TIMING-22: Missing External Delay on MMCM - 2021.1 English

Vivado Design Suite User Guide: Design Analysis and Closure Techniques (UG906)

Document ID
UG906
Release Date
2021-06-30
Version
2021.1 English

The MMCM <CELL_NAME> has an external feedback loop but no external delay has been specified between FBOUT and FBIN. It is recommended to specify an external delay with set_external_delay between the two ports connected to the pins FBOUT and FBIN with an external feedback loop.