When I implement a design that utilizes the example MMCM instantiation generated by the GTX Transceiver Wizard, errors similar to the following occur:
"ERROR:PhysDesignRules:1997 - The computed value for the VCO operating frequency of MMCM_ADV instance txoutclk_mmcm0_i/mmcm_adv_i is calculated to be 468.750000 MHz. This falls below the operating range of the MMCM VCO frequency for this device of 600.000000 - 1440.000000 MHz. Please adjust either the input frequency CLKINx_PERIOD, multiplication factor CLKFBOUT_MULT_F or the division factor DIVCLK_DIVIDE, in order to achieve a VCO frequency within the rated operating range for this device."
"ERROR:PhysDesignRules:2063 - A CLKFBOUT_MULT_F setting of 4.0 for MMCM_ADV (block txoutclk_mmcm0_i/mmcm_adv_i) can not be supported at this time."
For designs using 11.4 ISEdesign toolsor previous versions, these issues do not error out, but might cause failures on the board.
This Answer Record discusses what actions can be taken to re-generate the MMCM to work around these errors.
These errors are related to the new MMCM requirements for CLKFBOUT_MULT_F and the VCO minimum frequency of 600 MHz.
To work around these errors, the MMCM instance needs to be updated with correct settings: