Interview question for Coverage Driven Verification

[kamalkundu]

coverage driven verification

Hello everybody,

Yesterday I was interviewed @Intel. I got a question which I could not explain. Please help me with that :

Given a 256-input NAND gate how many test cases are required to verify it and how much coverage it will give ? Do we need to run all 2^256 cases to get 100% coverage.

 

[kulyapinav]

verification interview question

We need 256+1 testcase:
256 tests contain only one "zero"
1 test contains all "ones"

 

[kamalkundu]

Thank you very much for response. I understand that you are giving almost complete exercise to the design but can you tell me that what would be coverage ? and how would we get satisfied that the verification is done.

 

[ljxpjpjljx]

verify the dut all conbination , that is the coverage! furthermore, coverage have many type!