AR# 34739

Virtex-6 Integrated Block Wrapper v1.3 for PCI Express - Incorrect MMCM VCO settings result in "ERROR:PhysDesignRules:1995 - The computed value for the VCO operating frequency..."


If ISE Design Suite 11.5 is used to implement the v1.3 wrapper, MAP fails with theh following error:

"ERROR:PhysDesignRules:1995 - The computed value for the VCO operating frequency of MMCM_ADV instance cgator_wrapper/rport/pcie_clocking_i/mmcm_adv_i is calculated to be 500.000000 MHz. This falls below the operating range of the MMCM VCO frequency for this device of 600.000000 - 1200.000000 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."

The MMCM attribute settings in the v1.3 core are incorrect. You should download the files provided in this Answer Record to obtain the correct settings. Implementation with ISE 11.3 design tools does not indicate any error message, but the settings should be updated.


An update is available in (Xilinx Answer 34279); download the ZIP file titled "" from the Answer Record.

The ZIP file contains a file titled "pcie_clocking_v6.v" which contains new settings for the MMCM VCO parameters. Place this file in your generated core's source directory.

Note that this ZIP file is cumulative and can contain fixes for other problems as described in (Xilinx Answer 34279).

Revision History:
03/15/2010 - Initial Release
AR# 34739
Date 03/12/2010
Status Active
Type Known Issues