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Applying Asynchronous Circuits in Contactless Smart Cards

Applying Asynchronous Circuits in Contactless Smart Cards. Joep Kessels, Torsten Kramer Gerrit den Besten, Ad Peeters, Volker Timm. Esprit project Descale. Period: 1998-1999 Participants: Philips Semiconductors, MAZ, Philips Research

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Applying Asynchronous Circuits in Contactless Smart Cards

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  1. ApplyingAsynchronous Circuits in Contactless Smart Cards Joep Kessels, Torsten Kramer Gerrit den Besten, Ad Peeters, Volker Timm

  2. Esprit project Descale • Period: 1998-1999 • Participants: Philips Semiconductors, MAZ, Philips Research • Goal: find out advantages of asynchronous circuits in contactless smart cards

  3. Outline • Designing asynchronous circuits • Contactless smart cards • Applying asynchronous circuits in contactless smart cards

  4. VLSI programming of Handshake circuits • Designing asynchronous circuits (handshake circuits) • in a high level programming language (Tangram) • using a compiler for translation (transparent)

  5. ; B A Sequential composition Tangram Handshake circuit A ; B

  6. || B A Parallel composition Tangram Handshake circuit A || B

  7. Synchronousversusasynchronous Clock drivenDemand driven Less average power Central clock Distributed Smaller current peaks handshakes Less EM emission Clock timedSelf timed Performance adaptation to supply voltage (1..3 V)

  8. Contactless smart card Tuned circuit: • Power • Clock • Communication

  9. Mifare (ISO standard) - Proximity card (10 cm) with two way communication - 70 M cards sold - Clock: 13.56 MHz; Bitrate: 106 Kbit/sec - Power: few mW; Transaction time: 200 msec

  10. Differences in power characteristics • Supply Constant Fluctuating • Voltage Minimizing Average Peak Power

  11. Digital Circuit • Peripherals: • DES • RSA • UART • Memories: • 2 kbyte RAM (10 nsec) • 32 kbyte EEPROM (read/write 180/4000 nsec) • 38 kbyte ROM (30 nsec)

  12. Power 80C51 in time domain Synchronous Asynchronous

  13. Synchronous Asynchronous Power 80C51 in frequency domain 0 100 200 300 400 MHz 0 100 200 300 400 MHz

  14. Performance adaptation asynchronous 80C51

  15. Descale chip 5-layer metal 0.35 mm 18 mm2

  16. Area/Power contactless digital circuitry Async about 12% of contactless digital circuit area

  17. Effect asynchronous design

  18. Power regulator

  19. Improvements in Tangram Toolset • Redefinition Tangram • communication through variables • Use of conventional tools for data-path part • Optimizer & Technology mapper to reduce area (10%) • Timing analysis tool to tune matching delays (up to 50%)

  20. Conventional solution • Synchronous digital circuit with fixed speed • superfluous power thrown away • too little power: transaction is canceled • Performance 80C51 limited by power received • Buffer capacitor of several nF (large area)

  21. Advantages asynchronous design • Maximum performance for power received • power efficiency: factor 2 • adaptation property: factor 2 • More robustness and/or smaller buffer capacitor • smaller current peaks • adaptation property

  22. Conclusion Results so convincing that a product is being designed based on these asynchronous circuits

  23. Mifare Applications • Seoul: six million bus cards • Lufthansa: Frequent Flyers cards • China: highway toll cards • Brasil: cards for civil servants (identification & electronic purse) • Shell: Mifare technology in car keys

  24. Modifications in 80C51 • Instruction prefetching (30% more performance) • Early write completion • Immediate halt signal • Quasi synchronous mode (performance 50% of free-running mode)

  25. DES convertor • Transaction contains up to 10 DES conversions • Software conversion : 10 msec, 30 mJ • Hardware conversion: 1.25 ms, 12 nJ • Area 3,250 GE - 57% combinational logic - 35% latches/flipflops - 8% delay matching and C-elements

  26. Power 80C51 and DES co-processor @ 3.3V

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