Evidence for the input nobody wrote a test for

A flight control loop runs on a fixed frame and has to be right on every frame, on every input. What a simulation campaign establishes is correct behavior on the stimulus somebody wrote. What the requirement is about is behavior nobody wrote a test for.

What a campaign establishes, and what the requirement asks

Verification is reported to consume 60 to 70% of engineering effort in chip projects, per Wilson Research Group functional verification study data, and a program carrying an evidence requirement spends more than that (Source: Harry Foster, Siemens EDA, Verification Horizons, September 2025(opens in a new tab)).

The distance between those two statements is not closed by adding engineers or simulation hours, and a respin is the most expensive way to discover it was still open.

A flight control loop running on a fixed frameAn aircraft in plan view. Three points on it, at the nose, the fuselage and the tail, connect to a loop of three stages below: sense, compute, actuate, closing back to sense for the next frame. Under the loop a ruler marks the frames the loop runs on, at a fixed period, one after another.SenseComputeActuateNext FrameEvery FrameOne Frame, Fixed PeriodTime
A flight control loop on a fixed frame: sense, compute, actuate, then the next frame. The requirement is correct behavior on every frame and every input, which no set of test vectors enumerates.

Signoff

What can be claimed at tapeout

Signoff addresses a part that is still a netlist, where the decision is what can be claimed at tapeout. The obligation that the lowering preserves the specification is discharged by proof, and the certificate is the evidence that travels with the part. The engagement is described under Design signoff.

The signoff engagement first? Design signoff

Carrying an evidence requirement into tapeout?

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