This document answers some Frequently Asked Questions (FAQs) about the certification of computer software for medical applications. The answers to the questions are not intended to provide a definitive technical answer but rather to inform the reader in a general manner.
SAFETY AGENCIES
SAFETY CERTIFICATION STANDARDS
Q. What does IEC-601508 require?
Q. What are safety integrity levels?
Q. Who determines which safety integrity level is required?
Q. What is the total list of potential deliverables I will need to create for certification?
Q. How is a software verification performed?
Validated Software Corporation’s Validation Suite
Q. What are Validated’s Validation Suites?
Q. What comprises a Validation Suite?
Q. Is the Validation Suite a special version of the product code?
Q. Can the Validation Suite be reused on new projects?
Q. How do I order the Validation Suite?
Answers
SAFETY AGENCIES
IEC is the acronym for the International Electrotechnical Commission, the international standards and conformity assessment body for electrotechnology; specifically, functional safety of electrical/electronic/programmable electronic (E/E/PE) systems.
IEC is located in Geneva, Switzerland.
The IEC’s web site is: : www.iec.ch
CENELEC is the European Committee for Electrotechnical Standardization. Most CENELEC standards are identical or very closely based on IEC international standards. Typically, IEC standards in the 60000 to 69999 range map directly to CENELEC standards, for example, IEC 61508 to EN 61508. CENELEC’s web site is: www.cenelec.org
MISRA is the acronym for the Motor Industry Software Reliability Association. Its mission is "To provide assistance to the automotive industry in the application and creation within vehicle systems of safe and reliable software".
It is not a certification agency, but an association that publishes guidelines for writing more reliable software for automotive systems manufacturers. It has published a "Guidelines for The Use Of The C Language In Vehicle Based Software" manual that is available directly from their web site.
The MISRA web site is: www.misra.org.uk
SAFETY CERTIFICATION STANDARDS
IEC-61508 was developed to create a standard for the functional safety of electrical/electronic/programmable electronic safety-related systems. IEC-61508 allows for the standalone certification of a software component, unlike FDA/CDRH. The documentation requirements of IEC-61508 tend to lean more heavily on design, usage, and manufacturing, due to the standalone component aspects of this certification. One of the most critical documents is the Safety Manual, which contains the rules and guidelines on how to use the software component in a system that is certified.
The IEC has a great FAQ at: http://www.iec.ch/61508/index.htm
Q. What does IEC-601508 require?
The IEC standard is published in seven parts, as shown in the table below:
IEC-61508 Part References
Reference
Full Part Title
61508-1
IEC 61508-1:1998, Functional safety of E/E/PE safety-related systems - Part 1: General requirements
61508-2
IEC 61508-2:2000, Functional safety of E/E/PE safety-related systems - Part 2: Requirements for E/E/PE safety-related systems
61508-3
IEC 61508-3:1998, Functional safety of E/E/PE safety-related systems - Part 3: Software requirements
61508-4
IEC 61508-4:1998, Functional safety of E/E/PE safety-related systems - Part 4: Definitions and abbreviations
61508-5
IEC 61508-5:1998, Functional safety of E/E/PE safety-related systems - Part 5: Examples of methods for the determination of safety integrity levels
61508-6
IEC 61508-6:2000, Functional safety of E/E/PE safety-related systems - Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3
61508-7
IEC 61508-7:2000, Functional safety of E/E/PE safety-related systems - Part 7: Overview of techniques and measures
The first four parts of IEC-61508 define the way to comply with the specification. IEC-61508 can be used in a broad variety of safety-critical systems, including emergency shutdown systems in power plants, turbine controls, railway signaling systems, and other electromechanical systems in safety-critical environments.
Q. What are safety integrity levels?
The International Electrotechnical Commission Safety specifies Safety Integrity Levels (SILs) to quantify the chance of dangerous failures in electrical or electronic safety devices. The SIL is based on the probability of the device failing in performing its safety function.
SIL Probability of Failure 4 10-5 to 10-4 3 10-4 to 10-3 2 10-3 to 10-2 1 10-2 to 10-1
Q. Who determines which safety integrity level is requried?
The level to which a particular system must be certified is selected by a process of failure analysis and input from the device manufacturers and the certifying authority (IEC authorized certifying agency, e.g., TÜV).
