Chapter 9: Tools
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9-7: Network Consistency Checking (NCC)
9-7-1: Introduction to NCC |
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Electric can compare two different cells and determine whether their networks have the same topology.
This operation is sometimes called Layout vs. Schematic (LVS),
but because Electric can compare any two circuits (including two layouts or two schematics)
we use the term Network Consistency Checking (NCC).
The Electric Network Consistency Checker has two algorithms for matching networks:
- NCC firsts attempts to discover circuit mismatches using an algorithm called "Local Partitioning".
Local Partitioning provides precise and intelligible mismatch diagnostics.
- After Local Partitioning, NCC uses the Gemini algorithm
(Ebeling, Carl, "GeminiII: A Second Generation Layout Validation Program", Proceedings of ICCAD 1988,
p322-325.)
In practice upwards of 95% of all errors are found by Local Partitioning.
NCC has a "hierarchical" mode which starts at the bottom of the hierarchy in the leaf cells
and proceeds upward.
This mode is recommended because it allows the Local Partitioning algorithm to provide even
more precise and intelligible mismatch diagnostics.
Example
For an example of network consistency checking, open the Samples
library with the Load Sample Cells Library command (in menu Help) and compare the
cells "tool-NCC{lay}" and "tool-NCC{sch}". These two cells are
equivalent and the checker will find them to be so.
Calibre
Electric is able to work with Calibre LVS, and it can read the results of that program.
Use the Import Calibre LVS Errors for Current Cell... command (in menu Tools / NCC)
and select the Calibre error file (with the ".db" extension).
