1. NTU Confidential Introduction to the Applications of Asynchronous Circuits Presenter: Po-Chun Hsieh Advisor:Tzi-Dar Chiueh Date: 2003/09/22

2. NTU Confidential 2 Outline Asynchronous Circuits Review Applications - High-Speed - Low-Power - Low Noise and Low Emission - Heterogeneous Systems Conclusion Reference

3. NTU Confidential 3 Asynchronous Circuits Review (1/4) Synchronous Asynchronous

4. NTU Confidential 4 Asynchronous Circuits Review (2/4) Synchronous Asynchronous

5. NTU Confidential 5 Asynchronous Circuits Review (3/4)

6. NTU Confidential 6 Asynchronous Circuits Review (4/4) Benefits: –No global clock to distribute –Early completion (Data-dependent delays and Stage- dependent delays) –Low Power Drawbacks: –There are not many asynchronous tools –Not easy to test –Area cost

7. NTU Confidential Applications for High-Speed Circuits

8. NTU Confidential 8 Average-Case delay [4]

9. NTU Confidential 9 Single-Rail vs. Dual-Rail Protocol (1/2) Single-Rail ： Bounded delay, not easy to do early completion detection. Sometimes we can use multi-case delay

10. NTU Confidential 10 Single-Rail vs. Dual-Rail Protocol (2/2) Dual-Rail: Encode every signal, Xi, with two wires, Xi,H and Xi,L [1] [2]

11. NTU Confidential 11 Multi-case delay look-ahead adder [3]

12. NTU Confidential 12 Dual-rail circuits Differential Cascode Voltage Switch Logic (DCVSL) Reduced direct logic (RDL)

13. NTU Confidential 13 Dual-rail Adder [4] A. Martin (1991) Asynchronous adder transistor count =34

14. NTU Confidential 14 Comparison Bounded delayDual-rail AreaBetterWorse Early CompletionWorseBetter PowerBetter ?Worse ?

15. NTU Confidential Low-Power Circuits No global clock Functions work only when needed

16. NTU Confidential 16 Dissipating when and where active Functions work only when needed In Synchronous systems, we may use Gated Clock

17. NTU Confidential Low Noise and Low Emission

18. NTU Confidential 18 What speed clock brings Noise When voltage drops across parasitic inductances  emit EM wave [1]

19. NTU Confidential 19 Frequency spectra of the two 80C51 microcontrollers In synchronous circuit with 3.6 MHz clock rate, there are a series of harmonics [1]

20. NTU Confidential Heterogeneous Systems (GALS)

21. NTU Confidential 21 Globally-Asynchronous Locally-Synchronous Synchronous Circuits are easy to design Low Power: No PLL, No clock driver, Functions work only when needed. An approach for System-on-Chip timing

22. NTU Confidential 22 Synchronous-Asynchronous interfaces – asynchronous wrapper h

23. NTU Confidential 23 Conclusion Due to average-case delay, asynchronous circuits have high performance. No clock driver, No high-speed oscillator, No PLL, and the Functions work only needed, asynchronous circuits have low power dissipation. No global clock  No high frequency current component  Low Noise and Low EM wave emission Due to the Increasing reuse of building blocks (IP), and integration of entire system, heterogeneous systems may be well used in the future.

24. NTU Confidential 24 Reference [1] Scanning the Technology:Applications of asynchronous circuits C. H. (Kees) van Berkel, Mark B. Josephs, and Steven M. Nowick. Proceedings of the IEEE, 87(2):223--233, February 1999. [2] Designing asynchronous circuits for low power: An IFIR filter bank for a digital hearing aid L. S. Nielsen and J. Sparsø, this issue, pp. 268-281. [3] VLSI circuits for low-power high-speed asynchronous addition S.Perri, P.Corsonello, G. Cocorullo; IEEE Trans. On VLSI Systems, In Press 2002 [4] The systematic Design of asynchronous circuits ICCA 95 [5] An asynchronous low-power 80c51 microcontroller H. van Gageldonk, D. Baumann, K. van Berkel, D. Gloor, A. Peeters, and G. Stegmann, in Proc. Int. Symp. Advanced Researchin Asynchronous Circuits and Systems, 1998, pp. 96–107.