1 Scope
1.1 This part of GB/T 20438 contains an overview of various safety techniques and measures relevant to GB/T 20438.2 and GB/T 20438.3.
Note: The references should be considered as basic references to methods and tools or as examples, and may not represent the state of the art.
1.2 GB/T 20438.1, GB/T 20438.2, GB/T 20438.3 and GB/T 20438.4 are basic safety publications, although this status does not apply in the context of low-complexity E/E/PE safety-related systems (see 3.4.4 of GB/T 20438.4-2006). As basic safety standards, they are intended for use by technical committees in the preparation of standards in accordance with the principles contained in IEC Guide 104 and ISO/IEC Guide 51. GB/T 20438 is also intended for use as a stand-alone standard.
One of the responsibilities of a technical committee is, wherever applicable, to make use of basic safety standards in the preparation of its own standards. In this context, the requirements, test methods or test conditions of this basic safety standard will not apply unless specifically referred to or included in the standards prepared by those technical committees.
Note: The functional safety of an E/E/PE safety-related system can only be achieved when all related requirements are met. Therefore it is important that all related requirements are carefully considered and adequately referenced.
1.3 Figure 1 shows the overall framework of GB/T 20438 and indicates the role that GB/T 20438.7 plays in the achievement of functional safety for E/E/PE safety-related systems.
Figure 1 Overall Framework of GB/T 20438
2 Normative References
The following documents contain provisions which, through reference in this text, constitute provisions of this part of GB/T 20438. For dated reference, subsequent amendments to (excluding any corrigendum), or revisions of, any of these publications do not apply. However, parties to agreements based on this part are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. For any undated references, the latest edition of the document referred to applies.
GB/T 20438.1-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 1: General Requirements (IEC 61508-1:1998, IDT)
GB/T 20438.2-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 2: Requirements for Electrical/Electronic/Programmable Electronic Safety-related Systems (IEC 61508-2:2000, IDT)
GB/T 20438.3-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 3: Software Requirements (IEC 61508-3:1998, IDT)
GB/T 20438.4-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 4: Definitions and Abbreviations (IEC 61508-4:1998, IDT)
GB/T 20438.5-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 5: Examples of Methods for the Determination of Safety Integrity Levels (IEC 61508-5:1998, IDT)
GB/T 20438.6-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 6: Guidelines on the Application of GB/T 20438.2 and GB/T 20438.3 (IEC 61508-6:2000, IDT)
IEC Guide 104:1997 The Preparation of Safety Publications and the Use of Basic Safety Publications and Group Safety Publications
ISO/IEC Guide 51:1990 Guidelines for the Inclusion of Safety Aspects in Standards
3 Definitions and Abbreviations
For the purposes of this part of GB/T 20438, the definitions and abbreviations given in GB/T 20438.4 apply.
Foreword i
Introduction ii
1 Scope
2 Normative References
3 Definitions and Abbreviations
Appendix A (Informative) Overview of Techniques and Measures for E/E/PES: Control of Random Hardware Failures
A.1 Electrical
A.2 Electronic
A.3 Processing Units
A.4 Invariable Memory Ranges
A.5 Variable Memory Ranges
A.6 I/O-units and Interfaces (External Communication)
A.7 Data Paths (Internal Communication)
A.8 Power Supply
A.9 Temporal and Logical Program Sequence Monitoring
A.10 Ventilation and Heating
A.11 Communication and Mass-storage
A.12 Sensors
A.13 Final Elements (Actuators)
A.14 Measures against the Physical Environment
Appendix B (Informative) Overview of Techniques and Measures for E/E/PES: Avoidance of Systematic Failures
B.1 General Measures and Techniques
B.2 E/E/PES Safety Requirements Specification
B.3 E/E/PES Design and Development
B.4 E/E/PES Operation and Maintenance Procedures
B.5 E/E/PES Integration
B.6 E/E/PES Safety Validation
Appendix C (Informative) Overview of Techniques and Measures for Achieving Software Safety Integrity
C.1 General
C.2 Requirements and Detailed Design
C.3 Architecture Design
C.4 Development Tools and Programming Languages
C.5 Verification and Modification
C.6 Functional Safety Assessment
Appendix D (Informative) A Probabilistic Approach to Determining Software Safety Integrity for Pre-developed Software
D.1 General
D.2 Statistical Testing Formulae and Examples of Their Use
D.3 References
Bibliography
Index
Figure 1 Overall Framework of GB/T 20438
Table C.1 Recommendations for Specific Programming Languages
Table D.1 Necessary History for Confidence to Safety Integrity Levels
Table D.2 Probabilities of Failure for Low Demand Mode of Operation
Table D.3 Mean Distances of Two Test Points
Table D.4 Probabilities of Failure for High Demand or Continuous Mode of Operation
Table D.5 Probability of Testing All Program Properties
