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Z. Stamenkovi ć. An Implementation Study on Fault Tolerant LEON-3 Processor System. Outline. Radiation and fault tolerance System description Implementation details Test results Under way. Reliability Issues in Radiation Environments. Single-event upset (SEU)

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An Implementation Study on Fault Tolerant LEON-3 Processor System

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Z stamenkovi

Z. Stamenković

An Implementation Study on Fault Tolerant LEON-3 Processor System



  • Radiation and fault tolerance

  • System description

  • Implementation details

  • Test results

  • Under way

Reliability issues in radiation environments

Reliability Issues in Radiation Environments

  • Single-event upset (SEU)

    • A change of state caused by a charged particle strike to a sensitive volume in a microelectronic device

      • Alpha particles (helium-4 nuclei) emitted by radioactive atoms found in packaging materials

      • Thermal neutrons in certain device materials that are heavily doped with 10B

      • High-energy terrestrial cosmic rays (play a major role)

  • SEU-induced latch-up

    • A failure mechanism of CMOS integrated circuits characterized by excessive current due to parasitic PNPN paths

  • Fault tolerance of leon 3 processor

    Fault Tolerance of LEON-3 Processor

    • SEU tolerance by design (Gaisler Research)

      • Triple-module-redundancy (TMR) on all flip-flops

        • Three copies of a flip-flop

        • Two of three voting on output

      • Register file error-correction (up to 4 errors per 32-bit word)

      • Cache RAM error-correction (up to 4 errors per tag or 32-bit word)

      • Autonomous and software transparent error handling

      • No timing impact due to error detection or correction

      • Fault-tolerant memory controller

        • Provides an Error Detection And Correction Unit (EDAC)

        • Corrects one and detects two errors

  • Not immune to SEU-induced latch-up (in present IHP technology)

  • Leon 3 processor system


    FT Add-on

    Scan Test

    UART 0

    Serial 0

    2 kByte

    I- Cache

    UART 1

    Serial 1

    8 x GPIO


    LEON_3FT Core

    8 Reg. Windows





    2 kByte

    D- Cache

    FT Memory


    1 x 24bitTimer

    FT Add-on



    LEON-3 Processor System

    An implementation study on fault tolerant leon 3 processor system

    Implementation Details

    • Installation of the release

    • Adaptation of the configuration tool (to include IHP’s library)

    • Implementation of data and instruction caches

    • Logic synthesis of the design

    • Implementation of scan chain

    • Generation of the chip layout

    • Simulation (functional, post-synthesis and post-layout net-list)

    • Scan test vectors generation (ATPG)

    • Scan test simulation

    • Adaptation of testbenches

    • EVCD test vectors generation

    • Test specification

    • Documentation

    Chip features

    Chip Features

    Test system gaisler research

    Test System (Gaisler Research)

    • Target hardware consists of a small mezzanine with Fault Tolerant LEON-3 device mounted on a development board (Pender Electronic Design)

    • Board communicates with a host system (a laptop PC) over one of the on-chip UARTs

    Test execution gaisler research

    Test Execution (Gaisler Research)

    • Heavy-ion-error injection

      • Chamber with the vacuum of 10-2 mbar

      • Californium (Cf-252) source

      • Flux of 25 particles/s/cm2 at the device surface for 3 hours

  • “Paranoia” program makes a large number of calculations and registers any computational error or anomaly

  • On-chip monitoring logic reported 281 effective SEU errors, of which 99% were corrected

  • Cross-section for a memory RAM bit was measured to 7.2x10-8 cm2

  • Under way

    Under Way

    Protection against SEU-induced latch-up

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