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AR# 64772

MIG UltraScale RLDRAM3 - timing failures in mmcm_clk0 domain as a result of too many logic levels


Version Found: MIG UltraScale v7.1
Version Resolved: See (Xilinx Answer 58435)

The following path (or similar paths) might fail timing for MIG UltraScale RLDRAM3 designs as a result of too many logic levels:

Slack (VIOLATED) : -0.370ns (required time - arrival time)
Source: u_SN33_kintexuRLDRAM3_933MHz_36bit_vivado_ssit/inst/u_rld3_mem_intfc/u_rld_mc/start_idx_reg[0]/C
(rising edge-triggered cell FDRE clocked by mmcm_clkout0 {rise@0.000ns fall@2.142ns period=4.284ns})
Destination: u_SN33_kintexuRLDRAM3_933MHz_36bit_vivado_ssit/inst/u_rld3_mem_intfc/u_rld_ui/usr_addr_fifo/u_af1.u_af/RDEN
(rising edge-triggered cell FIFO36E2 clocked by mmcm_clkout0 {rise@0.000ns fall@2.142ns period=4.284ns})
Path Group: mmcm_clkout0
Path Type: Setup (Max at Slow Process Corner)
Requirement: 4.284ns (mmcm_clkout0 rise@4.284ns - mmcm_clkout0 rise@0.000ns)
Data Path Delay: 3.393ns (logic 1.076ns (31.712%) route 2.317ns (68.288%))
Logic Levels: 6 (LUT2=1 LUT3=1 LUT6=4)
Clock Path Skew: -0.188ns (DCD - SCD + CPR)


To work around this issue, try using a number of different implementation strategies (for example, register balancing, retiming, etc.).

If the user logic is being driven by the mmcm_clk domain try inserting an additional BUFG for the user logic to allow Vivado to properly balance the user and MIG domain.

If these violations are still seen please open a Service Request for assistance:


Revision History:
06/30/2015- Initial Release
07/06/2015 - Updated solution

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
58435 DDR4, DDR3, QDRIV, QDRII+, RLDRAM3, LPDDR3 UltraScale and UltraScale+ - IP Release Notes and Known Issues N/A N/A
AR# 64772
Date 07/07/2015
Status Active
Type Known Issues
  • Kintex UltraScale
  • Virtex UltraScale
  • MIG UltraScale