Metastability
From Biocrawler, the free encyclopedia.
Metastability is the ability of a non-equilibrium state to persist for a long period of time.
Metastability in molecules
Usually metastability is due to a relatively slow phase transformation. For example at room temperature diamonds are metastable because the phase transformation to the stable graphite form is extremely slow. At higher temperatures the rate of phase transformation is increased and the diamond will transform to graphite.
Martensite is a metastable phase used to control the hardness of most steel. The bonds between the building blocks of polymers such as DNA, RNA and proteins are also metastable.
Metastability in electronics
In electronics, the flip-flop is a device that suffers from metastability. It has two well-defined stable states, traditionally designated 0 and 1, but under certain conditions it can hover between them for longer than the normal decision time.
Synchronous design techniques make circuits that are immune to the race conditions that can be caused by metastability. Asynchronous circuits must be carefully designed to avoid metastability. See the book Computation Structures by Stephen A. Ward and Robert H. Halstead, Jr. (c)1990 for details.
