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AR# 31200

10.1 ChipScope Pro - Where is the option to Disable BUFG insertion on my JTAG clock for the ICON?


ChipScope Pro ICON v1.0.3 has removed "Disable BUFG on JTAG clock" from CORE Generator and Core Inserter to improve timing results when using ChipScope cores.


If you still need this feature from a resource point-of-view and need to debug without the BUFG option, there is a way to do this in both the Inserter and CORE Generator flows. This is not recommended.

CORE Generator

The BUFG can be disabled by setting the new xco parameter called "enable_jtag_bufg" to false. This will need to be manually modified in the xco file. The core can then be regenerated either by command line or by using the GUI form your CORE Generator project.

CSET enable_jtag_bufg=false

This option is only valid for 10.1; in CORE Generator 11.1, you cannot disable the BUFG used for the ICON Core.


You can enable this in the Inserter GUI as follows: Edit -> Preferences -> Miscellaneous -> Show Manual JTAG Global Clock Buffer Control in ICON Panel.

This option is only valid for 10.1; in Inserter 11.1, you cannot disable the BUFG used for the ICON Core.

Be aware that removing the BUFG can potentially cause timing issues on the ChipScope cores. Disabling this BUFG will result in problems with Core Detection and Core Triggering for many designs. If the design and packed and you need to disable the BUFG to free up the resource, it is highly likely that ChipScope will not work correctly on the board.

This feature has been modified in the latest 10.1 Service Pack, available at:

The first service pack containing the fix is 10.1 Service Pack 2.

AR# 31200
Date Created 06/18/2008
Last Updated 12/15/2012
Status Active
Type General Article