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!

AR# 34294

14.x Timing Analysis - "WARNING:Timing:3379 - The REFERENCE_PIN xxx on constraint xxx ... was not included as part of analysis"

Description

I have this OFFSET OUT constraint in my UCF:

TIMEGRP "pad_group" OFFSET = OUT 7.69ns after "ClkIn" REFERENCE_PIN "ClkOut" TIMEGRP "reg_group";

However, I receive the following warning during Process "Generate Post-Place & Route Static Timing":

WARNING:Timing:3379 - The REFERENCE_PIN ClkOut on constraint TIMEGRP "pad_group" OFFSET = OUT 7.69 ns AFTER COMP "ClkIn" REFERENCE_PIN BEL"ClkOut" TIMEGRP reg_group; was not included as part of analysis. The REFERENCE_PIN keyword is being ignored.

How can I resolve this issue?

Solution

Solution 1: Use group specific OFFSET OUT

To use REFERENCE_PIN keyword in the group specific OFFSET OUT constraint, the following requirements must be met.

  • The reference output clock (ClkOut) must be a regenerated clock using an ODDR or any other sequential element.

In a source-synchronous design, a typical usage is regenerating the output clock using an ODDR. The REFERENCE_PIN keyword will not work if the reference output clock pad is directly connecting from BUFG or the clock source (input clock pad or DCM/PLL/MMCM output clock).



  • The reference output clock pad must be included in the same pad group of output data pads.
  • The reference output clock ODDR must be included in the same register group of output data registers.

Example 1:

#create pad group and include the output clock pad into the same group

NET "<data_pad_name_pattern>" TNM = pad_group;

NET "ClkOut" TNM = pad_group;

#create register group and include the output clock ODDR into the same group

INST "<data_registers_name_pattern>" TNM = register_group;

INST "ClkOutODDR" TNM = reg_group;

#write OFFSET OUT constraint

TIMEGRP "pad_group" OFFSET = OUT AFTER "Clkin" REFERENCE_PIN "ClkOut" TIMEGRP "reg_group";


Solution 2 : Use global OFFSET OUT

The reference output clock (ClkOut) must be a regenerated clock using an ODDR or any other sequential element as well when using global OFFSET OUT with REFERENCE_PIN keyword.

Example 2:

#write the global OFFSET OUT constraint.

OFFSET = OUT AFTER "Clkin" REFERENCE_PIN "ClkOut";

AR# 34294
Date Created 02/16/2010
Last Updated 01/14/2014
Status Active
Type General Article
Tools
  • ISE Design Suite - 11.4
  • ISE Design Suite - 11.5
  • ISE Design Suite - 12.1
  • More
  • ISE Design Suite - 12.2
  • ISE Design Suite - 12.3
  • ISE Design Suite - 12.4
  • ISE Design Suite - 13.1
  • ISE Design Suite - 13.2
  • ISE Design Suite - 13.3
  • ISE Design Suite - 13.4
  • ISE Design Suite - 14.1
  • ISE Design Suite - 14.2
  • ISE Design Suite - 14.3
  • ISE Design Suite - 14.4
  • Less