This plot shows what is happening when you first turn on the ignition switch and not start the motor.  You get four cycles of turning on and off the IAC motor then it is left in the off state (I'm looking at the ECU driver side. The other side of the motor is tied to the switched 12 volts).  This is the clicking you first hear when the key is turned.  Normally the pulse applied to the IAC motor are much shorter in duration and doesn't drive it to the rail.  A little more than 3 seconds after the key is turned the ECU shuts off the relay feeding power to the IAC motor, Fuel Pump, O2 Heater, and the Injectors.

    This plot just expands on the above.  You can see that the total period is about .5 seconds with a 50% duty cycle.  When the motor is running the total period is 6.666 ms.  The reason for the initial banging is this exaggerated pulse width.  Why this is done is a mystery.  Are they letting use know that the IAC is there and working ?  Or maybe this is done to exercise the IAC motor to its stops, perhaps to assure freedom of movement ?  Anybody's guess here.

    The above three plots show what is happening at several RPMs and displayed duty cycles.  The total period is always 6.666 ms.  Looking at these plots it is not obvious exactly what the controller is telling us at different percentages.  50% is on longer than 30%, but 60% is on less than 50% ?