Methodology DRCs with Impact on Signoff Quality and Hardware Stability - 2024.1 English

UltraFast Design Methodology Guide for FPGAs and SoCs (UG949)

Document ID
UG949
Release Date
2024-05-30
Version
2024.1 English

The DRCs shown in the following table do not usually flag issues that impact the ease of closing timing. Instead, these DRCs flag problems with timing analysis accuracy due to non-recommended constraints. Even when setup and hold slacks are positive, the hardware might not function properly under all operating conditions. Most checks refer to clocks not defined on the boundary of the design, clocks with unexpected waveform, missing timing requirements, or inappropriate CDC circuitry. For this last category, use the report_cdc command to perform a more comprehensive analysis.

Important: Carefully verify timing checks with a severity of Critical Warning.
Table 1. Signoff Quality Methodology DRCs
Check Severity Description
TIMING-1, TIMING-2, TIMING-3, TIMING-4, TIMING-27 Critical Warning Non-recommended clock source point definition
TIMING-5, TIMING-25, TIMING-19 Critical Warning Unexpected clock waveform
TIMING-9, TIMING-10 Warning Unknown or incomplete CDC circuitry
TIMING-11 Warning Inappropriate set_max_delay -datapath_only command
TIMING-12 Warning Clock Reconvergence Pessimism Removal disabled
TIMING-13, TIMING-23 Warning Incomplete timing analysis due to broken paths
TIMING-17 Critical Warning Non-clocked sequential cell
TIMING-18, TIMING-20, TIMING-26 Warning Missing clock or input/output delay constraints
TIMING-21, TIMING-22 Warning Issues with MMCM compensation
TIMING-24 Warning Overridden set_max_delay -datapath_only command
TIMING-29 Warning Inconsistent pair of multicycle paths
TIMING-35 Critical Warning No common node in paths with the same clock
TIMING-40, TIMING-43 Warning Inappropriate clock topologies or requirements
TIMING-41 Warning Invalid forwarded clock defined on an internal pin
TIMING-46 Warning Multicycle path with tied CE pins
TIMING-47 Warning False path or asynchronous clock group between synchronous clocks
TIMING-51 Critical Warning No common phase between related clocks from parallel MMCMs or PLLs
TIMING-52 Critical Warning No common phase between related clocks from Spread Spectrum MMCM
TIMING-54 Critical Warning Scoped false path, clock group or max delay datapath only constraint between clocks
TIMING-55 Critical Warning Multiple clocks reaching a CMB deskew pin
TIMING-56 Warning Missing logically or physically excluded clock groups constraint
TIMING-57 Warning Unsupported configuration with PHASESHIFT_MODE and digital deskew