( ESNUG 349 Item 1 ) --------------------------------------------- [4/18/00]
From: [ The Great Gatsby ]
Subject: WARNING: Using transform_csa w/ DW Multipliers Creates Bad Logic!
Hi John,
Here's another Bad Logic bug we found in Design Compiler with the Synopsys
workaround included below:
PROBLEM:
When the transform_csa command is used on designs containing multipliers,
incorrect logic might be produced in the output netlist. You will
experience this problem with DesignWare Foundation only in version 98.08
EST or later.
SOLUTION:
In the 98.08 EST release and beyond, DesignWare Foundation has two
architectures for DW02_multp (partial product multiplier): wall and nbw.
The existence of more than one architecture causes a problem in the tool.
The workaround is to set only one of the previous architectures (wall or
nbw) before using transform_csa.
For example:
set_dont_use dw02.sldb/DW02_multp/wall
transform_csa
Because there are no issues with DW02_multp architectures, you can use
either nbw or wall depending on your design needs.
This, too, bit us while taping out our 1.3 million gate design. Hopefully,
by bringing this up in ESNUG, other users won't have to discover this bug
the hard way (like we did.) Please keep me anon.
- [ The Great Gatsby ]
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