# Presentation: 102200

## Multi-Bit Upsets in the Virtex Devices

- Heather Quinn, Paul Graham, Jim Krone, Michael Caffrey
- Los Alamos National Laboratory
- Gary Swift, Jeff George, Fayez Chayab
- XRTC

## Multi-Bit Upsets

- Multiple neighboring bits flipped from a single ionized particle strike
- Common to all memory devices
- FPGAs a unique case
- Heterogeneous layout affects the size, shape
- Domain crossing event (DCE) where an SEU affects two or more TMR modules are a concern

## MBU Research Plan

- Determine the event rate
- Determine the MBU frequency
- Multiple families of FPGAs: feature size, epi
- Radiation type: proton and heavy ion
- Strike angle
- Determine the DCEs frequency
- Early simulation results
- Early probabilistic model to predict DCEs

## Virtex Proton Test Setup: Crocker Nuclear Laboratory, UC-Davis

- SLAAC1-V

- Linux PC

- Proton
- Source

## LANL V2 and V4 Hardware Test Fixture

- Virtex-II AFX
- Board

- USB 2.0
- Interface to
- Linux PC

- Virtex-4 AFX
- Board

## LANL Software Test Fixture

- Text-based interface
- SSH'd into the test machine
- Instant access to incremental readback results
- Tight readback/scrubs cycle
- Saves differential bitstream for upsets
- Saves FAR, COR, and STAT registers
- Cycles approximately once a second
- Scrubs entire bitstream
- Data analyzed for MBUs post-collection

## Data Collection & Analysis

- Possibility of coincident SBUs _must be_ minimized
- Minimize the number of upsets per readback
- Fluence per readback cycle controlled
- SEFIs (or unexplained events) removed in post-collection data analysis procedures
- SEFIs present as numerous large MBUs: skew statistics
- Data cube insignificantly reduced, results cleaner

## Heavy Ion Accelerator Tests

- Done by Xilinx Radiation Testing Consortium
- Collected data for:

## Heavy Ion Event Bit Cross-Sections

## V4 Heavy Ion Event and Upsets Cross-Sections

**V4 Heavy Ion Event and Upsets Cross-Sections**

- 63 % decrease in cross-sections

## Percentage of MBU Events in Heavy Ion:Comparison Across Families

## V4 Percentage of Events by Resource:BRAM, CLB

## V4 MBUs from Angle Strikes Across Columns

## V4 MBUs from Angle Strikes Down Columns

## Proton Accelerator Tests

- Done by Los Alamos National Laboratory
- Collected data for:

## Percentage of MBU Events in Proton at 63 MeV:Comparison Across Families

## Proton Bit-Cross-Sections

## V4 Proton Event and Upsets Cross-Sections

**V4 Proton Event and Upsets Cross-Sections**

- 9 % decrease in cross-sections

## MBUs from Angle Strikes Down Columns

## TMR Studies

- TMR designs:
- Edge detection, max filter, min filter
- Each design has 2-3 implementations that vary module granularity
- LANL/BYU SEU simulation extended to simulate column MBUs:
- Observe, characterize, and determine the DCE rate
- Test both 1-bit and 2-bit column events
- Data inconclusive at best

## TMR Results: MBU Sensitive Bits

- Device: XC2V250 (Virtex-II) with 1.6 Million Bits

- Even without triplicated clocks, TMR improves the cross-section 4-6 times

## Given an MBU what is the probability of a DCE?

- SBUs

- MBUs

- BRAM

- CLB

- BRAMi

- IOB

- BRAM

- CLB

- BRAMi

- IOB

- Voted
- Out

- Voted
- Out

- DCE

- Need to determine what percentage of the event space are DCEs

## Probability of an MBU DCE in CLBs and BRAMi:Proton-Induced Radiation Events

## Probability of a DCE in CLBs and BRAMi:Heavy-Ion-Induced Radiation Events

## Summary

- MBU problem getting worse with each generation
- DCEs in TMR a concern
- Need more data collection, more simulation, more modeling
- Data collection: finish qualification
- Simulation: complete TMR studies with more designs and more devices
- Modeling: predict on-orbit SBU/MBU rates