SWITCHING NETWORK LOGIC APPROACH FOR THE DESIGN OF CMOS VLSI CIRCUITS

The method for the design of the CMOS logic by using the switching network logic (SNL) concept is shown to yield high layout density. With non-series-parallel-connected structures for the CMOS cells, the number of MOSFETs employed by using this method is considerably reduced in comparison with the boolean gate approach. Logic functions are divided into single-contact (SC) and multi-contact (MC) functions by the SNL theory. It is known that most functions encountered in logic circuit design are MC variables, and the lack of a synthesis technique to realize MC functions which are the functions more commonly encountered has been the main obstacle for applying the SNL theory to CMOS logic circuit design. In this paper, a test condition is presented for the identification of SC and MC functions. Based on the condition, procedures are then formulated to modify a given MC function so that the approach for the synthesis of an SC function can be directly adopted for that of an MC function. Some practical examples are also given to illustrate the various steps in the synthesis procedures.