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AR# 31574

10.1 to 14.7 Virtex-5 MAP - ERROR:PhysDesignRules:1577 - Illegal routing. The DCM_ADV block ...


My design fails in version 10.1 of ISE Design Suite with the following "illegal routing" error. 


ERROR:PhysDesignRules:1577 - Illegal routing. The DCM_ADV block
<i_srl_top/i_srl_pcix_clk_wrap/i_pci_clk_fpga/DCM_BASE_pci_clk/DCM_ADV> has CLK output pin <CLK90> with incomplete or incorrect connectivity. Routing from the <CLK90> pin to a BUFG, BUFGCTRL or PLL_ADV block type was not found. The DCM_ADV CLK output pins can only route to BUFG, BUFGCTRL or PLL_ADV block types.

This design worked without issues in ISE 9.2i.

What is the cause of this error?


This DRC error message is triggered by the presence of dangling output signals on the DCM_ADV that should have been trimmed but were not. 

Because the DRC check is looking for specific legal load pins on the signal, it fails when they are not detected. 

This specific trimming error relating to DCM_ADV outputs has been known to occur for two different reasons:


  1. "S" properties on DCM_ADV input nets can incorrectly affect the trimming behavior of output nets.

    This change is related to new trimming behavior in ISE 10.1.

    See (Xilinx Answer 30112)

    It is possible to avoid this behavior by setting an environment variable that restores the old 9.2 behavior:
    Linux and Solaris
    setenv XIL_MAP_OLD_SAVE 1
    For general information about setting ISE environment variables, see (Xilinx Answer 11630)
  2. This trimming problem can also be caused by Keep Hierarchy constraints.
    This problem can be avoided by using the MAP option -ignore_keep_hierarchy
For more general information about trimming issues, see (Xilinx Answer 23990).
AR# 31574
Date 01/08/2015
Status Active
Type General Article
  • ISE Design Suite
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