AsyncReview2

AsyncReview2 - Always a finite probability that...

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Montek Singh COMP790-084 Nov 1, 2011
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Review What is metastability Can we avoid it? How do we deal with it?
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What is  metastability? indecision
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… in which a discrete decision must be made  based on analog inputs can  never  be guaranteed to produce a correct output in  bounded time wow!
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Typically sample  values at clock  edges
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When clock edge and data  transition are close… output can take a long time to  settle closer the call, harder the  decision
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Analog model
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Closer the call, the longer the decision time!
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Practical circuits that  reduce  the chance of  persisting metastability cannot eliminate! give a full clock cycle for metastability to resolve
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Unformatted text preview: Always a finite probability that metastability persists for an arbitrarily long time diminishes fast with time Mean time to failure: Several scenarios possible depending on data and clock timing Sender-receiver pair (Note: error in figure b) frequently, buffering needed along with synchronization well suited for mesochronous clocks same frequency, but different phases best-known circuit for resolving metastability backbone of many modern arbiter circuits instead of waiting for a fixed time, includes metastability detection of course, no guarantees here either!...
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AsyncReview2 - Always a finite probability that...

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