Advanced timing of level-sensitive sequential circuits

Abstract

The paper addresses the advanced timing analysis of multiphase level-sensitive synchronous circuits under clock skew scheduling (Kourtev, I.S. and Friedman, E.G., "Optimization Through Clock Skew Scheduling", Kluwer Academic Publishers, 2000). The timing analysis framework previously offered for a single-phase clocking scheme (Taskin, B. and Kourtev, I.S., Proc. 15th IEEE Int. ASIC/SOC Conf. p.358-62, 2002) is enhanced to accommodate a multiphase clocking scheme. In particular, the timing analysis framework is used to formulate the clock period minimization problem of multiphase level-sensitive circuits. The modified big M method of Taskin and Kourtev is used to linearize the formulation of the clock period minimization problem and experiments are performed on the ISCAS'89 benchmark circuits. In single-phase level-sensitive circuits, up to 63% improvements over conventional zero clock skew, edge-triggered circuits are achieved through the simultaneous application of non-zero clock skew scheduling and time borrowing. Comparable improvements of up to 62% are achieved for the same circuit topologies under a multiphase clocking scheme.