Synthesis shell generation and use in asic design

Abstract

A practical approach for synthesis for million gate ASICs is based on the use of synthesis shells. The synthesis shell is generated by beginning with a gate level description of a fully characterized and optimized block. This gate level description is reduced by removing internal gates to produce a synthesis shell of the synthesized block. The synthesis shell preserves input load and fanout for the block, output delay relative to clock for the block, setup/hold constraints on input signals relative to the clock for the block, and delay from input to output for pass through signals for the block. Such a synthesis shell can be used as a substitute for original design netlists and can be used for hierarchical synthesis in a customer's design environment, or as a deliverable from a provider of ASIC services in order to protect the intellectual property of such a provider. Since all the information that is needed by a synthesizer is available in the synthesis shell in netlist form, the shell is extremely accurate. The synthesis shell as mentioned above comprises a gate level description which is a subset of the synthesized block. This description is reduced by deleting elements of the gate level description according to a set of pre-specified criteria.