Often we have two implementations of a combinational circuit to check for equivalence. .latex For example, they might be:

- RTL version: pre-synthesis,
- Gate-level version: post-synthesis or post-layout.

Error sources: manual implementation of one of them, manual edits to synthesiser outputs and EDA tool faults.

Boolean equivalence: do the two functions produce the same output?

- For all input combinations ?
- For a subset of input combinations (some input patterns are don't cares).

Method: Create a *MITRE* of the two designs using a disjunction of XOR gate outputs.

Then: feed negation of mitre to a SAT solver.

Result: if there are no solutions, designs are equivalent.

21: (C) 2008-11, DJ Greaves, University of Cambridge, Computer Laboratory.