Q. What is the total list of potential deliverables I will need to create for certification?
The following table lists the documents and records you may need to provide for a 510(k) submission:
Software Life Cycle Data List
Document Title
Type Section PSAC
Plan for Software Aspects of Certification
Document 11.1 SDP
Software Development Plan
Document 11.2 SVP
Software Verification Plan
Document 11.3 SCMP
Software Configuration Management Plan
Document 11.4 SQAP
Software Quality Assurance Plan
Document 11.5 SRS
Software Requirements Standards
Document 11.6 SDS
Software Design Standards
Document 11.7 SCS
Software Code Standards
Document 11.8 SRD
Software Requirements Data
Document 11.9 SDD
Software Design Description
Document 11.10
Source Code
Software 11.11
Executable Object Code
Software 11.12 SVCP
Software Verification Cases and Procedures
Document 11.13 SVR
Software Verification Results
Records 11.14 SECI
Software Life Cycle Environment Configuration Index
Document 11.15 SCI
Software Configuration Index Document 11.16 PRs
Problem Reports Records 11.17
Software Configuration Management Records Records 11.18
Software Quality Assurance Records Records 11.19 SAS
Software Accomplishment Summary Document 11.20
Q. How is a software verification performed?
IEC-61508-3 defines specific verification objectives that must be satisfied; these include:
Verification of software development processes
Review of software development life cycle artifacts
Functional Verification of software
a. Requirements-based testing and analysis
b. Robustness testingStructural Coverage Analysis
Structural Coverage Analysis is generally perceived to be the most difficult task to undertake by people unfamiliar with rigorous code development and testing. Furthermore, an operating system is tightly integrated with the hardware, cache, interrupts, memory management, and process/task management, thereby making structural testing even more difficult. These low-level aspects create a significant challenge to the verification process.
A variety of commercial tools are available to assist in this challenging task.
See our Code Coverage Tools page for a list of known vendors in this space.
Validated Software Corporation’s Validation Suite™
Q. What are Validated’s Validation Suites?
Validated’s Validation Suites are packages of standards, plans, requirements, designs, and tests to address manufacturers requiring safety certification documentation for projects. Validation Suites are typically developed for software products widely used in safety-critical products. The use of our Validation Suites allows developers to concentrate on their core product and lower their costs by purchasing an essentially off-the-shelf Validation Suite as a component.
Q. What comprises a Validation Suite?
Due to different requirements for different certification levels, the amount of documentation will differ, but, in general, the following documentation will be provided in Level A through Level C Validation Suites.
Validation Suite Component
Item
Plan for Software Aspects of Certification (PSAC)
11.1
Software Development Plan (SDP)
11.2
Software Verification Plan (SVP)
11.3
Software Configuration Management Plan (SCMP)
11.4
Software Quality Assurance Plan
11.5
Software Requirements Standard
11.6
Software Design Standard
11.7
C Language Coding Standard
11.8
Software Requirements Document (SRD)
11.9
Microprocessor Port Requirements and Design Documents
11.9
Software Design Document
11.10
Software Source Code, Test Code and Build Code
11.11
Software Port Image
11.12
Software Unit Test Plans and Procedures
11.13
Software Integration Test Plans and Procedures
11.13
Software Unit Test Reports
11.14
Software Integration Test Report
11.14
Software Test Coverage Report
11.14
Software Life Cycle Environment Configuration Index
11.15
Software Configuration Index
11.16
Software Problem Report History
11.17
Software Change History
11.18
Software Quality Assurance Data
11.19
Software Accomplishment Summary (SAS)
11.20
In addition, Validated also offers port-specific documentation to provide all the board support package (BSP) documentation, for example:
Port Software Design Description, Special I/O
Port Software Design Description, Special 80x86 Protected Mode Port
Q. Do I also have to pay another manufacturer for a production license when I purchase a Validation Suite?
Yes. The Validated Suite does not include a production license for the software.
Yes. The Validation Suite contains all source code to the product and all source code to test files, all test scripts, and all build/make files. Please note however that all of the products we validate are licensed by another manufacturer. As such we can not ship source code to a product until we receive confirmation from the manufacturer that you have a valid license in place with them.
Q. Is the Validation Suite a special version of the product code?
No. The source code we provide is functionally identical to the manufacturers original code. In some cases the code may belong to a "safety-critical" version of the manufacturers product, but this is the exception not the rule.
Q. Can the Validation Suite be reused on new projects?
Yes. Depending upon the system changes between projects, the Validation Suite can be used for multiple projects. (Note that additional license fees for both MicroC/OS-II and the Validation Suite may apply, regardless of re-use.)
MicroC/OS-II was chosen for many reasons:
MicroC/OS-II is a very stable operating system that has been used in tens of thousands of systems and hundreds of commercial applications. It has been in use for over 10 years, with minor modifications made periodically.
MicroC/OS-II has been “open source” since its creation. Therefore, it has been reviewed by thousands of individuals. But, unlike some open source projects, revisions are tightly controlled and reviewed by Micrium, and then openly reviewed by the MicroC/OS-II community.
MicroC/OS-II was written against a very strict coding standard, which improves readability, understandability, and maintainability – all key aspects of creating software used in critical systems.
Every line of MicroC/OS-II is well documented. This is extremely rare in the software industry and is ideal for safety certification where the mapping of requirements to source code to test for every line of code is required.
Q. How do I order the Validation Suite?
All Validated Software products can be ordered from the Validated Software Sales office.