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POST CONDITIONS

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Robin Clark 2012-11-30 21:22:31 +00:00
parent 7746317e42
commit 08fad4c2f9
1 changed files with 19 additions and 2 deletions
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submission_thesis/CH5_Examples/software.tex
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@ -136,6 +136,20 @@ be executed.
% %
In implementation code, a pre-condition violation should cause In implementation code, a pre-condition violation should cause
an error to be generated, and thus a post condition to fail. an error to be generated, and thus a post condition to fail.
%
A function can fail for reasons other than the
a failure of one the variables/inputs or functions that it calls.
Variables can become corrupted, by radiation affecting RAM or
by another software function erroneously overwriting variables.
Current work on software FMEA generally focuses on mapping
variable corruption to failure modes~\cite{procsfmea,procsfmeadb,sfmeaauto,sfmea}.
However, errors other than variable corruption can occur,
for instance a microprocessor may have subtle bugs in its instruction set or
incorrectly handled
interrupt contention could cause side effects in software.
For the failure mode model of any software function
we must consider all failure modes of post condition
violations as well as those caused by `components'.
\paragraph{Mapping contract `invariant' violations to symptoms and failure modes.} \paragraph{Mapping contract `invariant' violations to symptoms and failure modes.}
@ -419,6 +433,7 @@ With these failure modes, we can analyse our first functional group, see table~\
5: $ADC_{LOW}$ & output low & $LOW$ \\ 5: $ADC_{LOW}$ & output low & $LOW$ \\
6: $ADC_{HIGH}$ & output high & $HIGH$ \\ \hline 6: $ADC_{HIGH}$ & output high & $HIGH$ \\ \hline
7: post condition fails & software fails & $V\_ERR$ \\ \hline
\hline \hline
@ -509,6 +524,8 @@ We now analyse this hardware/software combined {\fg}.
5: $CMATV_{LOW}$ & output low & $LOW$ \\ \hline 5: $CMATV_{LOW}$ & output low & $LOW$ \\ \hline
6: post condition fails & software fails & $VV\_ERR$ \\ \hline
\hline \hline