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# 31797

MIG v2.3 - Virtex-4 DDR/DDR2 Direct Clocking: Extra IDELAYCTRL instance LOC causing WARNING:Place:851

Description

While implementing the MIG v2.3 Virtex-4 DDR/DDR2 Direct Clocking design, I see the following warning:

WARNING:Place:851 - The delay controller "idelay_ctrl0/IDELAYCTRL_INST[1].u_idelayctrl" has been locked with the following location constraint:
COMP "idelay_ctrl0/IDELAYCTRL_INST[1].u_idelayctrl" LOCATE = SITE "IDELAYCTRL_X0Y10" LEVEL 1

However, none of the delay elements calibrated by this controller are being used. The controller will still use up a global clock resource from the clock region and consume power. Please refer to the usage document to use the controller efficiently.

Why is this warning occurring and can it be ignored?

Solution

The generated IDELAYCTRL LOC constraints in the MIG UCF should be based on DQ placement, because only DQ bits use the IDELAY elements. In MIG v.3, MIG is incorrectly considering both DQ and DQS placements even though IDELAY elements are not used for DQS. In certain pin-outs, this will result in unused IDELAYCTRL instances which will cause the following warning:

WARNING:Place:851 - The delay controller "idelay_ctrl0/IDELAYCTRL_INST[1].u_idelayctrl" has been locked with the following location constraint:
COMP "idelay_ctrl0/IDELAYCTRL_INST[1].u_idelayctrl" LOCATE = SITE "IDELAYCTRL_X0Y10" LEVEL 1

However, none of the delay elements calibrated by this controller are being used. The controller will still use up a global clock resource from the clock region and consume power. Please refer to the usage document to use the controller efficiently.

This is an extra IDELAYCTRL LOC which does not exist in the design. This warning can be ignored.

This issue will be resolved in MIG v3.0.
AR# 31797
Date Created 10/14/2008
Last Updated 12/15/2012
Status Archive
Type General Article
Devices
  • Virtex-4 FX
  • Virtex-4 LX
  • Virtex-4 SX
IP
  • MIG