Abstract
We demonstrate the design of a Globally Asynchronous Locally Synchronous (GALS) Discrete Fourier Transform circuit. Each locally synchronous stage is surrounded by an “Asynchronous Wrapper” which provides an asynchronous interface to an otherwise synchronous circuit. Every locally synchronous (LS) region operates independently, eliminating problems of clock skew and allowing each region to run at its own clock speed. Metastability can never occur because an asynchronous handshake “stretches” or “pauses” the local clock until data has stabilised. When new data is not available for processing the local clock stretches, automatically preventing the LS block from consuming power. When new data does arrive, the clock starts directly in phase with the handshake without wasted synchronisation time.
The internal DFT stages were designed using typical synchronous.techniques. We were therefore able to use VHDL to quickly compose and synthesise the circuit using industry standard tools. Most current asynchronous design methodologies require either manual design or complex specifications which become unwieldy as circuit size grows. Locally synchronous design allows us to take advantage of normal synchronous methods, reducing design time while providing a robust interface that delay-insensitively communicates with the environment.
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Bormann, D.S., Cheung, P.Y.K. (1997). A novel globally asynchronous locally synchronous sliding window DFT implementation. In: Reis, R., Claesen, L. (eds) VLSI: Integrated Systems on Silicon. IFIP — The International Federation for Information Processing. Springer, Boston, MA. https://doi.org/10.1007/978-0-387-35311-1_20
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DOI: https://doi.org/10.1007/978-0-387-35311-1_20
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