( ESNUG 371 Item 5 ) -------------------------------------------- [05/23/01]
From: Rajkumar Kadam <rkadam@asic.qntm.com>
Subject: DFT Compiler Chokes On Synchronizers With Inputs Tied To Zero
Hi, John,
I have a design in which there are some instances of synchronizers whose
inputs will be tied to zero depending on the requirement. The problem is
that Design Compiler does not remove such instances. It keeps the instance
with the input tied and the output not defined at all in the gate level
netlist. All this is fine for gate level simulation, etc., but the problem
occurs when I try to insert scan in the design. DFT Compiler sees a
sequential cell with inputs defined and no outputs and issues a Warning as
this cell cannot be included in the scan chain.
Is there anyway to optimize away the unsed instances, using some Synopsys
variable? I know only of two solutions:
1. ungroup -- but I do not want to run ungroup on the design.
2. grep manually for such unused cells and remove it. Ugly.
Any other solution is welcome.
- Rajkumar Kadam
Quantum Corp.
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