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AR# 11917

4.1i Virtex-II MAP - IOB (programmable) delay is incorrectly turned "On" for an IOB with a DCM-based clock.

Description

Keywords: Virtex-II, IOB, programmable, delay, on, default, DCM

Urgency: Standard

General Description:
In a Virtex-II design, the IOB delay is turned "On" by default in an IOB where a flip-flop is clocked by a DCM-based clock. (This IOB delay should not be on in this case.)

Solution

To work around this problem, use the NODELAY attribute.

This can be done in the UCF or NCF files by using the following format:

NET RcvData* NODELAY ;
NET SelectOUT NODELAY ;

This problem is fixed in the latest 4.1i Service Pack, available at:
http://support.xilinx.com/support/techsup/sw_updates.
The first service pack containing the fix is 4.1i Service Pack 1.
AR# 11917
Date Created 07/10/2001
Last Updated 08/20/2003
Status Archive
Type General Article