How VectorCAST Assists Certification for IEC 61508
The standard presents a lifecycle approach including risk assessment, design, integration, testing, modification and maintenance and safety management.
The IEC 61508 complete standard is comprised of 7 parts. Part 3 defines the software requirements and sets the safety lifecycle for software, including validation and verification. The safety lifecycle begins with a risk analysis to determine the Safety Integrity Level (SIL) required. SIL is a quantification of the magnitude of risk reduction required.
| SAFETY INTEGRITY LEVEL |
PROBABILITY OF DANGEROUS FAILURE PER HOUR |
RISH REDUCTION FACTOR |
|---|
| SIL 4 |
>=105 to <104 |
100,000 to 10,000 |
| SIL 3 |
>=104 to <103 |
10,000 to 1,000 |
| SiL 2 |
>=103 to <102 |
1,000 to 100 |
| SIL 1 |
>=102 to <101 |
100 to 10 |
Based on the risk analysis, the following recommendations are made with respect to source code verification.
IEC 61508 Recommendations for Code Verification
(R = Recommended, HR = Highly Recommended)
| TECHNIQUE |
SIL 1 |
SIL 2 |
SIL 3 |
SIL 4 |
VECTORCAST |
|---|
| Formal Proof |
- |
R |
R |
HR |
|
| Probabilistic Testing |
- |
R |
R |
HR |
|
| Static Analysis |
R |
HR |
HR |
HR |
QA.C / QA.C++ |
| Dynamic Analysis and Testing |
R |
HR |
HR |
HR |
VectorCAST/C++/Ada VectorCAST/Cover |
| Software Complexity Metrics |
R |
R |
R |
R |
VectorCAST/C++/Ada VectorCAST/Cover |
For software systems, IEC 61508 suggests following a V-model development process. The V-model shows the necessary connection between requirements and validation throughout the entire development process. The VectorCAST tools are used during the verification and validation phases, and during the coding phase as depicted in the graphic below:
