Chips become more complex so it is so important to have design automation in the upper level of abstraction, where the trade-off is more effective and functionality is simpler for recognizing. This process (automating all or a part of the design process and shifting automation to the upper levels) has many advantages when it least to have different styles in design style and it makes faster designing process. Furthermore, we could reach a better output by design automation in comparison to previous methods for designing. Computer-aided tools were developed with success so, in different parts of the development cycle, they are used when in the design of microelectronic circuits, they become useful.