Waiting false path analysis of sequential logic circuits for performance optimization
Kazuhiro Nakamura, Kazuyoshi Takagi, Shinji Kimura, Katsumasa Watanabe · 1998
This paper introduces a new class of false path, which is sensi-tizable but does not affect the decision of the clock period. We call such false paths waiting false paths, which correspond to multi-cycle operations controlled by wait states. The allowable delay time of waiting false paths is greater than the clock pe-riod. When the number of allowable clock cycles for each path is determined, the delay of the path can be the product of the clock period and the allowable cycles. This paper presents a method to analyze allowable cycles and to detect waiting false paths based on symbolic traversal of FSM. We have applied our method to 30 ISCAS89 FSM benchmarks and found that 22 cir-cuits include such paths. 11 circuits among them include such paths which are critical paths, where the delay is measured as the number of gates on the path. Informations on such paths can be used in the logic synthesis to reduce the number of gates and in the layout synthesis to reduce the size of gates. 1