数字设计原理与实践九.

数字设计原理与实践(九).DO NOT COPY9c h a p t e rDO NOT COPYSequential-CircuitDesign ExamplesDO NOT ust about every real digital system is a sequential circuit―all it takes J is one feedback loop,latch,or flip-flop to make a circuit’s present behavior depend on its past inputs.However,if we were to design or analyze a typical digital system as a single sequential circuit,we COPY would end up with an enormous state table.For example,strictly speaking,a PC with only16Mbytes of main memory is a sequential circuit with well over2128,000,000states!