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Contributor
Contributor
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Registered: ‎05-03-2014

seu estimator

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I just started using the SEU Estimator 2018.3.  

Question: Under Mitigation Settings, there is just SEM IP and Readback CRC. I don't see None. In other words, I would like to see my FITs, mitigation ON and mitigation OFF. This is the motivation for doing all the work to get the SEM IP to work.

The FITs and MTBU in the upper right corner, are these before or after mitigation?

On the other hand, the Mitigation Settings don't seem to make any difference anyway. Does this function work?

 

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277 Views
Registered: ‎09-17-2018

Re: seu estimator

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Answers:

1. No.  Regardless of settings, failures will occur related only to your design, and how many bits are crtical to its function.

2.  They allow you to repair upsets, which if you designed your circuits properly, will allow your design to work properly (again).

As an example, if your system is the IR landing camera on a commercial airliner, if an upset occurs, you can signal the pilots to pull up and go around (this is an actual use case, in service and used).  I believe you would agree that trusting a potentially flawed landing system is not a good thing.Fail safe systems fail by failing to faul safely.  That said, one should not allow that to happen.  The SEM IP is just one way to meet the requirements in your system design (like landing safely).  In 2 above, the SEM IP will allow the pilot to go around after an upset, and land safely.  Of course you must inject errors to prove it all works.

The SEM IP is in effect required by any safety critical system following IEC 61508.  Xilinx FPGA devices are the only ones with this feature, proven to work, and in common use since Virtex 5.  If there is no RBCRC error, then the decision made by the design is accurate, and you are safe... 

l.e.o.

 

4 Replies
290 Views
Registered: ‎09-17-2018

Re: seu estimator

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e,

The mean time to fail is not likely to be affected by anything you can do as when a critical bit flips, it causes a failure (the definition of a critical bit).  The spreadsheet will estimate when an upset occurs.  Which upsets are critical, no one can tell you.  One can guess that a critical bit upset is one in ten (roughly).  So, for every ten upsets, one is likely to be critical, and manefest as a visible (observable) failure.

If the SEM IP is correcting upsets, the failure cannot be corrected until it occurs.  So, it is fixed, after a possible failure, which also prevents the failure from persisting (potentially your design resumes proper operation but you have to design it to do so).

The actual ratio of upsets to failures, is from more than one in twenty, to not less than one in ten.  Random injection of errors is used to determine this factor which is known as the AVF (architectual vulnerability factor).

In some designs, correcting may improve the MTBF, but not by more than 30% in my experience.

l.e.o.

Contributor
Contributor
286 Views
Registered: ‎05-03-2014

Re: seu estimator

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Thanks for the useful information.
As to answers to my specific asks:
1. Does the Mitigation Settings value affect the FITs & MTBU in any way?
2. Does the Mitigation Settings do, if anything?
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Highlighted
278 Views
Registered: ‎09-17-2018

Re: seu estimator

Jump to solution

Answers:

1. No.  Regardless of settings, failures will occur related only to your design, and how many bits are crtical to its function.

2.  They allow you to repair upsets, which if you designed your circuits properly, will allow your design to work properly (again).

As an example, if your system is the IR landing camera on a commercial airliner, if an upset occurs, you can signal the pilots to pull up and go around (this is an actual use case, in service and used).  I believe you would agree that trusting a potentially flawed landing system is not a good thing.Fail safe systems fail by failing to faul safely.  That said, one should not allow that to happen.  The SEM IP is just one way to meet the requirements in your system design (like landing safely).  In 2 above, the SEM IP will allow the pilot to go around after an upset, and land safely.  Of course you must inject errors to prove it all works.

The SEM IP is in effect required by any safety critical system following IEC 61508.  Xilinx FPGA devices are the only ones with this feature, proven to work, and in common use since Virtex 5.  If there is no RBCRC error, then the decision made by the design is accurate, and you are safe... 

l.e.o.

 

Contributor
Contributor
207 Views
Registered: ‎05-03-2014

Re: seu estimator

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Thanks it's OK now.

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