AR# 34015 Virtex-6 FPGA Embedded Tri-mode Ethernet MAC Wrapper v1.3 - The example design MMCM parameter values can cause Map errors or result in marginal operation
When the 16-bit client interface is selected, the Virtex-6 FPGA Embedded Tri-Mode Ethernet MAC Wrapper example design wrapper uses MMCM parameter values which can cause Map errors if configured for 2.5 Gb/s, or marginal operation if configured for 1 Gb/s or 2 Gb/s.
Solution
The ISE design tools 11.5 release of the Virtex-6 FPGA Embedded Tri-Mode Ethernet MAC Wrapper provides correct MMCM parameterization. For earlier core releases, the MMCM parameter values should be updated as follows:
For 1 Gb/s speeds:
CLKFBOUT_MULT_F: from 4.0 to 5.0 CLKOUT0_DIVIDE_F: from 4.0 to 5.0 CLKOUT1_DIVIDE: from 8 to 10
For 2 Gb/s or 2.5 Gb/s speeds:
CLKFBOUT_MULT_F: from 4.0 to 5.0 CLKOUT0_DIVIDE_F: from 2.0 to 2.5 CLKOUT1_DIVIDE: from 4 to 5