Basics of multi-cycle & false paths

Nitin Singh, Neha Agarwal,Arjun Pal Chowdhury (Freescale Semiconductor)
EDN (August 07, 2014)

One of the significant challenges to RTL designers is to identify complete timing exceptions upfront. This becomes an iterative process in complicated designs where additional timing exceptions are identified based upon critical path or failing path analysis from timing reports. This approach leaves a significant number of timing paths which may not be real, but these never get identified, since they may not come up in the critical path report. However, synthesis and timing tools will continue to expend resources optimizing these paths when it is not needed. At the same time, it can also impact area and power consumption of the device.

The intent of this document is to provide examples of false and multi cycle path exceptions that are easily missed by even experienced designers, and are identified through iterations on timing reports.

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