All posts by hongseoklee

Why are you born? Meaning of safety requirement existence

If some requirement are regarded as safety attribute, it means that in-achievement of safety requirement leads to threaten safety.

The rationale is explained in the somewhere. I believe that system FTA or system FMEA are proper means of why they are born.

After they are identified, safety engineers shall suggest methods how to handle them. Their suggestions are called safety mechanisms in ISO standard.

Sometimes, engineers forget this simple principle. So non-safety related requirements are mis-perceived as safety requirements.

All safety requirements have birth-registered? Unregistered has a potential to threat safety. Don’t forget to register. It is natural like happened in our society.


[Scrap] Fast Accurate Memory Test Code in C

IS026262의 Part5. 중 메모리에 대한 요구사항이 있다. 메모리 테스트에 대한 내용이 필요하여 아래 포스팅을 번역함. 재사용이 가능한 임베디드 소프트웨어가 있다면 메모리 테스트입니다. 이 포스팅에서는 세 가지 효율적이고 적용 가능한 메모리 테스트 기능 셋을 사용하여 가장 일반적인 메모리 문제를 테스트하는 방법을 보여줍니다. 거의 모든 임베디드 개발자는 자신의 경력 중 어느 시점에 도달하였을때 메모리 테스트를 작성하여야 합니다. 종종 프로토타입 하드웨어가 […]

방법: Fast Accurate Memory Test Code in C — ::Dump

Identifying safety requirement

My main job is to review all kinds of functional safety documents. Although I don’t know much detail of products, I can help engineers to make our products more safer.

Identifying safety requirement is a 2nd step of functional safety activity. Of course, 1st step is safety planning, and it is very important but many people don’t realize its importance.

Anyway, when I review requirements that regards as ‘safety’, I always ask this question to engineers;

“If this requirement doesn’t meet, it directly leads to violate safety goal?”

If it is safety requirement, it shall be always “yes”, but I experienced to get an answer “no” in many cases.  Then it is not real safety requirement.

Engineers seem to have a custom to identify them as ‘safety requirement’ which look ‘critical’.

For system which control vehicle, it is critical not to ‘sleep’. But not always for system which report to system which has a responsibility to control.

For control system, detecting who is liar is very important because it directly leads to incorrect decision, which results to control unsafely. Of course ‘not to sleep for a long time’ is also important.

But these principles are not always applicable to “reporters”. To tell a lie is worst. To tell nothing is better.

So, “to be honest” is a very important characteristic for “Subordinates”

To summarize, ask this question always. Do Not determine it with your custom.

the question is “If this requirement doesn’t meet, it directly leads to violate safety goal?”