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AR# 60022

Virtex-7 FPGA Gen3 Integrated Block for PCI Express v3.0 (Rev1) - TIMING-10#1 Warning Missing property on synchronizer

Description

Version Found: v3.0 (Rev1)

Version Resolved and other Known Issues: See (Xilinx Answer 54645)

When implementing the Virtex-7 FPGA Gen3 Integrated Block for PCI Express v3.0 (Rev1) core in either of the two Tandem Modes, the tool gives the following warning message if the "report_drc -ruledeck timing_checks" command is issued.

TIMING-10#1 Warning
Missing property on synchronizer 
A logic synchronizer with double-registers c_i_wrapper_support_i/c_i_wrapper_i/c_i_i/c_inst/inst/inst/c_i_c_inst_0_fast_cfg_init_cntr_i/cdc_reg1_reg and c_i_wrapper_support_i/c_i_wrapper_i/c_i_i/c_inst/inst/inst/c_i_c_inst_0_fast_cfg_init_cntr_i/cdc_reg2_reg has been detected between clock startupEosClk and clock userclk1 but the synchronizer does not have the property ASYNC_REG defined on one or both registers
Related violations: <none>

Solution

This warning is issued because the ASYNC_REG attribute is only applied to the first of two clock domain crossing registers.

While this produces the desired effect in the generated netlist, both registers should have the ASYNC_REG attribute applied to them.

While no action is required, the warning message can be eliminated by applying the ASYNC_REG property to the identified registers in the user constraints file.

The command to apply this constraint for the example above is shown below.

set_property ASYNC_REG TRUE [get_cells c_i_wrapper_support_i/c_i_wrapper_i/c_i_i/c_inst/inst/inst/c_i_c_inst_0_fast_cfg_init_cntr_i/cdc_reg2_reg]

This will be fixed in a future release of the core. 


Note: "Version Found" refers to the version where the problem was first discovered.

The problem might also exist in earlier versions, but no specific testing has been performed to verify earlier versions.


Revision History:

04/26/2014 - Initial Release

AR# 60022
Date Created 03/31/2014
Last Updated 09/09/2015
Status Active
Type Known Issues
IP
  • Virtex-7 FPGA Gen3 Integrated Block for PCI Express (PCIe)