Page 1121 - The Mechatronics Handbook

41.5 Concluding Remarks

Most digital designs are sequential systems. Such systems may be synchronous or asynchronous. Syn-
chronous systems have a clock that controls the operation of the system. The performance of such a
system is as good as the speed of its clock. But synchronous systems avoid the problems of hazards and
races. On the other hand, asynchronous circuits and controllers are much faster but may include races.
A race may occur whenever a state transition requires the change of two or more of the state variables
simultaneously. The race is between different variables to see which one changes first. A critical race may
force the circuit to end up in different stable states. Critical races may be eliminated by carefully studying
and analyzing the circuit.

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