Rep Power: 118

I am wondering how a car's ECU controls ignition timing, in a general sense. I am well aware of the fact that the ECU advances and retards timing based on load, RPM, intake air temp, coolant temp, throttle position, etc. But what I am wondering is if the ECU tries to advance the ignition timing as much as possible without the knock sensor detecting knock, or if the ECU just sets the timing to what it is programmed to and retards timing if it detects knock.

For example, if the car is cruising under a steady load, will the ECU advance the timing until it detects knock and then retard it slightly the timing advance is always as much is possible, or does it just set the timing to what it is programmed to and leave it alone unless it is detecting knock? Thanks in advance!