Synchronous circuit uses clock pulse to synchronize its subsystem, while asynchronous circuit does not use clock pulse to synchronize, and its subsystem uses special "start" and "end" signals to synchronize.
Second, the advantages are different.
Because asynchronous circuits have the following advantages-no clock offset, low power consumption, average performance rather than worst, modularity, composability and reusability-in recent years, the research on asynchronous circuits has increased rapidly, and the number of papers has doubled, so the design of Intel Pentium 4 processor has also begun to adopt asynchronous circuit design.
V asynchronous circuit is mainly a combinational logic circuit, which is used to generate read-write control signal pulses of address decoder, FIFO or RAM. Its logic output has nothing to do with any clock signal, and the glitch generated by the decoded output can usually be detected.
Synchronization circuit is a circuit composed of sequential circuits (registers and various triggers) and combinational logic circuits, and all its operations are completed under strict clock control. These sequential circuits * * * share the same clock CLK, and all state changes are completed at the rising edge (or falling edge) of the clock. ?
Third, the analysis is different
When analyzing asynchronous sequential logic circuits, it is necessary to simply look at the clock signal of each flip-flop. When the clock signal of a flip-flop comes, the state of the flip-flop changes according to the state equation, and when no clock signal comes, the state of the flip-flop will remain unchanged.
Extended data
Synchronization logic has two main disadvantages:
The 1. clock signal must be assigned to each flip-flop on the circuit. Clock is usually a high-frequency signal, which will lead to power consumption, that is, heating. Even if each trigger does nothing, it will consume a small amount of energy, resulting in waste heat.
2. The maximum possible clock frequency is determined by the slowest logic path in the circuit, that is, the critical path. This means that every logical operation, from the simplest to the most complex, should be completed in every clock cycle.
One way to eliminate this limitation is to divide a complex operation into several simple operations. This technology is called "pipeline". This technology is very important in microprocessors to help improve the clock frequency of today's processors.
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