326 / 975
Figure 2: Evolution of National Prescriptive Standard to
International Performance Base Standards
3.4.2 Application Execution in a SIL Compliant Environment
The use of diverse operating systems (using different technologies) including the use of third party certified
COTS and different execution path with different compiler rules extends the risk reduction found in the hardware
design to the firmware/software environment in the system, including the use of limited variability software
functions and provision of systematic capabilities as specified in the Functional Safety standards for critical
applications.
3.4.3. Systematic Capabilities and Human Error
The concept of systematic capabilities and its associated performance measurement was introduced in the
latest revision of IEC61508 standard; the concept did not exist as such in 1
st
Generation systems and was
emerging in 2
nd
generation systems.