A new improved cost-table-based technique for synthesis of 4-valued unary functions implemented using current-mode CMOS circuits

Abstract

In this paper, we introduce a new improved cost-table-based technique for synthesis of 4-valued one-variable functions for implementation using current-mode CMOS (CMCL) circuits. The technique uses a cost-table consisting of 38 positive functions and 10 negative functions as input. The algorithm used to synthesize all 256 4-valued unary functions proceeds as follows. In each step, the algorithm selectively adds two functions from those accumulated so far in the table. If the newly formed function exists in the table at a higher cost, then the function just formed will replace the existing one; otherwise the formed function will be ignored and the process repeats. The obtained results show that the maximum cost of any function is 17 compared to 19 using a previously introduced algorithm. The average cost per function is 9.54 compared to 10.41. Lower cost is achieved in synthesizing 157 (60%) functions using the proposed technique compared to our previously introduced technique.