Warning: Failed to find atom information in IOPLL SDC: ERROR: Cannot access ENUM_IOPLL_FEEDBACK data of the encrypted atom node 111916. This operation involves an encrypted atom node. Use the BOOL_ENCRYPTED test to avoid such nodes and the error.

Description

You may see this message in Quartus® Prime software versions 18.1 or earlier if the IOPLL IP  is encrypted in your design. Due to encryption, the IOPLL's auto-generated SDC file is unable to traverse the atom netlist to find the source of the IOPLL's refclk. 

Resolution

To work around this warning, manually create an SDC file for the IOPLL's refclk and output clocks to replace the SDC file that is auto-generated in the Quartus® Prime software.