Synchronous circuit
A synchronous circuit is a digital circuit composed of edge-triggered flip-flops which are all made timed from a central clock signal. Usually all complex integrated digital circuits such as microprocessors or different digital peripheral blocks are built as synchronous digital circuit, as this allows controllable time relationships between the individual circuit elements. Synchronous circuits are the preferred design method of digital circuits in field programmable gate arrays ( FPGAs) dar.
Synchronous circuits with feedback paths can be described as a synchronous circuit works or synchronous state machine. Transitions from one state to the next place in the fixed time frame of the clock signal. Typical synchronous sequential circuits are microprocessors which are operated with a central clock as so-called Eintaktsystem. There are also multi- clock systems in which all clock signals have to each other a defined phase and frequency relationship and are referred to in the broader sense as synchronous.
The contrast represent asynchronous circuits which have no central clock signal and having due to the difficult handling in more complex circuits, with a few exceptions, only limited practical relevance.
Properties
An essential feature of digital synchronous circuits, the clock frequency. This is received in edge-triggered flip-flops which serve as the basic storage elements, the clock edge, the state of input into the memory and held until the next clock edge. The period of time that is the time between two adjacent clock edges, is the maximum " processing speed " of a synchronous circuit. Limit the frequency up or the period is down among other things by the signal propagation times of the data signal paths between the steps and the time which is required for logical links between the memory elements. It should be noted that not only the data signals have a certain period of time, but also the clock signal, leading to unwanted race conditions and timing offset (English clock skew ) can result.