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Research and Development of Deployable IV&V Methods for

FPGA Applications

Northrop Grumman, KeyLogic Systems,Mountain State Information Systems, Inc.,

The University of Montana and West Virginia University

July 20, 2006

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• FPGAs in the 1990s attained a threshold in performance and gate counts that permitted replacement of ASICs instead of just prototyping of the boards.

• Engineers also realized that many common functions handled by micro-processors could be transferred to FPGAs, relieving processors of some duties and matching or exceeding performance and improving reliability.

FPGA Overview

FPGA

Supporting Circuitry

ASICsMicro-Processor Executed Functions

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FPGA Overview• The first FPGA in 1985 (Xilinx) had ~1,000 gates. Gate counts now exceed 10 Million -

a 10,000 fold increase while gate sizes and power consumption have fallen.

• Hardware Description Languages (HDL), first VHDL and later Verilog were developed to describe, document and simulate VHSIC and later evolved into a means to synthesize FPGAs.

• Initial FPGA designs could be accomplished with minimal attention to development lifecycle and instead retained “design & test” engineering practices.

• Increased gates and complexity lead to difficulties in implementation, to failures, lessons-learned and is now leading to adoption of more formal development practices.

• Some Common Failures in real FPGA development lifecycles are*:– No Specifications or the Specifications were not followed– Features added or deleted during development and not documented– No Stable Specification creating delays to Project (belated HW delivery to I&T)– Drifting software or system requirements impacted FPGA development– Reliance on logic simulators with insufficient time for V&V

* A summary of development failures from presentation "Logic Design Pathology and Space Flight Electronics", R.Katz, et al.

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• Creation of formal development practices and a lifecycle for FPGAs are still underway. Engineers realize that a software development lifecycle is applicable to FPGA development.

Concept Requirements Design Implementation Test

• FPGA design practices will continue to closely mirror software development but there are differences.

• With FPGA engineering practices being formalized and with added complexity and impact on spacecraft system designs, the V&V of the FPGAs will become the responsibility of specialists.

FPGA Overview

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• As a comparison, software designs have become more complex and the importance of V&V is taking on a greater role and greater percentage of project resources.

• Independent verification and validation has provided added assurance directly by identification of issues and indirectly by supporting adoption of formal methods.

• FPGA development is following a similar trend toward formalized methods. This NASA IV&V supported project will develop IV&V methods and assess their feasibility. The questions – Is FPGA IV&V feasible, practical and effective, will be answered.

• Could NASA IV&V analysts competently execute FPGA IV&V? NASA IV&V analysts have a wide range of expertise from software development, spacecraft design to electrical and aerospace engineering. With the commencement of FPGA IV&V, NASA IV&V will have analysts amongst their ranks qualified to undertake the tasks of FPGA verification and validation.

FPGAs & IV&V

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Deployable IV&V Methods for FPGAs

1. Surveying and cataloging existing FPGA applications

2. Concept/Requirements Phase: • Methods for Concept/Requirements analysis• Identify potential methods for full-lifecycle analysis

3. Design/Implementation Phase: • Dynamic analysis including functional and timing simulations at

the unit level • Envisioned work instructions build on successful past analysis

methods 4. Test Phase:

• Define the types of design and implementation validation that can be practically accomplished via subsystem testing

5. Project transference: Continue with pilot and other projects

This initiative will involve 5 steps towards development of a deployable FPGA IV&V method

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Deployable IV&V Methods for FPGAs1. Surveying and cataloging existing FPGA

Applications • We will answer the question, how are FPGAs being utilized

in aerospace applications?

• A survey will be undertaken to identify the types and breadth of functions that FPGAs are taking.

• The survey is expected to locate FPGA designs that can be acquired and used as test cases for this project.

• Cataloging these applications will include an assessment of their design complexity.

Teams will be able to prioritize FPGA by their importance to overall system design.

Knowledge of complexities will permit IV&V teams to estimate resource requirements

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Deployable IV&V Methods for FPGAs2. Concept/Requirements Phase

• The project will decompose the content of FPGA concept and requirement documents.

• Understanding the common aspects of FPGA design documents will permit creation of a methodology and to an IV&V checklist for the content of these documents.

This Project will define how to complete the IV&V tasks as defined in IEEE 1012 and NASA IV&V SLP 09-1 for FPGA designs.

• As with software development, FPGA IV&V will look for completeness, consistency and accuracy.

• How will we verify requirements flowdown for FPGA design?

• How will interface between FPGAs and the subsystem in which it is embedded be verified?

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Deployable IV&V Methods for FPGAs2. Concept/Requirements Phase (continued)

• Past NASA IV&V FPGA analysis included:

Verifying architectural diagrams against requirements & assertions.

Applying IEEE/ISA standards for HDL code (IEEE 1076 Standard VHDL) and verifying that engineers adhered to these standards

Verification of State Diagrams

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Deployable IV&V Methods for FPGAs3. Design/Implementation Phase

• Design Analysis can include validation of state diagrams

Documented diagrams can be analyzed.

Analyzer generated stated diagrams can validate design

• Functional Simulations will provide initial validation of timing requirements and input and output signals.

• Timing Simulations are required to validate FPGAs, i.e. Very High Speed Integrated Circuits (VHSIC).

• Timing simulations are a challenge to the limited resources of the IV&V effort. Concise methods will be necessary to lead to efficient setup and execution of these simulations.

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Deployable IV&V Methods for FPGAs3. Design/Implementation Phase (continued)

• Past NASA IV&V FPGA analysis included:

Manual Walk-Throughs of the VHDL

Static analysis of the VHDL by the Active-HDL debugger

Functional Simulations that verified or found issues with state diagrams

Timing simulations

Trade study of FPGA developer tools

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Deployable IV&V Methods for FPGAs4. Test Phase

• Potential tools for validating FPGAs embedded in a subsystem include:

Simulink and Active-HDL or other applications that interface, but a trade study will be necessary to identify and assess all 3rd party utilities.

Evaluating the potential of simple test beds for validating FPGAs using off-the-shelf development boards.

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Deployable IV&V Methods for FPGAs5. Project Transference

• Steps 1-4 are scheduled within the first year of the project. Deliverables will justify the continuation into year two and feasibility of methods.

• Final step is a pilot project that will assess and validate the feasibility of FPGA IV&V during the second year.

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Project Status• Commencement of project funding was June 2006

• A kick-off meeting with the NASA POC (K. Costello) was completed.

• Initial team meetings in July 2006 are being scheduled.

• Project staffing will merge the expertise of a FPGA design engineer, senior IV&V analysts and university researchers.

• A Project Repository has been created (NG IMAP) and its structure is under construction. Team members are collecting reference documents for upload to the repository.

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Backup Slides

Specifications

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Active-HDL and FPGA Analysis