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AR# 694

5.2.0 PPR - issues error 5846 on designs where the aclk or gclk is fed from a clb and the clb location is constrained


PPR 5.2.0 may issue this error on a legally constrained design:
*** PPR: ERROR 5846:
The ACLK symbol `global buffer
'/$1I274/$1I312/$1I634' (type=ACLK, output
signal=/RCVCLK)' is sourced directly from the pad
signal `/$1I274/$1I312/RVCLK' and must use the
dedicated pad. However, it has been constrained to a non-dedicated
location. Correct or remove the constraint (no constraint is
necessary since only one location is possible).

The constrain that causes this is on a clb that feeds the aclk:
PLACE BLOCK /$1I274/$1I312/RVCLK: QN; This happens with either the
aclk or the gclk.


This problem arises because PPR fails to check the source of the aclk or gclk but does check the constraints on the source. There are several workarounds:

1. Don't constrain this location. The floorplanner will automatically write out a constraint for this if the block is floorplanned. Edit the <design>.cst file and remove the constraint.

2. Constrain the block to only one possible location using a NOTPLACE BLOCK constraint.
Use the following syntax:


Notice that this blocks out the four regions around the desired location (QN); by default
the block will be place in the correct location (QN)

3. Use version 5.1.0 of PPR. This problem doesn't appear in that version.
AR# 694
Date Created 08/31/2007
Last Updated 03/22/2000
Status Archive