kessels-async2000 - Applying Asynchronous Circuits in...

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Applying Asynchronous Circuits in Contactless Smart Cards Joep Kessels (Philips Research) Torsten Kramer (MAZ Hamburg) Gerrit den Besten, Ad Peeters (Philips Research) Volker Timm (Philips Semiconductors) Abstract We have designed an asynchronous chip for contactless smart cards. Asynchronous circuits have two power prop- erties that make them very suitable for contactless devices: low average power and small current peaks. The fact that asynchronous circuits operate over a wide range of the sup- ply voltage, while automatically adapting their speed, has been used to obtain a circuit that is very resilient to voltage drops while giving maximum performance for the power be- ing received. The asynchronous circuit has been built, tested and evaluated and the results were so convincing that, based on the circuits presented, a product is being designed. Keywords: low-power asynchronous circuits, smart cards, contactless devices, DES cryptography. 1. Introduction Since their introduction in the eighties, smart cards have been used in a continuously growing number of appli- cations, such as banking, telephony (telephone and SIM cards), access control (Pay-TV), health-care, tickets for public transport, electronic signatures and identification. Currently, most cards have contacts and, for that reason, need to be inserted into a reader. For applications in which the fast handling of transactions is important, so-called con- tactless smart cards have been introduced requiring only close proximity to a reader (typically several centimeters). The chip on such a card must be extremely power efficient, since it is powered by electromagnetic radiation. Asynchronous CMOS circuits have the potential for very low power consumption, since they only dissipate when and where active. However, asynchronous circuits are difficult to design at the level of gates and registers. Therefore the [email protected] [email protected] high-level design language Tangram was defined [10] and a so-called silicon compiler has been implemented that trans- lates Tangram programs into asynchronous circuits. Tan- gram is a conventional programming language, like C or Pascal, extended to include constructs for expressing con- currency and communication in a way similar to the lan- guage CSP [2]. Similar approaches have been proposed in [1, 3]. The Tangram compiler generates a special class of asyn- chronous circuits called handshake circuits [8, 6]. Hand- shake circuits are constructed from a set of about 30 ba- sic components that use 4-phase single-rail handshake sig- nalling for communication. Several chips have been designed in Tangram [9, 11] and if we compare these chips to existing clocked implementa- tions, then the asynchronous versions are generally about 20% larger in area and consume about 25% of the power.
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This note was uploaded on 11/28/2011 for the course COMP 790 taught by Professor Staff during the Fall '08 term at UNC.

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kessels-async2000 - Applying Asynchronous Circuits in...

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