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AR# 22105

10.1 PACE - DRC error "Placement mismatch" on a bidirectional differential I/O

Description

Keyword: IOBUFDS, P TYPE, N TYPE

When I run a DRC check on my pin assignments, I receive errors on my bidirectional differential I/Os similar to the following:

"DDR_2_DQS_N<0> : Placement mismatch. Please check the following: 1. if this differential (sic) IO is placed in a differential IOB. 2. if it is placed in the same type (P or N TYPE) of differential IOB or if its a local clock IO, it is place in opposite type (P for N)"

Is this a valid error?

Solution

In some cases, PACE misinterprets the differential pairs. If you have verified that the location constraints are correct, you can ignore these errors.

AR# 22105
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article