0. Focus on ISO26262 Part 3 (Concept Phase); Part 4 (Product Development: System Level); and Part 5 (Product Development: Hardware Level)
1. Determine ASIL and create Safety Mechanism specifications
Note, the ASIL level is determined by safety-criticality of the component under development. An automotive ASSP is developed by applying SEooC (Safety Element out of Context) of the ISO26262 standard. It starts with the item definition of an automobile function. Fig. 1 shows the flow and outline of each process from item definition to hardware safety requirement specifications.
(A) Item definition: ISO26262-3 (ISO26262 Part3: same below)
This is the stage of defining the input, output and functions of the component associated with an automobile function.
(B) HARA (Hazard Analysis and Risk Assessment): ISO26262-3
Hazard analysis and risk assessment for the item defined in (A) is performed, and ASIL is determined at this stage based on the evaluation results of HARA: Severity class (S1-S3), Exposure class (E1-E4) and Controllability class (C1-C3).
(C) Functional safety concept: ISO26262-3
Safety measures are taken for failures that infringe on the safety of Intended Functions (IF) of the item defined in (A), and functional safety requirements (FSR) are derived. This is the stage of implementing an architecture-level safety design for the (IF).
(D) Technical safety concept: ISO26262-4
The input / output of the item defined in (A) has expanded to the internal elements at signal level. Based on the results of the functional safety concept, the technical safety concept is carried out at the signal level. And the Technical Safety Requirements (TSR) are derived. At this stage, the signal level specifications related to functional safety are finalized for the ASSP and safety measures are implemented for failures that violate safety for the Intended Functions inside the ASSP at the architecture level.
(E) Hardware safety requirement specifications: ISO26262-5
Based on TSR, safety measures are implemented against the failures of the logic inside ASSP and Hardware Safety Requirements (HSR) are derived. At this stage, specifications of safety mechanism requirements are determined.
It is necessary to carry out the above (A)-(E) consistently based on the standard requirements of ISO26262,and prepare documents as evidence.