digital electronics Digital electronics is a field of electronics involving the study of digital signals and the engineering of devices that use or produce them. This is in contrast to analog electronics and analog signals. Digital electronic circuits are usual ...

, a synchronous circuit is a digital circuit in which the changes in the

state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * ''The State'' (newspaper), a daily newspaper in Columbia, South Carolina, United States * '' Our ...

of memory elements are synchronized by a

clock signal In electronics and especially synchronous digital circuits, a clock signal (historically also known as ''logic beat'') oscillates between a high and a low state and is used like a metronome to coordinate actions of digital circuits. A clock s ...

. In a sequential

digital logic A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic ga ...

circuit, data are stored in memory devices called flip-flops or latches. The output of a flip-flop is constant until a pulse is applied to its "clock" input, upon which the input of the flip-flop is latched into its output. In a synchronous logic circuit, an electronic oscillator called the ''

clock A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and t ...

'' generates a string (sequence) of pulses, the "clock signal". This clock signal is applied to every storage element, so in an ideal synchronous circuit, every change in the logical levels of its storage components is simultaneous. Ideally, the input to each storage element has reached its final value before the next clock occurs, so the behaviour of the whole circuit can be predicted exactly. Practically, some delay is required for each logical operation, resulting in a maximum speed limitations at which each synchronous system can run. To make these circuits work correctly, a great deal of care is needed in the design of the clock distribution networks. Static timing analysis is often used to determine the maximum safe operating speed. Nearly all digital circuits, and in particular nearly all CPUs, are fully synchronous circuits with a global clock. Exceptions are often compared to fully synchronous circuits. Exceptions include self-synchronous circuits, Devlin, B. ; Ueki, H. ; Mori, S. ; Miyauchi, S. ; Ikeda, M. ; Asada, K
"Performance and side-channel attack analysis of a self synchronous montgomery multiplier processing element for RSA in 40nm CMOS"
2012. globally asynchronous locally synchronous circuits, and fully

asynchronous circuit Asynchronous circuit (clockless or self-timed circuit) is a sequential digital logic circuit that does not use a global clock circuit or signal generator to synchronize its components. Instead, the components are driven by a handshaking circui ...

References

{{DEFAULTSORT:Synchronous Circuit Automata (computation) Clock signal

See also

References