I’ve encountered Functional Safety concepts, most recently at ArmTechCon, and wanted to capture some of the terminology. To orient the discussion, think of airbags, seat-belts, and tire-pressure-monitoring-systems as safety features in a car.
Safety Function: A function to take a system to a safe outcome when certain prerequisites on system inputs are not met. For example, turn on a warning indicator when seat-belt is not used or when the tire-pressure is below safe level, or deploy airbags when a collision is detected. Also called Safety Instrumented Function
Safety Related Control Function: This is the control mechanism by which the safety function is achieved. Collision above a certain impact threshold leads to airbag deployment by an airbag control module. ‘The airbag control module is installed inside the center console and contains a safety sensor, G sensor, ignition judgment circuit, and a backup power supply.’
Safety Integrity Level: The reliability of a safety-related-control-function is captured with a Safety Integrity Level or SIL.
A standard is ISO26262. The V shaped functional safety process diagram is here. This process is used to achieve a Safety Integrity Level (SIL) where the SIL1, SIL2, SIL3, SIL4 reduce risk by a progressive factor of 10, i.e. by 10x, 100x, 1000x and 10000x. A hazard and operability study ( HAZOP ) is undertaken to understand the risks of the mechanism behaving incorrectly.
An Nvidia safe driving report is here.