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AR# 13276

4.1i PAR - "WARNING:Place:2015 - A clock IOB/clock component pair have been found that are not placed in a good clock IOB/clock site pair..."

Description

Keywords: PAR, place, 2015, clock, BUFG, IOB

Urgency: Standard

General Description:
The following warning occurs during PAR; however, the pin I chose should have been a direct-connect to the BUFGMUX in the pin-out:

"WARNING:Place:2015 - A clock IOB/clock component pair have been found that are not placed in a good clock IOB/clock site pair. The clock component <top/CLKMUX> is placed at site BUFGMUX4P. The clock IO site that is paired with this clock buffer site is W11. The IO component DV_2_CLK is placed at site V11. This will not allow the use of the fast path between the IO and the Clock buffer. You may want to analyze why this problem exists and correct it. This is not an error so processing will continue."

This only occurs when the BUFGMUX is used as a MUX. Is the pin-out incorrect? Will the fast routing be used? How do I avoid this warning?

Solution

The pin-out should be correct. What may have happened is that the IOBs were connected to the incorrect BUFGMUX pin. The associated IOB of a particular BUFGMUX can only source one of the input pins (I0 and I1) of the global buffer using the fast routing. Thus, the warning is correct in that the fast routing cannot be used.

To fix this issue, try swapping the input pins of the BUFGMUX. This should allow the correct IOB to use its direct route to the buffer.
AR# 13276
Date Created 08/29/2007
Last Updated 10/20/2008
Status Archive
Type General Article