Enable free fall detection using Arduino
Sitting an accelerometer flatly on a bench will produce a value of 1G in one of the 3 axes.

Free fall of an accelerometer (assuming you haven't reached terminal velocity) should read near zero on all 3 axes.

I am not aware of a mode you can set for this, but if you check the values of the 3 axes and all are close to zero, you are probably in a free fall condition.