTFE) is close to indestructible (until you get it hot enough) but it does flow.

http://www.parrinst.com/products/sample-preparation/acid-digestion/design-features/the-nature-of-ptfe/

--  
Bill Sloman, Sydney

Re: Robust configuration memory
snipped-for-privacy@notreal.com wrote:
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    MMMmmm with embedded chip..

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