Programmable Logic Device PLD Approval Issues RTCA DO 254 Design Assurance Guidance for Electronic H

1
Programmable Logic Device (PLD) Approval Issues
RTCA DO 254 Design Assurance Guidance for
Electronic Hardware Issued on April 19th 2000

• Ian Glazebrook
• ERA Technology

2
Presentation Overview

• Introduction to RTCA DO 254
• Objectives
• Approval (Certification) Issues and Problems
• Coded Components including
• Field Programmable Gate Array (FPGA)
• Programmable Systems-on-Chip (PSoC)
• Complex Programmable Logic Device (CPLD)
• Application Specific Integrated Circuit (ASIC)

3
Presentation Overview

• Approval is a system function and is granted for
  a product

4
Standards Hierarchy Context
JSP 553 Regulations FAR, CS eg FAR/CS 251309
Safety Assessment SAE ARP 4761
Def Stan 00-56 System SafetySAE ARP 4754,CS
251309
Software Safety RTCA DO-178B Def Stan 00-55
Hardware Safety RTCA DO-254 Def Stan 00-54
Environmental RTCA DO-160Def Stan Def Stan
59-411
5
RTCA DO 254 Introduction

• Guidelines for the production of PLDs for
  airborne systems and equipment
• Given "force" by the FAA AC 20-152 on 30th June
  2005
• Based on RTCA DO 178B (Software), often
  considered the same as SW as they are programmed
  like SW - Incorrect

6
RTCA DO254 Introduction

• Provides level of rigor based on severity
• Objectives for Hardware life cycle processes
• Descriptions of design considerations and
  activities for achieving those objectives
• Descriptions of the evidence that indicate that
  the objectives have been satisfied

7
Objectives By Assurance Level
Based on Table A-1, RTCA DO 254, Page A-2
8
Approval (Certification) Process
RTCA DO 254 Figure 2.3, Page 18
9
Complex PLD Issues

• Similar to Software
• Cannot be 100 tested for all combinations of
  inputs and paths
• Are more likely to have design or implementation
  errors
• Are prone to unanticipated interactions

10
Complex PLD Issues

• Similar to Software
• It is a common observation during development
  that the requirements are inadequate or
  incomplete
• They are developed by tools which may introduce
  additional errors and gives rise to Tool
  Qualification (See Section 11.4)

11
Additional Considerations for PLDs

• Issues over and above Software
• Performance of time-related functions
• Signal noise and cross-talk and signal timing
  relationships
• Signal glitches in asynchronous logic circuits
• Possible state transitions, anticipated or not
• Supply voltage and current demands
• Obsolescence
• Single Event Upset (SEU)

12
Commercial Off The Shelf (COTS) Considerations

• The rigor of the development processes for COTS
  should be commensurate with its Assurance Level
  and intended use
• When COTS data is not available approval
  approaches for COTS could include
• Electronic Component Management as recommended by
  RTCA DO 254 Section 11.2
• Product Service Experience as recommended by RTCA
  DO 254 Section 11.3

13
Tool Assessment and Qualification

• For Levels A and B assurance compliance should be
  provided
• Development Tools
• Verification Tools
• A claim for credit of relevant tool history will
  need to be justified (See Section 11.4.1, Item 5)
• Possible tools need to be included as part of
  planning and Supplier Selection process

14
Tool Assessment and Qualification

• Use of tools requires Authority (Approval)
  Agreement
• Tool data and evidence that show they perform
  their intended functions - Difficult

15
Conclusions and Recommendations

• Robust and accurate plans early in the programme
• Agree PHAC, DAL and the certification basis at
  programme start
• Future proofing and obsolescence robustness
  assessments
• Focus on proven techniques and approaches
• Leading / bleeding edge is not always the best
  solution

16
Conclusions and Recommendations

• Ensure robust and controlled Transition Criteria
• Ensure Requirements are controlled and accurate,
  including provision for Derived Requirements

17
QUESTIONS?

• Additional ReferencesIPT Guidance for
  Acquisition of Systems with Complex Programmable
  Hardware using DO-254http//www.era.co.uk/assc/sy
  stems.aspFAA System Safety Handbook
  http//www.faa.gov/library/manuals/aviation/risk_
  management/ss_handbook/

18
QUESTIONS?
Advisory Circulars, including 20-152
http//www.airweb.faa.gov/Regulatory_and_Guidance
_Library/rgAdvisoryCircular.nsf/Certification
Authorities Software Team (CAST) Position Papers
http//www.faa.gov/aircraft/air_cert/design_appro
vals/air_software/cast/cast_papers/