( ESNUG 280 Item 1 ) ------------------------------------------------ [2/12/98]
From: "Anders Nordstrom" <andersn@nortel.ca>
Subject: Subtle Alignment Problems In ECO Compiler With Scanned Designs
John,
I have been working with Synopsys new ECO compiler for a while and I found
some strange behaviour by the tool. I am doing an ECO to a scan inserted
netlist and the eco_align_design command fails sometimes. The same number
of registers exists in both designs so that is not the problem.
When runnign eco_align_design it reports:
NOTHING TO REPORT!
ALIGNMENT COMPLETE!!
This to me indicates that it worked fine but, oh no, it is followed by:
Error: Alignment not complete. Must use eco_align_design command. (ECO-95)
Error: Complete alignment of all ports & registers not satisfied. (ECO-83)
The problem turned out to be that two registers called TTR_CS_reg[4] and
TTR_CS_reg[5] were using the same type of flip flop but with different
drive strength. As far as I know this is only a problem when working with
scannable flip flops.
Solution: manually align the two registers with the commands:
set_eco_align cell TTR_CS_reg[4] TTR_CS_reg[4]
set_eco_align cell TTR_CS_reg[5] TTR_CS_reg[5]
- Anders Nordstrom
Northern Telecom Ltd. Ottawa, Canada
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