UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!
  1. Xilinx - Adaptable. Intelligent.
  2. Support
  3. AR# 52834: 2012.3 Vivado Timing Analysis - Why is the MMCM output generated clock value incorrect?

AR# 52834

2012.3 Vivado Timing Analysis - Why is the MMCM output generated clock value incorrect?

Description


I have an MMCM which takes a 5 ns input clock and generates a 400 MHz (2.5ns) output clock, but I get 2.20e-07 value. This derived clock is incorrect and causes downstream timing errors.

Pulse Width Checks
--------------------------------------------------------------------------------------
Clock Name: u_memc_ui_top_axi/mem_intfc0/ddr_phy_top0/u_ddr_mc_phy_wrapper/u_ddr_mc_phy/ddr_phy_4lanes
_0.ddr_phy_4lanes/ddr_byte_lane_A.ddr_byte_lane_A/iserdes_clkdiv
Waveform: { 0.15625 1.40625 }
Sources: { system_i/DDR3_SDRAM/DDR3_SDRAM/u_memc_ui_top_axi/mem_intfc0/ddr_phy_top0/u_ddr_mc_phy_wrap
per/u_ddr_mc_phy/ddr_phy_4lanes_0.ddr_phy_4lanes/ddr_byte_lane_A.ddr_byte_lane_A/phaser_in_gen.phaser_in/ICLKDIV }

Check Type Lib Pin Reference Pin Required Actual Slack Location Pin
Min Period IN_FIFO/WRCLK 2.500 2.500 -2.220e-07 IN_FIFO_X1Y8 system_i/DDR3_SDRAM/DDR3_SDRAM/u_memc_ui_top_axi/mem_intfc0/ddr_phy_top0/u_ddr_mc_phy_wrap
per/u_ddr_mc_phy/ddr_phy_4lanes_0.ddr_phy_4lanes/ddr_byte_lane_A.ddr_byte_lane_A/in_fifo_gen.in_fifo/WRCLK
Low Pulse Width IN_FIFO/WRCLK 1.075 1.250 0.175 IN_FIFO_X1Y8 system_i/DDR3_SDRAM/DDR3_SDRAM/u_memc_ui_top_axi/mem_intfc0/ddr_phy_top0/u_ddr_mc_phy_wrap
per/u_ddr_mc_phy/ddr_phy_4lanes_0.ddr_phy_4lanes/ddr_byte_lane_A.ddr_byte_lane_A/in_fifo_gen.in_fifo/WRCLK



Why is the MMCM output generated clock value incorrect?

Solution

This issue is scheduled to be fixed in the next major release of the Vivado software.
AR# 52834
Date 11/08/2012
Status Active
Type Known Issues
Tools
  • Vivado - 2012.3
  • ??????
Page Bookmarked