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AR# 13816

4.1isp3 XST - "WARNING:Xst:164 - Inserting OBUF on port xxx driven by tristate(s), possible simulation mismatch"

Description

Keywords: XST, tri, state, bi, directional, OBUFT, OBUFE, INOUT

Urgency: Standard

General Description:
When bidirectional ports are used, XST issues the following warning:

"WARNING:Xst:164 - Inserting OBUF on port xxx driven by tristate(s), possible simulation mismatch."

XST inserts an OBUF instead of an IOBUF when a bidirectional HDL port code is in a sub module and the "Keep Hierarchy" option is checked.

This problem has been fixed with the release of software version 5.1i.

Solution

1

To avoid this warning, remove the "Keep Hierarchy" option:

ISE:

1. Right-click on the "Synthesize" process and select "Properties".
2. Select "Synthesis Options".
3. Deselect "Keep Hierarchy".

XST Command Line:

-keep_hierarchy No

2

Also, move the bidirectional description into the top level of a hierarchy.
AR# 13816
Date Created 02/07/2002
Last Updated 08/06/2003
Status Archive
Type General Article