Abstract: In digital circuit's design, the succession design is a system performance outstanding feature, in the top level design method, also correspondingly enhances to sequential control's abstract, therefore in design difficult assurance, but in understood that the TTL electric circuit succession model in the foundation, uses the reasonable design method in the design complex number system is effective, after many design examples proved that selects this method to be possible to make electric circuit's simulation capacity to enhance greatly, and system's operating frequency may achieve a high level. Now electronic products' design and the manufacture process cannot leave computer's help, this time will use electronic softwares and so on multism8, protel99se to realize the simulation and to draw up the PCB board chart. key words: Clock circuit multism8 Simulation protel99se
